1 .TH "unbound.conf" "5" "Jun 9, 2016" "NLnet Labs" "unbound 1.5.9"
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 ip\-freebind: \fI<yes or no>
281 If yes, then use IP_FREEBIND socket option on sockets where unbound
282 is listening to incoming traffic. Default no. Allows you to bind to
283 IP addresses that are nonlocal or do not exist, like when the network
284 interface or IP adress is down. Exists only on Linux, where the similar
285 ip\-transparent option is also available.
287 .B rrset\-cache\-size: \fI<number>
288 Number of bytes size of the RRset cache. Default is 4 megabytes.
289 A plain number is in bytes, append 'k', 'm' or 'g' for kilobytes, megabytes
290 or gigabytes (1024*1024 bytes in a megabyte).
292 .B rrset\-cache\-slabs: \fI<number>
293 Number of slabs in the RRset cache. Slabs reduce lock contention by threads.
294 Must be set to a power of 2.
296 .B cache\-max\-ttl: \fI<seconds>
297 Time to live maximum for RRsets and messages in the cache. Default is
298 86400 seconds (1 day). If the maximum kicks in, responses to clients
299 still get decrementing TTLs based on the original (larger) values.
300 When the internal TTL expires, the cache item has expired.
301 Can be set lower to force the resolver to query for data often, and not
302 trust (very large) TTL values.
304 .B cache\-min\-ttl: \fI<seconds>
305 Time to live minimum for RRsets and messages in the cache. Default is 0.
306 If the minimum kicks in, the data is cached for longer than the domain
307 owner intended, and thus less queries are made to look up the data.
308 Zero makes sure the data in the cache is as the domain owner intended,
309 higher values, especially more than an hour or so, can lead to trouble as
310 the data in the cache does not match up with the actual data any more.
312 .B cache\-max\-negative\-ttl: \fI<seconds>
313 Time to live maximum for negative responses, these have a SOA in the
314 authority section that is limited in time. Default is 3600.
316 .B infra\-host\-ttl: \fI<seconds>
317 Time to live for entries in the host cache. The host cache contains
318 roundtrip timing, lameness and EDNS support information. Default is 900.
320 .B infra\-cache\-slabs: \fI<number>
321 Number of slabs in the infrastructure cache. Slabs reduce lock contention
322 by threads. Must be set to a power of 2.
324 .B infra\-cache\-numhosts: \fI<number>
325 Number of hosts for which information is cached. Default is 10000.
327 .B infra\-cache\-min\-rtt: \fI<msec>
328 Lower limit for dynamic retransmit timeout calculation in infrastructure
329 cache. Default is 50 milliseconds. Increase this value if using forwarders
330 needing more time to do recursive name resolution.
332 .B do\-ip4: \fI<yes or no>
333 Enable or disable whether ip4 queries are answered or issued. Default is yes.
335 .B do\-ip6: \fI<yes or no>
336 Enable or disable whether ip6 queries are answered or issued. Default is yes.
337 If disabled, queries are not answered on IPv6, and queries are not sent on
338 IPv6 to the internet nameservers. With this option you can disable the
339 ipv6 transport for sending DNS traffic, it does not impact the contents of
340 the DNS traffic, which may have ip4 and ip6 addresses in it.
342 .B do\-udp: \fI<yes or no>
343 Enable or disable whether UDP queries are answered or issued. Default is yes.
345 .B do\-tcp: \fI<yes or no>
346 Enable or disable whether TCP queries are answered or issued. Default is yes.
348 .B tcp\-mss: \fI<number>
349 Maximum segment size (MSS) of TCP socket on which the server responds
350 to queries. Value lower than common MSS on Ethernet
351 (1220 for example) will address path MTU problem.
352 Note that not all platform supports socket option to set MSS (TCP_MAXSEG).
353 Default is system default MSS determined by interface MTU and
354 negotiation between server and client.
356 .B outgoing\-tcp\-mss: \fI<number>
357 Maximum segment size (MSS) of TCP socket for outgoing queries
358 (from Unbound to other servers). Value lower than
359 common MSS on Ethernet (1220 for example) will address path MTU problem.
360 Note that not all platform supports socket option to set MSS (TCP_MAXSEG).
361 Default is system default MSS determined by interface MTU and
362 negotiation between Unbound and other servers.
364 .B tcp\-upstream: \fI<yes or no>
365 Enable or disable whether the upstream queries use TCP only for transport.
366 Default is no. Useful in tunneling scenarios.
368 .B ssl\-upstream: \fI<yes or no>
369 Enabled or disable whether the upstream queries use SSL only for transport.
370 Default is no. Useful in tunneling scenarios. The SSL contains plain DNS in
371 TCP wireformat. The other server must support this (see \fBssl\-service\-key\fR).
373 .B ssl\-service-key: \fI<file>
374 If enabled, the server provider SSL service on its TCP sockets. The clients
375 have to use ssl\-upstream: yes. The file is the private key for the TLS
376 session. The public certificate is in the ssl\-service\-pem file. Default
377 is "", turned off. Requires a restart (a reload is not enough) if changed,
378 because the private key is read while root permissions are held and before
379 chroot (if any). Normal DNS TCP service is not provided and gives errors,
380 this service is best run with a different \fBport:\fR config or \fI@port\fR
381 suffixes in the \fBinterface\fR config.
383 .B ssl\-service\-pem: \fI<file>
384 The public key certificate pem file for the ssl service. Default is "",
387 .B ssl\-port: \fI<number>
388 The port number on which to provide TCP SSL service, default 853, only
389 interfaces configured with that port number as @number get the SSL service.
391 .B do\-daemonize: \fI<yes or no>
392 Enable or disable whether the unbound server forks into the background as
393 a daemon. Default is yes.
395 .B access\-control: \fI<IP netblock> <action>
396 The netblock is given as an IP4 or IP6 address with /size appended for a
397 classless network block. The action can be \fIdeny\fR, \fIrefuse\fR,
398 \fIallow\fR, \fIallow_snoop\fR, \fIdeny_non_local\fR or \fIrefuse_non_local\fR.
399 The most specific netblock match is used, if none match \fIdeny\fR is used.
401 The action \fIdeny\fR stops queries from hosts from that netblock.
403 The action \fIrefuse\fR stops queries too, but sends a DNS rcode REFUSED
406 The action \fIallow\fR gives access to clients from that netblock.
407 It gives only access for recursion clients (which is
408 what almost all clients need). Nonrecursive queries are refused.
410 The \fIallow\fR action does allow nonrecursive queries to access the
411 local\-data that is configured. The reason is that this does not involve
412 the unbound server recursive lookup algorithm, and static data is served
413 in the reply. This supports normal operations where nonrecursive queries
414 are made for the authoritative data. For nonrecursive queries any replies
415 from the dynamic cache are refused.
417 The action \fIallow_snoop\fR gives nonrecursive access too. This give
418 both recursive and non recursive access. The name \fIallow_snoop\fR refers
419 to cache snooping, a technique to use nonrecursive queries to examine
420 the cache contents (for malicious acts). However, nonrecursive queries can
421 also be a valuable debugging tool (when you want to examine the cache
422 contents). In that case use \fIallow_snoop\fR for your administration host.
424 By default only localhost is \fIallow\fRed, the rest is \fIrefuse\fRd.
425 The default is \fIrefuse\fRd, because that is protocol\-friendly. The DNS
426 protocol is not designed to handle dropped packets due to policy, and
427 dropping may result in (possibly excessive) retried queries.
429 The deny_non_local and refuse_non_local settings are for hosts that are
430 only allowed to query for the authoritative local\-data, they are not
431 allowed full recursion but only the static data. With deny_non_local,
432 messages that are disallowed are dropped, with refuse_non_local they
433 receive error code REFUSED.
435 .B chroot: \fI<directory>
436 If chroot is enabled, you should pass the configfile (from the
437 commandline) as a full path from the original root. After the
438 chroot has been performed the now defunct portion of the config
439 file path is removed to be able to reread the config after a reload.
441 All other file paths (working dir, logfile, roothints, and
442 key files) can be specified in several ways:
443 as an absolute path relative to the new root,
444 as a relative path to the working directory, or
445 as an absolute path relative to the original root.
446 In the last case the path is adjusted to remove the unused portion.
448 The pidfile can be either a relative path to the working directory, or
449 an absolute path relative to the original root. It is written just prior
450 to chroot and dropping permissions. This allows the pidfile to be
451 /var/run/unbound.pid and the chroot to be /var/unbound, for example.
453 Additionally, unbound may need to access /dev/random (for entropy)
454 from inside the chroot.
456 If given a chroot is done to the given directory. The default is
457 "@UNBOUND_CHROOT_DIR@". If you give "" no chroot is performed.
459 .B username: \fI<name>
460 If given, after binding the port the user privileges are dropped. Default is
461 "@UNBOUND_USERNAME@". If you give username: "" no user change is performed.
463 If this user is not capable of binding the
464 port, reloads (by signal HUP) will still retain the opened ports.
465 If you change the port number in the config file, and that new port number
466 requires privileges, then a reload will fail; a restart is needed.
468 .B directory: \fI<directory>
469 Sets the working directory for the program. Default is "@UNBOUND_RUN_DIR@".
470 On Windows the string "%EXECUTABLE%" tries to change to the directory
471 that unbound.exe resides in.
473 .B logfile: \fI<filename>
474 If "" is given, logging goes to stderr, or nowhere once daemonized.
475 The logfile is appended to, in the following format:
477 [seconds since 1970] unbound[pid:tid]: type: message.
479 If this option is given, the use\-syslog is option is set to "no".
480 The logfile is reopened (for append) when the config file is reread, on
483 .B use\-syslog: \fI<yes or no>
484 Sets unbound to send log messages to the syslogd, using
486 The log facility LOG_DAEMON is used, with identity "unbound".
487 The logfile setting is overridden when use\-syslog is turned on.
488 The default is to log to syslog.
490 .B log\-time\-ascii: \fI<yes or no>
491 Sets logfile lines to use a timestamp in UTC ascii. Default is no, which
492 prints the seconds since 1970 in brackets. No effect if using syslog, in
493 that case syslog formats the timestamp printed into the log files.
495 .B log\-queries: \fI<yes or no>
496 Prints one line per query to the log, with the log timestamp and IP address,
497 name, type and class. Default is no. Note that it takes time to print these
498 lines which makes the server (significantly) slower. Odd (nonprintable)
499 characters in names are printed as '?'.
501 .B pidfile: \fI<filename>
502 The process id is written to the file. Default is "@UNBOUND_PIDFILE@".
505 kill \-HUP `cat @UNBOUND_PIDFILE@`
509 kill \-TERM `cat @UNBOUND_PIDFILE@`
511 gracefully terminates.
513 .B root\-hints: \fI<filename>
514 Read the root hints from this file. Default is nothing, using builtin hints
515 for the IN class. The file has the format of zone files, with root
516 nameserver names and addresses only. The default may become outdated,
517 when servers change, therefore it is good practice to use a root\-hints file.
519 .B hide\-identity: \fI<yes or no>
520 If enabled id.server and hostname.bind queries are refused.
522 .B identity: \fI<string>
523 Set the identity to report. If set to "", the default, then the hostname
524 of the server is returned.
526 .B hide\-version: \fI<yes or no>
527 If enabled version.server and version.bind queries are refused.
529 .B version: \fI<string>
530 Set the version to report. If set to "", the default, then the package
533 .B target\-fetch\-policy: \fI<"list of numbers">
534 Set the target fetch policy used by unbound to determine if it should fetch
535 nameserver target addresses opportunistically. The policy is described per
538 The number of values determines the maximum dependency depth
539 that unbound will pursue in answering a query.
540 A value of \-1 means to fetch all targets opportunistically for that dependency
541 depth. A value of 0 means to fetch on demand only. A positive value fetches
542 that many targets opportunistically.
544 Enclose the list between quotes ("") and put spaces between numbers.
545 The default is "3 2 1 0 0". Setting all zeroes, "0 0 0 0 0" gives behaviour
546 closer to that of BIND 9, while setting "\-1 \-1 \-1 \-1 \-1" gives behaviour
547 rumoured to be closer to that of BIND 8.
549 .B harden\-short\-bufsize: \fI<yes or no>
550 Very small EDNS buffer sizes from queries are ignored. Default is off, since
551 it is legal protocol wise to send these, and unbound tries to give very
552 small answers to these queries, where possible.
554 .B harden\-large\-queries: \fI<yes or no>
555 Very large queries are ignored. Default is off, since it is legal protocol
556 wise to send these, and could be necessary for operation if TSIG or EDNS
557 payload is very large.
559 .B harden\-glue: \fI<yes or no>
560 Will trust glue only if it is within the servers authority. Default is on.
562 .B harden\-dnssec\-stripped: \fI<yes or no>
563 Require DNSSEC data for trust\-anchored zones, if such data is absent,
564 the zone becomes bogus. If turned off, and no DNSSEC data is received
565 (or the DNSKEY data fails to validate), then the zone is made insecure,
566 this behaves like there is no trust anchor. You could turn this off if
567 you are sometimes behind an intrusive firewall (of some sort) that
568 removes DNSSEC data from packets, or a zone changes from signed to
569 unsigned to badly signed often. If turned off you run the risk of a
570 downgrade attack that disables security for a zone. Default is on.
572 .B harden\-below\-nxdomain: \fI<yes or no>
573 From draft\-vixie\-dnsext\-resimprove, returns nxdomain to queries for a name
574 below another name that is already known to be nxdomain. DNSSEC mandates
575 noerror for empty nonterminals, hence this is possible. Very old software
576 might return nxdomain for empty nonterminals (that usually happen for reverse
577 IP address lookups), and thus may be incompatible with this. To try to avoid
578 this only DNSSEC-secure nxdomains are used, because the old software does not
579 have DNSSEC. Default is off.
580 Currently, draft\-ietf\-dnsop\-nxdomain\-cut promotes this technique.
582 .B harden\-referral\-path: \fI<yes or no>
583 Harden the referral path by performing additional queries for
584 infrastructure data. Validates the replies if trust anchors are configured
585 and the zones are signed. This enforces DNSSEC validation on nameserver
586 NS sets and the nameserver addresses that are encountered on the referral
588 Default off, because it burdens the authority servers, and it is
589 not RFC standard, and could lead to performance problems because of the
590 extra query load that is generated. Experimental option.
591 If you enable it consider adding more numbers after the target\-fetch\-policy
592 to increase the max depth that is checked to.
594 .B harden\-algo\-downgrade: \fI<yes or no>
595 Harden against algorithm downgrade when multiple algorithms are
596 advertised in the DS record. If no, allows the weakest algorithm to
597 validate the zone. Default is no. Zone signers must produce zones
598 that allow this feature to work, but sometimes they do not, and turning
599 this option off avoids that validation failure.
601 .B use\-caps\-for\-id: \fI<yes or no>
602 Use 0x20\-encoded random bits in the query to foil spoof attempts.
603 This perturbs the lowercase and uppercase of query names sent to
604 authority servers and checks if the reply still has the correct casing.
606 This feature is an experimental implementation of draft dns\-0x20.
608 .B caps\-whitelist: \fI<domain>
609 Whitelist the domain so that it does not receive caps\-for\-id perturbed
610 queries. For domains that do not support 0x20 and also fail with fallback
611 because they keep sending different answers, like some load balancers.
612 Can be given multiple times, for different domains.
614 .B qname\-minimisation: \fI<yes or no>
615 Send minimum amount of information to upstream servers to enhance privacy.
616 Only sent minimum required labels of the QNAME and set QTYPE to NS when
617 possible. Best effort approach, full QNAME and original QTYPE will be sent when
618 upstream replies with a RCODE other than NOERROR. Default is off.
620 .B private\-address: \fI<IP address or subnet>
621 Give IPv4 of IPv6 addresses or classless subnets. These are addresses
622 on your private network, and are not allowed to be returned for
623 public internet names. Any occurrence of such addresses are removed
624 from DNS answers. Additionally, the DNSSEC validator may mark the
625 answers bogus. This protects against so\-called DNS Rebinding, where
626 a user browser is turned into a network proxy, allowing remote access
627 through the browser to other parts of your private network. Some names
628 can be allowed to contain your private addresses, by default all the
629 \fBlocal\-data\fR that you configured is allowed to, and you can specify
630 additional names using \fBprivate\-domain\fR. No private addresses are
631 enabled by default. We consider to enable this for the RFC1918 private
632 IP address space by default in later releases. That would enable private
633 addresses for 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 169.254.0.0/16
634 fd00::/8 and fe80::/10, since the RFC standards say these addresses
635 should not be visible on the public internet. Turning on 127.0.0.0/8
636 would hinder many spamblocklists as they use that. Adding ::ffff:0:0/96
637 stops IPv4-mapped IPv6 addresses from bypassing the filter.
639 .B private\-domain: \fI<domain name>
640 Allow this domain, and all its subdomains to contain private addresses.
641 Give multiple times to allow multiple domain names to contain private
642 addresses. Default is none.
644 .B unwanted\-reply\-threshold: \fI<number>
645 If set, a total number of unwanted replies is kept track of in every thread.
646 When it reaches the threshold, a defensive action is taken and a warning
647 is printed to the log. The defensive action is to clear the rrset and
648 message caches, hopefully flushing away any poison. A value of 10 million
649 is suggested. Default is 0 (turned off).
651 .B do\-not\-query\-address: \fI<IP address>
652 Do not query the given IP address. Can be IP4 or IP6. Append /num to
653 indicate a classless delegation netblock, for example like
654 10.2.3.4/24 or 2001::11/64.
656 .B do\-not\-query\-localhost: \fI<yes or no>
657 If yes, localhost is added to the do\-not\-query\-address entries, both
658 IP6 ::1 and IP4 127.0.0.1/8. If no, then localhost can be used to send
659 queries to. Default is yes.
661 .B prefetch: \fI<yes or no>
662 If yes, message cache elements are prefetched before they expire to
663 keep the cache up to date. Default is no. Turning it on gives about
664 10 percent more traffic and load on the machine, but popular items do
665 not expire from the cache.
667 .B prefetch-key: \fI<yes or no>
668 If yes, fetch the DNSKEYs earlier in the validation process, when a DS
669 record is encountered. This lowers the latency of requests. It does use
670 a little more CPU. Also if the cache is set to 0, it is no use. Default is no.
672 .B rrset-roundrobin: \fI<yes or no>
673 If yes, Unbound rotates RRSet order in response (the random number is taken
674 from the query ID, for speed and thread safety). Default is no.
676 .B minimal-responses: \fI<yes or no>
677 If yes, Unbound doesn't insert authority/additional sections into response
678 messages when those sections are not required. This reduces response
679 size significantly, and may avoid TCP fallback for some responses.
680 This may cause a slight speedup. The default is no, because the DNS
681 protocol RFCs mandate these sections, and the additional content could
682 be of use and save roundtrips for clients.
684 .B disable-dnssec-lame-check: \fI<yes or no>
685 If true, disables the DNSSEC lameness check in the iterator. This check
686 sees if RRSIGs are present in the answer, when dnssec is expected,
687 and retries another authority if RRSIGs are unexpectedly missing.
688 The validator will insist in RRSIGs for DNSSEC signed domains regardless
689 of this setting, if a trust anchor is loaded.
691 .B module\-config: \fI<"module names">
692 Module configuration, a list of module names separated by spaces, surround
693 the string with quotes (""). The modules can be validator, iterator.
694 Setting this to "iterator" will result in a non\-validating server.
695 Setting this to "validator iterator" will turn on DNSSEC validation.
696 The ordering of the modules is important.
697 You must also set trust\-anchors for validation to be useful.
699 .B trust\-anchor\-file: \fI<filename>
700 File with trusted keys for validation. Both DS and DNSKEY entries can appear
701 in the file. The format of the file is the standard DNS Zone file format.
702 Default is "", or no trust anchor file.
704 .B auto\-trust\-anchor\-file: \fI<filename>
705 File with trust anchor for one zone, which is tracked with RFC5011 probes.
706 The probes are several times per month, thus the machine must be online
707 frequently. The initial file can be one with contents as described in
708 \fBtrust\-anchor\-file\fR. The file is written to when the anchor is updated,
709 so the unbound user must have write permission. Write permission to the file,
710 but also to the directory it is in (to create a temporary file, which is
711 necessary to deal with filesystem full events).
713 .B trust\-anchor: \fI<"Resource Record">
714 A DS or DNSKEY RR for a key to use for validation. Multiple entries can be
715 given to specify multiple trusted keys, in addition to the trust\-anchor\-files.
716 The resource record is entered in the same format as 'dig' or 'drill' prints
717 them, the same format as in the zone file. Has to be on a single line, with
718 "" around it. A TTL can be specified for ease of cut and paste, but is ignored.
719 A class can be specified, but class IN is default.
721 .B trusted\-keys\-file: \fI<filename>
722 File with trusted keys for validation. Specify more than one file
723 with several entries, one file per entry. Like \fBtrust\-anchor\-file\fR
724 but has a different file format. Format is BIND\-9 style format,
725 the trusted\-keys { name flag proto algo "key"; }; clauses are read.
726 It is possible to use wildcards with this statement, the wildcard is
727 expanded on start and on reload.
729 .B dlv\-anchor\-file: \fI<filename>
730 This option was used during early days DNSSEC deployment when no parent-side
731 DS record registrations were easily available. Nowadays, it is best to have
732 DS records registered with the parent zone (many top level zones are signed).
733 File with trusted keys for DLV (DNSSEC Lookaside Validation). Both DS and
734 DNSKEY entries can be used in the file, in the same format as for
735 \fItrust\-anchor\-file:\fR statements. Only one DLV can be configured, more
736 would be slow. The DLV configured is used as a root trusted DLV, this
737 means that it is a lookaside for the root. Default is "", or no dlv anchor file.
738 DLV is going to be decommissioned. Please do not use it any more.
740 .B dlv\-anchor: \fI<"Resource Record">
741 Much like trust\-anchor, this is a DLV anchor with the DS or DNSKEY inline.
742 DLV is going to be decommissioned. Please do not use it any more.
744 .B domain\-insecure: \fI<domain name>
745 Sets domain name to be insecure, DNSSEC chain of trust is ignored towards
746 the domain name. So a trust anchor above the domain name can not make the
747 domain secure with a DS record, such a DS record is then ignored.
748 Also keys from DLV are ignored for the domain. Can be given multiple times
749 to specify multiple domains that are treated as if unsigned. If you set
750 trust anchors for the domain they override this setting (and the domain
753 This can be useful if you want to make sure a trust anchor for external
754 lookups does not affect an (unsigned) internal domain. A DS record
755 externally can create validation failures for that internal domain.
757 .B val\-override\-date: \fI<rrsig\-style date spec>
758 Default is "" or "0", which disables this debugging feature. If enabled by
759 giving a RRSIG style date, that date is used for verifying RRSIG inception
760 and expiration dates, instead of the current date. Do not set this unless
761 you are debugging signature inception and expiration. The value \-1 ignores
762 the date altogether, useful for some special applications.
764 .B val\-sig\-skew\-min: \fI<seconds>
765 Minimum number of seconds of clock skew to apply to validated signatures.
766 A value of 10% of the signature lifetime (expiration \- inception) is
767 used, capped by this setting. Default is 3600 (1 hour) which allows for
768 daylight savings differences. Lower this value for more strict checking
769 of short lived signatures.
771 .B val\-sig\-skew\-max: \fI<seconds>
772 Maximum number of seconds of clock skew to apply to validated signatures.
773 A value of 10% of the signature lifetime (expiration \- inception)
774 is used, capped by this setting. Default is 86400 (24 hours) which
775 allows for timezone setting problems in stable domains. Setting both
776 min and max very low disables the clock skew allowances. Setting both
777 min and max very high makes the validator check the signature timestamps
780 .B val\-bogus\-ttl: \fI<number>
781 The time to live for bogus data. This is data that has failed validation;
782 due to invalid signatures or other checks. The TTL from that data cannot be
783 trusted, and this value is used instead. The value is in seconds, default 60.
784 The time interval prevents repeated revalidation of bogus data.
786 .B val\-clean\-additional: \fI<yes or no>
787 Instruct the validator to remove data from the additional section of secure
788 messages that are not signed properly. Messages that are insecure, bogus,
789 indeterminate or unchecked are not affected. Default is yes. Use this setting
790 to protect the users that rely on this validator for authentication from
791 potentially bad data in the additional section.
793 .B val\-log\-level: \fI<number>
794 Have the validator print validation failures to the log. Regardless of
795 the verbosity setting. Default is 0, off. At 1, for every user query
796 that fails a line is printed to the logs. This way you can monitor what
797 happens with validation. Use a diagnosis tool, such as dig or drill,
798 to find out why validation is failing for these queries. At 2, not only
799 the query that failed is printed but also the reason why unbound thought
800 it was wrong and which server sent the faulty data.
802 .B val\-permissive\-mode: \fI<yes or no>
803 Instruct the validator to mark bogus messages as indeterminate. The security
804 checks are performed, but if the result is bogus (failed security), the
805 reply is not withheld from the client with SERVFAIL as usual. The client
806 receives the bogus data. For messages that are found to be secure the AD bit
807 is set in replies. Also logging is performed as for full validation.
808 The default value is "no".
810 .B ignore\-cd\-flag: \fI<yes or no>
811 Instruct unbound to ignore the CD flag from clients and refuse to
812 return bogus answers to them. Thus, the CD (Checking Disabled) flag
813 does not disable checking any more. This is useful if legacy (w2008)
814 servers that set the CD flag but cannot validate DNSSEC themselves are
815 the clients, and then unbound provides them with DNSSEC protection.
816 The default value is "no".
818 .B val\-nsec3\-keysize\-iterations: \fI<"list of values">
819 List of keysize and iteration count values, separated by spaces, surrounded
820 by quotes. Default is "1024 150 2048 500 4096 2500". This determines the
821 maximum allowed NSEC3 iteration count before a message is simply marked
822 insecure instead of performing the many hashing iterations. The list must
823 be in ascending order and have at least one entry. If you set it to
824 "1024 65535" there is no restriction to NSEC3 iteration values.
825 This table must be kept short; a very long list could cause slower operation.
827 .B add\-holddown: \fI<seconds>
828 Instruct the \fBauto\-trust\-anchor\-file\fR probe mechanism for RFC5011
829 autotrust updates to add new trust anchors only after they have been
830 visible for this time. Default is 30 days as per the RFC.
832 .B del\-holddown: \fI<seconds>
833 Instruct the \fBauto\-trust\-anchor\-file\fR probe mechanism for RFC5011
834 autotrust updates to remove revoked trust anchors after they have been
835 kept in the revoked list for this long. Default is 30 days as per
838 .B keep\-missing: \fI<seconds>
839 Instruct the \fBauto\-trust\-anchor\-file\fR probe mechanism for RFC5011
840 autotrust updates to remove missing trust anchors after they have been
841 unseen for this long. This cleans up the state file if the target zone
842 does not perform trust anchor revocation, so this makes the auto probe
843 mechanism work with zones that perform regular (non\-5011) rollovers.
844 The default is 366 days. The value 0 does not remove missing anchors,
847 .B permit\-small\-holddown: \fI<yes or no>
848 Debug option that allows the autotrust 5011 rollover timers to assume
849 very small values. Default is no.
851 .B key\-cache\-size: \fI<number>
852 Number of bytes size of the key cache. Default is 4 megabytes.
853 A plain number is in bytes, append 'k', 'm' or 'g' for kilobytes, megabytes
854 or gigabytes (1024*1024 bytes in a megabyte).
856 .B key\-cache\-slabs: \fI<number>
857 Number of slabs in the key cache. Slabs reduce lock contention by threads.
858 Must be set to a power of 2. Setting (close) to the number of cpus is a
861 .B neg\-cache\-size: \fI<number>
862 Number of bytes size of the aggressive negative cache. Default is 1 megabyte.
863 A plain number is in bytes, append 'k', 'm' or 'g' for kilobytes, megabytes
864 or gigabytes (1024*1024 bytes in a megabyte).
866 .B unblock\-lan\-zones: \fI<yesno>
867 Default is disabled. If enabled, then for private address space,
868 the reverse lookups are no longer filtered. This allows unbound when
869 running as dns service on a host where it provides service for that host,
870 to put out all of the queries for the 'lan' upstream. When enabled,
871 only localhost, 127.0.0.1 reverse and ::1 reverse zones are configured
872 with default local zones. Disable the option when unbound is running
873 as a (DHCP-) DNS network resolver for a group of machines, where such
874 lookups should be filtered (RFC compliance), this also stops potential
875 data leakage about the local network to the upstream DNS servers.
877 .B insecure\-lan\-zones: \fI<yesno>
878 Default is disabled. If enabled, then reverse lookups in private
879 address space are not validated. This is usually required whenever
880 \fIunblock\-lan\-zones\fR is used.
882 .B local\-zone: \fI<zone> <type>
883 Configure a local zone. The type determines the answer to give if
884 there is no match from local\-data. The types are deny, refuse, static,
885 transparent, redirect, nodefault, typetransparent, inform, inform_deny,
886 and are explained below. After that the default settings are listed. Use
887 local\-data: to enter data into the local zone. Answers for local zones
888 are authoritative DNS answers. By default the zones are class IN.
890 If you need more complicated authoritative data, with referrals, wildcards,
891 CNAME/DNAME support, or DNSSEC authoritative service, setup a stub\-zone for
892 it as detailed in the stub zone section below.
895 Do not send an answer, drop the query.
896 If there is a match from local data, the query is answered.
899 Send an error message reply, with rcode REFUSED.
900 If there is a match from local data, the query is answered.
903 If there is a match from local data, the query is answered.
904 Otherwise, the query is answered with nodata or nxdomain.
905 For a negative answer a SOA is included in the answer if present
906 as local\-data for the zone apex domain.
908 \h'5'\fItransparent\fR
909 If there is a match from local data, the query is answered.
910 Otherwise if the query has a different name, the query is resolved normally.
911 If the query is for a name given in localdata but no such type of data is
912 given in localdata, then a noerror nodata answer is returned.
913 If no local\-zone is given local\-data causes a transparent zone
914 to be created by default.
916 \h'5'\fItypetransparent\fR
917 If there is a match from local data, the query is answered. If the query
918 is for a different name, or for the same name but for a different type,
919 the query is resolved normally. So, similar to transparent but types
920 that are not listed in local data are resolved normally, so if an A record
921 is in the local data that does not cause a nodata reply for AAAA queries.
924 The query is answered from the local data for the zone name.
925 There may be no local data beneath the zone name.
926 This answers queries for the zone, and all subdomains of the zone
927 with the local data for the zone.
928 It can be used to redirect a domain to return a different address record
929 to the end user, with
930 local\-zone: "example.com." redirect and
931 local\-data: "example.com. A 127.0.0.1"
932 queries for www.example.com and www.foo.example.com are redirected, so
933 that users with web browsers cannot access sites with suffix example.com.
936 The query is answered normally. The client IP address (@portnumber)
937 is printed to the logfile. The log message is: timestamp, unbound-pid,
938 info: zonename inform IP@port queryname type class. This option can be
939 used for normal resolution, but machines looking up infected names are
940 logged, eg. to run antivirus on them.
942 \h'5'\fIinform_deny\fR
943 The query is dropped, like 'deny', and logged, like 'inform'. Ie. find
944 infected machines without answering the queries.
947 Used to turn off default contents for AS112 zones. The other types
948 also turn off default contents for the zone. The 'nodefault' option
949 has no other effect than turning off default contents for the
950 given zone. Use \fInodefault\fR if you use exactly that zone, if you want to
951 use a subzone, use \fItransparent\fR.
953 The default zones are localhost, reverse 127.0.0.1 and ::1, the onion and
954 the AS112 zones. The AS112 zones are reverse DNS zones for private use and
955 reserved IP addresses for which the servers on the internet cannot provide
956 correct answers. They are configured by default to give nxdomain (no reverse
957 information) answers. The defaults can be turned off by specifying your
958 own local\-zone of that name, or using the 'nodefault' type. Below is a
959 list of the default zone contents.
962 The IP4 and IP6 localhost information is given. NS and SOA records are provided
963 for completeness and to satisfy some DNS update tools. Default content:
965 local\-zone: "localhost." static
966 local\-data: "localhost. 10800 IN NS localhost."
967 local\-data: "localhost. 10800 IN
968 SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
969 local\-data: "localhost. 10800 IN A 127.0.0.1"
970 local\-data: "localhost. 10800 IN AAAA ::1"
973 \h'5'\fIreverse IPv4 loopback\fR
976 local\-zone: "127.in\-addr.arpa." static
977 local\-data: "127.in\-addr.arpa. 10800 IN NS localhost."
978 local\-data: "127.in\-addr.arpa. 10800 IN
979 SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
980 local\-data: "1.0.0.127.in\-addr.arpa. 10800 IN
984 \h'5'\fIreverse IPv6 loopback\fR
987 local\-zone: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
988 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa." static
989 local\-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
990 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN
992 local\-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
993 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN
994 SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
995 local\-data: "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
996 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa. 10800 IN
1000 \h'5'\fIonion (RFC 7686)\fR
1003 local\-zone: "onion." static
1004 local\-data: "onion. 10800 IN NS localhost."
1005 local\-data: "onion. 10800 IN
1006 SOA localhost. nobody.invalid. 1 3600 1200 604800 10800"
1009 \h'5'\fIreverse RFC1918 local use zones\fR
1010 Reverse data for zones 10.in\-addr.arpa, 16.172.in\-addr.arpa to
1011 31.172.in\-addr.arpa, 168.192.in\-addr.arpa.
1012 The \fBlocal\-zone:\fR is set static and as \fBlocal\-data:\fR SOA and NS
1013 records are provided.
1015 \h'5'\fIreverse RFC3330 IP4 this, link\-local, testnet and broadcast\fR
1016 Reverse data for zones 0.in\-addr.arpa, 254.169.in\-addr.arpa,
1017 2.0.192.in\-addr.arpa (TEST NET 1), 100.51.198.in\-addr.arpa (TEST NET 2),
1018 113.0.203.in\-addr.arpa (TEST NET 3), 255.255.255.255.in\-addr.arpa.
1019 And from 64.100.in\-addr.arpa to 127.100.in\-addr.arpa (Shared Address Space).
1021 \h'5'\fIreverse RFC4291 IP6 unspecified\fR
1022 Reverse data for zone
1024 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.
1025 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa.
1028 \h'5'\fIreverse RFC4193 IPv6 Locally Assigned Local Addresses\fR
1029 Reverse data for zone D.F.ip6.arpa.
1031 \h'5'\fIreverse RFC4291 IPv6 Link Local Addresses\fR
1032 Reverse data for zones 8.E.F.ip6.arpa to B.E.F.ip6.arpa.
1034 \h'5'\fIreverse IPv6 Example Prefix\fR
1035 Reverse data for zone 8.B.D.0.1.0.0.2.ip6.arpa. This zone is used for
1036 tutorials and examples. You can remove the block on this zone with:
1038 local\-zone: 8.B.D.0.1.0.0.2.ip6.arpa. nodefault
1040 You can also selectively unblock a part of the zone by making that part
1041 transparent with a local\-zone statement.
1042 This also works with the other default zones.
1043 .\" End of local-zone listing.
1045 .B local\-data: \fI"<resource record string>"
1046 Configure local data, which is served in reply to queries for it.
1047 The query has to match exactly unless you configure the local\-zone as
1048 redirect. If not matched exactly, the local\-zone type determines
1049 further processing. If local\-data is configured that is not a subdomain of
1050 a local\-zone, a transparent local\-zone is configured.
1051 For record types such as TXT, use single quotes, as in
1052 local\-data: 'example. TXT "text"'.
1054 If you need more complicated authoritative data, with referrals, wildcards,
1055 CNAME/DNAME support, or DNSSEC authoritative service, setup a stub\-zone for
1056 it as detailed in the stub zone section below.
1058 .B local\-data\-ptr: \fI"IPaddr name"
1059 Configure local data shorthand for a PTR record with the reversed IPv4 or
1060 IPv6 address and the host name. For example "192.0.2.4 www.example.com".
1061 TTL can be inserted like this: "2001:DB8::4 7200 www.example.com"
1063 .B ratelimit: \fI<number or 0>
1064 Enable ratelimiting of queries sent to nameserver for performing recursion.
1065 If 0, the default, it is disabled. This option is experimental at this time.
1066 The ratelimit is in queries per second that are allowed. More queries are
1067 turned away with an error (servfail). This stops recursive floods, eg. random
1068 query names, but not spoofed reflection floods. Cached responses are not
1069 ratelimited by this setting. The zone of the query is determined by examining
1070 the nameservers for it, the zone name is used to keep track of the rate.
1071 For example, 1000 may be a suitable value to stop the server from being
1072 overloaded with random names, and keeps unbound from sending traffic to the
1073 nameservers for those zones.
1075 .B ratelimit\-size: \fI<memory size>
1076 Give the size of the data structure in which the current ongoing rates are
1077 kept track in. Default 4m. In bytes or use m(mega), k(kilo), g(giga).
1078 The ratelimit structure is small, so this data structure likely does
1079 not need to be large.
1081 .B ratelimit\-slabs: \fI<number>
1082 Give power of 2 number of slabs, this is used to reduce lock contention
1083 in the ratelimit tracking data structure. Close to the number of cpus is
1084 a fairly good setting.
1086 .B ratelimit\-factor: \fI<number>
1087 Set the amount of queries to rate limit when the limit is exceeded.
1088 If set to 0, all queries are dropped for domains where the limit is
1089 exceeded. If set to another value, 1 in that number is allowed through
1090 to complete. Default is 10, allowing 1/10 traffic to flow normally.
1091 This can make ordinary queries complete (if repeatedly queried for),
1092 and enter the cache, whilst also mitigating the traffic flow by the
1095 .B ratelimit\-for\-domain: \fI<domain> <number qps>
1096 Override the global ratelimit for an exact match domain name with the listed
1097 number. You can give this for any number of names. For example, for
1098 a top\-level\-domain you may want to have a higher limit than other names.
1100 .B ratelimit\-below\-domain: \fI<domain> <number qps>
1101 Override the global ratelimit for a domain name that ends in this name.
1102 You can give this multiple times, it then describes different settings
1103 in different parts of the namespace. The closest matching suffix is used
1104 to determine the qps limit. The rate for the exact matching domain name
1105 is not changed, use ratelimit\-for\-domain to set that, you might want
1106 to use different settings for a top\-level\-domain and subdomains.
1107 .SS "Remote Control Options"
1110 clause are the declarations for the remote control facility. If this is
1111 enabled, the \fIunbound\-control\fR(8) utility can be used to send
1112 commands to the running unbound server. The server uses these clauses
1113 to setup SSLv3 / TLSv1 security for the connection. The
1114 \fIunbound\-control\fR(8) utility also reads the \fBremote\-control\fR
1115 section for options. To setup the correct self\-signed certificates use the
1116 \fIunbound\-control\-setup\fR(8) utility.
1118 .B control\-enable: \fI<yes or no>
1119 The option is used to enable remote control, default is "no".
1120 If turned off, the server does not listen for control commands.
1122 .B control\-interface: \fI<ip address or path>
1123 Give IPv4 or IPv6 addresses or local socket path to listen on for
1125 By default localhost (127.0.0.1 and ::1) is listened to.
1126 Use 0.0.0.0 and ::0 to listen to all interfaces.
1127 If you change this and permissions have been dropped, you must restart
1128 the server for the change to take effect.
1130 .B control\-port: \fI<port number>
1131 The port number to listen on for IPv4 or IPv6 control interfaces,
1133 If you change this and permissions have been dropped, you must restart
1134 the server for the change to take effect.
1136 .B control\-use\-cert: \fI<yes or no>
1137 Whether to require certificate authentication of control connections.
1138 The default is "yes".
1139 This should not be changed unless there are other mechanisms in place
1140 to prevent untrusted users from accessing the remote control
1143 .B server\-key\-file: \fI<private key file>
1144 Path to the server private key, by default unbound_server.key.
1145 This file is generated by the \fIunbound\-control\-setup\fR utility.
1146 This file is used by the unbound server, but not by \fIunbound\-control\fR.
1148 .B server\-cert\-file: \fI<certificate file.pem>
1149 Path to the server self signed certificate, by default unbound_server.pem.
1150 This file is generated by the \fIunbound\-control\-setup\fR utility.
1151 This file is used by the unbound server, and also by \fIunbound\-control\fR.
1153 .B control\-key\-file: \fI<private key file>
1154 Path to the control client private key, by default unbound_control.key.
1155 This file is generated by the \fIunbound\-control\-setup\fR utility.
1156 This file is used by \fIunbound\-control\fR.
1158 .B control\-cert\-file: \fI<certificate file.pem>
1159 Path to the control client certificate, by default unbound_control.pem.
1160 This certificate has to be signed with the server certificate.
1161 This file is generated by the \fIunbound\-control\-setup\fR utility.
1162 This file is used by \fIunbound\-control\fR.
1163 .SS "Stub Zone Options"
1165 There may be multiple
1167 clauses. Each with a name: and zero or more hostnames or IP addresses.
1168 For the stub zone this list of nameservers is used. Class IN is assumed.
1169 The servers should be authority servers, not recursors; unbound performs
1170 the recursive processing itself for stub zones.
1172 The stub zone can be used to configure authoritative data to be used
1173 by the resolver that cannot be accessed using the public internet servers.
1174 This is useful for company\-local data or private zones. Setup an
1175 authoritative server on a different host (or different port). Enter a config
1176 entry for unbound with
1178 <ip address of host[@port]>.
1179 The unbound resolver can then access the data, without referring to the
1180 public internet for it.
1182 This setup allows DNSSEC signed zones to be served by that
1183 authoritative server, in which case a trusted key entry with the public key
1184 can be put in config, so that unbound can validate the data and set the AD
1185 bit on replies for the private zone (authoritative servers do not set the
1186 AD bit). This setup makes unbound capable of answering queries for the
1187 private zone, and can even set the AD bit ('authentic'), but the AA
1188 ('authoritative') bit is not set on these replies.
1190 Consider adding \fBserver:\fR statements for \fBdomain\-insecure:\fR and
1191 for \fBlocal\-zone:\fI name nodefault\fR for the zone if it is a locally
1192 served zone. The insecure clause stops DNSSEC from invalidating the
1193 zone. The local zone nodefault (or \fItransparent\fR) clause makes the
1194 (reverse\-) zone bypass unbound's filtering of RFC1918 zones.
1196 .B name: \fI<domain name>
1197 Name of the stub zone.
1199 .B stub\-host: \fI<domain name>
1200 Name of stub zone nameserver. Is itself resolved before it is used.
1202 .B stub\-addr: \fI<IP address>
1203 IP address of stub zone nameserver. Can be IP 4 or IP 6.
1204 To use a nondefault port for DNS communication append '@' with the port number.
1206 .B stub\-prime: \fI<yes or no>
1207 This option is by default off. If enabled it performs NS set priming,
1208 which is similar to root hints, where it starts using the list of nameservers
1209 currently published by the zone. Thus, if the hint list is slightly outdated,
1210 the resolver picks up a correct list online.
1212 .B stub\-first: \fI<yes or no>
1213 If enabled, a query is attempted without the stub clause if it fails.
1214 The data could not be retrieved and would have caused SERVFAIL because
1215 the servers are unreachable, instead it is tried without this clause.
1217 .SS "Forward Zone Options"
1219 There may be multiple
1221 clauses. Each with a \fBname:\fR and zero or more hostnames or IP
1222 addresses. For the forward zone this list of nameservers is used to
1223 forward the queries to. The servers listed as \fBforward\-host:\fR and
1224 \fBforward\-addr:\fR have to handle further recursion for the query. Thus,
1225 those servers are not authority servers, but are (just like unbound is)
1226 recursive servers too; unbound does not perform recursion itself for the
1227 forward zone, it lets the remote server do it. Class IN is assumed.
1228 A forward\-zone entry with name "." and a forward\-addr target will
1229 forward all queries to that other server (unless it can answer from
1232 .B name: \fI<domain name>
1233 Name of the forward zone.
1235 .B forward\-host: \fI<domain name>
1236 Name of server to forward to. Is itself resolved before it is used.
1238 .B forward\-addr: \fI<IP address>
1239 IP address of server to forward to. Can be IP 4 or IP 6.
1240 To use a nondefault port for DNS communication append '@' with the port number.
1242 .B forward\-first: \fI<yes or no>
1243 If enabled, a query is attempted without the forward clause if it fails.
1244 The data could not be retrieved and would have caused SERVFAIL because
1245 the servers are unreachable, instead it is tried without this clause.
1247 .SS "Python Module Options"
1251 clause gives the settings for the \fIpython\fR(1) script module. This module
1252 acts like the iterator and validator modules do, on queries and answers.
1253 To enable the script module it has to be compiled into the daemon,
1254 and the word "python" has to be put in the \fBmodule\-config:\fR option
1255 (usually first, or between the validator and iterator).
1257 .B python\-script: \fI<python file>\fR
1258 The script file to load.
1259 .SS "DNS64 Module Options"
1261 The dns64 module must be configured in the \fBmodule\-config:\fR "dns64
1262 validator iterator" directive and be compiled into the daemon to be
1263 enabled. These settings go in the \fBserver:\fR section.
1265 .B dns64\-prefix: \fI<IPv6 prefix>\fR
1266 This sets the DNS64 prefix to use to synthesize AAAA records with.
1267 It must be /96 or shorter. The default prefix is 64:ff9b::/96.
1269 .B dns64\-synthall: \fI<yes or no>\fR
1270 Debug option, default no. If enabled, synthesize all AAAA records
1271 despite the presence of actual AAAA records.
1272 .SH "MEMORY CONTROL EXAMPLE"
1273 In the example config settings below memory usage is reduced. Some service
1274 levels are lower, notable very large data and a high TCP load are no longer
1275 supported. Very large data and high TCP loads are exceptional for the DNS.
1276 DNSSEC validation is enabled, just add trust anchors.
1277 If you do not have to worry about programs using more than 3 Mb of memory,
1278 the below example is not for you. Use the defaults to receive full service,
1279 which on BSD\-32bit tops out at 30\-40 Mb after heavy usage.
1282 # example settings that reduce memory usage
1285 outgoing\-num\-tcp: 1 # this limits TCP service, uses less buffers.
1286 incoming\-num\-tcp: 1
1287 outgoing\-range: 60 # uses less memory, but less performance.
1288 msg\-buffer\-size: 8192 # note this limits service, 'no huge stuff'.
1289 msg\-cache\-size: 100k
1290 msg\-cache\-slabs: 1
1291 rrset\-cache\-size: 100k
1292 rrset\-cache\-slabs: 1
1293 infra\-cache\-numhosts: 200
1294 infra\-cache\-slabs: 1
1295 key\-cache\-size: 100k
1296 key\-cache\-slabs: 1
1297 neg\-cache\-size: 10k
1298 num\-queries\-per\-thread: 30
1299 target\-fetch\-policy: "2 1 0 0 0 0"
1300 harden\-large\-queries: "yes"
1301 harden\-short\-bufsize: "yes"
1305 .I @UNBOUND_RUN_DIR@
1306 default unbound working directory.
1308 .I @UNBOUND_CHROOT_DIR@
1314 unbound configuration file.
1316 .I @UNBOUND_PIDFILE@
1317 default unbound pidfile with process ID of the running daemon.
1320 unbound log file. default is to log to
1324 \fIunbound\-checkconf\fR(8).
1327 was written by NLnet Labs. Please see CREDITS file
1328 in the distribution for further details.
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