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+.TH "unbound.conf" "5" "Mar 12, 2014" "NLnet Labs" "unbound 1.4.22"
+.\"
+.\" unbound.conf.5 -- unbound.conf manual
+.\"
+.\" Copyright (c) 2007, NLnet Labs. All rights reserved.
+.\"
+.\" See LICENSE for the license.
+.\"
+.\"
+.SH "NAME"
+.LP
+.B unbound.conf
+\- Unbound configuration file.
+.SH "SYNOPSIS"
+.LP
+.B unbound.conf
+.SH "DESCRIPTION"
+.LP
+.B unbound.conf
+is used to configure
+\fIunbound\fR(8).
+The file format has attributes and values. Some attributes have attributes inside them.
+The notation is: attribute: value.
+.P
+Comments start with # and last to the end of line. Empty lines are
+ignored as is whitespace at the beginning of a line.
+.P
+The utility
+\fIunbound\-checkconf\fR(8)
+can be used to check unbound.conf prior to usage.
+.SH "EXAMPLE"
+An example config file is shown below. Copy this to /etc/unbound/unbound.conf
+and start the server with:
+.P
+.nf
+ $ unbound \-c /etc/unbound/unbound.conf
+.fi
+.P
+Most settings are the defaults. Stop the server with:
+.P
+.nf
+ $ kill `cat /etc/unbound/unbound.pid`
+.fi
+.P
+Below is a minimal config file. The source distribution contains an extensive
+example.conf file with all the options.
+.P
+.nf
+# 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
+.fi
+.SH "FILE FORMAT"
+.LP
+There must be whitespace between keywords. Attribute keywords end with a colon ':'. An attribute
+is followed by its containing attributes, or a value.
+.P
+Files can be included using the
+.B include:
+directive. It can appear anywhere, 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. Wildcards can be used to include multiple files, see \fIglob\fR(7).
+.SS "Server Options"
+These options are part of the
+.B server:
+clause.
+.TP
+.B verbosity: \fI<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 commandline, see \fIunbound\fR(8).
+.TP
+.B statistics\-interval: \fI<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.
+.TP
+.B statistics\-cumulative: \fI<yes or no>
+If enabled, statistics are cumulative since starting unbound, without clearing
+the statistics counters after logging the statistics. Default is no.
+.TP
+.B extended\-statistics: \fI<yes or no>
+If enabled, extended statistics are printed from \fIunbound\-control\fR(8).
+Default is off, because keeping track of more statistics takes time. The
+counters are listed in \fIunbound\-control\fR(8).
+.TP
+.B num\-threads: \fI<number>
+The number of threads to create to serve clients. Use 1 for no threading.
+.TP
+.B port: \fI<port number>
+The port number, default 53, on which the server responds to queries.
+.TP
+.B interface: \fI<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 localhost.
+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 specified the default port (from
+\fBport\fR) is used.
+.TP
+.B ip\-address: \fI<ip address[@port]>
+Same as interface: (for easy of compatibility with nsd.conf).
+.TP
+.B interface\-automatic: \fI<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.
+.TP
+.B outgoing\-interface: \fI<ip address>
+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 interfaces. If none are given the
+default (all) is used. You can specify the same interfaces in
+.B interface:
+and
+.B outgoing\-interface:
+lines, the interfaces are then used for both purposes. Outgoing queries are
+sent via a random outgoing interface to counter spoofing.
+.TP
+.B outgoing\-range: \fI<number>
+Number of ports to open. This number of file descriptors can be opened per
+thread. Must be at least 1. Default depends on compile options. Larger
+numbers need extra resources from the operating system. For performance a
+a very large value is best, use libevent to make this possible.
+.TP
+.B outgoing\-port\-permit: \fI<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.
+.IP
+The \fBoutgoing\-port\-permit\fR and \fBoutgoing\-port\-avoid\fR statements
+are processed in the line order of the config file, adding the permitted ports
+and subtracting the avoided ports from the set of allowed ports. The
+processing starts with the non IANA allocated ports above 1024 in the set
+of allowed ports.
+.TP
+.B outgoing\-port\-avoid: \fI<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.
+.TP
+.B outgoing\-num\-tcp: \fI<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.
+.TP
+.B incoming\-num\-tcp: \fI<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.
+.TP
+.B edns\-buffer\-size: \fI<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 fragmentation reassembly problems, usually seen as timeouts,
+then a value of 1480 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).
+.TP
+.B max\-udp\-size: \fI<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.
+.TP
+.B msg\-buffer\-size: \fI<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.
+.TP
+.B msg\-cache\-size: \fI<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).
+.TP
+.B msg\-cache\-slabs: \fI<number>
+Number of slabs in the message 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.
+.TP
+.B num\-queries\-per\-thread: \fI<number>
+The number of queries that every thread will service simultaneously.
+If more queries arrive that need servicing, and no queries can be jostled out
+(see \fIjostle\-timeout\fR), 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.
+.TP
+.B jostle\-timeout: \fI<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
+(numqueriesperthread / 2) / (average time for such long queries) qps.
+The qps for short queries can be about (numqueriesperthread / 2)
+/ (jostletimeout in whole seconds) qps per thread, about (1024/2)*5 = 2560
+qps by default.
+.TP
+.B delay\-close: \fI<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 packets, and unwanted packets are added to the
+unwanted packet counter.
+.TP
+.B so\-rcvbuf: \fI<number>
+If not 0, then set the SO_RCVBUF socket option to get more buffer
+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.
+.TP
+.B so\-sndbuf: \fI<number>
+If not 0, then set the SO_SNDBUF socket option to get more buffer 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 system 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.
+.TP
+.B so\-reuseport: \fI<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 no. Only
+supported on Linux >= 3.9. You can enable it (on any platform and kernel),
+it then attempts to open the port and passes the option if it was available
+at compile time, if that works it is used, if it fails, it continues
+silently (unless verbosity 3) without the option.
+.TP
+.B rrset\-cache\-size: \fI<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 kilobytes, megabytes
+or gigabytes (1024*1024 bytes in a megabyte).
+.TP
+.B rrset\-cache\-slabs: \fI<number>
+Number of slabs in the RRset cache. Slabs reduce lock contention by threads.
+Must be set to a power of 2.
+.TP
+.B cache\-max\-ttl: \fI<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.
+.TP
+.B cache\-min\-ttl: \fI<seconds>
+Time to live minimum for RRsets and messages in the cache. Default is 0.
+If the 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.
+.TP
+.B infra\-host\-ttl: \fI<seconds>
+Time to live for entries in the host cache. The host cache contains
+roundtrip timing, lameness and EDNS support information. Default is 900.
+.TP
+.B infra\-cache\-slabs: \fI<number>
+Number of slabs in the infrastructure cache. Slabs reduce lock contention
+by threads. Must be set to a power of 2.
+.TP
+.B infra\-cache\-numhosts: \fI<number>
+Number of hosts for which information is cached. Default is 10000.
+.TP
+.B do\-ip4: \fI<yes or no>
+Enable or disable whether ip4 queries are answered or issued. Default is yes.
+.TP
+.B do\-ip6: \fI<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.
+.TP
+.B do\-udp: \fI<yes or no>
+Enable or disable whether UDP queries are answered or issued. Default is yes.
+.TP
+.B do\-tcp: \fI<yes or no>
+Enable or disable whether TCP queries are answered or issued. Default is yes.
+.TP
+.B tcp\-upstream: \fI<yes or no>
+Enable or disable whether the upstream queries use TCP only for transport.
+Default is no. Useful in tunneling scenarios.
+.TP
+.B ssl\-upstream: \fI<yes or no>
+Enabled or disable whether the upstream queries use SSL only for transport.
+Default is no. Useful in tunneling scenarios. The SSL contains plain DNS in
+TCP wireformat. The other server must support this (see \fBssl\-service\-key\fR).
+.TP
+.B ssl\-service-key: \fI<file>
+If enabled, the server provider SSL service on its TCP sockets. The clients
+have to use ssl\-upstream: yes. The file is the private key for the TLS
+session. The public certificate is in the ssl\-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 \fBport:\fR config or \fI@port\fR
+suffixes in the \fBinterface\fR config.
+.TP
+.B ssl\-service\-pem: \fI<file>
+The public key certificate pem file for the ssl service. Default is "",
+turned off.
+.TP
+.B ssl\-port: \fI<number>
+The port number on which to provide TCP SSL service, default 443, only
+interfaces configured with that port number as @number get the SSL service.
+.TP
+.B do\-daemonize: \fI<yes or no>
+Enable or disable whether the unbound server forks into the background as
+a daemon. Default is yes.
+.TP
+.B access\-control: \fI<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 \fIdeny\fR, \fIrefuse\fR,
+\fIallow\fR, \fIallow_snoop\fR, \fIdeny_non_local\fR or \fIrefuse_non_local\fR.
+.IP
+The action \fIdeny\fR stops queries from hosts from that netblock.
+.IP
+The action \fIrefuse\fR stops queries too, but sends a DNS rcode REFUSED
+error message back.
+.IP
+The action \fIallow\fR 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.
+.IP
+The \fIallow\fR 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 operations where nonrecursive queries
+are made for the authoritative data. For nonrecursive queries any replies
+from the dynamic cache are refused.
+.IP
+The action \fIallow_snoop\fR gives nonrecursive access too. This give
+both recursive and non recursive access. The name \fIallow_snoop\fR 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 \fIallow_snoop\fR for your administration host.
+.IP
+By default only localhost is \fIallow\fRed, the rest is \fIrefuse\fRd.
+The default is \fIrefuse\fRd, because that is protocol\-friendly. The DNS
+protocol is not designed to handle dropped packets due to policy, and
+dropping may result in (possibly excessive) retried queries.
+.IP
+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.
+.TP
+.B chroot: \fI<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.
+.IP
+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 portion.
+.IP
+The pidfile can be either a relative path to the working directory, 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.
+.IP
+Additionally, unbound may need to access /dev/random (for entropy)
+from inside the chroot.
+.IP
+If given a chroot is done to the given directory. The default is
+"@UNBOUND_CHROOT_DIR@". If you give "" no chroot is performed.
+.TP
+.B username: \fI<name>
+If given, after binding the port the user privileges are dropped. Default is
+"@UNBOUND_USERNAME@". If you give username: "" no user change is performed.
+.IP
+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.
+.TP
+.B directory: \fI<directory>
+Sets the working directory for the program. Default is "@UNBOUND_RUN_DIR@".
+.TP
+.B logfile: \fI<filename>
+If "" is given, logging goes to stderr, or nowhere once daemonized.
+The logfile is appended to, in the following format:
+.nf
+[seconds since 1970] unbound[pid:tid]: type: message.
+.fi
+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.
+.TP
+.B use\-syslog: \fI<yes or no>
+Sets unbound to send log messages to the syslogd, using
+\fIsyslog\fR(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.
+.TP
+.B log\-time\-ascii: \fI<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.
+.TP
+.B log\-queries: \fI<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 (significantly) slower. Odd (nonprintable)
+characters in names are printed as '?'.
+.TP
+.B pidfile: \fI<filename>
+The process id is written to the file. Default is "@UNBOUND_PIDFILE@".
+So,
+.nf
+kill \-HUP `cat @UNBOUND_PIDFILE@`
+.fi
+triggers a reload,
+.nf
+kill \-QUIT `cat @UNBOUND_PIDFILE@`
+.fi
+gracefully terminates.
+.TP
+.B root\-hints: \fI<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.
+.TP
+.B hide\-identity: \fI<yes or no>
+If enabled id.server and hostname.bind queries are refused.
+.TP
+.B identity: \fI<string>
+Set the identity to report. If set to "", the default, then the hostname
+of the server is returned.
+.TP
+.B hide\-version: \fI<yes or no>
+If enabled version.server and version.bind queries are refused.
+.TP
+.B version: \fI<string>
+Set the version to report. If set to "", the default, then the package
+version is returned.
+.TP
+.B target\-fetch\-policy: \fI<"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.
+.IP
+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.
+.IP
+Enclose the list between quotes ("") and put spaces between numbers.
+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.
+.TP
+.B harden\-short\-bufsize: \fI<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.
+.TP
+.B harden\-large\-queries: \fI<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.
+.TP
+.B harden\-glue: \fI<yes or no>
+Will trust glue only if it is within the servers authority. Default is on.
+.TP
+.B harden\-dnssec\-stripped: \fI<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.
+.TP
+.B harden\-below\-nxdomain: \fI<yes or no>
+From draft\-vixie\-dnsext\-resimprove, returns nxdomain to queries for a name
+below another name that is already known to be nxdomain. DNSSEC mandates
+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 off.
+.TP
+.B harden\-referral\-path: \fI<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 validation on nameserver
+NS sets and the nameserver addresses that are encountered on the referral
+path to the answer.
+Default off, 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 target\-fetch\-policy
+to increase the max depth that is checked to.
+.TP
+.B use\-caps\-for\-id: \fI<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.
+.TP
+.B private\-address: \fI<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 occurence 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 \fBlocal\-data\fR
+that you configured is allowed to, and you can specify additional
+names using \fBprivate\-domain\fR. 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 spamblocklists as they use that.
+.TP
+.B private\-domain: \fI<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.
+.TP
+.B unwanted\-reply\-threshold: \fI<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).
+.TP
+.B do\-not\-query\-address: \fI<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.
+.TP
+.B do\-not\-query\-localhost: \fI<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.
+.TP
+.B prefetch: \fI<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.
+.TP
+.B prefetch-key: \fI<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.
+.TP
+.B rrset-roundrobin: \fI<yes or no>
+If yes, Unbound rotates RRSet order in response (the random number is taken
+from the query ID, for speed and thread safety). Default is no.
+.TP
+.B minimal-responses: \fI<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 no, because the DNS
+protocol RFCs mandate these sections, and the additional content could
+be of use and save roundtrips for clients.
+.TP
+.B module\-config: \fI<"module names">
+Module configuration, a list of module names separated by spaces, 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.
+.TP
+.B trust\-anchor\-file: \fI<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.
+.TP
+.B auto\-trust\-anchor\-file: \fI<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
+\fBtrust\-anchor\-file\fR. The file is written to when the anchor is updated,
+so the unbound user must have write permission.
+.TP
+.B trust\-anchor: \fI<"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 addition 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.
+.TP
+.B trusted\-keys\-file: \fI<filename>
+File with trusted keys for validation. Specify more than one file
+with several entries, one file per entry. Like \fBtrust\-anchor\-file\fR
+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.
+.TP
+.B dlv\-anchor\-file: \fI<filename>
+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
+\fItrust\-anchor\-file:\fR 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.
+.TP
+.B dlv\-anchor: \fI<"Resource Record">
+Much like trust\-anchor, this is a DLV anchor with the DS or DNSKEY inline.
+.TP
+.B domain\-insecure: \fI<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).
+.IP
+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.
+.TP
+.B val\-override\-date: \fI<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 verifying RRSIG inception
+and expiration dates, instead of the current date. Do not set this unless
+you are debugging signature inception and expiration. The value \-1 ignores
+the date altogether, useful for some special applications.
+.TP
+.B val\-sig\-skew\-min: \fI<seconds>
+Minimum number of seconds of clock skew to apply to validated signatures.
+A value of 10% of the signature lifetime (expiration \- 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 signatures.
+.TP
+.B val\-sig\-skew\-max: \fI<seconds>
+Maximum number of seconds of clock skew to apply to validated signatures.
+A value of 10% of the signature lifetime (expiration \- 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.
+.TP
+.B val\-bogus\-ttl: \fI<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.
+.TP
+.B val\-clean\-additional: \fI<yes or no>
+Instruct the validator to remove data from the additional section 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
+protentially bad data in the additional section.
+.TP
+.B val\-log\-level: \fI<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.
+.TP
+.B val\-permissive\-mode: \fI<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".
+.TP
+.B ignore\-cd\-flag: \fI<yes or no>
+Instruct unbound to ignore the CD flag from clients and refuse to
+return bogus answers to them. Thus, the CD (Checking Disabled) flag
+does not disable checking any more. This is useful if legacy (w2008)
+servers that set the CD flag but cannot validate DNSSEC themselves are
+the clients, and then unbound provides them with DNSSEC protection.
+The default value is "no".
+.TP
+.B val\-nsec3\-keysize\-iterations: \fI<"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.
+.TP
+.B add\-holddown: \fI<seconds>
+Instruct the \fBauto\-trust\-anchor\-file\fR 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.
+.TP
+.B del\-holddown: \fI<seconds>
+Instruct the \fBauto\-trust\-anchor\-file\fR 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.
+.TP
+.B keep\-missing: \fI<seconds>
+Instruct the \fBauto\-trust\-anchor\-file\fR 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.
+.TP
+.B key\-cache\-size: \fI<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 kilobytes, megabytes
+or gigabytes (1024*1024 bytes in a megabyte).
+.TP
+.B key\-cache\-slabs: \fI<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.
+.TP
+.B neg\-cache\-size: \fI<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).
+.TP
+.B local\-zone: \fI<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, typetransparent, 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.
+.IP
+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.
+.TP 10
+\h'5'\fIdeny\fR
+Do not send an answer, drop the query.
+If there is a match from local data, the query is answered.
+.TP 10
+\h'5'\fIrefuse\fR
+Send an error message reply, with rcode REFUSED.
+If there is a match from local data, the query is answered.
+.TP 10
+\h'5'\fIstatic\fR
+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.
+.TP 10
+\h'5'\fItransparent\fR
+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.
+.TP 10
+\h'5'\fItypetransparent\fR
+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.
+.TP 10
+\h'5'\fIredirect\fR
+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.example.com and www.foo.example.com are redirected, so
+that users with web browsers cannot access sites with suffix example.com.
+.TP 10
+\h'5'\fInodefault\fR
+Used to turn off default contents for AS112 zones. The other types
+also turn off default contents for the zone. The 'nodefault' option
+has no other effect than turning off default contents for the
+given zone.
+.P
+The default zones are localhost, reverse 127.0.0.1 and ::1, 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 contents.
+.TP 10
+\h'5'\fIlocalhost\fR
+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:
+.nf
+local\-zone: "localhost." static
+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"
+.fi
+.TP 10
+\h'5'\fIreverse IPv4 loopback\fR
+Default content:
+.nf
+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."
+.fi
+.TP 10
+\h'5'\fIreverse IPv6 loopback\fR
+Default content:
+.nf
+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."
+.fi
+.TP 10
+\h'5'\fIreverse RFC1918 local use zones\fR
+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 \fBlocal\-zone:\fR is set static and as \fBlocal\-data:\fR SOA and NS
+records are provided.
+.TP 10
+\h'5'\fIreverse RFC3330 IP4 this, link\-local, testnet and broadcast\fR
+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.
+.TP 10
+\h'5'\fIreverse RFC4291 IP6 unspecified\fR
+Reverse data for zone
+.nf
+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.
+.fi
+.TP 10
+\h'5'\fIreverse RFC4193 IPv6 Locally Assigned Local Addresses\fR
+Reverse data for zone D.F.ip6.arpa.
+.TP 10
+\h'5'\fIreverse RFC4291 IPv6 Link Local Addresses\fR
+Reverse data for zones 8.E.F.ip6.arpa to B.E.F.ip6.arpa.
+.TP 10
+\h'5'\fIreverse IPv6 Example Prefix\fR
+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:
+.nf
+ local\-zone: 8.B.D.0.1.0.0.2.ip6.arpa. nodefault
+.fi
+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.
+.\" End of local-zone listing.
+.TP 5
+.B local\-data: \fI"<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 determines
+further processing. If local\-data is configured that is not a subdomain of
+a local\-zone, a transparent local\-zone is configured.
+For record types such as TXT, use single quotes, as in
+local\-data: 'example. TXT "text"'.
+.IP
+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.
+.TP 5
+.B local\-data\-ptr: \fI"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"
+.SS "Remote Control Options"
+In the
+.B remote\-control:
+clause are the declarations for the remote control facility. If this is
+enabled, the \fIunbound\-control\fR(8) utility can be used to send
+commands to the running unbound server. The server uses these clauses
+to setup SSLv3 / TLSv1 security for the connection. The
+\fIunbound\-control\fR(8) utility also reads the \fBremote\-control\fR
+section for options. To setup the correct self\-signed certificates use the
+\fIunbound\-control\-setup\fR(8) utility.
+.TP 5
+.B control\-enable: \fI<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.
+.TP 5
+.B control\-interface: <ip address>
+Give IPv4 or IPv6 addresses 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.
+.TP 5
+.B control\-port: <port number>
+The port number to listen on for control commands, default is 8953.
+If you change this port number, and permissions have been dropped,
+a reload is not sufficient to open the port again, you must then restart.
+.TP 5
+.B server\-key\-file: "<private key file>"
+Path to the server private key, by default unbound_server.key.
+This file is generated by the \fIunbound\-control\-setup\fR utility.
+This file is used by the unbound server, but not by \fIunbound\-control\fR.
+.TP 5
+.B server\-cert\-file: "<certificate file.pem>"
+Path to the server self signed certificate, by default unbound_server.pem.
+This file is generated by the \fIunbound\-control\-setup\fR utility.
+This file is used by the unbound server, and also by \fIunbound\-control\fR.
+.TP 5
+.B control\-key\-file: "<private key file>"
+Path to the control client private key, by default unbound_control.key.
+This file is generated by the \fIunbound\-control\-setup\fR utility.
+This file is used by \fIunbound\-control\fR.
+.TP 5
+.B control\-cert\-file: "<certificate file.pem>"
+Path to the control client certificate, by default unbound_control.pem.
+This certificate has to be signed with the server certificate.
+This file is generated by the \fIunbound\-control\-setup\fR utility.
+This file is used by \fIunbound\-control\fR.
+.SS "Stub Zone Options"
+.LP
+There may be multiple
+.B stub\-zone:
+clauses. Each with a name: and zero or more hostnames or IP addresses.
+For the stub zone this list of nameservers is used. Class IN is assumed.
+The servers should be authority servers, not recursors; unbound performs
+the recursive processing itself for stub zones.
+.P
+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
+.B stub\-addr:
+<ip address of host[@port]>.
+The unbound resolver can then access the data, without referring to the
+public internet for it.
+.P
+This setup allows DNSSEC signed zones to be served by that
+authoritative 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.
+.TP
+.B name: \fI<domain name>
+Name of the stub zone.
+.TP
+.B stub\-host: \fI<domain name>
+Name of stub zone nameserver. Is itself resolved before it is used.
+.TP
+.B stub\-addr: \fI<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.
+.TP
+.B stub\-prime: \fI<yes or no>
+This option is by default off. 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.
+.TP
+.B stub\-first: \fI<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.
+.SS "Forward Zone Options"
+.LP
+There may be multiple
+.B forward\-zone:
+clauses. Each with a \fBname:\fR 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 \fBforward\-host:\fR and
+\fBforward\-addr:\fR 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.
+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).
+.TP
+.B name: \fI<domain name>
+Name of the forward zone.
+.TP
+.B forward\-host: \fI<domain name>
+Name of server to forward to. Is itself resolved before it is used.
+.TP
+.B forward\-addr: \fI<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.
+.TP
+.B forward\-first: \fI<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.
+.SS "Python Module Options"
+.LP
+The
+.B python:
+clause gives the settings for the \fIpython\fR(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 \fBmodule\-config:\fR option
+(usually first, or between the validator and iterator).
+.TP
+.B python\-script: \fI<python file>\fR
+The script file to load.
+.SH "MEMORY CONTROL EXAMPLE"
+In the example config settings below memory usage is reduced. Some service
+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 service,
+which on BSD\-32bit tops out at 30\-40 Mb after heavy usage.
+.P
+.nf
+# 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"
+.fi
+.SH "FILES"
+.TP
+.I @UNBOUND_RUN_DIR@
+default unbound working directory.
+.TP
+.I @UNBOUND_CHROOT_DIR@
+default
+\fIchroot\fR(2)
+location.
+.TP
+.I @ub_conf_file@
+unbound configuration file.
+.TP
+.I @UNBOUND_PIDFILE@
+default unbound pidfile with process ID of the running daemon.
+.TP
+.I unbound.log
+unbound log file. default is to log to
+\fIsyslog\fR(3).
+.SH "SEE ALSO"
+\fIunbound\fR(8),
+\fIunbound\-checkconf\fR(8).
+.SH "AUTHORS"
+.B Unbound
+was written by NLnet Labs. Please see CREDITS file
+in the distribution for further details.
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