NAME¶
unbound.conf - Unbound configuration file.
SYNOPSIS¶
unbound.conf
DESCRIPTION¶
unbound.conf is used to configure
unbound(8). The file format has
attributes and values. Some attributes have attributes inside them. The
notation is: attribute: value.
Comments start with # and last to the end of line. Empty lines are ignored as is
whitespace at the beginning of a line.
The utility
unbound-checkconf(8) can be used to check unbound.conf prior
to usage.
EXAMPLE¶
An example config file is shown below. Copy this to /etc/unbound/unbound.conf
and start the server with:
$ unbound -c /etc/unbound/unbound.conf
Most settings are the defaults. Stop the server with:
$ kill `cat /etc/unbound/unbound.pid`
Below is a minimal config file. The source distribution contains an extensive
example.conf file with all the options.
# unbound.conf(5) config file for unbound(8).
server:
directory: "/etc/unbound"
username: unbound
# make sure unbound can access entropy from inside the chroot.
# e.g. on linux the use these commands (on BSD, devfs(8) is used):
# mount --bind -n /dev/random /etc/unbound/dev/random
# and mount --bind -n /dev/log /etc/unbound/dev/log
chroot: "/etc/unbound"
# logfile: "/etc/unbound/unbound.log" #uncomment to use logfile.
pidfile: "/etc/unbound/unbound.pid"
# verbosity: 1 # uncomment and increase to get more logging.
# listen on all interfaces, answer queries from the local subnet.
interface: 0.0.0.0
interface: ::0
access-control: 10.0.0.0/8 allow
access-control: 2001:DB8::/64 allow
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
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 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 commandline, 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 statistics. Default is
no.
- extended-statistics: <yes or no>
- If enabled, extended statistics are printed from
unbound-control(8). Default is off, because keeping track of more
statistics 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 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 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 interfaces. If none are given the
default (all) is used. You can specify the same interfaces in
interface: and outgoing-interface: lines, the interfaces are
then used for both purposes. Outgoing queries are sent via a random
outgoing interface to counter spoofing.
- If an IPv6 netblock is specified instead of an individual IPv6 address,
outgoing UDP queries will use a randomised source address taken from the
netblock to counter spoofing. Requires the IPv6 netblock to be routed to
the host running unbound, and requires OS support for unprivileged
non-local binds (currently only supported on Linux). Several netblocks may
be specified with multiple outgoing-interface: options, but do not
specify both an individual IPv6 address and an IPv6 netblock, or the
randomisation will be compromised. Consider combining with prefer-ip6:
yes to increase the likelihood of IPv6 nameservers being 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 compile options. Larger
numbers need extra resources from the operating system. For performance a
very large value is best, use libevent to make this possible.
- outgoing-port-permit: <port number or range>
- Permit unbound to open this port or range of ports for use to send
queries. A larger number of permitted outgoing ports increases resilience
against spoofing attempts. Make sure these ports are not needed by other
daemons. By default only ports above 1024 that have not been assigned by
IANA are used. Give a port number or a range of the form
"low-high", without spaces.
- The outgoing-port-permit and outgoing-port-avoid statements
are processed in the line order of the config file, adding the 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.
- outgoing-port-avoid: <port number or range>
- Do not permit unbound to open this port or range of ports for use to send
queries. Use this to make sure unbound does not grab a port that another
daemon needs. The port is avoided on all outgoing interfaces, both IP4 and
IP6. By default only ports above 1024 that have not been assigned by IANA
are used. Give a port number or a range of the form "low-high",
without spaces.
- outgoing-num-tcp: <number>
- Number of outgoing TCP buffers to allocate per thread. Default is 10. If
set to 0, or if do-tcp is "no", no TCP queries to authoritative
servers are done. For larger installations increasing this value is a good
idea.
- incoming-num-tcp: <number>
- Number of incoming TCP buffers to allocate per thread. Default is 10. If
set to 0, or if do-tcp is "no", no TCP queries from clients are
accepted. For larger installations increasing this value is a good
idea.
- edns-buffer-size: <number>
- Number of bytes size to advertise as the EDNS reassembly buffer size. This
is the value put into datagrams over UDP towards peers. The actual buffer
size is determined by msg-buffer-size (both for TCP and UDP). Do not set
higher than that value. Default is 4096 which is RFC recommended. If you
have 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).
- max-udp-size: <number>
- Maximum UDP response size (not applied to TCP response). 65536 disables
the udp response size maximum, and uses the choice from the client,
always. Suggested values are 512 to 4096. Default is 4096.
- msg-buffer-size: <number>
- Number of bytes size of the message buffers. Default is 65552 bytes,
enough for 64 Kb packets, the maximum DNS message size. No message larger
than this can be sent or received. Can be reduced to use less memory, but
some requests for DNS data, such as for huge resource records, will result
in a SERVFAIL reply to the client.
- msg-cache-size: <number>
- Number of bytes size of the message cache. Default is 4 megabytes. A plain
number is in bytes, append 'k', 'm' or 'g' for kilobytes, megabytes or
gigabytes (1024*1024 bytes in a megabyte).
- msg-cache-slabs: <number>
- Number of slabs in the message cache. Slabs reduce lock contention 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 simultaneously. If
more queries arrive that need servicing, and no queries can be jostled out
(see jostle-timeout), then the queries are dropped. This forces the
client to resend after a timeout; allowing the server time to work on the
existing queries. Default depends on compile options, 512 or 1024.
- jostle-timeout: <msec>
- Timeout used when the server is very busy. Set to a value that usually
results in one roundtrip to the authority servers. If too many queries
arrive, then 50% of the queries are allowed to run to completion, and the
other 50% are replaced with the new incoming query if they have already
spent more than their allowed time. This protects against denial of
service by slow queries or high query rates. Default 200 milliseconds. The
effect is that the qps for long-lasting queries is about
(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.
- 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 packets, 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 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.
- so-sndbuf: <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.
- 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 available 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-existant 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 permissions
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 unbound is
listening to incoming traffic. Default no. Allows you to bind to IP
addresses that are nonlocal or do not exist, like when the network
interface or IP address is down. Exists only on Linux, where the similar
ip-transparent option is also available.
- rrset-cache-size: <number>
- Number of bytes size of the RRset cache. Default is 4 megabytes. A plain
number is in bytes, append 'k', 'm' or 'g' for kilobytes, megabytes or
gigabytes (1024*1024 bytes in a megabyte).
- rrset-cache-slabs: <number>
- Number of slabs in the RRset cache. Slabs reduce lock contention by
threads. Must be set to a power of 2.
- cache-max-ttl: <seconds>
- Time to live maximum for RRsets and messages in the cache. Default is
86400 seconds (1 day). If the maximum kicks in, responses to clients still
get decrementing TTLs based on the original (larger) values. When the
internal TTL expires, the cache item has expired. Can be set lower to
force the resolver to query for data often, and not trust (very large) TTL
values.
- cache-min-ttl: <seconds>
- Time to live minimum for RRsets and messages in the cache. Default is 0.
If the minimum kicks in, the data is cached for longer than the domain
owner intended, and thus less queries are made to look up the data. Zero
makes sure the data in the cache is as the domain owner intended, higher
values, especially more than an hour or so, can lead to trouble as the
data in the cache does not match up with the actual data any more.
- cache-max-negative-ttl: <seconds>
- Time to live maximum for negative responses, these have a SOA in the
authority section that is limited in time. Default is 3600.
- infra-host-ttl: <seconds>
- Time to live for entries in the host cache. The host cache contains
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 infrastructure
cache. Default is 50 milliseconds. Increase this value if using forwarders
needing more time to do recursive name resolution.
- define-tag: <"list of tags">
- Define the tags that can be used with local-zone and access-control.
Enclose the list between quotes ("") and put spaces between
tags.
- do-ip4: <yes or no>
- Enable or disable whether ip4 queries are answered or issued. Default is
yes.
- do-ip6: <yes or no>
- Enable or disable whether ip6 queries are answered or issued. Default is
yes. If disabled, queries are not answered on IPv6, and queries are not
sent on IPv6 to the internet nameservers. With this option you can disable
the ipv6 transport for sending DNS traffic, it does not impact the
contents of the DNS traffic, which may have ip4 and ip6 addresses in
it.
- prefer-ip6: <yes or no>
- If enabled, prefer IPv6 transport for sending DNS queries to internet
nameservers. Default is no.
- do-udp: <yes or no>
- Enable or disable whether UDP queries are answered or issued. Default is
yes.
- do-tcp: <yes or no>
- Enable or disable whether TCP queries are answered or issued. Default is
yes.
- tcp-mss: <number>
- Maximum segment size (MSS) of TCP socket on which the server responds to
queries. Value lower than common MSS on Ethernet (1220 for example) will
address path MTU problem. Note that not all platform supports socket
option to set MSS (TCP_MAXSEG). Default is system default MSS determined
by interface MTU and negotiation between server and client.
- outgoing-tcp-mss: <number>
- Maximum segment size (MSS) of TCP socket for outgoing queries (from
Unbound to other servers). Value lower than common MSS on Ethernet (1220
for example) will address path MTU problem. Note that not all platform
supports socket option to set MSS (TCP_MAXSEG). Default is system default
MSS determined by interface MTU and negotiation between Unbound and other
servers.
- tcp-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 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
port: config or @port suffixes in the interface
config.
- ssl-service-pem: <file>
- The public key certificate pem file for the ssl service. Default 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 appended 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 REFUSED
error message back.
- The action allow gives access to clients from that netblock. It
gives only access for recursion clients (which is what almost all clients
need). Nonrecursive queries are refused.
- The allow action does allow nonrecursive queries to access the
local-data that is configured. The reason is that this does not involve
the unbound server recursive lookup algorithm, and static data is served
in the reply. This supports normal operations 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 policy, and
dropping may result in (possibly excessive) retried queries.
- The deny_non_local and refuse_non_local settings are for hosts that are
only allowed to query for the authoritative local-data, they are not
allowed full recursion but only the static data. With deny_non_local,
messages that are disallowed are dropped, with refuse_non_local they
receive error code REFUSED.
- access-control-tag: <IP netblock> <"list of
tags">
- Assign tags to access-control elements. Clients using this access control
element use localzones that are tagged with one of these tags. Tags must
be defined in define-tags. Enclose list of tags in quotes
("") and put spaces between tags. If access-control-tag is
configured for a netblock that does not have an access-control, an
access-control element with action allow is configured for this
netblock.
- access-control-tag-action: <IP netblock> <tag>
<action>
- Set action for particular tag for given access control element. If you
have multiple tag values, the tag used to lookup the action is the first
tag match between access-control-tag and local-zone-tag where
"first" comes from the order of the define-tag values.
- access-control-tag-data: <IP netblock> <tag>
<"resource record string">
- Set redirect data for particular tag for given access control
element.
- access-control-view: <IP netblock> <view
name>
- Set view for given access control element.
- chroot: <directory>
- If chroot is enabled, you should pass the configfile (from the
commandline) as a full path from the original root. After the chroot has
been performed the now defunct portion of the config file path is removed
to be able to reread the config after a reload.
- All other file paths (working dir, logfile, roothints, and key files) can
be specified in several ways: as an absolute path relative to the new
root, as a relative path to the working directory, or as an absolute path
relative to the original root. In the last case the path is adjusted to
remove the unused portion.
- 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.
- Additionally, unbound may need to access /dev/random (for entropy) from
inside the chroot.
- If given a chroot is done to the given directory. The default is
"/etc/unbound". If you give "" no chroot is
performed.
- username: <name>
- If given, after binding the port the user privileges are dropped. Default
is "unbound". If you give username: "" no user change
is performed.
- If this user is not capable of binding the port, reloads (by signal HUP)
will still retain the opened ports. If you change the port number in the
config file, and that new port number requires privileges, then a reload
will fail; a restart is needed.
- directory: <directory>
- Sets the working directory for the program. Default is
"/etc/unbound". On Windows the string "%EXECUTABLE%"
tries to change to the directory that unbound.exe resides in. If you give
a server: directory: dir before include: file statements then those
includes can be relative to the working directory.
- logfile: <filename>
- If "" is given, logging goes to stderr, or nowhere once
daemonized. 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 syslog(3).
The log facility LOG_DAEMON is used, with identity "unbound".
The logfile setting is overridden when use-syslog is turned on. The
default is to log to syslog.
- log-identity: <string>
- If "" is given (default), then the name of the executable,
usually "unbound" is used to report to the log. Enter a string
to override it with that, which is useful on systems that run more than
one instance of unbound, with different configurations, so that the logs
can be easily distinguished against.
- log-time-ascii: <yes or no>
- Sets logfile lines to use a timestamp in UTC ascii. Default is no, which
prints the seconds since 1970 in brackets. No effect if using syslog, in
that case syslog formats the timestamp printed into the log files.
- log-queries: <yes or no>
- Prints one line per query to the log, with the log timestamp and IP
address, name, type and class. Default is no. Note that it takes time to
print these lines which makes the server (significantly) slower. Odd
(nonprintable) characters in names are printed as '?'.
- pidfile: <filename>
- The process id is written to the file. Default is
"/run/unbound.pid". So,
kill -HUP `cat /run/unbound.pid`
triggers a reload,
kill -TERM `cat /run/unbound.pid`
gracefully terminates.
- root-hints: <filename>
- Read the root hints from this file. Default is nothing, using builtin
hints for the IN class. The file has the format of zone files, with root
nameserver names and addresses only. The default may become outdated, when
servers change, therefore it is good practice to use a root-hints
file.
- hide-identity: <yes or no>
- If enabled id.server and hostname.bind queries are refused.
- identity: <string>
- Set the identity to report. If set to "", the default, then the
hostname of the server is returned.
- hide-version: <yes or no>
- If enabled version.server and version.bind queries are refused.
- version: <string>
- Set the version to report. If set to "", the default, then the
package version is returned.
- 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
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.
- harden-short-bufsize: <yes or no>
- Very small EDNS buffer sizes from queries are ignored. Default is off,
since it is legal protocol wise to send these, and unbound tries to give
very small answers to these queries, where possible.
- harden-large-queries: <yes or no>
- Very large queries are ignored. Default is off, since it is legal protocol
wise to send these, and could be necessary for operation if TSIG or EDNS
payload is very large.
- harden-glue: <yes or no>
- Will trust glue only if it is within the servers authority. Default is
on.
- harden-dnssec-stripped: <yes or no>
- Require DNSSEC data for trust-anchored zones, if such data is absent, the
zone becomes bogus. If turned off, and no DNSSEC data is received (or the
DNSKEY data fails to validate), then the zone is made insecure, this
behaves like there is no trust anchor. You could turn this off if you are
sometimes behind an intrusive firewall (of some sort) that removes DNSSEC
data from packets, or a zone changes from signed to unsigned to badly
signed often. If turned off you run the risk of a downgrade attack that
disables security for a zone. Default is on.
- harden-below-nxdomain: <yes or no>
- From RFC 8020 (with title "NXDOMAIN: There Really Is Nothing
Underneath"), returns nxdomain to queries for a name below another
name that is already known to be nxdomain. DNSSEC 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. The nxdomain must be secure, this means
nsec3 with optout is insufficient.
- harden-referral-path: <yes or no>
- Harden the referral path by performing additional queries for
infrastructure data. Validates the replies if trust anchors are configured
and the zones are signed. This enforces DNSSEC 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.
- harden-algo-downgrade: <yes or no>
- Harden against algorithm downgrade when multiple algorithms are advertised
in the DS record. If no, allows the weakest algorithm to validate the
zone. Default is no. Zone signers must produce zones that allow this
feature to work, but sometimes they do not, and turning this option off
avoids that validation failure.
- use-caps-for-id: <yes or no>
- Use 0x20-encoded random bits in the query to foil spoof attempts. This
perturbs the lowercase and uppercase of query names sent to authority
servers and checks if the reply still has the correct casing. Disabled by
default. This feature is an experimental implementation of draft
dns-0x20.
- caps-whitelist: <domain>
- Whitelist the domain so that it does not receive caps-for-id perturbed
queries. For domains that do not support 0x20 and also fail with fallback
because they keep sending different answers, like some load balancers. Can
be given multiple times, for different domains.
- qname-minimisation: <yes or no>
- Send minimum amount of information to upstream servers to enhance privacy.
Only sent minimum required labels of the QNAME and set QTYPE to NS when
possible. Best effort approach; full QNAME and original QTYPE will be sent
when upstream replies with a RCODE other than NOERROR, except when
receiving NXDOMAIN from a DNSSEC signed zone. Default is off.
- qname-minimisation-strict: <yes or no>
- QNAME minimisation in strict mode. Do not fall-back to sending full QNAME
to potentially broken nameservers. A lot of domains will not be resolvable
when this option in enabled. Only use if you know what you are doing. This
option only has effect when qname-minimisation is enabled. Default is
off.
- private-address: <IP address or subnet>
- Give IPv4 of IPv6 addresses or classless subnets. These are addresses on
your private network, and are not allowed to be returned for public
internet names. Any occurrence of such addresses are removed from DNS
answers. Additionally, the DNSSEC validator may mark the answers bogus.
This protects against so-called DNS Rebinding, where a user browser is
turned into a network proxy, allowing remote access through the browser to
other parts of your private network. Some names can be allowed to contain
your private addresses, by default all the local-data that you
configured is allowed to, and you can specify additional names using
private-domain. No private addresses are enabled by default. We
consider to enable this for the RFC1918 private IP address space by
default in later releases. That would enable private addresses for
10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 169.254.0.0/16 fd00::/8 and
fe80::/10, since the RFC standards say these addresses should not be
visible on the public internet. Turning on 127.0.0.0/8 would hinder many
spamblocklists as they use that. Adding ::ffff:0:0/96 stops IPv4-mapped
IPv6 addresses from bypassing the filter.
- private-domain: <domain name>
- Allow this domain, and all its subdomains to contain private addresses.
Give multiple times to allow multiple domain names to contain private
addresses. Default is none.
- unwanted-reply-threshold: <number>
- If set, a total number of unwanted replies is kept track of in every
thread. When it reaches the threshold, a defensive action is taken and a
warning is printed to the log. The defensive action is to clear the rrset
and message caches, hopefully flushing away any poison. A value of 10
million is suggested. Default is 0 (turned off).
- do-not-query-address: <IP address>
- Do not query the given IP address. Can be IP4 or IP6. Append /num to
indicate a classless delegation netblock, for example like 10.2.3.4/24 or
2001::11/64.
- do-not-query-localhost: <yes or no>
- If yes, localhost is added to the do-not-query-address entries, both IP6
::1 and IP4 127.0.0.1/8. If no, then localhost can be used to send queries
to. Default is yes.
- prefetch: <yes or no>
- If yes, message cache elements are prefetched before they expire to keep
the cache up to date. Default is no. Turning it on gives about 10 percent
more traffic and load on the machine, but popular items do not expire from
the cache.
- prefetch-key: <yes or no>
- If yes, fetch the DNSKEYs earlier in the validation process, when a DS
record is encountered. This lowers the latency of requests. It does use a
little more CPU. Also if the cache is set to 0, it is no use. Default is
no.
- rrset-roundrobin: <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.
- 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 unexpectedly missing. The
validator will insist in RRSIGs for DNSSEC signed domains regardless of
this setting, if a trust anchor is loaded.
- module-config: <"module names">
- Module configuration, a list of module names separated by 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.
- trust-anchor-file: <filename>
- File with trusted keys for validation. Both DS and DNSKEY entries can
appear in the file. The format of the file is the standard DNS Zone file
format. Default is "", or no trust anchor file.
- auto-trust-anchor-file: <filename>
- File with trust anchor for one zone, which is tracked with RFC5011 probes.
The probes are several times per month, thus the machine must be online
frequently. The initial file can be one with contents as described in
trust-anchor-file. The file is written to when the anchor is
updated, so the unbound user must have write permission. Write permission
to the file, but also to the directory it is in (to create a temporary
file, which is necessary to deal with filesystem full events).
- trust-anchor: <"Resource Record">
- A DS or DNSKEY RR for a key to use for validation. Multiple entries can be
given to specify multiple trusted keys, in 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.
- trusted-keys-file: <filename>
- File with trusted keys for validation. Specify more than one file with
several entries, one file per entry. Like trust-anchor-file but has
a different file format. Format is BIND-9 style format, the trusted-keys {
name flag proto algo "key"; }; clauses are read. It is possible
to use wildcards with this statement, the wildcard is expanded on start
and on reload.
- 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 parent zone (many top level
zones are signed). File with trusted keys for DLV (DNSSEC Lookaside
Validation). Both DS and DNSKEY entries can be used in the file, in the
same format as for trust-anchor-file: statements. Only one DLV can
be configured, more would be slow. The DLV configured is used as a root
trusted DLV, this means that it is a lookaside for the root. Default is
"", or no dlv anchor file. DLV is going to be decommissioned.
Please do not use it any more.
- dlv-anchor: <"Resource Record">
- Much like trust-anchor, this is a DLV anchor with the DS or DNSKEY inline.
DLV is going to be decommissioned. Please do not use it any more.
- domain-insecure: <domain name>
- Sets domain name to be insecure, DNSSEC chain of trust is ignored towards
the domain name. So a trust anchor above the domain name can not make the
domain secure with a DS record, such a DS record is then ignored. Also
keys from DLV are ignored for the domain. Can be given multiple times to
specify multiple domains that are treated as if unsigned. If you set trust
anchors for the domain they override this setting (and the domain is
secured).
- This can be useful if you want to make sure a trust anchor for external
lookups does not affect an (unsigned) internal domain. A DS record
externally can create validation failures for that internal domain.
- val-override-date: <rrsig-style date spec>
- Default is "" or "0", which disables this debugging
feature. If enabled by giving a RRSIG style date, that date is used for
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.
- 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 (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.
- 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 (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.
- val-bogus-ttl: <number>
- The time to live for bogus data. This is data that has failed validation;
due to invalid signatures or other checks. The TTL from that data cannot
be trusted, and this value is used instead. The value is in seconds,
default 60. The time interval prevents repeated revalidation of bogus
data.
- val-clean-additional: <yes or no>
- Instruct the validator to remove data from the additional 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 potentially bad data in the additional section.
- val-log-level: <number>
- Have the validator print validation failures to the log. Regardless of the
verbosity setting. Default is 0, off. At 1, for every user query that
fails a line is printed to the logs. This way you can monitor what happens
with validation. Use a diagnosis tool, such as dig or drill, to find out
why validation is failing for these queries. At 2, not only the query that
failed is printed but also the reason why unbound thought it was wrong and
which server sent the faulty data.
- val-permissive-mode: <yes or no>
- Instruct the validator to mark bogus messages as indeterminate. The
security checks are performed, but if the result is bogus (failed
security), the reply is not withheld from the client with SERVFAIL as
usual. The client receives the bogus data. For messages that are found to
be secure the AD bit is set in replies. Also logging is performed as for
full validation. The default value is "no".
- ignore-cd-flag: <yes or no>
- Instruct unbound to ignore the CD flag from clients and refuse to return
bogus answers to them. Thus, the CD (Checking 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".
- serve-expired: <yes or no>
- If enabled, unbound attempts to serve old responses from cache with a TTL
of 0 in the response without waiting for the actual resolution to finish.
The actual resolution answer ends up in the cache later on. Default is
"no".
- 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 kilobytes, 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 network 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 private 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, typetransparent, inform, inform_deny,
always_transparent, always_refuse, always_nxdomain, and are explained
below. After that the default settings are listed. Use local-data: to
enter data into the local zone. Answers for local zones are authoritative
DNS answers. By default the zones are class IN.
- If you need more complicated authoritative data, with referrals,
wildcards, CNAME/DNAME support, or DNSSEC authoritative service, setup a
stub-zone for it as detailed in the stub zone section below.
- deny
- Do not send an answer, drop the query. If there is a match from local
data, the query is answered.
- refuse
- Send an error message reply, with rcode REFUSED. If there is a match from
local data, the query is answered.
- static
- If there is a match from local data, the query is answered. Otherwise, the
query is answered with nodata or nxdomain. For a negative answer a SOA is
included in the answer if present as local-data for the zone apex
domain.
- transparent
- If there is a match from local data, the query is answered. Otherwise if
the query has a different name, the query is resolved normally. If the
query is for a name given in localdata but no such type of data is given
in localdata, then a noerror nodata answer is returned. If no local-zone
is given local-data causes a transparent zone to be created by
default.
- typetransparent
- If there is a match from local data, the query is answered. If the query
is for a different name, or for the same name but for a different type,
the query is resolved normally. So, similar to transparent but types that
are not listed in local data are resolved normally, so if an A record is
in the local data that does not cause a nodata reply for AAAA
queries.
- redirect
- The query is answered from the local data for the zone name. There may be
no local data beneath the zone name. This answers queries for the zone,
and all subdomains of the zone with the local data for the zone. It can be
used to redirect a domain to return a different address record to the end
user, with local-zone: "example.com." redirect and local-data:
"example.com. A 127.0.0.1" queries for www.example.com and
www.foo.example.com are redirected, so that users with web browsers cannot
access sites with suffix example.com.
- inform
- The query is answered normally, same as transparent. The client IP address
(@portnumber) is printed to the logfile. The log message is: timestamp,
unbound-pid, info: zonename inform IP@port queryname type class. This
option can be used for normal resolution, but machines looking up infected
names are logged, eg. to run antivirus on them.
- inform_deny
- The query is dropped, like 'deny', and logged, like 'inform'. Ie. find
infected machines without answering the queries.
- always_transparent
- Like transparent, but ignores local data and resolves normally.
- 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 'nodefault' option has no
other effect than turning off default contents for the given zone. Use
nodefault if you use exactly that zone, if you want to use a
subzone, use transparent.
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 'nodefault' 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 local-zone: is set
static and as local-data: SOA and NS records are provided.
- reverse RFC3330 IP4 this, link-local, testnet and broadcast
- Reverse data for zones 0.in-addr.arpa, 254.169.in-addr.arpa,
2.0.192.in-addr.arpa (TEST NET 1), 100.51.198.in-addr.arpa (TEST NET 2),
113.0.203.in-addr.arpa (TEST NET 3), 255.255.255.255.in-addr.arpa. And
from 64.100.in-addr.arpa to 127.100.in-addr.arpa (Shared Address
Space).
- reverse RFC4291 IP6 unspecified
- Reverse data for zone
0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.
- reverse RFC4193 IPv6 Locally Assigned Local Addresses
- Reverse data for zone D.F.ip6.arpa.
- reverse RFC4291 IPv6 Link Local Addresses
- Reverse data for zones 8.E.F.ip6.arpa to B.E.F.ip6.arpa.
- reverse IPv6 Example Prefix
- Reverse data for zone 8.B.D.0.1.0.0.2.ip6.arpa. This zone is used for
tutorials and examples. You can remove the block on this zone with:
local-zone: 8.B.D.0.1.0.0.2.ip6.arpa. nodefault
You can also selectively unblock a part of the zone by making that part
transparent with a local-zone statement. This also works with the other
default zones.
- local-data: "<resource record string>"
- Configure local data, which is served in reply to queries for it. The
query has to match exactly unless you configure the local-zone as
redirect. If not matched exactly, the local-zone type 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"'.
- If you need more complicated authoritative data, with referrals,
wildcards, CNAME/DNAME support, or DNSSEC authoritative service, setup a
stub-zone for it as detailed in the stub zone section below.
- local-data-ptr: "IPaddr name"
- Configure local data shorthand for a PTR record with the reversed IPv4 or
IPv6 address and the host name. For example "192.0.2.4
www.example.com". TTL can be inserted like this: "2001:DB8::4
7200 www.example.com"
- local-zone-tag: <zone> <"list of
tags">
- Assign tags to localzones. Tagged localzones will only be applied when the
used access-control element has a matching tag. Tags must be defined in
define-tags. Enclose list of tags in quotes ("") and put
spaces between tags.
- local-zone-override: <zone> <IP netblock>
<type>
- Override the localzone type for queries from addresses matching netblock.
Use this localzone type, regardless the type configured for the local-zone
(both tagged and untagged) and regardless the type configured using
access-control-tag-action.
- ratelimit: <number or 0>
- Enable ratelimiting of queries sent to nameserver for performing
recursion. If 0, the default, it is disabled. This option is experimental
at this time. The ratelimit is in queries per second that are allowed.
More queries are turned away with an error (servfail). This stops
recursive floods, eg. random query names, but not spoofed reflection
floods. Cached responses are not ratelimited 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 contention in
the ratelimit tracking data structure. Close to the number of cpus is a
fairly good setting.
- ratelimit-factor: <number>
- Set the amount of queries to rate limit when the limit is exceeded. If set
to 0, all queries are dropped for domains where the limit is exceeded. If
set to another value, 1 in that number is allowed through to complete.
Default is 10, allowing 1/10 traffic to flow normally. This can make
ordinary queries complete (if repeatedly queried for), and enter the
cache, whilst also mitigating 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 different 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 ratelimit-for-domain to set that, you might want to use
different settings for a top-level-domain and subdomains.
Remote Control Options¶
In the
remote-control: clause are the declarations for the remote control
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
unbound-control-setup(8) utility.
- control-enable: <yes or no>
- The option is used to enable remote control, default is "yes".
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 effect.
- control-use-cert: <yes or no>
- Whether to require certificate authentication of control connections. 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 unbound_server.pem.
This file is generated by the unbound-control-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_control.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_control.pem.
This certificate has to be signed with the server certificate. 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 nameservers is
used. Class IN is assumed. The servers should be authority servers, not
recursors; unbound performs the recursive processing itself for stub zones.
The stub zone can be used to configure authoritative data to be used by the
resolver that cannot be accessed using the public internet servers. This is
useful for company-local data or private zones. Setup an authoritative server
on a different host (or different port). Enter a config entry for unbound with
stub-addr: <ip address of host[@port]>. The unbound resolver can
then access the data, without referring to the public internet for it.
This setup allows DNSSEC signed zones to be served by that 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.
Consider adding
server: statements for
domain-insecure: and for
local-zone: name nodefault for the zone if it is a locally
served zone. The insecure clause stops DNSSEC from invalidating the zone. The
local zone nodefault (or
transparent) clause makes the (reverse-) zone
bypass unbound's filtering of RFC1918 zones.
- name: <domain name>
- Name of the stub zone.
- stub-host: <domain name>
- Name of stub zone nameserver. Is itself resolved before it is used.
- stub-addr: <IP address>
- IP address of stub zone nameserver. Can be IP 4 or IP 6. To use a
nondefault port for DNS communication append '@' with the port
number.
- stub-prime: <yes or no>
- This option is by default 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.
- stub-ssl-upstream: <yes or no>
- Enabled or disable whether the queries to this stub use SSL for transport.
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 forward-addr
target will forward all queries to that other server (unless it can answer
from the cache).
- name: <domain name>
- Name of the forward zone.
- forward-host: <domain name>
- Name of server to forward to. Is itself resolved before it is used.
- forward-addr: <IP address>
- IP address of server to forward to. Can be IP 4 or IP 6. To use a
nondefault port for DNS communication append '@' with the port
number.
- forward-first: <yes or no>
- If enabled, a query is attempted without the forward clause if it fails.
The data could not be retrieved and would have caused SERVFAIL because the
servers are unreachable, instead it is tried without this clause. The
default is no.
- forward-ssl-upstream: <yes or no>
- Enabled or disable whether the queries to this forwarder use SSL for
transport. Default is no.
View Options¶
There may be multiple
view: clauses. Each with a
name: and zero or
more
local-zone and
local-data elements. View can be mapped to
requests by specifying the view name in an
access-control-view element.
Options from matching views will override global options. Global options will
be used if no matching view is found.
- name: <view name>
- Name of the view. Must be unique. This name is used in access-control-view
elements.
- local-zone: <zone> <type>
- View specific local-zone elements. Has the same types and behaviour as the
global local-zone elements.
- local-data: "<resource record string>"
- View specific local-data elements. Has the same behaviour as the global
local-data elements.
- view-first: <yes or no>
- If enabled, it attempts to use the global local-zone and local-data if
there is no match in the view specific options. The default is no.
Python Module Options¶
The
python: clause gives the settings for the
python(1) script
module. This module acts like the iterator and validator modules do, on
queries and answers. To enable the script module it has to be compiled into
the daemon, and the word "python" has to be put in the
module-config: option (usually first, or between the validator and
iterator).
- python-script: <python file>
- The script file to load.
DNS64 Module Options¶
The dns64 module must be configured in the
module-config: "dns64
validator iterator" directive and be compiled into the daemon to be
enabled. These settings go in the
server: section.
- dns64-prefix: <IPv6 prefix>
- This sets the DNS64 prefix to use to synthesize AAAA records with. It must
be /96 or shorter. The default prefix is 64:ff9b::/96.
- dns64-synthall: <yes or no>
- Debug option, default no. If enabled, synthesize all AAAA records despite
the presence of actual AAAA records.
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.
# 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¶
- /etc/unbound
- default unbound working directory.
- /etc/unbound
- default chroot(2) location.
- /etc/unbound/unbound.conf
- unbound configuration file.
- /run/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
distribution for further details.