1 .TH "unbound.conf" "5" "Mar 2, 2016" "NLnet Labs" "unbound 1.5.8"
3 .\" unbound.conf.5 -- unbound.conf manual
5 .\" Copyright (c) 2007, NLnet Labs. All rights reserved.
7 .\" See LICENSE for the license.
12 \- Unbound configuration file.
19 The file format has attributes and values. Some attributes have attributes inside them.
20 The notation is: attribute: value.
22 Comments start with # and last to the end of line. Empty lines are
23 ignored as is whitespace at the beginning of a line.
26 \fIunbound\-checkconf\fR(8)
27 can be used to check unbound.conf prior to usage.
29 An example config file is shown below. Copy this to /etc/unbound/unbound.conf
30 and start the server with:
33 $ unbound \-c /etc/unbound/unbound.conf
36 Most settings are the defaults. Stop the server with:
39 $ kill `cat /etc/unbound/unbound.pid`
42 Below is a minimal config file. The source distribution contains an extensive
43 example.conf file with all the options.
46 # unbound.conf(5) config file for unbound(8).
48 directory: "/etc/unbound"
50 # make sure unbound can access entropy from inside the chroot.
51 # e.g. on linux the use these commands (on BSD, devfs(8) is used):
52 # mount \-\-bind \-n /dev/random /etc/unbound/dev/random
53 # and mount \-\-bind \-n /dev/log /etc/unbound/dev/log
54 chroot: "/etc/unbound"
55 # logfile: "/etc/unbound/unbound.log" #uncomment to use logfile.
56 pidfile: "/etc/unbound/unbound.pid"
57 # verbosity: 1 # uncomment and increase to get more logging.
58 # listen on all interfaces, answer queries from the local subnet.
61 access\-control: 10.0.0.0/8 allow
62 access\-control: 2001:DB8::/64 allow
65 There must be whitespace between keywords. Attribute keywords end with a colon ':'. An attribute
66 is followed by its containing attributes, or a value.
68 Files can be included using the
70 directive. It can appear anywhere, it accepts a single file name as argument.
71 Processing continues as if the text from the included file was copied into
72 the config file at that point. If also using chroot, using full path names
73 for the included files works, relative pathnames for the included names work
74 if the directory where the daemon is started equals its chroot/working
75 directory. Wildcards can be used to include multiple files, see \fIglob\fR(7).
77 These options are part of the
81 .B verbosity: \fI<number>
82 The verbosity number, level 0 means no verbosity, only errors. Level 1
83 gives operational information. Level 2 gives detailed operational
84 information. Level 3 gives query level information, output per query.
85 Level 4 gives algorithm level information. Level 5 logs client
86 identification for cache misses. Default is level 1.
87 The verbosity can also be increased from the commandline, see \fIunbound\fR(8).
89 .B statistics\-interval: \fI<seconds>
90 The number of seconds between printing statistics to the log for every thread.
91 Disable with value 0 or "". Default is disabled. The histogram statistics
92 are only printed if replies were sent during the statistics interval,
93 requestlist statistics are printed for every interval (but can be 0).
94 This is because the median calculation requires data to be present.
96 .B statistics\-cumulative: \fI<yes or no>
97 If enabled, statistics are cumulative since starting unbound, without clearing
98 the statistics counters after logging the statistics. Default is no.
100 .B extended\-statistics: \fI<yes or no>
101 If enabled, extended statistics are printed from \fIunbound\-control\fR(8).
102 Default is off, because keeping track of more statistics takes time. The
103 counters are listed in \fIunbound\-control\fR(8).
105 .B num\-threads: \fI<number>
106 The number of threads to create to serve clients. Use 1 for no threading.
108 .B port: \fI<port number>
109 The port number, default 53, on which the server responds to queries.
111 .B interface: \fI<ip address[@port]>
112 Interface to use to connect to the network. This interface is listened to
113 for queries from clients, and answers to clients are given from it.
114 Can be given multiple times to work on several interfaces. If none are
115 given the default is to listen to localhost.
116 The interfaces are not changed on a reload (kill \-HUP) but only on restart.
117 A port number can be specified with @port (without spaces between
118 interface and port number), if not specified the default port (from
121 .B ip\-address: \fI<ip address[@port]>
122 Same as interface: (for easy of compatibility with nsd.conf).
124 .B interface\-automatic: \fI<yes or no>
125 Detect source interface on UDP queries and copy them to replies. This
126 feature is experimental, and needs support in your OS for particular socket
127 options. Default value is no.
129 .B outgoing\-interface: \fI<ip address>
130 Interface to use to connect to the network. This interface is used to send
131 queries to authoritative servers and receive their replies. Can be given
132 multiple times to work on several interfaces. If none are given the
133 default (all) is used. You can specify the same interfaces in
136 .B outgoing\-interface:
137 lines, the interfaces are then used for both purposes. Outgoing queries are
138 sent via a random outgoing interface to counter spoofing.
140 .B outgoing\-range: \fI<number>
141 Number of ports to open. This number of file descriptors can be opened per
142 thread. Must be at least 1. Default depends on compile options. Larger
143 numbers need extra resources from the operating system. For performance a
144 a very large value is best, use libevent to make this possible.
146 .B outgoing\-port\-permit: \fI<port number or range>
147 Permit unbound to open this port or range of ports for use to send queries.
148 A larger number of permitted outgoing ports increases resilience against
149 spoofing attempts. Make sure these ports are not needed by other daemons.
150 By default only ports above 1024 that have not been assigned by IANA are used.
151 Give a port number or a range of the form "low\-high", without spaces.
153 The \fBoutgoing\-port\-permit\fR and \fBoutgoing\-port\-avoid\fR statements
154 are processed in the line order of the config file, adding the permitted ports
155 and subtracting the avoided ports from the set of allowed ports. The
156 processing starts with the non IANA allocated ports above 1024 in the set
159 .B outgoing\-port\-avoid: \fI<port number or range>
160 Do not permit unbound to open this port or range of ports for use to send
161 queries. Use this to make sure unbound does not grab a port that another
162 daemon needs. The port is avoided on all outgoing interfaces, both IP4 and IP6.
163 By default only ports above 1024 that have not been assigned by IANA are used.
164 Give a port number or a range of the form "low\-high", without spaces.
166 .B outgoing\-num\-tcp: \fI<number>
167 Number of outgoing TCP buffers to allocate per thread. Default is 10. If
168 set to 0, or if do\-tcp is "no", no TCP queries to authoritative servers
169 are done. For larger installations increasing this value is a good idea.
171 .B incoming\-num\-tcp: \fI<number>
172 Number of incoming TCP buffers to allocate per thread. Default is
173 10. If set to 0, or if do\-tcp is "no", no TCP queries from clients are
174 accepted. For larger installations increasing this value is a good idea.
176 .B edns\-buffer\-size: \fI<number>
177 Number of bytes size to advertise as the EDNS reassembly buffer size.
178 This is the value put into datagrams over UDP towards peers. The actual
179 buffer size is determined by msg\-buffer\-size (both for TCP and UDP). Do
180 not set higher than that value. Default is 4096 which is RFC recommended.
181 If you have fragmentation reassembly problems, usually seen as timeouts,
182 then a value of 1480 can fix it. Setting to 512 bypasses even the most
183 stringent path MTU problems, but is seen as extreme, since the amount
184 of TCP fallback generated is excessive (probably also for this resolver,
185 consider tuning the outgoing tcp number).
187 .B max\-udp\-size: \fI<number>
188 Maximum UDP response size (not applied to TCP response). 65536 disables the
189 udp response size maximum, and uses the choice from the client, always.
190 Suggested values are 512 to 4096. Default is 4096.
192 .B msg\-buffer\-size: \fI<number>
193 Number of bytes size of the message buffers. Default is 65552 bytes, enough
194 for 64 Kb packets, the maximum DNS message size. No message larger than this
195 can be sent or received. Can be reduced to use less memory, but some requests
196 for DNS data, such as for huge resource records, will result in a SERVFAIL
199 .B msg\-cache\-size: \fI<number>
200 Number of bytes size of the message cache. Default is 4 megabytes.
201 A plain number is in bytes, append 'k', 'm' or 'g' for kilobytes, megabytes
202 or gigabytes (1024*1024 bytes in a megabyte).
204 .B msg\-cache\-slabs: \fI<number>
205 Number of slabs in the message cache. Slabs reduce lock contention by threads.
206 Must be set to a power of 2. Setting (close) to the number of cpus is a
209 .B num\-queries\-per\-thread: \fI<number>
210 The number of queries that every thread will service simultaneously.
211 If more queries arrive that need servicing, and no queries can be jostled out
212 (see \fIjostle\-timeout\fR), then the queries are dropped. This forces
213 the client to resend after a timeout; allowing the server time to work on
214 the existing queries. Default depends on compile options, 512 or 1024.
216 .B jostle\-timeout: \fI<msec>
217 Timeout used when the server is very busy. Set to a value that usually
218 results in one roundtrip to the authority servers. If too many queries
219 arrive, then 50% of the queries are allowed to run to completion, and
220 the other 50% are replaced with the new incoming query if they have already
221 spent more than their allowed time. This protects against denial of
222 service by slow queries or high query rates. Default 200 milliseconds.
223 The effect is that the qps for long-lasting queries is about
224 (numqueriesperthread / 2) / (average time for such long queries) qps.
225 The qps for short queries can be about (numqueriesperthread / 2)
226 / (jostletimeout in whole seconds) qps per thread, about (1024/2)*5 = 2560
229 .B delay\-close: \fI<msec>
230 Extra delay for timeouted UDP ports before they are closed, in msec.
231 Default is 0, and that disables it. This prevents very delayed answer
232 packets from the upstream (recursive) servers from bouncing against
233 closed ports and setting off all sort of close-port counters, with
234 eg. 1500 msec. When timeouts happen you need extra sockets, it checks
235 the ID and remote IP of packets, and unwanted packets are added to the
236 unwanted packet counter.
238 .B so\-rcvbuf: \fI<number>
239 If not 0, then set the SO_RCVBUF socket option to get more buffer
240 space on UDP port 53 incoming queries. So that short spikes on busy
241 servers do not drop packets (see counter in netstat \-su). Default is
242 0 (use system value). Otherwise, the number of bytes to ask for, try
243 "4m" on a busy server. The OS caps it at a maximum, on linux unbound
244 needs root permission to bypass the limit, or the admin can use sysctl
245 net.core.rmem_max. On BSD change kern.ipc.maxsockbuf in /etc/sysctl.conf.
246 On OpenBSD change header and recompile kernel. On Solaris ndd \-set
247 /dev/udp udp_max_buf 8388608.
249 .B so\-sndbuf: \fI<number>
250 If not 0, then set the SO_SNDBUF socket option to get more buffer space on
251 UDP port 53 outgoing queries. This for very busy servers handles spikes
252 in answer traffic, otherwise 'send: resource temporarily unavailable'
253 can get logged, the buffer overrun is also visible by netstat \-su.
254 Default is 0 (use system value). Specify the number of bytes to ask
255 for, try "4m" on a very busy server. The OS caps it at a maximum, on
256 linux unbound needs root permission to bypass the limit, or the admin
257 can use sysctl net.core.wmem_max. On BSD, Solaris changes are similar
260 .B so\-reuseport: \fI<yes or no>
261 If yes, then open dedicated listening sockets for incoming queries for each
262 thread and try to set the SO_REUSEPORT socket option on each socket. May
263 distribute incoming queries to threads more evenly. Default is no. On Linux
264 it is supported in kernels >= 3.9. On other systems, FreeBSD, OSX it may
265 also work. You can enable it (on any platform and kernel),
266 it then attempts to open the port and passes the option if it was available
267 at compile time, if that works it is used, if it fails, it continues
268 silently (unless verbosity 3) without the option.
270 .B ip\-transparent: \fI<yes or no>
271 If yes, then use IP_TRANSPARENT socket option on sockets where unbound
272 is listening for incoming traffic. Default no. Allows you to bind to
273 non\-local interfaces. For example for non\-existant IP addresses that
274 are going to exist later on, with host failover configuration. This is
275 a lot like interface\-automatic, but that one services all interfaces
276 and with this option you can select which (future) interfaces unbound
277 provides service on. This option needs unbound to be started with root
278 permissions on some systems. The option uses IP_BINDANY on FreeBSD systems.
280 .B rrset\-cache\-size: \fI<number>
281 Number of bytes size of the RRset cache. Default is 4 megabytes.
282 A plain number is in bytes, append 'k', 'm' or 'g' for kilobytes, megabytes
283 or gigabytes (1024*1024 bytes in a megabyte).
285 .B rrset\-cache\-slabs: \fI<number>
286 Number of slabs in the RRset cache. Slabs reduce lock contention by threads.
287 Must be set to a power of 2.
289 .B cache\-max\-ttl: \fI<seconds>
290 Time to live maximum for RRsets and messages in the cache. Default is
291 86400 seconds (1 day). If the maximum kicks in, responses to clients
292 still get decrementing TTLs based on the original (larger) values.
293 When the internal TTL expires, the cache item has expired.
294 Can be set lower to force the resolver to query for data often, and not
295 trust (very large) TTL values.
297 .B cache\-min\-ttl: \fI<seconds>
298 Time to live minimum for RRsets and messages in the cache. Default is 0.
299 If the minimum kicks in, the data is cached for longer than the domain
300 owner intended, and thus less queries are made to look up the data.
301 Zero makes sure the data in the cache is as the domain owner intended,
302 higher values, especially more than an hour or so, can lead to trouble as
303 the data in the cache does not match up with the actual data any more.
305 .B cache\-max\-negative\-ttl: \fI<seconds>
306 Time to live maximum for negative responses, these have a SOA in the
307 authority section that is limited in time. Default is 3600.
309 .B infra\-host\-ttl: \fI<seconds>
310 Time to live for entries in the host cache. The host cache contains
311 roundtrip timing, lameness and EDNS support information. Default is 900.
313 .B infra\-cache\-slabs: \fI<number>
314 Number of slabs in the infrastructure cache. Slabs reduce lock contention
315 by threads. Must be set to a power of 2.
317 .B infra\-cache\-numhosts: \fI<number>
318 Number of hosts for which information is cached. Default is 10000.
320 .B infra\-cache\-min\-rtt: \fI<msec>
321 Lower limit for dynamic retransmit timeout calculation in infrastructure
322 cache. Default is 50 milliseconds. Increase this value if using forwarders
323 needing more time to do recursive name resolution.
325 .B do\-ip4: \fI<yes or no>
326 Enable or disable whether ip4 queries are answered or issued. Default is yes.
328 .B do\-ip6: \fI<yes or no>
329 Enable or disable whether ip6 queries are answered or issued. Default is yes.
330 If disabled, queries are not answered on IPv6, and queries are not sent on
331 IPv6 to the internet nameservers. With this option you can disable the
332 ipv6 transport for sending DNS traffic, it does not impact the contents of
333 the DNS traffic, which may have ip4 and ip6 addresses in it.
335 .B do\-udp: \fI<yes or no>
336 Enable or disable whether UDP queries are answered or issued. Default is yes.
338 .B do\-tcp: \fI<yes or no>
339 Enable or disable whether TCP queries are answered or issued. Default is yes.
341 .B tcp\-mss: \fI<number>
342 Maximum segment size (MSS) of TCP socket on which the server responds
343 to queries. Value lower than common MSS on Ethernet
344 (1220 for example) will address path MTU problem.
345 Note that not all platform supports socket option to set MSS (TCP_MAXSEG).
346 Default is system default MSS determined by interface MTU and
347 negotiation between server and client.
349 .B outgoing\-tcp\-mss: \fI<number>
350 Maximum segment size (MSS) of TCP socket for outgoing queries
351 (from Unbound to other servers). Value lower than
352 common MSS on Ethernet (1220 for example) will address path MTU problem.
353 Note that not all platform supports socket option to set MSS (TCP_MAXSEG).
354 Default is system default MSS determined by interface MTU and
355 negotiation between Unbound and other servers.
357 .B tcp\-upstream: \fI<yes or no>
358 Enable or disable whether the upstream queries use TCP only for transport.
359 Default is no. Useful in tunneling scenarios.
361 .B ssl\-upstream: \fI<yes or no>
362 Enabled or disable whether the upstream queries use SSL only for transport.
363 Default is no. Useful in tunneling scenarios. The SSL contains plain DNS in
364 TCP wireformat. The other server must support this (see \fBssl\-service\-key\fR).
366 .B ssl\-service-key: \fI<file>
367 If enabled, the server provider SSL service on its TCP sockets. The clients
368 have to use ssl\-upstream: yes. The file is the private key for the TLS
369 session. The public certificate is in the ssl\-service\-pem file. Default
370 is "", turned off. Requires a restart (a reload is not enough) if changed,
371 because the private key is read while root permissions are held and before
372 chroot (if any). Normal DNS TCP service is not provided and gives errors,
373 this service is best run with a different \fBport:\fR config or \fI@port\fR
374 suffixes in the \fBinterface\fR config.
376 .B ssl\-service\-pem: \fI<file>
377 The public key certificate pem file for the ssl service. Default is "",
380 .B ssl\-port: \fI<number>
381 The port number on which to provide TCP SSL service, default 853, only
382 interfaces configured with that port number as @number get the SSL service.
384 .B do\-daemonize: \fI<yes or no>
385 Enable or disable whether the unbound server forks into the background as
386 a daemon. Default is yes.
388 .B access\-control: \fI<IP netblock> <action>
389 The netblock is given as an IP4 or IP6 address with /size appended for a
390 classless network block. The action can be \fIdeny\fR, \fIrefuse\fR,
391 \fIallow\fR, \fIallow_snoop\fR, \fIdeny_non_local\fR or \fIrefuse_non_local\fR.
392 The most specific netblock match is used, if none match \fIdeny\fR is used.
394 The action \fIdeny\fR stops queries from hosts from that netblock.
396 The action \fIrefuse\fR stops queries too, but sends a DNS rcode REFUSED
399 The action \fIallow\fR gives access to clients from that netblock.
400 It gives only access for recursion clients (which is
401 what almost all clients need). Nonrecursive queries are refused.
403 The \fIallow\fR action does allow nonrecursive queries to access the
404 local\-data that is configured. The reason is that this does not involve
405 the unbound server recursive lookup algorithm, and static data is served
406 in the reply. This supports normal operations where nonrecursive queries
407 are made for the authoritative data. For nonrecursive queries any replies
408 from the dynamic cache are refused.
410 The action \fIallow_snoop\fR gives nonrecursive access too. This give
411 both recursive and non recursive access. The name \fIallow_snoop\fR refers
412 to cache snooping, a technique to use nonrecursive queries to examine
413 the cache contents (for malicious acts). However, nonrecursive queries can
414 also be a valuable debugging tool (when you want to examine the cache
415 contents). In that case use \fIallow_snoop\fR for your administration host.
417 By default only localhost is \fIallow\fRed, the rest is \fIrefuse\fRd.
418 The default is \fIrefuse\fRd, because that is protocol\-friendly. The DNS
419 protocol is not designed to handle dropped packets due to policy, and
420 dropping may result in (possibly excessive) retried queries.
422 The deny_non_local and refuse_non_local settings are for hosts that are
423 only allowed to query for the authoritative local\-data, they are not
424 allowed full recursion but only the static data. With deny_non_local,
425 messages that are disallowed are dropped, with refuse_non_local they
426 receive error code REFUSED.
428 .B chroot: \fI<directory>
429 If chroot is enabled, you should pass the configfile (from the
430 commandline) as a full path from the original root. After the
431 chroot has been performed the now defunct portion of the config
432 file path is removed to be able to reread the config after a reload.
434 All other file paths (working dir, logfile, roothints, and
435 key files) can be specified in several ways:
436 as an absolute path relative to the new root,
437 as a relative path to the working directory, or
438 as an absolute path relative to the original root.
439 In the last case the path is adjusted to remove the unused portion.
441 The pidfile can be either a relative path to the working directory, or
442 an absolute path relative to the original root. It is written just prior
443 to chroot and dropping permissions. This allows the pidfile to be
444 /var/run/unbound.pid and the chroot to be /var/unbound, for example.
446 Additionally, unbound may need to access /dev/random (for entropy)
447 from inside the chroot.
449 If given a chroot is done to the given directory. The default is
450 "/var/unbound". If you give "" no chroot is performed.
452 .B username: \fI<name>
453 If given, after binding the port the user privileges are dropped. Default is
454 "unbound". If you give username: "" no user change is performed.
456 If this user is not capable of binding the
457 port, reloads (by signal HUP) will still retain the opened ports.
458 If you change the port number in the config file, and that new port number
459 requires privileges, then a reload will fail; a restart is needed.
461 .B directory: \fI<directory>
462 Sets the working directory for the program. Default is "/var/unbound".
463 On Windows the string "%EXECUTABLE%" tries to change to the directory
464 that unbound.exe resides in.
466 .B logfile: \fI<filename>
467 If "" is given, logging goes to stderr, or nowhere once daemonized.
468 The logfile is appended to, in the following format:
470 [seconds since 1970] unbound[pid:tid]: type: message.
472 If this option is given, the use\-syslog is option is set to "no".
473 The logfile is reopened (for append) when the config file is reread, on
476 .B use\-syslog: \fI<yes or no>
477 Sets unbound to send log messages to the syslogd, using
479 The log facility LOG_DAEMON is used, with identity "unbound".
480 The logfile setting is overridden when use\-syslog is turned on.
481 The default is to log to syslog.
483 .B log\-time\-ascii: \fI<yes or no>
484 Sets logfile lines to use a timestamp in UTC ascii. Default is no, which
485 prints the seconds since 1970 in brackets. No effect if using syslog, in
486 that case syslog formats the timestamp printed into the log files.
488 .B log\-queries: \fI<yes or no>
489 Prints one line per query to the log, with the log timestamp and IP address,
490 name, type and class. Default is no. Note that it takes time to print these
491 lines which makes the server (significantly) slower. Odd (nonprintable)
492 characters in names are printed as '?'.
494 .B pidfile: \fI<filename>
495 The process id is written to the file. Default is "/var/unbound/unbound.pid".
498 kill \-HUP `cat /var/unbound/unbound.pid`
502 kill \-TERM `cat /var/unbound/unbound.pid`
504 gracefully terminates.
506 .B root\-hints: \fI<filename>
507 Read the root hints from this file. Default is nothing, using builtin hints
508 for the IN class. The file has the format of zone files, with root
509 nameserver names and addresses only. The default may become outdated,
510 when servers change, therefore it is good practice to use a root\-hints file.
512 .B hide\-identity: \fI<yes or no>
513 If enabled id.server and hostname.bind queries are refused.
515 .B identity: \fI<string>
516 Set the identity to report. If set to "", the default, then the hostname
517 of the server is returned.
519 .B hide\-version: \fI<yes or no>
520 If enabled version.server and version.bind queries are refused.
522 .B version: \fI<string>
523 Set the version to report. If set to "", the default, then the package
526 .B target\-fetch\-policy: \fI<"list of numbers">
527 Set the target fetch policy used by unbound to determine if it should fetch
528 nameserver target addresses opportunistically. The policy is described per
531 The number of values determines the maximum dependency depth
532 that unbound will pursue in answering a query.
533 A value of \-1 means to fetch all targets opportunistically for that dependency
534 depth. A value of 0 means to fetch on demand only. A positive value fetches
535 that many targets opportunistically.
537 Enclose the list between quotes ("") and put spaces between numbers.
538 The default is "3 2 1 0 0". Setting all zeroes, "0 0 0 0 0" gives behaviour
539 closer to that of BIND 9, while setting "\-1 \-1 \-1 \-1 \-1" gives behaviour
540 rumoured to be closer to that of BIND 8.
542 .B harden\-short\-bufsize: \fI<yes or no>
543 Very small EDNS buffer sizes from queries are ignored. Default is off, since
544 it is legal protocol wise to send these, and unbound tries to give very
545 small answers to these queries, where possible.
547 .B harden\-large\-queries: \fI<yes or no>
548 Very large queries are ignored. Default is off, since it is legal protocol
549 wise to send these, and could be necessary for operation if TSIG or EDNS
550 payload is very large.
552 .B harden\-glue: \fI<yes or no>
553 Will trust glue only if it is within the servers authority. Default is on.
555 .B harden\-dnssec\-stripped: \fI<yes or no>
556 Require DNSSEC data for trust\-anchored zones, if such data is absent,
557 the zone becomes bogus. If turned off, and no DNSSEC data is received
558 (or the DNSKEY data fails to validate), then the zone is made insecure,
559 this behaves like there is no trust anchor. You could turn this off if
560 you are sometimes behind an intrusive firewall (of some sort) that
561 removes DNSSEC data from packets, or a zone changes from signed to
562 unsigned to badly signed often. If turned off you run the risk of a
563 downgrade attack that disables security for a zone. Default is on.
565 .B harden\-below\-nxdomain: \fI<yes or no>
566 From draft\-vixie\-dnsext\-resimprove, returns nxdomain to queries for a name
567 below another name that is already known to be nxdomain. DNSSEC mandates
568 noerror for empty nonterminals, hence this is possible. Very old software
569 might return nxdomain for empty nonterminals (that usually happen for reverse
570 IP address lookups), and thus may be incompatible with this. To try to avoid
571 this only DNSSEC-secure nxdomains are used, because the old software does not
572 have DNSSEC. Default is off.
574 .B harden\-referral\-path: \fI<yes or no>
575 Harden the referral path by performing additional queries for
576 infrastructure data. Validates the replies if trust anchors are configured
577 and the zones are signed. This enforces DNSSEC validation on nameserver
578 NS sets and the nameserver addresses that are encountered on the referral
580 Default off, because it burdens the authority servers, and it is
581 not RFC standard, and could lead to performance problems because of the
582 extra query load that is generated. Experimental option.
583 If you enable it consider adding more numbers after the target\-fetch\-policy
584 to increase the max depth that is checked to.
586 .B harden\-algo\-downgrade: \fI<yes or no>
587 Harden against algorithm downgrade when multiple algorithms are
588 advertised in the DS record. If no, allows the weakest algorithm to
589 validate the zone. Default is no. Zone signers must produce zones
590 that allow this feature to work, but sometimes they do not, and turning
591 this option off avoids that validation failure.
593 .B use\-caps\-for\-id: \fI<yes or no>
594 Use 0x20\-encoded random bits in the query to foil spoof attempts.
595 This perturbs the lowercase and uppercase of query names sent to
596 authority servers and checks if the reply still has the correct casing.
598 This feature is an experimental implementation of draft dns\-0x20.
600 .B caps\-whitelist: \fI<domain>
601 Whitelist the domain so that it does not receive caps\-for\-id perturbed
602 queries. For domains that do not support 0x20 and also fail with fallback
603 because they keep sending different answers, like some load balancers.
604 Can be given multiple times, for different domains.
606 .B qname\-minimisation: \fI<yes or no>
607 Send minimum amount of information to upstream servers to enhance privacy.
608 Only sent minimum required labels of the QNAME and set QTYPE to NS when
609 possible. Best effort approach, full QNAME and original QTYPE will be sent when
610 upstream replies with a RCODE other than NOERROR. Default is off.
612 .B private\-address: \fI<IP address or subnet>
613 Give IPv4 of IPv6 addresses or classless subnets. These are addresses
614 on your private network, and are not allowed to be returned for
615 public internet names. Any occurrence of such addresses are removed
616 from DNS answers. Additionally, the DNSSEC validator may mark the
617 answers bogus. This protects against so\-called DNS Rebinding, where
618 a user browser is turned into a network proxy, allowing remote access
619 through the browser to other parts of your private network. Some names
620 can be allowed to contain your private addresses, by default all the
621 \fBlocal\-data\fR that you configured is allowed to, and you can specify
622 additional names using \fBprivate\-domain\fR. No private addresses are
623 enabled by default. We consider to enable this for the RFC1918 private
624 IP address space by default in later releases. That would enable private
625 addresses for 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 169.254.0.0/16
626 fd00::/8 and fe80::/10, since the RFC standards say these addresses
627 should not be visible on the public internet. Turning on 127.0.0.0/8
628 would hinder many spamblocklists as they use that. Adding ::ffff:0:0/96
629 stops IPv4-mapped IPv6 addresses from bypassing the filter.
631 .B private\-domain: \fI<domain name>
632 Allow this domain, and all its subdomains to contain private addresses.
633 Give multiple times to allow multiple domain names to contain private
634 addresses. Default is none.
636 .B unwanted\-reply\-threshold: \fI<number>
637 If set, a total number of unwanted replies is kept track of in every thread.
638 When it reaches the threshold, a defensive action is taken and a warning
639 is printed to the log. The defensive action is to clear the rrset and
640 message caches, hopefully flushing away any poison. A value of 10 million
641 is suggested. Default is 0 (turned off).
643 .B do\-not\-query\-address: \fI<IP address>
644 Do not query the given IP address. Can be IP4 or IP6. Append /num to
645 indicate a classless delegation netblock, for example like
646 10.2.3.4/24 or 2001::11/64.
648 .B do\-not\-query\-localhost: \fI<yes or no>
649 If yes, localhost is added to the do\-not\-query\-address entries, both
650 IP6 ::1 and IP4 127.0.0.1/8. If no, then localhost can be used to send
651 queries to. Default is yes.
653 .B prefetch: \fI<yes or no>
654 If yes, message cache elements are prefetched before they expire to
655 keep the cache up to date. Default is no. Turning it on gives about
656 10 percent more traffic and load on the machine, but popular items do
657 not expire from the cache.
659 .B prefetch-key: \fI<yes or no>
660 If yes, fetch the DNSKEYs earlier in the validation process, when a DS
661 record is encountered. This lowers the latency of requests. It does use
662 a little more CPU. Also if the cache is set to 0, it is no use. Default is no.
664 .B rrset-roundrobin: \fI<yes or no>
665 If yes, Unbound rotates RRSet order in response (the random number is taken
666 from the query ID, for speed and thread safety). Default is no.
668 .B minimal-responses: \fI<yes or no>
669 If yes, Unbound doesn't insert authority/additional sections into response
670 messages when those sections are not required. This reduces response
671 size significantly, and may avoid TCP fallback for some responses.
672 This may cause a slight speedup. The default is no, because the DNS
673 protocol RFCs mandate these sections, and the additional content could
674 be of use and save roundtrips for clients.
676 .B module\-config: \fI<"module names">
677 Module configuration, a list of module names separated by spaces, surround
678 the string with quotes (""). The modules can be validator, iterator.
679 Setting this to "iterator" will result in a non\-validating server.
680 Setting this to "validator iterator" will turn on DNSSEC validation.
681 The ordering of the modules is important.
682 You must also set trust\-anchors for validation to be useful.
684 .B trust\-anchor\-file: \fI<filename>
685 File with trusted keys for validation. Both DS and DNSKEY entries can appear
686 in the file. The format of the file is the standard DNS Zone file format.
687 Default is "", or no trust anchor file.
689 .B auto\-trust\-anchor\-file: \fI<filename>
690 File with trust anchor for one zone, which is tracked with RFC5011 probes.
691 The probes are several times per month, thus the machine must be online
692 frequently. The initial file can be one with contents as described in
693 \fBtrust\-anchor\-file\fR. The file is written to when the anchor is updated,
694 so the unbound user must have write permission.
696 .B trust\-anchor: \fI<"Resource Record">
697 A DS or DNSKEY RR for a key to use for validation. Multiple entries can be
698 given to specify multiple trusted keys, in addition to the trust\-anchor\-files.
699 The resource record is entered in the same format as 'dig' or 'drill' prints
700 them, the same format as in the zone file. Has to be on a single line, with
701 "" around it. A TTL can be specified for ease of cut and paste, but is ignored.
702 A class can be specified, but class IN is default.
704 .B trusted\-keys\-file: \fI<filename>
705 File with trusted keys for validation. Specify more than one file
706 with several entries, one file per entry. Like \fBtrust\-anchor\-file\fR
707 but has a different file format. Format is BIND\-9 style format,
708 the trusted\-keys { name flag proto algo "key"; }; clauses are read.
709 It is possible to use wildcards with this statement, the wildcard is
710 expanded on start and on reload.
712 .B dlv\-anchor\-file: \fI<filename>
713 This option was used during early days DNSSEC deployment when no parent-side
714 DS record registrations were easily available. Nowadays, it is best to have
715 DS records registered with the parent zone (many top level zones are signed).
716 File with trusted keys for DLV (DNSSEC Lookaside Validation). Both DS and
717 DNSKEY entries can be used in the file, in the same format as for
718 \fItrust\-anchor\-file:\fR statements. Only one DLV can be configured, more
719 would be slow. The DLV configured is used as a root trusted DLV, this
720 means that it is a lookaside for the root. Default is "", or no dlv anchor file.
721 DLV is going to be decommissioned. Please do not use it any more.
723 .B dlv\-anchor: \fI<"Resource Record">
724 Much like trust\-anchor, this is a DLV anchor with the DS or DNSKEY inline.
725 DLV is going to be decommissioned. Please do not use it any more.
727 .B domain\-insecure: \fI<domain name>
728 Sets domain name to be insecure, DNSSEC chain of trust is ignored towards
729 the domain name. So a trust anchor above the domain name can not make the
730 domain secure with a DS record, such a DS record is then ignored.
731 Also keys from DLV are ignored for the domain. Can be given multiple times
732 to specify multiple domains that are treated as if unsigned. If you set
733 trust anchors for the domain they override this setting (and the domain
736 This can be useful if you want to make sure a trust anchor for external
737 lookups does not affect an (unsigned) internal domain. A DS record
738 externally can create validation failures for that internal domain.
740 .B val\-override\-date: \fI<rrsig\-style date spec>
741 Default is "" or "0", which disables this debugging feature. If enabled by
742 giving a RRSIG style date, that date is used for verifying RRSIG inception
743 and expiration dates, instead of the current date. Do not set this unless
744 you are debugging signature inception and expiration. The value \-1 ignores
745 the date altogether, useful for some special applications.
747 .B val\-sig\-skew\-min: \fI<seconds>
748 Minimum number of seconds of clock skew to apply to validated signatures.
749 A value of 10% of the signature lifetime (expiration \- inception) is
750 used, capped by this setting. Default is 3600 (1 hour) which allows for
751 daylight savings differences. Lower this value for more strict checking
752 of short lived signatures.
754 .B val\-sig\-skew\-max: \fI<seconds>
755 Maximum number of seconds of clock skew to apply to validated signatures.
756 A value of 10% of the signature lifetime (expiration \- inception)
757 is used, capped by this setting. Default is 86400 (24 hours) which
758 allows for timezone setting problems in stable domains. Setting both
759 min and max very low disables the clock skew allowances. Setting both
760 min and max very high makes the validator check the signature timestamps
763 .B val\-bogus\-ttl: \fI<number>
764 The time to live for bogus data. This is data that has failed validation;
765 due to invalid signatures or other checks. The TTL from that data cannot be
766 trusted, and this value is used instead. The value is in seconds, default 60.
767 The time interval prevents repeated revalidation of bogus data.
769 .B val\-clean\-additional: \fI<yes or no>
770 Instruct the validator to remove data from the additional section of secure
771 messages that are not signed properly. Messages that are insecure, bogus,
772 indeterminate or unchecked are not affected. Default is yes. Use this setting
773 to protect the users that rely on this validator for authentication from
774 potentially bad data in the additional section.
776 .B val\-log\-level: \fI<number>
777 Have the validator print validation failures to the log. Regardless of
778 the verbosity setting. Default is 0, off. At 1, for every user query
779 that fails a line is printed to the logs. This way you can monitor what
780 happens with validation. Use a diagnosis tool, such as dig or drill,
781 to find out why validation is failing for these queries. At 2, not only
782 the query that failed is printed but also the reason why unbound thought
783 it was wrong and which server sent the faulty data.
785 .B val\-permissive\-mode: \fI<yes or no>
786 Instruct the validator to mark bogus messages as indeterminate. The security
787 checks are performed, but if the result is bogus (failed security), the
788 reply is not withheld from the client with SERVFAIL as usual. The client
789 receives the bogus data. For messages that are found to be secure the AD bit
790 is set in replies. Also logging is performed as for full validation.
791 The default value is "no".
793 .B ignore\-cd\-flag: \fI<yes or no>
794 Instruct unbound to ignore the CD flag from clients and refuse to
795 return bogus answers to them. Thus, the CD (Checking Disabled) flag
796 does not disable checking any more. This is useful if legacy (w2008)
797 servers that set the CD flag but cannot validate DNSSEC themselves are
798 the clients, and then unbound provides them with DNSSEC protection.
799 The default value is "no".
801 .B val\-nsec3\-keysize\-iterations: \fI<"list of values">
802 List of keysize and iteration count values, separated by spaces, surrounded
803 by quotes. Default is "1024 150 2048 500 4096 2500". This determines the
804 maximum allowed NSEC3 iteration count before a message is simply marked
805 insecure instead of performing the many hashing iterations. The list must
806 be in ascending order and have at least one entry. If you set it to
807 "1024 65535" there is no restriction to NSEC3 iteration values.
808 This table must be kept short; a very long list could cause slower operation.
810 .B add\-holddown: \fI<seconds>
811 Instruct the \fBauto\-trust\-anchor\-file\fR probe mechanism for RFC5011
812 autotrust updates to add new trust anchors only after they have been
813 visible for this time. Default is 30 days as per the RFC.
815 .B del\-holddown: \fI<seconds>
816 Instruct the \fBauto\-trust\-anchor\-file\fR probe mechanism for RFC5011
817 autotrust updates to remove revoked trust anchors after they have been
818 kept in the revoked list for this long. Default is 30 days as per
821 .B keep\-missing: \fI<seconds>
822 Instruct the \fBauto\-trust\-anchor\-file\fR probe mechanism for RFC5011
823 autotrust updates to remove missing trust anchors after they have been
824 unseen for this long. This cleans up the state file if the target zone
825 does not perform trust anchor revocation, so this makes the auto probe
826 mechanism work with zones that perform regular (non\-5011) rollovers.
827 The default is 366 days. The value 0 does not remove missing anchors,
830 .B permit\-small\-holddown: \fI<yes or no>
831 Debug option that allows the autotrust 5011 rollover timers to assume
832 very small values. Default is no.
834 .B key\-cache\-size: \fI<number>
835 Number of bytes size of the key cache. Default is 4 megabytes.
836 A plain number is in bytes, append 'k', 'm' or 'g' for kilobytes, megabytes
837 or gigabytes (1024*1024 bytes in a megabyte).
839 .B key\-cache\-slabs: \fI<number>
840 Number of slabs in the key cache. Slabs reduce lock contention by threads.
841 Must be set to a power of 2. Setting (close) to the number of cpus is a
844 .B neg\-cache\-size: \fI<number>
845 Number of bytes size of the aggressive negative cache. Default is 1 megabyte.
846 A plain number is in bytes, append 'k', 'm' or 'g' for kilobytes, megabytes
847 or gigabytes (1024*1024 bytes in a megabyte).
849 .B unblock\-lan\-zones: \fI<yesno>
850 Default is disabled. If enabled, then for private address space,
851 the reverse lookups are no longer filtered. This allows unbound when
852 running as dns service on a host where it provides service for that host,
853 to put out all of the queries for the 'lan' upstream. When enabled,
854 only localhost, 127.0.0.1 reverse and ::1 reverse zones are configured
855 with default local zones. Disable the option when unbound is running
856 as a (DHCP-) DNS network resolver for a group of machines, where such
857 lookups should be filtered (RFC compliance), this also stops potential
858 data leakage about the local network to the upstream DNS servers.
860 .B insecure\-lan\-zones: \fI<yesno>
861 Default is disabled. If enabled, then reverse lookups in private
862 address space are not validated. This is usually required whenever
863 \fIunblock\-lan\-zones\fR is used.
865 .B local\-zone: \fI<zone> <type>
866 Configure a local zone. The type determines the answer to give if
867 there is no match from local\-data. The types are deny, refuse, static,
868 transparent, redirect, nodefault, typetransparent, inform, inform_deny,
869 and are explained below. After that the default settings are listed. Use
870 local\-data: to enter data into the local zone. Answers for local zones
871 are authoritative DNS answers. By default the zones are class IN.
873 If you need more complicated authoritative data, with referrals, wildcards,
874 CNAME/DNAME support, or DNSSEC authoritative service, setup a stub\-zone for
875 it as detailed in the stub zone section below.
878 Do not send an answer, drop the query.
879 If there is a match from local data, the query is answered.
882 Send an error message reply, with rcode REFUSED.
883 If there is a match from local data, the query is answered.
886 If there is a match from local data, the query is answered.
887 Otherwise, the query is answered with nodata or nxdomain.
888 For a negative answer a SOA is included in the answer if present
889 as local\-data for the zone apex domain.
891 \h'5'\fItransparent\fR
892 If there is a match from local data, the query is answered.
893 Otherwise if the query has a different name, the query is resolved normally.
894 If the query is for a name given in localdata but no such type of data is
895 given in localdata, then a noerror nodata answer is returned.
896 If no local\-zone is given local\-data causes a transparent zone
897 to be created by default.
899 \h'5'\fItypetransparent\fR
900 If there is a match from local data, the query is answered. If the query
901 is for a different name, or for the same name but for a different type,
902 the query is resolved normally. So, similar to transparent but types
903 that are not listed in local data are resolved normally, so if an A record
904 is in the local data that does not cause a nodata reply for AAAA queries.
907 The query is answered from the local data for the zone name.
908 There may be no local data beneath the zone name.
909 This answers queries for the zone, and all subdomains of the zone
910 with the local data for the zone.
911 It can be used to redirect a domain to return a different address record
912 to the end user, with
913 local\-zone: "example.com." redirect and
914 local\-data: "example.com. A 127.0.0.1"
915 queries for www.example.com and www.foo.example.com are redirected, so
916 that users with web browsers cannot access sites with suffix example.com.
919 The query is answered normally. The client IP address (@portnumber)
920 is printed to the logfile. The log message is: timestamp, unbound-pid,
921 info: zonename inform IP@port queryname type class. This option can be
922 used for normal resolution, but machines looking up infected names are
923 logged, eg. to run antivirus on them.
925 \h'5'\fIinform_deny\fR
926 The query is dropped, like 'deny', and logged, like 'inform'. Ie. find
927 infected machines without answering the queries.
930 Used to turn off default contents for AS112 zones. The other types
931 also turn off default contents for the zone. The 'nodefault' option
932 has no other effect than turning off default contents for the
933 given zone. Use \fInodefault\fR if you use exactly that zone, if you want to
934 use a subzone, use \fItransparent\fR.
936 The default zones are localhost, reverse 127.0.0.1 and ::1, the onion and
937 the AS112 zones. The AS112 zones are reverse DNS zones for private use and
938 reserved IP addresses for which the servers on the internet cannot provide
939 correct answers. They are configured by default to give nxdomain (no reverse
940 information) answers. The defaults can be turned off by specifying your
941 own local\-zone of that name, or using the 'nodefault' type. Below is a
942 list of the default zone contents.
945 The IP4 and IP6 localhost information is given. NS and SOA records are provided
946 for completeness and to satisfy some DNS update tools. Default content:
948 local\-zone: "localhost." static
949 local\-data: "localhost. 10800 IN NS localhost."
950 local\-data: "localhost. 10800 IN
951 SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
952 local\-data: "localhost. 10800 IN A 127.0.0.1"
953 local\-data: "localhost. 10800 IN AAAA ::1"
956 \h'5'\fIreverse IPv4 loopback\fR
959 local\-zone: "127.in\-addr.arpa." static
960 local\-data: "127.in\-addr.arpa. 10800 IN NS localhost."
961 local\-data: "127.in\-addr.arpa. 10800 IN
962 SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
963 local\-data: "1.0.0.127.in\-addr.arpa. 10800 IN
967 \h'5'\fIreverse IPv6 loopback\fR
970 local\-zone: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
971 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa." static
972 local\-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
973 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN
975 local\-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
976 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN
977 SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
978 local\-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
979 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN
983 \h'5'\fIonion (RFC 7686)\fR
986 local\-zone: "onion." static
987 local\-data: "onion. 10800 IN NS localhost."
988 local\-data: "onion. 10800 IN
989 SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
992 \h'5'\fIreverse RFC1918 local use zones\fR
993 Reverse data for zones 10.in\-addr.arpa, 16.172.in\-addr.arpa to
994 31.172.in\-addr.arpa, 168.192.in\-addr.arpa.
995 The \fBlocal\-zone:\fR is set static and as \fBlocal\-data:\fR SOA and NS
996 records are provided.
998 \h'5'\fIreverse RFC3330 IP4 this, link\-local, testnet and broadcast\fR
999 Reverse data for zones 0.in\-addr.arpa, 254.169.in\-addr.arpa,
1000 2.0.192.in\-addr.arpa (TEST NET 1), 100.51.198.in\-addr.arpa (TEST NET 2),
1001 113.0.203.in\-addr.arpa (TEST NET 3), 255.255.255.255.in\-addr.arpa.
1002 And from 64.100.in\-addr.arpa to 127.100.in\-addr.arpa (Shared Address Space).
1004 \h'5'\fIreverse RFC4291 IP6 unspecified\fR
1005 Reverse data for zone
1007 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
1008 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.
1011 \h'5'\fIreverse RFC4193 IPv6 Locally Assigned Local Addresses\fR
1012 Reverse data for zone D.F.ip6.arpa.
1014 \h'5'\fIreverse RFC4291 IPv6 Link Local Addresses\fR
1015 Reverse data for zones 8.E.F.ip6.arpa to B.E.F.ip6.arpa.
1017 \h'5'\fIreverse IPv6 Example Prefix\fR
1018 Reverse data for zone 8.B.D.0.1.0.0.2.ip6.arpa. This zone is used for
1019 tutorials and examples. You can remove the block on this zone with:
1021 local\-zone: 8.B.D.0.1.0.0.2.ip6.arpa. nodefault
1023 You can also selectively unblock a part of the zone by making that part
1024 transparent with a local\-zone statement.
1025 This also works with the other default zones.
1026 .\" End of local-zone listing.
1028 .B local\-data: \fI"<resource record string>"
1029 Configure local data, which is served in reply to queries for it.
1030 The query has to match exactly unless you configure the local\-zone as
1031 redirect. If not matched exactly, the local\-zone type determines
1032 further processing. If local\-data is configured that is not a subdomain of
1033 a local\-zone, a transparent local\-zone is configured.
1034 For record types such as TXT, use single quotes, as in
1035 local\-data: 'example. TXT "text"'.
1037 If you need more complicated authoritative data, with referrals, wildcards,
1038 CNAME/DNAME support, or DNSSEC authoritative service, setup a stub\-zone for
1039 it as detailed in the stub zone section below.
1041 .B local\-data\-ptr: \fI"IPaddr name"
1042 Configure local data shorthand for a PTR record with the reversed IPv4 or
1043 IPv6 address and the host name. For example "192.0.2.4 www.example.com".
1044 TTL can be inserted like this: "2001:DB8::4 7200 www.example.com"
1046 .B ratelimit: \fI<number or 0>
1047 Enable ratelimiting of queries sent to nameserver for performing recursion.
1048 If 0, the default, it is disabled. This option is experimental at this time.
1049 The ratelimit is in queries per second that are allowed. More queries are
1050 turned away with an error (servfail). This stops recursive floods, eg. random
1051 query names, but not spoofed reflection floods. Cached responses are not
1052 ratelimited by this setting. The zone of the query is determined by examining
1053 the nameservers for it, the zone name is used to keep track of the rate.
1054 For example, 1000 may be a suitable value to stop the server from being
1055 overloaded with random names, and keeps unbound from sending traffic to the
1056 nameservers for those zones.
1058 .B ratelimit\-size: \fI<memory size>
1059 Give the size of the data structure in which the current ongoing rates are
1060 kept track in. Default 4m. In bytes or use m(mega), k(kilo), g(giga).
1061 The ratelimit structure is small, so this data structure likely does
1062 not need to be large.
1064 .B ratelimit\-slabs: \fI<number>
1065 Give power of 2 number of slabs, this is used to reduce lock contention
1066 in the ratelimit tracking data structure. Close to the number of cpus is
1067 a fairly good setting.
1069 .B ratelimit\-factor: \fI<number>
1070 Set the amount of queries to rate limit when the limit is exceeded.
1071 If set to 0, all queries are dropped for domains where the limit is
1072 exceeded. If set to another value, 1 in that number is allowed through
1073 to complete. Default is 10, allowing 1/10 traffic to flow normally.
1074 This can make ordinary queries complete (if repeatedly queried for),
1075 and enter the cache, whilst also mitigating the traffic flow by the
1078 .B ratelimit\-for\-domain: \fI<domain> <number qps>
1079 Override the global ratelimit for an exact match domain name with the listed
1080 number. You can give this for any number of names. For example, for
1081 a top\-level\-domain you may want to have a higher limit than other names.
1083 .B ratelimit\-below\-domain: \fI<domain> <number qps>
1084 Override the global ratelimit for a domain name that ends in this name.
1085 You can give this multiple times, it then describes different settings
1086 in different parts of the namespace. The closest matching suffix is used
1087 to determine the qps limit. The rate for the exact matching domain name
1088 is not changed, use ratelimit\-for\-domain to set that, you might want
1089 to use different settings for a top\-level\-domain and subdomains.
1090 .SS "Remote Control Options"
1093 clause are the declarations for the remote control facility. If this is
1094 enabled, the \fIunbound\-control\fR(8) utility can be used to send
1095 commands to the running unbound server. The server uses these clauses
1096 to setup SSLv3 / TLSv1 security for the connection. The
1097 \fIunbound\-control\fR(8) utility also reads the \fBremote\-control\fR
1098 section for options. To setup the correct self\-signed certificates use the
1099 \fIunbound\-control\-setup\fR(8) utility.
1101 .B control\-enable: \fI<yes or no>
1102 The option is used to enable remote control, default is "no".
1103 If turned off, the server does not listen for control commands.
1105 .B control\-interface: \fI<ip address or path>
1106 Give IPv4 or IPv6 addresses or local socket path to listen on for
1108 By default localhost (127.0.0.1 and ::1) is listened to.
1109 Use 0.0.0.0 and ::0 to listen to all interfaces.
1110 If you change this and permissions have been dropped, you must restart
1111 the server for the change to take effect.
1113 .B control\-port: \fI<port number>
1114 The port number to listen on for IPv4 or IPv6 control interfaces,
1116 If you change this and permissions have been dropped, you must restart
1117 the server for the change to take effect.
1119 .B control\-use\-cert: \fI<yes or no>
1120 Whether to require certificate authentication of control connections.
1121 The default is "yes".
1122 This should not be changed unless there are other mechanisms in place
1123 to prevent untrusted users from accessing the remote control
1126 .B server\-key\-file: \fI<private key file>
1127 Path to the server private key, by default unbound_server.key.
1128 This file is generated by the \fIunbound\-control\-setup\fR utility.
1129 This file is used by the unbound server, but not by \fIunbound\-control\fR.
1131 .B server\-cert\-file: \fI<certificate file.pem>
1132 Path to the server self signed certificate, by default unbound_server.pem.
1133 This file is generated by the \fIunbound\-control\-setup\fR utility.
1134 This file is used by the unbound server, and also by \fIunbound\-control\fR.
1136 .B control\-key\-file: \fI<private key file>
1137 Path to the control client private key, by default unbound_control.key.
1138 This file is generated by the \fIunbound\-control\-setup\fR utility.
1139 This file is used by \fIunbound\-control\fR.
1141 .B control\-cert\-file: \fI<certificate file.pem>
1142 Path to the control client certificate, by default unbound_control.pem.
1143 This certificate has to be signed with the server certificate.
1144 This file is generated by the \fIunbound\-control\-setup\fR utility.
1145 This file is used by \fIunbound\-control\fR.
1146 .SS "Stub Zone Options"
1148 There may be multiple
1150 clauses. Each with a name: and zero or more hostnames or IP addresses.
1151 For the stub zone this list of nameservers is used. Class IN is assumed.
1152 The servers should be authority servers, not recursors; unbound performs
1153 the recursive processing itself for stub zones.
1155 The stub zone can be used to configure authoritative data to be used
1156 by the resolver that cannot be accessed using the public internet servers.
1157 This is useful for company\-local data or private zones. Setup an
1158 authoritative server on a different host (or different port). Enter a config
1159 entry for unbound with
1161 <ip address of host[@port]>.
1162 The unbound resolver can then access the data, without referring to the
1163 public internet for it.
1165 This setup allows DNSSEC signed zones to be served by that
1166 authoritative server, in which case a trusted key entry with the public key
1167 can be put in config, so that unbound can validate the data and set the AD
1168 bit on replies for the private zone (authoritative servers do not set the
1169 AD bit). This setup makes unbound capable of answering queries for the
1170 private zone, and can even set the AD bit ('authentic'), but the AA
1171 ('authoritative') bit is not set on these replies.
1173 Consider adding \fBserver:\fR statements for \fBdomain\-insecure:\fR and
1174 for \fBlocal\-zone:\fI name nodefault\fR for the zone if it is a locally
1175 served zone. The insecure clause stops DNSSEC from invalidating the
1176 zone. The local zone nodefault (or \fItransparent\fR) clause makes the
1177 (reverse\-) zone bypass unbound's filtering of RFC1918 zones.
1179 .B name: \fI<domain name>
1180 Name of the stub zone.
1182 .B stub\-host: \fI<domain name>
1183 Name of stub zone nameserver. Is itself resolved before it is used.
1185 .B stub\-addr: \fI<IP address>
1186 IP address of stub zone nameserver. Can be IP 4 or IP 6.
1187 To use a nondefault port for DNS communication append '@' with the port number.
1189 .B stub\-prime: \fI<yes or no>
1190 This option is by default off. If enabled it performs NS set priming,
1191 which is similar to root hints, where it starts using the list of nameservers
1192 currently published by the zone. Thus, if the hint list is slightly outdated,
1193 the resolver picks up a correct list online.
1195 .B stub\-first: \fI<yes or no>
1196 If enabled, a query is attempted without the stub clause if it fails.
1197 The data could not be retrieved and would have caused SERVFAIL because
1198 the servers are unreachable, instead it is tried without this clause.
1200 .SS "Forward Zone Options"
1202 There may be multiple
1204 clauses. Each with a \fBname:\fR and zero or more hostnames or IP
1205 addresses. For the forward zone this list of nameservers is used to
1206 forward the queries to. The servers listed as \fBforward\-host:\fR and
1207 \fBforward\-addr:\fR have to handle further recursion for the query. Thus,
1208 those servers are not authority servers, but are (just like unbound is)
1209 recursive servers too; unbound does not perform recursion itself for the
1210 forward zone, it lets the remote server do it. Class IN is assumed.
1211 A forward\-zone entry with name "." and a forward\-addr target will
1212 forward all queries to that other server (unless it can answer from
1215 .B name: \fI<domain name>
1216 Name of the forward zone.
1218 .B forward\-host: \fI<domain name>
1219 Name of server to forward to. Is itself resolved before it is used.
1221 .B forward\-addr: \fI<IP address>
1222 IP address of server to forward to. Can be IP 4 or IP 6.
1223 To use a nondefault port for DNS communication append '@' with the port number.
1225 .B forward\-first: \fI<yes or no>
1226 If enabled, a query is attempted without the forward clause if it fails.
1227 The data could not be retrieved and would have caused SERVFAIL because
1228 the servers are unreachable, instead it is tried without this clause.
1230 .SS "Python Module Options"
1234 clause gives the settings for the \fIpython\fR(1) script module. This module
1235 acts like the iterator and validator modules do, on queries and answers.
1236 To enable the script module it has to be compiled into the daemon,
1237 and the word "python" has to be put in the \fBmodule\-config:\fR option
1238 (usually first, or between the validator and iterator).
1240 .B python\-script: \fI<python file>\fR
1241 The script file to load.
1242 .SS "DNS64 Module Options"
1244 The dns64 module must be configured in the \fBmodule\-config:\fR "dns64
1245 validator iterator" directive and be compiled into the daemon to be
1246 enabled. These settings go in the \fBserver:\fR section.
1248 .B dns64\-prefix: \fI<IPv6 prefix>\fR
1249 This sets the DNS64 prefix to use to synthesize AAAA records with.
1250 It must be /96 or shorter. The default prefix is 64:ff9b::/96.
1252 .B dns64\-synthall: \fI<yes or no>\fR
1253 Debug option, default no. If enabled, synthesize all AAAA records
1254 despite the presence of actual AAAA records.
1255 .SH "MEMORY CONTROL EXAMPLE"
1256 In the example config settings below memory usage is reduced. Some service
1257 levels are lower, notable very large data and a high TCP load are no longer
1258 supported. Very large data and high TCP loads are exceptional for the DNS.
1259 DNSSEC validation is enabled, just add trust anchors.
1260 If you do not have to worry about programs using more than 3 Mb of memory,
1261 the below example is not for you. Use the defaults to receive full service,
1262 which on BSD\-32bit tops out at 30\-40 Mb after heavy usage.
1265 # example settings that reduce memory usage
1268 outgoing\-num\-tcp: 1 # this limits TCP service, uses less buffers.
1269 incoming\-num\-tcp: 1
1270 outgoing\-range: 60 # uses less memory, but less performance.
1271 msg\-buffer\-size: 8192 # note this limits service, 'no huge stuff'.
1272 msg\-cache\-size: 100k
1273 msg\-cache\-slabs: 1
1274 rrset\-cache\-size: 100k
1275 rrset\-cache\-slabs: 1
1276 infra\-cache\-numhosts: 200
1277 infra\-cache\-slabs: 1
1278 key\-cache\-size: 100k
1279 key\-cache\-slabs: 1
1280 neg\-cache\-size: 10k
1281 num\-queries\-per\-thread: 30
1282 target\-fetch\-policy: "2 1 0 0 0 0"
1283 harden\-large\-queries: "yes"
1284 harden\-short\-bufsize: "yes"
1289 default unbound working directory.
1296 .I /var/unbound/unbound.conf
1297 unbound configuration file.
1299 .I /var/unbound/unbound.pid
1300 default unbound pidfile with process ID of the running daemon.
1303 unbound log file. default is to log to
1307 \fIunbound\-checkconf\fR(8).
1310 was written by NLnet Labs. Please see CREDITS file
1311 in the distribution for further details.
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