unbound.conf(5)                  unbound 1.8.3                 unbound.conf(5)



NAME
       unbound.conf - Unbound configuration file.

SYNOPSIS
       unbound.conf

DESCRIPTION
       unbound.conf  is  used  to  configure  unbound(8).  The file format has
       attributes and values. Some attributes  have  attributes  inside  them.
       The notation is: attribute: value.

       Comments  start  with  #  and  last to the end of line. Empty lines are
       ignored as is whitespace at the beginning of a line.

       The utility unbound-checkconf(8) can  be  used  to  check  unbound.conf
       prior to usage.

EXAMPLE
       An    example    config   file   is   shown   below.   Copy   this   to
       /etc/unbound/unbound.conf and start the server with:

            $ unbound -c /etc/unbound/unbound.conf

       Most settings are the defaults. Stop the server with:

            $ kill `cat /etc/unbound/unbound.pid`

       Below is a minimal config file. The  source  distribution  contains  an
       extensive example.conf file with all the options.

       # unbound.conf(5) config file for unbound(8).
       server:
            directory: "/etc/unbound"
            username: unbound
            # make sure unbound can access entropy from inside the chroot.
            # e.g. on linux the use these commands (on BSD, devfs(8) is used):
            #      mount --bind -n /dev/random /etc/unbound/dev/random
            # and  mount --bind -n /dev/log /etc/unbound/dev/log
            chroot: "/etc/unbound"
            # logfile: "/etc/unbound/unbound.log"  #uncomment to use logfile.
            pidfile: "/etc/unbound/unbound.pid"
            # verbosity: 1      # uncomment and increase to get more logging.
            # listen on all interfaces, answer queries from the local subnet.
            interface: 0.0.0.0
            interface: ::0
            access-control: 10.0.0.0/8 allow
            access-control: 2001:DB8::/64 allow

FILE FORMAT
       There  must be whitespace between keywords. Attribute keywords end with
       a colon ':'.  An attribute is followed by its containing attributes, or
       a value.

       Files  can be included using the include: directive. It can appear any-
       where, it accepts a single file name as argument.  Processing continues
       as  if  the text from the included file was copied into the config file
       at that point.  If also using chroot, using full  path  names  for  the
       included files works, relative pathnames for the included names work if
       the directory where the daemon is  started  equals  its  chroot/working
       directory  or is specified before the include statement with directory:
       dir.  Wildcards can be used to include multiple files, see glob(7).

   Server Options
       These options are part of the server: clause.

       verbosity: <number>
              The verbosity number, level 0 means no verbosity,  only  errors.
              Level  1  gives  operational information. Level 2 gives detailed
              operational information. Level 3 gives query level  information,
              output  per  query.   Level 4 gives algorithm level information.
              Level 5 logs client identification for cache misses.  Default is
              level  1.  The verbosity can also be increased from the command-
              line, see unbound(8).

       statistics-interval: <seconds>
              The number of seconds between printing statistics to the log for
              every  thread.  Disable with value 0 or "". Default is disabled.
              The histogram statistics are only printed if replies  were  sent
              during  the  statistics  interval,  requestlist  statistics  are
              printed for every interval (but can be 0).  This is because  the
              median calculation requires data to be present.

       statistics-cumulative: <yes or no>
              If  enabled,  statistics  are cumulative since starting unbound,
              without clearing the statistics counters after logging the  sta-
              tistics. Default is no.

       extended-statistics: <yes or no>
              If  enabled,  extended  statistics are printed from unbound-con-
              trol(8).  Default is off, because keeping track of more  statis-
              tics takes time.  The counters are listed in unbound-control(8).

       num-threads: <number>
              The  number  of threads to create to serve clients. Use 1 for no
              threading.

       port: <port number>
              The port number, default 53, on which  the  server  responds  to
              queries.

       interface: <ip address[@port]>
              Interface  to  use  to connect to the network. This interface is
              listened to for queries from clients, and answers to clients are
              given  from  it.  Can be given multiple times to work on several
              interfaces. If none are given the default is to listen to local-
              host.   The  interfaces  are not changed on a reload (kill -HUP)
              but only on restart.  A port number can be specified with  @port
              (without spaces between interface and port number), if not spec-
              ified the default port (from port) is used.

       ip-address: <ip address[@port]>
              Same as interface: (for ease of compatibility with nsd.conf).

       interface-automatic: <yes or no>
              Detect source interface on UDP queries and copy them to replies.
              This  feature  is experimental, and needs support in your OS for
              particular socket options.  Default value is no.

       outgoing-interface: <ip address or ip6 netblock>
              Interface to use to connect to the network.  This  interface  is
              used  to send queries to authoritative servers and receive their
              replies. Can be given multiple times to work on  several  inter-
              faces.  If  none  are  given  the default (all) is used. You can
              specify the same interfaces in  interface:  and  outgoing-inter-
              face:  lines,  the  interfaces  are then used for both purposes.
              Outgoing queries are sent via a  random  outgoing  interface  to
              counter spoofing.

              If  an  IPv6 netblock is specified instead of an individual IPv6
              address, outgoing UDP  queries  will  use  a  randomised  source
              address  taken  from  the netblock to counter spoofing. Requires
              the IPv6 netblock to be routed to the host running unbound,  and
              requires  OS support for unprivileged non-local binds (currently
              only supported on Linux). Several  netblocks  may  be  specified
              with  multiple  outgoing-interface:  options, but do not specify
              both an individual IPv6 address and an  IPv6  netblock,  or  the
              randomisation will be compromised.  Consider combining with pre-
              fer-ip6: yes to increase  the  likelihood  of  IPv6  nameservers
              being  selected  for  queries.  On Linux you need these two com-
              mands to be able to use the freebind socket  option  to  receive
              traffic  for  the ip6 netblock: ip -6 addr add mynetblock/64 dev
              lo && ip -6 route add local mynetblock/64 dev lo

       outgoing-range: <number>
              Number of ports to open. This number of file descriptors can  be
              opened  per  thread. Must be at least 1. Default depends on com-
              pile options. Larger numbers need extra resources from the oper-
              ating  system.   For performance a very large value is best, use
              libevent to make this possible.

       outgoing-port-permit: <port number or range>
              Permit unbound to open this port or range of ports  for  use  to
              send  queries.   A  larger  number  of  permitted outgoing ports
              increases resilience against spoofing attempts. Make sure  these
              ports  are  not  needed by other daemons.  By default only ports
              above 1024 that have not been assigned by IANA are used.  Give a
              port number or a range of the form "low-high", without spaces.

              The  outgoing-port-permit and outgoing-port-avoid statements are
              processed in the line order of the config file, adding the  per-
              mitted  ports  and subtracting the avoided ports from the set of
              allowed ports.  The processing starts with the  non  IANA  allo-
              cated ports above 1024 in the set of allowed ports.

       outgoing-port-avoid: <port number or range>
              Do  not  permit  unbound to open this port or range of ports for
              use to send queries. Use this to make sure unbound does not grab
              a  port  that  another  daemon needs. The port is avoided on all
              outgoing interfaces, both IP4 and IP6.  By  default  only  ports
              above 1024 that have not been assigned by IANA are used.  Give a
              port number or a range of the form "low-high", without spaces.

       outgoing-num-tcp: <number>
              Number of outgoing TCP buffers to allocate per  thread.  Default
              is  10.  If  set  to  0, or if do-tcp is "no", no TCP queries to
              authoritative  servers  are  done.   For  larger   installations
              increasing this value is a good idea.

       incoming-num-tcp: <number>
              Number  of  incoming TCP buffers to allocate per thread. Default
              is 10. If set to 0, or if do-tcp is "no", no  TCP  queries  from
              clients  are  accepted. For larger installations increasing this
              value is a good idea.

       edns-buffer-size: <number>
              Number of bytes size to advertise as the EDNS reassembly  buffer
              size.   This  is  the  value put into datagrams over UDP towards
              peers.  The actual buffer size is determined by  msg-buffer-size
              (both  for  TCP  and  UDP).   Do not set higher than that value.
              Default is 4096 which is RFC recommended.  If you have  fragmen-
              tation  reassembly  problems,  usually  seen as timeouts, then a
              value of 1472 can fix it.  Setting to 512 bypasses even the most
              stringent  path  MTU problems, but is seen as extreme, since the
              amount of TCP fallback generated is excessive (probably also for
              this resolver, consider tuning the outgoing tcp number).

       max-udp-size: <number>
              Maximum  UDP response size (not applied to TCP response).  65536
              disables the udp response size maximum, and uses the choice from
              the  client,  always.  Suggested values are 512 to 4096. Default
              is 4096.

       msg-buffer-size: <number>
              Number of bytes size of the message buffers.  Default  is  65552
              bytes,  enough  for 64 Kb packets, the maximum DNS message size.
              No message larger than this can be  sent  or  received.  Can  be
              reduced to use less memory, but some requests for DNS data, such
              as for huge resource records, will result in a SERVFAIL reply to
              the client.

       msg-cache-size: <number>
              Number  of  bytes  size  of  the  message  cache.  Default  is 4
              megabytes.  A plain number is in bytes, append 'k', 'm'  or  'g'
              for  kilobytes,  megabytes  or  gigabytes  (1024*1024 bytes in a
              megabyte).

       msg-cache-slabs: <number>
              Number of slabs in the message cache.  Slabs  reduce  lock  con-
              tention  by  threads.   Must  be  set  to  a power of 2. Setting
              (close) to the number of cpus is a reasonable guess.

       num-queries-per-thread: <number>
              The number of queries that every thread will service  simultane-
              ously.   If  more  queries  arrive  that  need servicing, and no
              queries can  be  jostled  out  (see  jostle-timeout),  then  the
              queries  are  dropped.  This forces the client to resend after a
              timeout; allowing the  server  time  to  work  on  the  existing
              queries. Default depends on compile options, 512 or 1024.

       jostle-timeout: <msec>
              Timeout  used when the server is very busy.  Set to a value that
              usually results in one roundtrip to the authority  servers.   If
              too  many queries arrive, then 50% of the queries are allowed to
              run to completion, and the other 50% are replaced with  the  new
              incoming  query  if  they  have  already  spent  more than their
              allowed time.  This protects against denial of service  by  slow
              queries  or  high  query  rates.  Default 200 milliseconds.  The
              effect is that the qps for long-lasting queries is  about  (num-
              queriesperthread  /  2)  /  (average time for such long queries)
              qps.  The qps  for  short  queries  can  be  about  (numqueries-
              perthread  /  2)  /  (jostletimeout  in  whole  seconds) qps per
              thread, about (1024/2)*5 = 2560 qps by default.

       delay-close: <msec>
              Extra delay for timeouted UDP ports before they are  closed,  in
              msec.   Default  is 0, and that disables it.  This prevents very
              delayed answer packets from  the  upstream  (recursive)  servers
              from  bouncing  against closed ports and setting off all sort of
              close-port counters, with eg. 1500 msec.  When  timeouts  happen
              you  need extra sockets, it checks the ID and remote IP of pack-
              ets, and unwanted packets  are  added  to  the  unwanted  packet
              counter.

       unknown-server-time-limit: <msec>
              The  wait  time  in  msec  for  waiting for an unknown server to
              reply.  Increase this if you are behind a slow  satellite  link,
              to  eg.  1128.   That would then avoid re-querying every initial
              query because it times out.  Default is 376 msec.

       so-rcvbuf: <number>
              If not 0, then set the SO_RCVBUF socket option to get more  buf-
              fer space on UDP port 53 incoming queries.  So that short spikes
              on busy servers do not drop  packets  (see  counter  in  netstat
              -su).   Default  is 0 (use system value).  Otherwise, the number
              of bytes to ask for, try "4m" on a busy server.  The OS caps  it
              at  a  maximum, on linux unbound needs root permission to bypass
              the limit, or the admin can use  sysctl  net.core.rmem_max.   On
              BSD  change kern.ipc.maxsockbuf in /etc/sysctl.conf.  On OpenBSD
              change header and recompile kernel. On Solaris ndd -set /dev/udp
              udp_max_buf 8388608.

       so-sndbuf: <number>
              If  not 0, then set the SO_SNDBUF socket option to get more buf-
              fer space on UDP port 53 outgoing queries.  This for  very  busy
              servers  handles  spikes  in  answer  traffic,  otherwise 'send:
              resource temporarily unavailable' can  get  logged,  the  buffer
              overrun  is also visible by netstat -su.  Default is 0 (use sys-
              tem value).  Specify the number of bytes to ask for, try "4m" on
              a  very  busy  server.   The  OS  caps it at a maximum, on linux
              unbound needs root permission to bypass the limit, or the  admin
              can  use  sysctl net.core.wmem_max.  On BSD, Solaris changes are
              similar to so-rcvbuf.

       so-reuseport: <yes or no>
              If yes, then  open  dedicated  listening  sockets  for  incoming
              queries  for  each thread and try to set the SO_REUSEPORT socket
              option on each  socket.   May  distribute  incoming  queries  to
              threads  more evenly.  Default is yes.  On Linux it is supported
              in kernels >= 3.9.  On other systems, FreeBSD, OSX it  may  also
              work.   You  can enable it (on any platform and kernel), it then
              attempts to open the port and passes the option if it was avail-
              able  at compile time, if that works it is used, if it fails, it
              continues silently (unless verbosity 3) without the option.

       ip-transparent: <yes or no>
              If yes, then use IP_TRANSPARENT socket option on  sockets  where
              unbound  is listening for incoming traffic.  Default no.  Allows
              you to bind to non-local interfaces.  For example for  non-exis-
              tent  IP  addresses  that are going to exist later on, with host
              failover configuration.  This is a lot like interface-automatic,
              but  that  one  services all interfaces and with this option you
              can select which (future) interfaces  unbound  provides  service
              on.   This  option needs unbound to be started with root permis-
              sions on some systems.  The option uses  IP_BINDANY  on  FreeBSD
              systems and SO_BINDANY on OpenBSD systems.

       ip-freebind: <yes or no>
              If  yes,  then  use  IP_FREEBIND  socket option on sockets where
              unbound is listening to incoming traffic.  Default  no.   Allows
              you  to  bind to IP addresses that are nonlocal or do not exist,
              like when the network interface or IP address is  down.   Exists
              only  on  Linux, where the similar ip-transparent option is also
              available.

       rrset-cache-size: <number>
              Number of bytes size of the RRset cache. Default is 4 megabytes.
              A  plain  number  is  in bytes, append 'k', 'm' or 'g' for kilo-
              bytes, megabytes or gigabytes (1024*1024 bytes in a megabyte).

       rrset-cache-slabs: <number>
              Number of slabs in the RRset cache. Slabs reduce lock contention
              by threads.  Must be set to a power of 2.

       cache-max-ttl: <seconds>
              Time  to  live  maximum  for  RRsets  and messages in the cache.
              Default is 86400 seconds (1  day).  If  the  maximum  kicks  in,
              responses  to  clients  still get decrementing TTLs based on the
              original (larger) values.  When the internal  TTL  expires,  the
              cache  item has expired.  Can be set lower to force the resolver
              to query for data often, and not trust (very large) TTL values.

       cache-min-ttl: <seconds>
              Time to live minimum for  RRsets  and  messages  in  the  cache.
              Default  is  0.  If the minimum kicks in, the data is cached for
              longer than the domain owner intended, and thus less queries are
              made to look up the data.  Zero makes sure the data in the cache
              is as the domain owner intended, higher values, especially  more
              than an hour or so, can lead to trouble as the data in the cache
              does not match up with the actual data any more.

       cache-max-negative-ttl: <seconds>
              Time to live maximum for negative responses, these have a SOA in
              the authority section that is limited in time.  Default is 3600.
              This applies to nxdomain and nodata answers.

       infra-host-ttl: <seconds>
              Time to live for entries in the host cache. The host cache  con-
              tains  roundtrip  timing, lameness and EDNS support information.
              Default is 900.

       infra-cache-slabs: <number>
              Number of slabs in the infrastructure cache. Slabs  reduce  lock
              contention by threads. Must be set to a power of 2.

       infra-cache-numhosts: <number>
              Number  of  hosts  for  which  information is cached. Default is
              10000.

       infra-cache-min-rtt: <msec>
              Lower limit for dynamic retransmit timeout calculation in infra-
              structure cache. Default is 50 milliseconds. Increase this value
              if using forwarders needing more time to do recursive name reso-
              lution.

       define-tag: <"list of tags">
              Define the tags that can be used with local-zone and access-con-
              trol.  Enclose the list  between  quotes  ("")  and  put  spaces
              between tags.

       do-ip4: <yes or no>
              Enable  or  disable  whether ip4 queries are answered or issued.
              Default is yes.

       do-ip6: <yes or no>
              Enable or disable whether ip6 queries are  answered  or  issued.
              Default  is yes.  If disabled, queries are not answered on IPv6,
              and queries are not sent on IPv6 to  the  internet  nameservers.
              With  this option you can disable the ipv6 transport for sending
              DNS traffic, it does not impact the contents of the DNS traffic,
              which may have ip4 and ip6 addresses in it.

       prefer-ip6: <yes or no>
              If  enabled,  prefer  IPv6  transport for sending DNS queries to
              internet nameservers. Default is no.

       do-udp: <yes or no>
              Enable or disable whether UDP queries are  answered  or  issued.
              Default is yes.

       do-tcp: <yes or no>
              Enable  or  disable  whether TCP queries are answered or issued.
              Default is yes.

       tcp-mss: <number>
              Maximum segment size (MSS) of TCP socket  on  which  the  server
              responds  to  queries.  Value  lower than common MSS on Ethernet
              (1220 for example) will address path MTU problem.  Note that not
              all  platform  supports  socket  option to set MSS (TCP_MAXSEG).
              Default is system default MSS determined by  interface  MTU  and
              negotiation between server and client.

       outgoing-tcp-mss: <number>
              Maximum  segment  size  (MSS) of TCP socket for outgoing queries
              (from Unbound to other servers). Value lower than common MSS  on
              Ethernet (1220 for example) will address path MTU problem.  Note
              that  not  all  platform  supports  socket  option  to  set  MSS
              (TCP_MAXSEG).   Default  is  system  default  MSS  determined by
              interface MTU and negotiation between Unbound and other servers.

       tcp-idle-timeout: <msec>
              The period Unbound will wait for a query on  a  TCP  connection.
              If  this  timeout  expires  Unbound closes the connection.  This
              option defaults to 30000 milliseconds.  When the number of  free
              incoming TCP buffers falls below 50% of the total number config-
              ured, the option value used is progressively reduced,  first  to
              1% of the configured value, then to 0.2% of the configured value
              if the number of free buffers falls below 35% of the total  num-
              ber  configured,  and finally to 0 if the number of free buffers
              falls below 20% of the total number configured. A minimum  time-
              out  of  200  milliseconds  is observed regardless of the option
              value used.

       edns-tcp-keepalive: <yes or no>
              Enable or disable EDNS TCP Keepalive. Default is no.

       edns-tcp-keepalive-timeout: <msec>
              The period Unbound will wait for a query  on  a  TCP  connection
              when  EDNS  TCP  Keepalive  is  active.  If this timeout expires
              Unbound closes the connection. If the client supports  the  EDNS
              TCP  Keepalive  option,  Unbound  sends the timeout value to the
              client to encourage it to close the connection before the server
              times  out.   This option defaults to 120000 milliseconds.  When
              the number of free incoming TCP buffers falls below 50%  of  the
              total number configured, the advertised timeout is progressively
              reduced to 1% of the configured value, then to 0.2% of the  con-
              figured  value  if the number of free buffers falls below 35% of
              the total number configured, and finally to 0 if the  number  of
              free  buffers falls below 20% of the total number configured.  A
              minimum actual timeout of 200 milliseconds is  observed  regard-
              less of the advertised timeout.

       tcp-upstream: <yes or no>
              Enable  or disable whether the upstream queries use TCP only for
              transport.  Default is no.  Useful in tunneling scenarios.

       udp-upstream-without-downstream: <yes or no>
              Enable udp upstream even if do-udp is no.  Default  is  no,  and
              this   does   not  change  anything.   Useful  for  TLS  service
              providers, that want no udp downstream but use udp to fetch data
              upstream.

       tls-upstream: <yes or no>
              Enabled or disable whether the upstream queries use TLS only for
              transport.  Default is no.  Useful in tunneling scenarios.   The
              TLS contains plain DNS in TCP wireformat.  The other server must
              support this (see tls-service-key).  If you  enable  this,  also
              configure  a  tls-cert-bundle  or  use  tls-win-cert  to load CA
              certs, otherwise the connections cannot be authenticated.

       ssl-upstream: <yes or no>
              Alternate syntax for tls-upstream.  If both are present  in  the
              config file the last is used.

       tls-service-key: <file>
              If  enabled, the server provider TLS service on its TCP sockets.
              The clients have to use tls-upstream: yes.  The file is the pri-
              vate  key for the TLS session.  The public certificate is in the
              tls-service-pem file.  Default is "", turned  off.   Requires  a
              restart (a reload is not enough) if changed, because the private
              key is read while root permissions are held  and  before  chroot
              (if  any).   Normal  DNS  TCP  service is not provided and gives
              errors, this service is best run with a different  port:  config
              or @port suffixes in the interface config.

       ssl-service-key: <file>
              Alternate syntax for tls-service-key.

       tls-service-pem: <file>
              The  public  key  certificate  pem  file  for  the  tls service.
              Default is "", turned off.

       ssl-service-pem: <file>
              Alternate syntax for tls-service-pem.

       tls-port: <number>
              The port number on which to provide  TCP  TLS  service,  default
              853, only interfaces configured with that port number as @number
              get the TLS service.

       ssl-port: <number>
              Alternate syntax for tls-port.

       tls-cert-bundle: <file>
              If null or "", no file is used.  Set it to the certificate  bun-
              dle file, for example "/etc/pki/tls/certs/ca-bundle.crt".  These
              certificates are used for  authenticating  connections  made  to
              outside  peers.   For  example auth-zone urls, and also DNS over
              TLS connections.

       ssl-cert-bundle: <file>
              Alternate syntax for tls-cert-bundle.

       tls-win-cert: <yes or no>
              Add the system certificates to the cert bundle certificates  for
              authentication.   If no cert bundle, it uses only these certifi-
              cates.  Default is no.  On windows this option uses the certifi-
              cates  from  the  cert store.  Use the tls-cert-bundle option on
              other systems.

       tls-additional-port: <portnr>
              List portnumbers as tls-additional-port, and when interfaces are
              defined,  eg.  with  the @port suffix, as this port number, they
              provide dns over TLS service.  Can list multiple, each on a  new
              statement.

       use-systemd: <yes or no>
              Enable or disable systemd socket activation.  Default is no.

       do-daemonize: <yes or no>
              Enable  or  disable  whether  the  unbound server forks into the
              background as a daemon.  Set the value to no when  unbound  runs
              as systemd service.  Default is yes.

       tcp-connection-limit: <IP netblock> <limit>
              Allow  up  to  limit simultaneous TCP connections from the given
              netblock.  When at the limit, further connections  are  accepted
              but  closed  immediately.   This  option is experimental at this
              time.

       access-control: <IP netblock> <action>
              The netblock is given as  an  IP4  or  IP6  address  with  /size
              appended  for a classless network block. The action can be deny,
              refuse,  allow,  allow_setrd,  allow_snoop,  deny_non_local   or
              refuse_non_local.   The most specific netblock match is used, if
              none match deny is used.

              The action deny stops queries from hosts from that netblock.

              The action refuse stops queries  too,  but  sends  a  DNS  rcode
              REFUSED error message back.

              The action allow gives access to clients from that netblock.  It
              gives only access for recursion clients (which  is  what  almost
              all clients need).  Nonrecursive queries are refused.

              The  allow  action does allow nonrecursive queries to access the
              local-data that is configured.  The reason is that this does not
              involve  the  unbound  server  recursive  lookup  algorithm, and
              static data is served in the reply.  This supports normal opera-
              tions  where nonrecursive queries are made for the authoritative
              data.  For nonrecursive queries any  replies  from  the  dynamic
              cache are refused.

              The  allow_setrd  action  ignores the recursion desired (RD) bit
              and treats all requests as if the recursion desired bit is  set.
              Note  that  this  behavior violates RFC 1034 which states that a
              name server should never perform recursive service unless  asked
              via  the  RD  bit since this interferes with trouble shooting of
              name servers and their databases. This prohibited  behavior  may
              be  useful  if another DNS server must forward requests for spe-
              cific zones to a resolver DNS server,  but  only  supports  stub
              domains and sends queries to the resolver DNS server with the RD
              bit cleared.

              The action allow_snoop gives nonrecursive access too.  This give
              both  recursive  and non recursive access.  The name allow_snoop
              refers to  cache  snooping,  a  technique  to  use  nonrecursive
              queries  to  examine  the  cache  contents (for malicious acts).
              However, nonrecursive queries can also be a  valuable  debugging
              tool (when you want to examine the cache contents). In that case
              use allow_snoop for your administration host.

              By default only localhost is allowed, the rest is refused.   The
              default  is  refused, because that is protocol-friendly. The DNS
              protocol is not designed to handle dropped packets due  to  pol-
              icy,  and  dropping  may  result in (possibly excessive) retried
              queries.

              The deny_non_local and refuse_non_local settings are  for  hosts
              that are only allowed to query for the authoritative local-data,
              they are not allowed full recursion but only  the  static  data.
              With  deny_non_local,  messages that are disallowed are dropped,
              with refuse_non_local they receive error code REFUSED.

       access-control-tag: <IP netblock> <"list of tags">
              Assign tags  to  access-control  elements.  Clients  using  this
              access  control  element use localzones that are tagged with one
              of these tags. Tags must be  defined  in  define-tags.   Enclose
              list  of  tags  in  quotes  ("") and put spaces between tags. If
              access-control-tag is configured for a netblock  that  does  not
              have  an  access-control,  an access-control element with action
              allow is configured for this netblock.

       access-control-tag-action: <IP netblock> <tag> <action>
              Set action for particular tag for given access control  element.
              If  you  have  multiple  tag  values, the tag used to lookup the
              action is the first tag  match  between  access-control-tag  and
              local-zone-tag where "first" comes from the order of the define-
              tag values.

       access-control-tag-data: <IP netblock> <tag> <"resource record string">
              Set redirect data for particular tag for  given  access  control
              element.

       access-control-view: <IP netblock> <view name>
              Set view for given access control element.

       chroot: <directory>
              If  chroot  is enabled, you should pass the configfile (from the
              commandline) as a full path from the original  root.  After  the
              chroot  has been performed the now defunct portion of the config
              file path is removed to be able to reread  the  config  after  a
              reload.

              All  other  file paths (working dir, logfile, roothints, and key
              files) can be specified in several ways:  as  an  absolute  path
              relative  to  the  new  root,  as a relative path to the working
              directory, or as an absolute path relative to the original root.
              In  the last case the path is adjusted to remove the unused por-
              tion.

              The pidfile can be either a relative path to the working  direc-
              tory,  or  an absolute path relative to the original root. It is
              written just prior to  chroot  and  dropping  permissions.  This
              allows  the pidfile to be /var/run/unbound.pid and the chroot to
              be /var/unbound, for example.

              Additionally,  unbound  may  need  to  access  /dev/random  (for
              entropy) from inside the chroot.

              If  given  a  chroot  is done to the given directory. By default
              chroot is enabled and the default  is  "/usr/local/etc/unbound".
              If you give "" no chroot is performed.

       username: <name>
              If  given,  after  binding  the  port  the  user  privileges are
              dropped. Default is "unbound". If you give username: "" no  user
              change is performed.

              If  this  user  is  not capable of binding the port, reloads (by
              signal HUP) will still retain the opened ports.  If  you  change
              the  port  number  in  the config file, and that new port number
              requires privileges, then a  reload  will  fail;  a  restart  is
              needed.

       directory: <directory>
              Sets   the   working  directory  for  the  program.  Default  is
              "/usr/local/etc/unbound".  On Windows the string  "%EXECUTABLE%"
              tries  to  change  to the directory that unbound.exe resides in.
              If you give a server: directory: dir before include: file state-
              ments  then those includes can be relative to the working direc-
              tory.

       logfile: <filename>
              If "" is given, logging goes to stderr, or nowhere  once  daemo-
              nized.  The logfile is appended to, in the following format:
              [seconds since 1970] unbound[pid:tid]: type: message.
              If  this  option  is  given,  the use-syslog is option is set to
              "no".  The logfile is reopened (for append) when the config file
              is reread, on SIGHUP.

       use-syslog: <yes or no>
              Sets  unbound  to  send  log messages to the syslogd, using sys-
              log(3).  The log facility  LOG_DAEMON  is  used,  with  identity
              "unbound".  The logfile setting is overridden when use-syslog is
              turned on.  The default is to log to syslog.

       log-identity: <string>
              If "" is given (default), then the name of the executable,  usu-
              ally  "unbound" is used to report to the log.  Enter a string to
              override it with that, which is useful on systems that run  more
              than  one instance of unbound, with different configurations, so
              that the logs can be easily distinguished against.

       log-time-ascii: <yes or no>
              Sets logfile lines to use a timestamp in UTC ascii.  Default  is
              no,  which  prints the seconds since 1970 in brackets. No effect
              if using syslog, in  that  case  syslog  formats  the  timestamp
              printed into the log files.

       log-queries: <yes or no>
              Prints one line per query to the log, with the log timestamp and
              IP address, name, type and class.  Default is no.  Note that  it
              takes time to print these lines which makes the server (signifi-
              cantly) slower.  Odd  (nonprintable)  characters  in  names  are
              printed as '?'.

       log-replies: <yes or no>
              Prints one line per reply to the log, with the log timestamp and
              IP address, name, type, class, return  code,  time  to  resolve,
              from  cache  and  response  size.   Default is no.  Note that it
              takes time to print these lines which makes the server (signifi-
              cantly)  slower.   Odd  (nonprintable)  characters  in names are
              printed as '?'.

       log-local-actions: <yes or no>
              Print log lines to inform about local zone actions.  These lines
              are  like  the  local-zone  type inform prints out, but they are
              also printed for the other types of local zones.

       log-servfail: <yes or no>
              Print log lines that say why queries return SERVFAIL to clients.
              This  is  separate  from the verbosity debug logs, much smaller,
              and printed at the error level, not the info level of debug info
              from verbosity.

       pidfile: <filename>
              The   process   id   is   written   to   the  file.  Default  is
              "/usr/local/etc/unbound/unbound.pid".  So,
              kill -HUP `cat /usr/local/etc/unbound/unbound.pid`
              triggers a reload,
              kill -TERM `cat /usr/local/etc/unbound/unbound.pid`
              gracefully terminates.

       root-hints: <filename>
              Read the root hints from this file. Default  is  nothing,  using
              builtin  hints for the IN class. The file has the format of zone
              files, with  root  nameserver  names  and  addresses  only.  The
              default  may  become outdated, when servers change, therefore it
              is good practice to use a root-hints file.

       hide-identity: <yes or no>
              If enabled id.server and hostname.bind queries are refused.

       identity: <string>
              Set the identity to report. If set to "", the default, then  the
              hostname of the server is returned.

       hide-version: <yes or no>
              If enabled version.server and version.bind queries are refused.

       version: <string>
              Set  the  version to report. If set to "", the default, then the
              package version is returned.

       hide-trustanchor: <yes or no>
              If enabled trustanchor.unbound queries are refused.

       target-fetch-policy: <"list of numbers">
              Set the target fetch policy used by unbound to determine  if  it
              should  fetch nameserver target addresses opportunistically. The
              policy is described per dependency depth.

              The number of values determines  the  maximum  dependency  depth
              that  unbound  will  pursue in answering a query.  A value of -1
              means to fetch all targets opportunistically for that dependency
              depth.  A  value  of 0 means to fetch on demand only. A positive
              value fetches that many targets opportunistically.

              Enclose the list between quotes ("") and put spaces between num-
              bers.   The default is "3 2 1 0 0". Setting all zeroes, "0 0 0 0
              0" gives behaviour closer to that of BIND 9, while  setting  "-1
              -1  -1  -1  -1" gives behaviour rumoured to be closer to that of
              BIND 8.

       harden-short-bufsize: <yes or no>
              Very small EDNS buffer sizes from queries are  ignored.  Default
              is  off,  since  it  is  legal  protocol wise to send these, and
              unbound tries to give very small answers to these queries, where
              possible.

       harden-large-queries: <yes or no>
              Very  large  queries  are  ignored.  Default is off, since it is
              legal protocol wise to send these, and could  be  necessary  for
              operation if TSIG or EDNS payload is very large.

       harden-glue: <yes or no>
              Will  trust  glue  only  if  it is within the servers authority.
              Default is on.

       harden-dnssec-stripped: <yes or no>
              Require DNSSEC data for trust-anchored zones, if  such  data  is
              absent,  the  zone  becomes  bogus. If turned off, and no DNSSEC
              data is received (or the DNSKEY data fails  to  validate),  then
              the  zone  is made insecure, this behaves like there is no trust
              anchor. You could turn this off if you are sometimes  behind  an
              intrusive  firewall (of some sort) that removes DNSSEC data from
              packets, or a zone changes from  signed  to  unsigned  to  badly
              signed  often.  If  turned  off  you run the risk of a downgrade
              attack that disables security for a zone. Default is on.

       harden-below-nxdomain: <yes or no>
              From RFC 8020 (with title "NXDOMAIN:  There  Really  Is  Nothing
              Underneath"),  returns  nxdomain  to  queries  for  a name below
              another name that is already known to be nxdomain.  DNSSEC  man-
              dates  noerror  for  empty nonterminals, hence this is possible.
              Very old software might return nxdomain for  empty  nonterminals
              (that  usually  happen for reverse IP address lookups), and thus
              may be incompatible with  this.   To  try  to  avoid  this  only
              DNSSEC-secure  nxdomains are used, because the old software does
              not have DNSSEC.  Default is on.  The nxdomain must  be  secure,
              this means nsec3 with optout is insufficient.

       harden-referral-path: <yes or no>
              Harden  the  referral  path by performing additional queries for
              infrastructure data.  Validates the replies if trust anchors are
              configured and the zones are signed.  This enforces DNSSEC vali-
              dation on nameserver NS sets and the nameserver  addresses  that
              are encountered on the referral path to the answer.  Default no,
              because it burdens the authority servers,  and  it  is  not  RFC
              standard,  and could lead to performance problems because of the
              extra query load that is generated.   Experimental  option.   If
              you  enable  it  consider  adding  more  numbers  after the tar-
              get-fetch-policy to increase the max depth that is checked to.

       harden-algo-downgrade: <yes or no>
              Harden against algorithm downgrade when multiple algorithms  are
              advertised  in  the  DS record.  If no, allows the weakest algo-
              rithm to validate the zone.  Default is no.  Zone  signers  must
              produce  zones  that  allow  this feature to work, but sometimes
              they do not, and turning this option off avoids that  validation
              failure.

       use-caps-for-id: <yes or no>
              Use  0x20-encoded  random  bits  in  the  query  to  foil  spoof
              attempts.  This perturbs the lowercase and  uppercase  of  query
              names  sent  to  authority servers and checks if the reply still
              has the correct casing.  Disabled by default.  This  feature  is
              an experimental implementation of draft dns-0x20.

       caps-whitelist: <domain>
              Whitelist  the  domain  so  that it does not receive caps-for-id
              perturbed queries.  For domains that do  not  support  0x20  and
              also  fail  with  fallback  because  they keep sending different
              answers, like some load balancers.  Can be given multiple times,
              for different domains.

       qname-minimisation: <yes or no>
              Send  minimum  amount  of  information  to  upstream  servers to
              enhance privacy.  Only sent minimum required labels of the QNAME
              and  set  QTYPE  to  A when possible. Best effort approach; full
              QNAME and original QTYPE will be sent when upstream replies with
              a  RCODE other than NOERROR, except when receiving NXDOMAIN from
              a DNSSEC signed zone. Default is yes.

       qname-minimisation-strict: <yes or no>
              QNAME minimisation in strict mode. Do not fall-back  to  sending
              full  QNAME  to potentially broken nameservers. A lot of domains
              will not be resolvable when this option in enabled. Only use  if
              you  know  what you are doing.  This option only has effect when
              qname-minimisation is enabled. Default is off.

       aggressive-nsec: <yes or no>
              Aggressive NSEC uses the DNSSEC NSEC chain to  synthesize  NXDO-
              MAIN  and  other  denials, using information from previous NXDO-
              MAINs answers.  Default is no.  It helps  to  reduce  the  query
              rate  towards  targets  that  get  a  very high nonexistent name
              lookup rate.

       private-address: <IP address or subnet>
              Give IPv4 of IPv6 addresses  or  classless  subnets.  These  are
              addresses  on  your  private  network, and are not allowed to be
              returned for public internet  names.   Any  occurrence  of  such
              addresses are removed from DNS answers. Additionally, the DNSSEC
              validator may mark the  answers  bogus.  This  protects  against
              so-called  DNS  Rebinding, where a user browser is turned into a
              network proxy, allowing remote access  through  the  browser  to
              other  parts of your private network.  Some names can be allowed
              to contain your private addresses, by default all the local-data
              that  you  configured  is  allowed to, and you can specify addi-
              tional names using private-domain.   No  private  addresses  are
              enabled  by default.  We consider to enable this for the RFC1918
              private IP address space by  default  in  later  releases.  That
              would  enable  private  addresses  for  10.0.0.0/8 172.16.0.0/12
              192.168.0.0/16 169.254.0.0/16 fd00::/8 and fe80::/10, since  the
              RFC  standards  say these addresses should not be visible on the
              public internet.  Turning on 127.0.0.0/8 would hinder many spam-
              blocklists   as  they  use  that.   Adding  ::ffff:0:0/96  stops
              IPv4-mapped IPv6 addresses from bypassing the filter.

       private-domain: <domain name>
              Allow this domain, and all its  subdomains  to  contain  private
              addresses.   Give  multiple times to allow multiple domain names
              to contain private addresses. Default is none.

       unwanted-reply-threshold: <number>
              If set, a total number of unwanted replies is kept track  of  in
              every thread.  When it reaches the threshold, a defensive action
              is taken and a warning is printed to  the  log.   The  defensive
              action  is  to  clear  the  rrset  and message caches, hopefully
              flushing away any poison.  A value of 10 million  is  suggested.
              Default is 0 (turned off).

       do-not-query-address: <IP address>
              Do  not  query  the  given IP address. Can be IP4 or IP6. Append
              /num to indicate a classless delegation  netblock,  for  example
              like 10.2.3.4/24 or 2001::11/64.

       do-not-query-localhost: <yes or no>
              If  yes, localhost is added to the do-not-query-address entries,
              both IP6 ::1 and IP4 127.0.0.1/8. If no, then localhost  can  be
              used to send queries to. Default is yes.

       prefetch: <yes or no>
              If yes, message cache elements are prefetched before they expire
              to keep the cache up to date.  Default is  no.   Turning  it  on
              gives about 10 percent more traffic and load on the machine, but
              popular items do not expire from the cache.

       prefetch-key: <yes or no>
              If yes, fetch the DNSKEYs earlier  in  the  validation  process,
              when  a  DS  record  is encountered.  This lowers the latency of
              requests.  It does use a little more CPU.  Also if the cache  is
              set to 0, it is no use. Default is no.

       deny-any: <yes or no>
              If  yes,  deny  queries  of  type  ANY  with  an empty response.
              Default is no.  If disabled, unbound responds with a short  list
              of  resource records if some can be found in the cache and makes
              the upstream type ANY query if there are none.

       rrset-roundrobin: <yes or no>
              If yes, Unbound rotates RRSet order in response (the random num-
              ber  is  taken  from the query ID, for speed and thread safety).
              Default is no.

       minimal-responses: <yes or no>
              If yes, Unbound  doesn't  insert  authority/additional  sections
              into  response  messages  when  those sections are not required.
              This reduces response size  significantly,  and  may  avoid  TCP
              fallback  for  some responses.  This may cause a slight speedup.
              The default is yes, even though the DNS  protocol  RFCs  mandate
              these  sections,  and the additional content could be of use and
              save roundtrips for clients.  Because they are not used, and the
              saved  roundtrips are easier saved with prefetch, whilst this is
              faster.

       disable-dnssec-lame-check: <yes or no>
              If true, disables the DNSSEC lameness  check  in  the  iterator.
              This check sees if RRSIGs are present in the answer, when dnssec
              is expected, and retries another authority if RRSIGs  are  unex-
              pectedly  missing.   The  validator  will  insist  in RRSIGs for
              DNSSEC signed domains regardless of this  setting,  if  a  trust
              anchor is loaded.

       module-config: <"module names">
              Module  configuration,  a list of module names separated by spa-
              ces, surround the string with quotes (""). The  modules  can  be
              validator,  iterator.  Setting this to "iterator" will result in
              a non-validating server.  Setting this to  "validator  iterator"
              will  turn on DNSSEC validation.  The ordering of the modules is
              important.  You must also set trust-anchors for validation to be
              useful.

       trust-anchor-file: <filename>
              File  with  trusted  keys  for  validation.  Both  DS and DNSKEY
              entries can appear in the file. The format of the  file  is  the
              standard  DNS  Zone  file  format.   Default  is "", or no trust
              anchor file.

       auto-trust-anchor-file: <filename>
              File with trust anchor for  one  zone,  which  is  tracked  with
              RFC5011  probes.   The  probes are several times per month, thus
              the machine must be online frequently.  The initial file can  be
              one  with  contents as described in trust-anchor-file.  The file
              is written to when the anchor is updated, so  the  unbound  user
              must  have  write permission.  Write permission to the file, but
              also to the directory it is in  (to  create  a  temporary  file,
              which is necessary to deal with filesystem full events), it must
              also be inside the chroot (if that is used).

       trust-anchor: <"Resource Record">
              A DS or DNSKEY RR for a key  to  use  for  validation.  Multiple
              entries  can be given to specify multiple trusted keys, in addi-
              tion to the trust-anchor-files.  The resource record is  entered
              in  the  same  format  as 'dig' or 'drill' prints them, the same
              format as in the zone file. Has to be on a single line, with  ""
              around it. A TTL can be specified for ease of cut and paste, but
              is ignored.  A class can be specified, but class IN is default.

       trusted-keys-file: <filename>
              File with trusted keys for validation.  Specify  more  than  one
              file   with   several   entries,   one   file  per  entry.  Like
              trust-anchor-file but has a different  file  format.  Format  is
              BIND-9  style  format,  the  trusted-keys { name flag proto algo
              "key"; }; clauses are read.  It is  possible  to  use  wildcards
              with  this  statement,  the wildcard is expanded on start and on
              reload.

       trust-anchor-signaling: <yes or no>
              Send RFC8145 key tag query after trust anchor  priming.  Default
              is on.

       root-key-sentinel: <yes or no>
              Root key trust anchor sentinel. Default is on.

       dlv-anchor-file: <filename>
              This option was used during early days DNSSEC deployment when no
              parent-side  DS  record  registrations  were  easily  available.
              Nowadays, it is best to have DS records registered with the par-
              ent zone (many top level zones are signed).  File  with  trusted
              keys  for  DLV (DNSSEC Lookaside Validation). Both DS and DNSKEY
              entries can be used in the file,  in  the  same  format  as  for
              trust-anchor-file:  statements.  Only one DLV can be configured,
              more would be slow. The DLV configured is used as a root trusted
              DLV,  this means that it is a lookaside for the root. Default is
              "", or no dlv anchor file. DLV is going  to  be  decommissioned.
              Please do not use it any more.

       dlv-anchor: <"Resource Record">
              Much  like  trust-anchor,  this  is  a DLV anchor with the DS or
              DNSKEY inline.  DLV is going to be  decommissioned.   Please  do
              not use it any more.

       domain-insecure: <domain name>
              Sets  domain  name  to  be  insecure,  DNSSEC  chain of trust is
              ignored towards the domain name.  So a trust  anchor  above  the
              domain  name  can  not  make the domain secure with a DS record,
              such a DS record is  then  ignored.   Also  keys  from  DLV  are
              ignored  for the domain.  Can be given multiple times to specify
              multiple domains that are treated as if unsigned.   If  you  set
              trust anchors for the domain they override this setting (and the
              domain is secured).

              This can be useful if you want to make sure a trust  anchor  for
              external  lookups does not affect an (unsigned) internal domain.
              A DS record externally can create validation failures  for  that
              internal domain.

       val-override-date: <rrsig-style date spec>
              Default  is "" or "0", which disables this debugging feature. If
              enabled by giving a RRSIG style date, that date is used for ver-
              ifying RRSIG inception and expiration dates, instead of the cur-
              rent date. Do not set this unless you  are  debugging  signature
              inception  and  expiration.  The value -1 ignores the date alto-
              gether, useful for some special applications.

       val-sig-skew-min: <seconds>
              Minimum number of seconds of clock skew to  apply  to  validated
              signatures.   A  value of 10% of the signature lifetime (expira-
              tion - inception) is used, capped by this setting.   Default  is
              3600  (1  hour)  which  allows for daylight savings differences.
              Lower this value for more strict checking of short lived  signa-
              tures.

       val-sig-skew-max: <seconds>
              Maximum  number  of  seconds of clock skew to apply to validated
              signatures.  A value of 10% of the signature  lifetime  (expira-
              tion  -  inception) is used, capped by this setting.  Default is
              86400 (24 hours) which allows for timezone setting  problems  in
              stable  domains.  Setting both min and max very low disables the
              clock skew allowances.  Setting both min and max very high makes
              the validator check the signature timestamps less strictly.

       val-bogus-ttl: <number>
              The  time  to  live for bogus data. This is data that has failed
              validation; due to invalid signatures or other checks.  The  TTL
              from  that  data  cannot  be  trusted,  and  this  value is used
              instead. The value is in seconds, default 60.  The time interval
              prevents repeated revalidation of bogus data.

       val-clean-additional: <yes or no>
              Instruct  the  validator to remove data from the additional sec-
              tion of secure messages that are not signed  properly.  Messages
              that  are  insecure,  bogus,  indeterminate or unchecked are not
              affected. Default is yes. Use this setting to protect the  users
              that  rely on this validator for authentication from potentially
              bad data in the additional section.

       val-log-level: <number>
              Have  the  validator  print  validation  failures  to  the  log.
              Regardless  of the verbosity setting.  Default is 0, off.  At 1,
              for every user query that fails a line is printed to  the  logs.
              This  way  you  can monitor what happens with validation.  Use a
              diagnosis tool, such as dig or drill, to find out why validation
              is  failing  for  these  queries.  At 2, not only the query that
              failed is printed but also the reason why unbound thought it was
              wrong and which server sent the faulty data.

       val-permissive-mode: <yes or no>
              Instruct  the validator to mark bogus messages as indeterminate.
              The security checks are performed, but if the  result  is  bogus
              (failed  security),  the  reply  is not withheld from the client
              with SERVFAIL as usual. The client receives the bogus data.  For
              messages  that  are  found  to  be  secure  the AD bit is set in
              replies. Also logging is performed as for full validation.   The
              default value is "no".

       ignore-cd-flag: <yes or no>
              Instruct  unbound  to ignore the CD flag from clients and refuse
              to return bogus answers to them.  Thus, the  CD  (Checking  Dis-
              abled)  flag does not disable checking any more.  This is useful
              if legacy (w2008) servers that set the CD flag but cannot  vali-
              date  DNSSEC  themselves  are the clients, and then unbound pro-
              vides them with DNSSEC protection.  The default value is "no".

       serve-expired: <yes or no>
              If enabled, unbound attempts to serve old responses  from  cache
              with  a  TTL of 0 in the response without waiting for the actual
              resolution to finish.  The actual resolution answer ends  up  in
              the cache later on.  Default is "no".

       serve-expired-ttl: <seconds>
              Limit  serving  of expired responses to configured seconds after
              expiration. 0 disables the limit. This option only applies  when
              serve-expired is enabled. The default is 0.

       serve-expired-ttl-reset: <yes or no>
              Set  the  TTL  of expired records to the serve-expired-ttl value
              after a failed attempt to retrieve  the  record  from  upstream.
              This  makes sure that the expired records will be served as long
              as there are queries for it. Default is "no".

       val-nsec3-keysize-iterations: <"list of values">
              List of keysize and iteration count values, separated by spaces,
              surrounded  by quotes. Default is "1024 150 2048 500 4096 2500".
              This determines the maximum allowed NSEC3 iteration count before
              a  message  is  simply marked insecure instead of performing the
              many hashing iterations. The list must be in ascending order and
              have  at least one entry. If you set it to "1024 65535" there is
              no restriction to NSEC3 iteration values.  This  table  must  be
              kept short; a very long list could cause slower operation.

       add-holddown: <seconds>
              Instruct  the auto-trust-anchor-file probe mechanism for RFC5011
              autotrust updates to add new trust anchors only after they  have
              been visible for this time.  Default is 30 days as per the RFC.

       del-holddown: <seconds>
              Instruct  the auto-trust-anchor-file probe mechanism for RFC5011
              autotrust updates to remove revoked  trust  anchors  after  they
              have been kept in the revoked list for this long.  Default is 30
              days as per the RFC.

       keep-missing: <seconds>
              Instruct the auto-trust-anchor-file probe mechanism for  RFC5011
              autotrust  updates  to  remove  missing trust anchors after they
              have been unseen for this long.  This cleans up the  state  file
              if  the target zone does not perform trust anchor revocation, so
              this makes the auto probe mechanism work with zones that perform
              regular  (non-5011)  rollovers.   The  default is 366 days.  The
              value 0 does not remove missing anchors, as per the RFC.

       permit-small-holddown: <yes or no>
              Debug option that allows the autotrust 5011 rollover  timers  to
              assume very small values.  Default is no.

       key-cache-size: <number>
              Number  of  bytes size of the key cache. Default is 4 megabytes.
              A plain number is in bytes, append 'k', 'm'  or  'g'  for  kilo-
              bytes, megabytes or gigabytes (1024*1024 bytes in a megabyte).

       key-cache-slabs: <number>
              Number  of  slabs in the key cache. Slabs reduce lock contention
              by threads.  Must be set to a power of 2. Setting (close) to the
              number of cpus is a reasonable guess.

       neg-cache-size: <number>
              Number  of  bytes size of the aggressive negative cache. Default
              is 1 megabyte.  A plain number is in bytes, append 'k',  'm'  or
              'g'  for kilobytes, megabytes or gigabytes (1024*1024 bytes in a
              megabyte).

       unblock-lan-zones: <yes or no>
              Default is disabled.   If  enabled,  then  for  private  address
              space,  the reverse lookups are no longer filtered.  This allows
              unbound when running as dns service on a host where it  provides
              service  for  that  host,  to put out all of the queries for the
              'lan' upstream.  When enabled, only localhost, 127.0.0.1 reverse
              and  ::1  reverse zones are configured with default local zones.
              Disable the option when unbound is running as a (DHCP-) DNS net-
              work resolver for a group of machines, where such lookups should
              be filtered (RFC compliance), this  also  stops  potential  data
              leakage about the local network to the upstream DNS servers.

       insecure-lan-zones: <yes or no>
              Default  is  disabled.  If enabled, then reverse lookups in pri-
              vate address space are not validated.  This is usually  required
              whenever unblock-lan-zones is used.

       local-zone: <zone> <type>
              Configure  a  local zone. The type determines the answer to give
              if there is no  match  from  local-data.  The  types  are  deny,
              refuse,  static, transparent, redirect, nodefault, typetranspar-
              ent,  inform,  inform_deny,  always_transparent,  always_refuse,
              always_nxdomain, noview, and are explained below. After that the
              default settings are listed. Use local-data: to enter data  into
              the  local  zone.  Answers for local zones are authoritative DNS
              answers. By default the zones are class IN.

              If you need more complicated authoritative data, with referrals,
              wildcards, CNAME/DNAME support, or DNSSEC authoritative service,
              setup a stub-zone for it as detailed in the  stub  zone  section
              below.

            deny Do  not  send an answer, drop the query.  If there is a match
                 from local data, the query is answered.

            refuse
                 Send an error message reply, with rcode REFUSED.  If there is
                 a match from local data, the query is answered.

            static
                 If  there  is a match from local data, the query is answered.
                 Otherwise, the query is answered  with  nodata  or  nxdomain.
                 For  a  negative  answer  a  SOA is included in the answer if
                 present as local-data for the zone apex domain.

            transparent
                 If there is a match from local data, the query  is  answered.
                 Otherwise  if  the  query  has a different name, the query is
                 resolved normally.  If the query  is  for  a  name  given  in
                 localdata  but  no  such  type of data is given in localdata,
                 then a noerror nodata answer is returned.  If  no  local-zone
                 is  given  local-data causes a transparent zone to be created
                 by default.

            typetransparent
                 If there is a match from local data, the query  is  answered.
                 If  the  query  is for a different name, or for the same name
                 but for a different type, the  query  is  resolved  normally.
                 So,  similar  to transparent but types that are not listed in
                 local data are resolved normally, so if an A record is in the
                 local  data  that  does  not  cause  a  nodata reply for AAAA
                 queries.

            redirect
                 The query is answered from the local data for the zone  name.
                 There  may  be  no  local  data  beneath the zone name.  This
                 answers queries for the zone, and all subdomains of the  zone
                 with the local data for the zone.  It can be used to redirect
                 a domain to return a different  address  record  to  the  end
                 user,    with   local-zone:   "example.com."   redirect   and
                 local-data: "example.com. A 127.0.0.1" queries for  www.exam-
                 ple.com and www.foo.example.com are redirected, so that users
                 with web browsers  cannot  access  sites  with  suffix  exam-
                 ple.com.

            inform
                 The  query  is  answered  normally, same as transparent.  The
                 client IP address (@portnumber) is printed  to  the  logfile.
                 The  log  message  is: timestamp, unbound-pid, info: zonename
                 inform IP@port queryname type class.  This option can be used
                 for normal resolution, but machines looking up infected names
                 are logged, eg. to run antivirus on them.

            inform_deny
                 The query is dropped, like 'deny', and logged, like 'inform'.
                 Ie. find infected machines without answering the queries.

            always_transparent
                 Like  transparent,  but  ignores local data and resolves nor-
                 mally.

            always_refuse
                 Like refuse, but ignores local data and refuses the query.

            always_nxdomain
                 Like static, but ignores local data and returns nxdomain  for
                 the query.

            noview
                 Breaks  out  of  that view and moves towards the global local
                 zones for answer to the query.  If  the  view  first  is  no,
                 it'll  resolve  normally.   If  view  first is enabled, it'll
                 break perform that step and check the  global  answers.   For
                 when  the  view has view specific overrides but some zone has
                 to be answered from global local zone contents.

            nodefault
                 Used to turn off default contents for AS112 zones. The  other
                 types also turn off default contents for the zone. The 'node-
                 fault' option has no other effect than  turning  off  default
                 contents  for  the  given  zone.   Use  nodefault  if you use
                 exactly that zone, if you want to use a subzone,  use  trans-
                 parent.

       The  default zones are localhost, reverse 127.0.0.1 and ::1, the onion,
       test, invalid and the AS112 zones. The  AS112  zones  are  reverse  DNS
       zones  for  private use and reserved IP addresses for which the servers
       on the internet cannot provide correct answers. They are configured  by
       default to give nxdomain (no reverse information) answers. The defaults
       can be turned off by specifying your own local-zone of  that  name,  or
       using  the  'nodefault'  type. Below is a list of the default zone con-
       tents.

            localhost
                 The IP4 and IP6 localhost information is given.  NS  and  SOA
                 records are provided for completeness and to satisfy some DNS
                 update tools. Default content:
                 local-zone: "localhost." redirect
                 local-data: "localhost. 10800 IN NS localhost."
                 local-data: "localhost. 10800 IN
                     SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
                 local-data: "localhost. 10800 IN A 127.0.0.1"
                 local-data: "localhost. 10800 IN AAAA ::1"

            reverse IPv4 loopback
                 Default content:
                 local-zone: "127.in-addr.arpa." static
                 local-data: "127.in-addr.arpa. 10800 IN NS localhost."
                 local-data: "127.in-addr.arpa. 10800 IN
                     SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
                 local-data: "1.0.0.127.in-addr.arpa. 10800 IN
                     PTR localhost."

            reverse IPv6 loopback
                 Default content:
                 local-zone: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
                     0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa." static
                 local-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
                     0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN
                     NS localhost."
                 local-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
                     0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN
                     SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
                 local-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
                     0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN
                     PTR localhost."

            onion (RFC 7686)
                 Default content:
                 local-zone: "onion." static
                 local-data: "onion. 10800 IN NS localhost."
                 local-data: "onion. 10800 IN
                     SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"

            test (RFC 2606)
                 Default content:
                 local-zone: "test." static
                 local-data: "test. 10800 IN NS localhost."
                 local-data: "test. 10800 IN
                     SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"

            invalid (RFC 2606)
                 Default content:
                 local-zone: "invalid." static
                 local-data: "invalid. 10800 IN NS localhost."
                 local-data: "invalid. 10800 IN
                     SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"

            reverse RFC1918 local use zones
                 Reverse data for zones  10.in-addr.arpa,  16.172.in-addr.arpa
                 to     31.172.in-addr.arpa,     168.192.in-addr.arpa.     The
                 local-zone: is set static  and  as  local-data:  SOA  and  NS
                 records are provided.

            reverse RFC3330 IP4 this, link-local, testnet and broadcast
                 Reverse  data for zones 0.in-addr.arpa, 254.169.in-addr.arpa,
                 2.0.192.in-addr.arpa (TEST  NET  1),  100.51.198.in-addr.arpa
                 (TEST   NET   2),   113.0.203.in-addr.arpa   (TEST   NET  3),
                 255.255.255.255.in-addr.arpa.  And  from  64.100.in-addr.arpa
                 to 127.100.in-addr.arpa (Shared Address Space).

            reverse RFC4291 IP6 unspecified
                 Reverse data for zone
                 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
                 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.

            reverse RFC4193 IPv6 Locally Assigned Local Addresses
                 Reverse data for zone D.F.ip6.arpa.

            reverse RFC4291 IPv6 Link Local Addresses
                 Reverse data for zones 8.E.F.ip6.arpa to B.E.F.ip6.arpa.

            reverse IPv6 Example Prefix
                 Reverse  data for zone 8.B.D.0.1.0.0.2.ip6.arpa. This zone is
                 used for tutorials and examples. You can remove the block  on
                 this zone with:
                   local-zone: 8.B.D.0.1.0.0.2.ip6.arpa. nodefault
                 You can also selectively unblock a part of the zone by making
                 that part transparent with a local-zone statement.  This also
                 works with the other default zones.

       local-data: "<resource record string>"
            Configure  local data, which is served in reply to queries for it.
            The query has to match exactly unless you configure the local-zone
            as  redirect.  If  not matched exactly, the local-zone type deter-
            mines further processing. If local-data is configured that is  not
            a  subdomain  of a local-zone, a transparent local-zone is config-
            ured.  For record types such as TXT,  use  single  quotes,  as  in
            local-data: 'example. TXT "text"'.

            If  you  need more complicated authoritative data, with referrals,
            wildcards, CNAME/DNAME support, or DNSSEC  authoritative  service,
            setup  a  stub-zone  for  it  as detailed in the stub zone section
            below.

       local-data-ptr: "IPaddr name"
            Configure local data shorthand for a PTR record with the  reversed
            IPv4  or  IPv6  address and the host name.  For example "192.0.2.4
            www.example.com".  TTL can be  inserted  like  this:  "2001:DB8::4
            7200 www.example.com"

       local-zone-tag: <zone> <"list of tags">
            Assign  tags to localzones. Tagged localzones will only be applied
            when the used access-control element has a matching tag. Tags must
            be  defined  in  define-tags.  Enclose list of tags in quotes ("")
            and put spaces between tags.

       local-zone-override: <zone> <IP netblock> <type>
            Override the localzone type for queries  from  addresses  matching
            netblock.  Use this localzone type, regardless the type configured
            for the local-zone (both tagged and untagged) and  regardless  the
            type configured using access-control-tag-action.

       ratelimit: <number or 0>
            Enable  ratelimiting  of queries sent to nameserver for performing
            recursion.  If 0, the default, it is  disabled.   This  option  is
            experimental at this time.  The ratelimit is in queries per second
            that are allowed.  More queries are  turned  away  with  an  error
            (servfail).   This stops recursive floods, eg. random query names,
            but not spoofed reflection floods.  Cached responses are not rate-
            limited  by  this setting.  The zone of the query is determined by
            examining the nameservers for it, the zone name is  used  to  keep
            track  of  the rate.  For example, 1000 may be a suitable value to
            stop the server from being overloaded with random names, and keeps
            unbound from sending traffic to the nameservers for those zones.

       ratelimit-size: <memory size>
            Give  the  size of the data structure in which the current ongoing
            rates are kept track in.  Default 4m.  In bytes  or  use  m(mega),
            k(kilo),  g(giga).  The ratelimit structure is small, so this data
            structure likely does not need to be large.

       ratelimit-slabs: <number>
            Give power of 2 number of slabs, this is used to reduce lock  con-
            tention  in  the  ratelimit tracking data structure.  Close to the
            number of cpus is a fairly good setting.

       ratelimit-factor: <number>
            Set the amount  of  queries  to  rate  limit  when  the  limit  is
            exceeded.   If set to 0, all queries are dropped for domains where
            the limit is exceeded.  If set to another value, 1 in that  number
            is  allowed  through  to  complete.   Default is 10, allowing 1/10
            traffic to flow normally.  This can make ordinary queries complete
            (if repeatedly queried for), and enter the cache, whilst also mit-
            igating the traffic flow by the factor given.

       ratelimit-for-domain: <domain> <number qps or 0>
            Override the global ratelimit for an exact match domain name  with
            the  listed  number.   You  can give this for any number of names.
            For example, for a top-level-domain you may want to have a  higher
            limit  than  other  names.  A value of 0 will disable ratelimiting
            for that domain.

       ratelimit-below-domain: <domain> <number qps or 0>
            Override the global ratelimit for a domain name that ends in  this
            name.  You can give this multiple times, it then describes differ-
            ent settings in different parts of  the  namespace.   The  closest
            matching  suffix is used to determine the qps limit.  The rate for
            the  exact  matching  domain  name  is  not  changed,  use   rate-
            limit-for-domain to set that, you might want to use different set-
            tings for a top-level-domain and subdomains.  A value  of  0  will
            disable ratelimiting for domain names that end in this name.

       ip-ratelimit: <number or 0>
            Enable global ratelimiting of queries accepted per ip address.  If
            0, the default, it is disabled.  This option  is  experimental  at
            this  time.   The  ratelimit  is  in  queries  per second that are
            allowed.  More queries are completely dropped and will not receive
            a  reply,  SERVFAIL  or otherwise.  IP ratelimiting happens before
            looking in the cache. This may be useful for mitigating amplifica-
            tion attacks.

       ip-ratelimit-size: <memory size>
            Give  the  size of the data structure in which the current ongoing
            rates are kept track in.  Default 4m.  In bytes  or  use  m(mega),
            k(kilo),  g(giga).   The  ip ratelimit structure is small, so this
            data structure likely does not need to be large.

       ip-ratelimit-slabs: <number>
            Give power of 2 number of slabs, this is used to reduce lock  con-
            tention in the ip ratelimit tracking data structure.  Close to the
            number of cpus is a fairly good setting.

       ip-ratelimit-factor: <number>
            Set the amount  of  queries  to  rate  limit  when  the  limit  is
            exceeded.   If  set  to  0,  all queries are dropped for addresses
            where the limit is exceeded.  If set to another value, 1  in  that
            number  is  allowed  through to complete.  Default is 10, allowing
            1/10 traffic to flow normally.  This  can  make  ordinary  queries
            complete  (if repeatedly queried for), and enter the cache, whilst
            also mitigating the traffic flow by the factor given.

       fast-server-permil: <number>
            Specify how many times out of 1000 to pick from the set of fastest
            servers.  0 turns the feature off.  A value of 900 would pick from
            the fastest servers 90 percent of the time, and would perform nor-
            mal  exploration  of  random  servers for the remaining time. When
            prefetch is enabled (or serve-expired), such  prefetches  are  not
            sped up, because there is no one waiting for it, and it presents a
            good moment to perform  server  exploration.  The  fast-server-num
            option can be used to specify the size of the fastest servers set.
            The default for fast-server-permil is 0.

       fast-server-num: <number>
            Set the number of servers that should  be  used  for  fast  server
            selection.  Only  use the fastest specified number of servers with
            the fast-server-permil option, that turns  this  on  or  off.  The
            default is to use the fastest 3 servers.

   Remote Control Options
       In  the remote-control: clause are the declarations for the remote con-
       trol facility.  If this is enabled, the unbound-control(8) utility  can
       be  used  to  send  commands to the running unbound server.  The server
       uses these clauses to setup TLSv1 security  for  the  connection.   The
       unbound-control(8)  utility  also  reads the remote-control section for
       options.   To  setup  the  correct  self-signed  certificates  use  the
       unbound-control-setup(8) utility.

       control-enable: <yes or no>
            The  option is used to enable remote control, default is "no".  If
            turned off, the server does not listen for control commands.

       control-interface: <ip address or path>
            Give IPv4 or IPv6 addresses or local socket path to listen on  for
            control  commands.   By  default  localhost (127.0.0.1 and ::1) is
            listened to.  Use 0.0.0.0 and ::0 to listen to all interfaces.  If
            you  change  this  and  permissions  have  been  dropped, you must
            restart the server for the change to take effect.

            If you set it to an absolute path, a local socket  is  used.   The
            local  socket  does  not  use  the certificates and keys, so those
            files need not be present.  To restrict access, unbound sets  per-
            missions on the file to the user and group that is configured, the
            access bits are set to allow the group members to access the  con-
            trol socket file.  Put users that need to access the socket in the
            that group.  To restrict access further, create a directory to put
            the control socket in and restrict access to that directory.

       control-port: <port number>
            The  port number to listen on for IPv4 or IPv6 control interfaces,
            default is 8953.  If you change this  and  permissions  have  been
            dropped,  you  must  restart  the  server  for  the change to take
            effect.

       control-use-cert: <yes or no>
            For localhost control-interface you can disable the use of TLS  by
            setting this option to "no", default is "yes".  For local sockets,
            TLS is disabled and the value of this option is ignored.

       server-key-file: <private key file>
            Path to the server private  key,  by  default  unbound_server.key.
            This file is generated by the unbound-control-setup utility.  This
            file is used by the unbound server, but not by unbound-control.

       server-cert-file: <certificate file.pem>
            Path  to  the  server  self   signed   certificate,   by   default
            unbound_server.pem.   This  file  is generated by the unbound-con-
            trol-setup utility.  This file is used by the unbound server,  and
            also by unbound-control.

       control-key-file: <private key file>
            Path  to  the  control client private key, by default unbound_con-
            trol.key.  This file is  generated  by  the  unbound-control-setup
            utility.  This file is used by unbound-control.

       control-cert-file: <certificate file.pem>
            Path  to  the  control client certificate, by default unbound_con-
            trol.pem.  This certificate has to be signed with the server  cer-
            tificate.   This  file  is  generated by the unbound-control-setup
            utility.  This file is used by unbound-control.

   Stub Zone Options
       There may be multiple stub-zone: clauses. Each with a name: and zero or
       more  hostnames  or IP addresses.  For the stub zone this list of name-
       servers is used. Class IN is assumed.  The servers should be  authority
       servers,  not  recursors;  unbound  performs  the  recursive processing
       itself for stub zones.

       The stub zone can be used to configure authoritative data to be used by
       the resolver that cannot be accessed using the public internet servers.
       This is useful for  company-local  data  or  private  zones.  Setup  an
       authoritative  server  on a different host (or different port). Enter a
       config entry for unbound with stub-addr: <ip address  of  host[@port]>.
       The unbound resolver can then access the data, without referring to the
       public internet for it.

       This setup allows DNSSEC signed zones to be served by  that  authorita-
       tive  server, in which case a trusted key entry with the public key can
       be put in config, so that unbound can validate the data and set the  AD
       bit  on  replies for the private zone (authoritative servers do not set
       the AD bit).  This setup makes unbound capable of answering queries for
       the private zone, and can even set the AD bit ('authentic'), but the AA
       ('authoritative') bit is not set on these replies.

       Consider  adding  server:  statements  for  domain-insecure:  and   for
       local-zone: name nodefault for the zone if it is a locally served zone.
       The insecure clause stops DNSSEC from invalidating the zone.  The local
       zone nodefault (or transparent) clause makes the (reverse-) zone bypass
       unbound's filtering of RFC1918 zones.

       name: <domain name>
              Name of the stub zone.

       stub-host: <domain name>
              Name of stub zone nameserver. Is itself resolved  before  it  is
              used.

       stub-addr: <IP address>
              IP address of stub zone nameserver. Can be IP 4 or IP 6.  To use
              a nondefault port for DNS communication append '@' with the port
              number.

       stub-prime: <yes or no>
              This  option  is  by  default no.  If enabled it performs NS set
              priming, which is similar to root hints, where it  starts  using
              the  list of nameservers currently published by the zone.  Thus,
              if the hint list is slightly outdated, the resolver picks  up  a
              correct list online.

       stub-first: <yes or no>
              If  enabled,  a query is attempted without the stub clause if it
              fails.  The data could not be retrieved and  would  have  caused
              SERVFAIL  because  the  servers  are  unreachable, instead it is
              tried without this clause.  The default is no.

       stub-tls-upstream: <yes or no>
              Enabled or disable whether the queries to this stub use TLS  for
              transport.  Default is no.

       stub-ssl-upstream: <yes or no>
              Alternate syntax for stub-tls-upstream.

       stub-no-cache: <yes or no>
              Default  is no.  If enabled, data inside the stub is not cached.
              This is useful when you want immediate changes to be visible.

   Forward Zone Options
       There may be multiple forward-zone: clauses. Each with a name: and zero
       or  more  hostnames or IP addresses.  For the forward zone this list of
       nameservers is used to forward the queries to. The  servers  listed  as
       forward-host:  and  forward-addr:  have to handle further recursion for
       the query.  Thus, those servers are  not  authority  servers,  but  are
       (just  like unbound is) recursive servers too; unbound does not perform
       recursion itself for the forward zone, it lets the remote server do it.
       Class  IN  is assumed.  CNAMEs are chased by unbound itself, asking the
       remote server for every name in the indirection chain, to  protect  the
       local  cache  from  illegal  indirect referenced items.  A forward-zone
       entry with name "." and a forward-addr target will forward all  queries
       to that other server (unless it can answer from the cache).

       name: <domain name>
              Name of the forward zone.

       forward-host: <domain name>
              Name  of  server  to forward to. Is itself resolved before it is
              used.

       forward-addr: <IP address>
              IP address of server to forward to. Can be IP 4 or IP 6.  To use
              a nondefault port for DNS communication append '@' with the port
              number.  If tls is enabled, then you can  append  a  '#'  and  a
              name,  then it'll check the tls authentication certificates with
              that name.  If you combine the '@' and '#', the '@' comes first.

              At high verbosity it logs the TLS certificate, with TLS enabled.
              If  you  leave  out the '#' and auth name from the forward-addr,
              any name is accepted.  The cert must also match a  CA  from  the
              tls-cert-bundle.   The  cert name match code needs OpenSSL 1.1.0
              or later to be enabled.

       forward-first: <yes or no>
              If enabled, a query is attempted without the forward  clause  if
              it fails.  The data could not be retrieved and would have caused
              SERVFAIL because the servers  are  unreachable,  instead  it  is
              tried without this clause.  The default is no.

       forward-tls-upstream: <yes or no>
              Enabled or disable whether the queries to this forwarder use TLS
              for transport.  Default is no.  If you enable this, also config-
              ure a tls-cert-bundle or use tls-win-cert to load CA certs, oth-
              erwise the connections cannot be authenticated.

       forward-ssl-upstream: <yes or no>
              Alternate syntax for forward-tls-upstream.

       forward-no-cache: <yes or no>
              Default is no.  If enabled,  data  inside  the  forward  is  not
              cached.   This  is  useful when you want immediate changes to be
              visible.

   Authority Zone Options
       Authority zones are configured with auth-zone:, and each one must  have
       a  name:.   There  can  be multiple ones, by listing multiple auth-zone
       clauses, each with a different name, pertaining to  that  part  of  the
       namespace.  The authority zone with the name closest to the name looked
       up is used.  Authority zones are processed after local-zones and before
       cache  (for-downstream: yes), and when used in this manner make unbound
       respond like an authority server.  Authority zones are  also  processed
       after  cache, just before going to the network to fetch information for
       recursion (for-upstream: yes), and when used in this manner  provide  a
       local copy of an authority server that speeds up lookups of that data.

       Authority zones can be read from zonefile.  And can be kept updated via
       AXFR and IXFR.  After update the zonefile  is  rewritten.   The  update
       mechanism  uses  the  SOA  timer values and performs SOA UDP queries to
       detect zone changes.

       If the update fetch fails, the timers in the SOA  record  are  used  to
       time  another  fetch  attempt.   Until the SOA expiry timer is reached.
       Then the zone is expired.  When a zone is expired,  queries  are  SERV-
       FAIL,  and  any  new serial number is accepted from the master (even if
       older), and if fallback is enabled, the  fallback  activates  to  fetch
       from the upstream instead of the SERVFAIL.

       name: <zone name>
              Name of the authority zone.

       master: <IP address or host name>
              Where  to  download a copy of the zone from, with AXFR and IXFR.
              Multiple masters can be specified.  They are all  tried  if  one
              fails.

       url: <url to zonefile>
              Where  to download a zonefile for the zone.  With http or https.
              An  example  for  the   url   is   "http://www.example.com/exam-
              ple.org.zone".   Multiple  url statements can be given, they are
              tried in turn.  If only urls are given the SOA refresh timer  is
              used  to  wait  for  making  new downloads.  If also masters are
              listed, the masters are first probed with UDP SOA queries to see
              if  the  SOA  serial  number has changed, reducing the number of
              downloads.  If none of the urls work, the masters are tried with
              IXFR  and AXFR.  For https, the tls-cert-bundle and the hostname
              from the url are used to authenticate the connection.

       allow-notify: <IP address or host name or netblockIP/prefix>
              With allow-notify you can specify additional  sources  of  noti-
              fies.   When  notified,  the  server attempts to first probe and
              then zone transfer.  If the notify is from a  master,  it  first
              attempts  that  master.   Otherwise other masters are attempted.
              If there are no masters, but only urls, the file  is  downloaded
              when  notified.  The masters from master: statements are allowed
              notify by default.

       fallback-enabled: <yes or no>
              Default no.  If enabled, unbound  falls  back  to  querying  the
              internet  as  a  resolver  for this zone when lookups fail.  For
              example for DNSSEC validation failures.

       for-downstream: <yes or no>
              Default yes.  If enabled, unbound serves authority responses  to
              downstream  clients  for  this  zone.  This option makes unbound
              behave, for the queries with names in this zone, like one of the
              authority  servers  for  that  zone.   Turn  it  off if you want
              unbound to provide recursion for the zone but have a local  copy
              of  zone data.  If for-downstream is no and for-upstream is yes,
              then unbound will DNSSEC  validate  the  contents  of  the  zone
              before serving the zone contents to clients and store validation
              results in the cache.

       for-upstream: <yes or no>
              Default yes.  If enabled, unbound fetches data  from  this  data
              collection  for answering recursion queries.  Instead of sending
              queries over the internet to  the  authority  servers  for  this
              zone, it'll fetch the data directly from the zone data.  Turn it
              on when you want unbound to  provide  recursion  for  downstream
              clients,  and  use  the  zone  data  as a local copy to speed up
              lookups.

       zonefile: <filename>
              The filename where the zone is stored.  If  not  given  then  no
              zonefile  is  used.   If  the  file  does not exist or is empty,
              unbound will attempt to fetch zone data  (eg.  from  the  master
              servers).

   View Options
       There may be multiple view: clauses. Each with a name: and zero or more
       local-zone and local-data elements. View can be mapped to  requests  by
       specifying  the  view  name  in an access-control-view element. Options
       from matching views will override global options. Global  options  will
       be  used  if  no matching view is found, or when the matching view does
       not have the option specified.

       name: <view name>
              Name of  the  view.  Must  be  unique.  This  name  is  used  in
              access-control-view elements.

       local-zone: <zone> <type>
              View specific local-zone elements. Has the same types and behav-
              iour as the global local-zone elements. When there is  at  least
              one  local-zone  specified  and  view-first  is  no, the default
              local-zones will be added to this view.  Defaults  can  be  dis-
              abled using the nodefault type. When view-first is yes or when a
              view does not have a local-zone, the global local-zone  will  be
              used including it's default zones.

       local-data: "<resource record string>"
              View specific local-data elements. Has the same behaviour as the
              global local-data elements.

       local-data-ptr: "IPaddr name"
              View specific local-data-ptr elements. Has the same behaviour as
              the global local-data-ptr elements.

       view-first: <yes or no>
              If  enabled,  it  attempts  to  use  the  global  local-zone and
              local-data if there is no match in the  view  specific  options.
              The default is no.

   Python Module Options
       The  python: clause gives the settings for the python(1) script module.
       This module acts like the iterator and validator modules do, on queries
       and  answers.   To  enable the script module it has to be compiled into
       the daemon, and the word "python" has to be put in  the  module-config:
       option (usually first, or between the validator and iterator).

       If the chroot: option is enabled, you should make sure Python's library
       directory structure is bind mounted in the new  root  environment,  see
       mount(8).  Also the python-script: path should be specified as an abso-
       lute path relative to the new root, or as a relative path to the  work-
       ing directory.

       python-script: <python file>
              The script file to load.

   DNS64 Module Options
       The  dns64  module must be configured in the module-config: "dns64 val-
       idator iterator" directive and  be  compiled  into  the  daemon  to  be
       enabled.  These settings go in the server: section.

       dns64-prefix: <IPv6 prefix>
              This  sets  the  DNS64  prefix to use to synthesize AAAA records
              with.  It must  be  /96  or  shorter.   The  default  prefix  is
              64:ff9b::/96.

       dns64-synthall: <yes or no>
              Debug  option,  default  no.   If  enabled,  synthesize all AAAA
              records despite the presence of actual AAAA records.

       dns64-ignore-aaaa: <name>
              List domain for which the AAAA records are  ignored  and  the  A
              record is used by dns64 processing instead.  Can be entered mul-
              tiple times, list a new domain for which  it  applies,  one  per
              line.  Applies also to names underneath the name given.

   DNSCrypt Options
       The  dnscrypt: clause gives the settings of the dnscrypt channel. While
       those options are available, they are only meaningful  if  unbound  was
       compiled with --enable-dnscrypt.  Currently certificate and secret/pub-
       lic keys cannot be generated by unbound.  You can use  dnscrypt-wrapper
       to  generate those: https://github.com/cofyc/dnscrypt-wrapper/blob/mas-
       ter/README.md#usage

       dnscrypt-enable: <yes or no>
              Whether or not the dnscrypt config should be  enabled.  You  may
              define configuration but not activate it.  The default is no.

       dnscrypt-port: <port number>
              On which port should dnscrypt should be activated. Note that you
              should have a matching interface option defined  in  the  server
              section for this port.

       dnscrypt-provider: <provider name>
              The  provider name to use to distribute certificates. This is of
              the form: 2.dnscrypt-cert.example.com.. The name MUST end with a
              dot.

       dnscrypt-secret-key: <path to secret key file>
              Path  to  the  time  limited secret key file. This option may be
              specified multiple times.

       dnscrypt-provider-cert: <path to cert file>
              Path to the certificate  related  to  the  dnscrypt-secret-keys.
              This option may be specified multiple times.

       dnscrypt-provider-cert-rotated: <path to cert file>
              Path  to  a certificate that we should be able to serve existing
              connection  from   but   do   not   want   to   advertise   over
              dnscrypt-provider's  TXT  record  certs distribution.  A typical
              use case is when rotating  certificates,  existing  clients  may
              still  use  the  client magic from the old cert in their queries
              until they fetch and update the new  cert.  Likewise,  it  would
              allow one to prime the new cert/key without distributing the new
              cert yet, this can be useful when using  a  network  of  servers
              using anycast and on which the configuration may not get updated
              at the exact same time. By priming the  cert,  the  servers  can
              handle  both  old  and new certs traffic while distributing only
              one.  This option may be specified multiple times.

       dnscrypt-shared-secret-cache-size: <memory size>
              Give the size of the data structure in which the  shared  secret
              keys  are  kept  in.   Default  4m.   In  bytes  or use m(mega),
              k(kilo), g(giga).  The shared secret cache is used when  a  same
              client  is making multiple queries using the same public key. It
              saves a substantial amount of CPU.

       dnscrypt-shared-secret-cache-slabs: <number>
              Give power of 2 number of slabs, this is  used  to  reduce  lock
              contention  in  the dnscrypt shared secrets cache.  Close to the
              number of cpus is a fairly good setting.

       dnscrypt-nonce-cache-size: <memory size>
              Give the size of the data structure in which the  client  nonces
              are  kept  in.   Default  4m.  In bytes or use m(mega), k(kilo),
              g(giga).  The nonce cache is used to  prevent  dnscrypt  message
              replaying.  Client nonce should be unique for any pair of client
              pk/server sk.

       dnscrypt-nonce-cache-slabs: <number>
              Give power of 2 number of slabs, this is  used  to  reduce  lock
              contention  in the dnscrypt nonce cache.  Close to the number of
              cpus is a fairly good setting.

   EDNS Client Subnet Module Options
       The ECS module must be configured in  the  module-config:  "subnetcache
       validator  iterator"  directive  and  be compiled into the daemon to be
       enabled.  These settings go in the server: section.

       If the destination address is whitelisted with  Unbound  will  add  the
       EDNS0  option to the query containing the relevant part of the client's
       address. When an answer contains the ECS option the  response  and  the
       option are placed in a specialized cache. If the authority indicated no
       support, the response is stored in the regular cache.

       Additionally, when a client includes the option in its queries, Unbound
       will  forward  the option to the authority if present in the whitelist,
       or client-subnet-always-forward is set to yes. In this case the  lookup
       in the regular cache is skipped.

       The  maximum size of the ECS cache is controlled by 'msg-cache-size' in
       the configuration file. On top of that, for each query only 100 differ-
       ent subnets are allowed to be stored for each address family. Exceeding
       that number, older entries will be purged from cache.

       send-client-subnet: <IP address>
              Send client source address to this  authority.  Append  /num  to
              indicate  a  classless  delegation  netblock,  for  example like
              10.2.3.4/24 or 2001::11/64. Can be given multiple times. Author-
              ities  not  listed  will  not  receive  edns-subnet information,
              unless domain in query is specified in client-subnet-zone.

       client-subnet-zone: <domain>
              Send client source address in queries for this  domain  and  its
              subdomains.  Can  be given multiple times. Zones not listed will
              not receive edns-subnet information, unless hosted by  authority
              specified in send-client-subnet.

       client-subnet-always-forward: <yes or no>
              Specify  whether  the  ECS  whitelist  check  (configured  using
              send-client-subnet) is applied for  all  queries,  even  if  the
              triggering query contains an ECS record, or only for queries for
              which the ECS record is generated using the querier address (and
              therefore  did  not  contain  ECS  data in the client query). If
              enabled, the whitelist check is skipped when  the  client  query
              contains an ECS record. Default is no.

       max-client-subnet-ipv6: <number>
              Specifies the maximum prefix length of the client source address
              we are willing to expose to third parties for IPv6.  Defaults to
              56.

       max-client-subnet-ipv4: <number>
              Specifies the maximum prefix length of the client source address
              we are willing to expose to third parties for IPv4. Defaults  to
              24.

       min-client-subnet-ipv6: <number>
              Specifies  the  minimum prefix length of the IPv6 source mask we
              are willing to accept in queries. Shorter source masks result in
              REFUSED answers. Source mask of 0 is always accepted. Default is
              0.

       min-client-subnet-ipv4: <number>
              Specifies the minimum prefix length of the IPv4 source  mask  we
              are willing to accept in queries. Shorter source masks result in
              REFUSED answers. Source mask of 0 is always accepted. Default is
              0.

       max-ecs-tree-size-ipv4: <number>
              Specifies  the maximum number of subnets ECS answers kept in the
              ECS radix tree.  This number applies for each qname/qclass/qtype
              tuple. Defaults to 100.

       max-ecs-tree-size-ipv6: <number>
              Specifies  the maximum number of subnets ECS answers kept in the
              ECS radix tree.  This number applies for each qname/qclass/qtype
              tuple. Defaults to 100.

   Opportunistic IPsec Support Module Options
       The  IPsec  module  must  be configured in the module-config: "ipsecmod
       validator iterator" directive and be compiled into  the  daemon  to  be
       enabled.  These settings go in the server: section.

       When  unbound  receives  an  A/AAAA  query that is not in the cache and
       finds a valid answer, it will withhold returning the answer and instead
       will  generate  an  IPSECKEY  subquery for the same domain name.  If an
       answer was found, unbound will call an external hook passing  the  fol-
       lowing arguments:

            QNAME
                 Domain name of the A/AAAA and IPSECKEY query.  In string for-
                 mat.

            IPSECKEY TTL
                 TTL of the IPSECKEY RRset.

            A/AAAA
                 String of space separated IP addresses present in the  A/AAAA
                 RRset.  The IP addresses are in string format.

            IPSECKEY
                 String  of  space  separated  IPSECKEY  RDATA  present in the
                 IPSECKEY RRset.  The IPSECKEY RDATA are in  DNS  presentation
                 format.

       The  A/AAAA  answer  is then cached and returned to the client.  If the
       external hook was called the TTL changes to ensure it  doesn't  surpass
       ipsecmod-max-ttl.

       The  same  procedure  is  also followed when prefetch: is used, but the
       A/AAAA answer is given to the client before the hook is called.  ipsec-
       mod-max-ttl  ensures  that  the A/AAAA answer given from cache is still
       relevant for opportunistic IPsec.

       ipsecmod-enabled: <yes or no>
              Specifies whether the IPsec module is enabled or not.  The IPsec
              module  still  needs  to be defined in the module-config: direc-
              tive.  This option facilitates turning on/off the module without
              restarting/reloading unbound.  Defaults to yes.

       ipsecmod-hook: <filename>
              Specifies  the  external  hook  that unbound will call with sys-
              tem(3).  The file can be specified as an absolute/relative path.
              The  file needs the proper permissions to be able to be executed
              by the same user that runs unbound.  It must be present when the
              IPsec module is defined in the module-config: directive.

       ipsecmod-strict: <yes or no>
              If  enabled  unbound requires the external hook to return a suc-
              cess value of 0.  Failing to do so unbound will reply with SERV-
              FAIL.   The  A/AAAA answer will also not be cached.  Defaults to
              no.

       ipsecmod-max-ttl: <seconds>
              Time to live maximum for A/AAAA cached records after calling the
              external hook.  Defaults to 3600.

       ipsecmod-ignore-bogus: <yes or no>
              Specifies  the  behaviour of unbound when the IPSECKEY answer is
              bogus.  If set to yes, the hook will be called  and  the  A/AAAA
              answer  will  be returned to the client.  If set to no, the hook
              will not be called and the answer to the A/AAAA  query  will  be
              SERVFAIL.  Mainly used for testing.  Defaults to no.

       ipsecmod-whitelist: <domain>
              Whitelist  the domain so that the module logic will be executed.
              Can be given multiple times,  for  different  domains.   If  the
              option  is  not  specified,  all  domains  are  treated as being
              whitelisted (default).

   Cache DB Module Options
       The Cache DB module must be configured in the module-config: "validator
       cachedb  iterator"  directive  and  be  compiled  into  the daemon with
       --enable-cachedb.  If this module is enabled and configured, the speci-
       fied  backend database works as a second level cache: When Unbound can-
       not find an answer to a query in its built-in in-memory cache, it  con-
       sults  the  specified backend.  If it finds a valid answer in the back-
       end, Unbound uses it to respond to the query without performing  itera-
       tive  DNS  resolution.   If  Unbound  cannot even find an answer in the
       backend, it resolves the query as usual, and stores the answer  in  the
       backend.

       If  Unbound  was  built  with  --with-libhiredis  on  a system that has
       installed the hiredis C client library of Redis, then the "redis" back-
       end  can  be  used.  This backend communicates with the specified Redis
       server over a TCP connection to store and retrieve cache data.  It  can
       be  used  as  a  persistent  and/or shared cache backend.  It should be
       noted that Unbound never removes data stored in the Redis server,  even
       if  some  data have expired in terms of DNS TTL or the Redis server has
       cached too much data; if necessary the Redis server must be  configured
       to  limit  the cache size, preferably with some kind of least-recently-
       used eviction policy.  This backend uses synchronous communication with
       the Redis server based on the assumption that the communication is sta-
       ble and sufficiently fast.  The thread waiting for a response from  the
       Redis server cannot handle other DNS queries.  Although the backend has
       the ability to reconnect to the server when the  connection  is  closed
       unexpectedly  and there is a configurable timeout in case the server is
       overly slow or hangs up, these cases are assumed to be very  rare.   If
       connection  close  or timeout happens too often, Unbound will be effec-
       tively unusable with this backend.  It's the administrator's  responsi-
       bility to make the assumption hold.

       The cachedb: clause gives custom settings of the cache DB module.

       backend: <backend name>
              Specify  the backend database name.  The default database is the
              in-memory backend named "testframe", which,  as  the  name  sug-
              gests, is not of any practical use.  Depending on the build-time
              configuration, "redis" backend may also  be  used  as  described
              above.

       secret-seed: <"secret string">
              Specify a seed to calculate a hash value from query information.
              This value will be used as the key of the  corresponding  answer
              for  the  backend  database  and  can  be customized if the hash
              should not be predictable operationally.  If the  backend  data-
              base is shared by multiple Unbound instances, all instances must
              use the same secret seed.  This option defaults to "default".

       The following cachedb otions are specific to the redis backend.

       redis-server-host: <server address or name>
              The IP (either v6 or v4) address or domain  name  of  the  Redis
              server.   In general an IP address should be specified as other-
              wise Unbound will have to resolve the name of the  server  every
              time  it  establishes  a  connection to the server.  This option
              defaults to "127.0.0.1".

       redis-server-port: <port number>
              The TCP port number of the Redis server.  This  option  defaults
              to 6379.

       redis-timeout: <msec>
              The  period  until  when  Unbound  waits for a response from the
              Redis sever.  If this timeout expires Unbound closes the connec-
              tion,  treats  it  as  if  the  Redis  server  does not have the
              requested data, and will try to re-establish  a  new  connection
              later.  This option defaults to 100 milliseconds.

MEMORY CONTROL EXAMPLE
       In the example config settings below memory usage is reduced. Some ser-
       vice levels are lower, notable very large data and a high TCP load  are
       no longer supported. Very large data and high TCP loads are exceptional
       for the DNS.  DNSSEC validation is enabled, just add trust anchors.  If
       you do not have to worry about programs using more than 3 Mb of memory,
       the below example is not for you. Use the defaults to receive full ser-
       vice, which on BSD-32bit tops out at 30-40 Mb after heavy usage.

       # example settings that reduce memory usage
       server:
            num-threads: 1
            outgoing-num-tcp: 1 # this limits TCP service, uses less buffers.
            incoming-num-tcp: 1
            outgoing-range: 60  # uses less memory, but less performance.
            msg-buffer-size: 8192   # note this limits service, 'no huge stuff'.
            msg-cache-size: 100k
            msg-cache-slabs: 1
            rrset-cache-size: 100k
            rrset-cache-slabs: 1
            infra-cache-numhosts: 200
            infra-cache-slabs: 1
            key-cache-size: 100k
            key-cache-slabs: 1
            neg-cache-size: 10k
            num-queries-per-thread: 30
            target-fetch-policy: "2 1 0 0 0 0"
            harden-large-queries: "yes"
            harden-short-bufsize: "yes"

FILES
       /usr/local/etc/unbound
              default unbound working directory.

       /usr/local/etc/unbound
              default chroot(2) location.

       /usr/local/etc/unbound/unbound.conf
              unbound configuration file.

       /usr/local/etc/unbound/unbound.pid
              default unbound pidfile with process ID of the running daemon.

       unbound.log
              unbound log file. default is to log to syslog(3).

SEE ALSO
       unbound(8), unbound-checkconf(8).

AUTHORS
       Unbound  was written by NLnet Labs. Please see CREDITS file in the dis-
       tribution for further details.



NLnet Labs                       Dec 11, 2018                  unbound.conf(5)