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unbound.conf(5) unbound 1.5.10 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 at- tributes 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 ig- nored 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/un- bound.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 ex- tensive 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 in- cluded files works, relative pathnames for the included names work if the directory where the daemon is started equals its chroot/working di- rectory 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 easy 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 ad- dress taken from the netblock to counter spoofing. Requires the IPv6 netblock to be routed to the host running unbound, and re- quires 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 be- ing selected for queries. On Linux you need these two commands 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 in- creases 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 au- thoritative servers are done. For larger installations increas- ing 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. De- fault is 4096 which is RFC recommended. If you have fragmenta- tion 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). 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 re- duced 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 al- lowed time. This protects against denial of service by slow queries or high query rates. Default 200 milliseconds. The ef- fect 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. 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: re- source temporarily unavailable' can get logged, the buffer over- run 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. 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 no. 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- tant 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. ip-freebind: _yes or no_ If yes, then use IP_FREEBIND socket option on sockets where un- bound 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 avail- able. 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. De- fault is 86400 seconds (1 day). If the maximum kicks in, re- sponses 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. De- fault 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. 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 be- tween 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 in- ternet 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 re- sponds 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). De- fault is system default MSS determined by interface MTU and ne- gotiation 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 in- terface MTU and negotiation between Unbound and other servers. tcp-upstream: _yes or no_ Enable or disable whether the upstream queries use TCP only for transport. Default is no. Useful in tunneling scenarios. ssl-upstream: _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 ssl-service-key). ssl-service-key: _file_ If enabled, the server provider SSL service on its TCP sockets. The clients have to use ssl-upstream: yes. The file is the pri- vate 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 er- rors, this service is best run with a different port: config or @port suffixes in the interface config. ssl-service-pem: _file_ The public key certificate pem file for the ssl service. De- fault is "", turned off. ssl-port: _number_ The port number on which to provide TCP SSL service, default 853, only interfaces configured with that port number as @number get the SSL service. do-daemonize: _yes or no_ Enable or disable whether the unbound server forks into the background as a daemon. Default is yes. access-control: _IP netblock_ _action_ The netblock is given as an IP4 or IP6 address with /size ap- pended for a classless network block. The action can be deny, refuse, allow, 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 RE- FUSED 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 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 ac- cess 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 ac- cess-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 ac- tion is the first tag match between access-control-tag and lo- cal-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. 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 di- rectory, 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 al- lows 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 en- tropy) from inside the chroot. If given a chroot is done to the given directory. The default is "/var/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 re- quires privileges, then a reload will fail; a restart is needed. directory: _directory_ Sets the working directory for the program. Default is "/var/un- bound". 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 statements then those includes can be relative to the working directory. 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 "un- bound". The logfile setting is overridden when use-syslog is turned on. The default is to log to syslog. 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 '?'. pidfile: _filename_ The process id is written to the file. Default is "/var/un- bound/unbound.pid". So, kill -HUP `cat /var/unbound/unbound.pid` triggers a reload, kill -TERM `cat /var/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 de- fault 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. 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 un- bound 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 le- gal protocol wise to send these, and could be necessary for op- eration if TSIG or EDNS payload is very large. harden-glue: _yes or no_ Will trust glue only if it is within the servers authority. De- fault 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 at- tack that disables security for a zone. Default is on. harden-below-nxdomain: _yes or no_ From draft-vixie-dnsext-resimprove, returns nxdomain to queries for a name below another name that is already known to be nxdo- main. 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. Currently, draft-ietf-dnsop-nxdomain-cut promotes this technique. 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 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 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 at- tempts. 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 an- swers, 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 en- hance privacy. Only sent minimum required labels of the QNAME and set QTYPE to NS when possible. Best effort approach, full QNAME and original QTYPE will be sent when upstream replies with a RCODE other than NOERROR. Default is off. private-address: _IP address or subnet_ Give IPv4 of IPv6 addresses or classless subnets. These are ad- dresses on your private network, and are not allowed to be re- turned for public internet names. Any occurrence of such ad- dresses 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 en- abled 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 ad- dresses. 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 ac- tion is to clear the rrset and message caches, hopefully flush- ing away any poison. A value of 10 million is suggested. De- fault 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 re- quests. It does use a little more CPU. Also if the cache is set to 0, it is no use. Default is no. 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 no, because the DNS protocol RFCs mandate these sections, and the additional content could be of use and save roundtrips for clients. 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 an- chor 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 en- tries can appear in the file. The format of the file is the standard DNS Zone file format. Default is "", or no trust an- chor 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). trust-anchor: _"Resource Record"_ A DS or DNSKEY RR for a key to use for validation. Multiple en- tries 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 ig- nored. 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-an- chor-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. 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 ig- nored towards the domain name. So a trust anchor above the do- main 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 do- mains that are treated as if unsigned. If you set trust anchors for the domain they override this setting (and the domain is se- cured). 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 in- stead. 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 af- fected. 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. Re- gardless 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". 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: _yesno_ 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: _yesno_ 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, al- ways_nxdomain, and are explained below. After that the default settings are listed. Use local-data: to enter data into the lo- cal 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 re- solved normally. If the query is for a name given in local- data 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 de- fault. 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 an- swers 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 lo- cal-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. The client IP address (@portnumber) is printed to the logfile. The log message is: timestamp, unbound-pid, info: zonename inform IP@port query- name type class. This option can be used for normal resolu- tion, 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. 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 ex- actly that zone, if you want to use a subzone, use transpar- ent. The default zones are localhost, reverse 127.0.0.1 and ::1, the onion 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 'node- fault' type. Below is a list of the default zone contents. 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." 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" 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" 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 lo- cal-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 lo- cal-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 be- low. 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 ex- perimental 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 ex- ceeded. 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_ 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. ratelimit-below-domain: _domain_ _number qps_ 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. 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 SSLv3 / 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 un- bound-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. 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 ef- fect. control-use-cert: _yes or no_ Whether to require certificate authentication of control connec- tions. The default is "yes". This should not be changed unless there are other mechanisms in place to prevent untrusted users from accessing the remote control interface. 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 un- bound_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 it- self 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 au- thoritative 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 lo- cal-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 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. 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. 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. A forward-zone entry with name "." and a for- ward-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. 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. 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). 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 en- abled. 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. 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 /var/unbound default unbound working directory. /var/unbound default chroot(2) location. /var/unbound/unbound.conf unbound configuration file. /var/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 Sep 27, 2016 unbound.conf(5)
NAME | SYNOPSIS | DESCRIPTION | EXAMPLE | FILE FORMAT | MEMORY CONTROL EXAMPLE | FILES | SEE ALSO | AUTHORS
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