unbound(8) NLnet Labs unbound(8)
unbound 1.12.0 unbound 1.12.0
Oct 8, 2020
NAME
unbound - Unbound DNS validating resolver 1.12.0.
SYNOPSIS
unbound [-h] [-d] [-p] [-v] [-c cfgfile]
DESCRIPTION
Unbound is a caching DNS resolver.
It uses a built in list of authoritative nameservers for the root zone
(.), the so called root hints. On receiving a DNS query it will ask
the root nameservers for an answer and will in almost all cases
receive a delegation to a top level domain (TLD) authoritative
nameserver. It will then ask that nameserver for an answer. It will
recursively continue until an answer is found or no answer is
available (NXDOMAIN). For performance and efficiency reasons that
answer is cached for a certain time (the answer's time-to-live or
TTL). A second query for the same name will then be answered from the
cache. Unbound can also do DNSSEC validation.
To use a locally running Unbound for resolving put
nameserver 127.0.0.1
into resolv.conf(5).
If authoritative DNS is needed as well using nsd(8), careful setup is
required because authoritative nameservers and resolvers are using the
same port number (53).
The available options are:
-h Show the version number and commandline option help, and exit.
-c cfgfile
Set the config file with settings for unbound to read instead of
reading the file at the default location,
/usr/local/etc/unbound/unbound.conf. The syntax is described in
unbound.conf(5).
-d Debug flag: do not fork into the background, but stay attached to
the console. This flag will also delay writing to the log file
until the thread-spawn time, so that most config and setup errors
appear on stderr. If given twice or more, logging does not switch
to the log file or to syslog, but the log messages are printed to
stderr all the time.
-p Don't use a pidfile. This argument should only be used by
supervision systems which can ensure that only one instance of
- 1 - Formatted: November 1, 2025
unbound(8) NLnet Labs unbound(8)
unbound 1.12.0 unbound 1.12.0
Oct 8, 2020
unbound will run concurrently.
-v Increase verbosity. If given multiple times, more information is
logged. This is in addition to the verbosity (if any) from the
config file.
-V Show the version number and build options, and exit.
SEE ALSO
unbound.conf(5), unbound-checkconf(8), nsd(8).
AUTHORS
Unbound developers are mentioned in the CREDITS file in the
distribution.
- 2 - Formatted: November 1, 2025
