.TH "unbound" "8" "Jul 16, 2025" "NLnet Labs" "unbound 1.23.1"
.\"
.\" unbound.8 -- unbound manual
.\"
.\" Copyright (c) 2007, NLnet Labs. All rights reserved.
.\"
.\" See LICENSE for the license.
.\"
.\"
.SH "NAME"
.B unbound
\- Unbound DNS validating resolver 1.23.1.
.SH "SYNOPSIS"
.B unbound
.RB [ \-h ]
.RB [ \-d ]
.RB [ \-p ]
.RB [ \-v ]
.RB [ \-c
.IR cfgfile ]
.SH "DESCRIPTION"
.B Unbound
is a caching DNS resolver.
.P
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.
.P
To use a locally running
.B Unbound
for resolving put
.sp
.RS 6n
nameserver 127.0.0.1
.RE
.sp
into
.IR resolv.conf (5).
.P
If authoritative DNS is needed as well using
.IR nsd (8),
careful setup is required because authoritative nameservers and
resolvers are using the same port number (53).
.P
The available options are:
.TP
.B \-h
Show the version number and commandline option help, and exit.
.TP
.B \-c\fI cfgfile
Set the config file with settings for Unbound to read instead of reading the
file at the default location, @ub_conf_file@. The syntax is
described in \fIunbound.conf\fR(5).
.TP
.B \-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.
.TP
.B \-p
Don't use a pidfile.  This argument should only be used by supervision
systems which can ensure that only one instance of Unbound will run
concurrently.
.TP
.B \-v
Increase verbosity. If given multiple times, more information is logged.
This is added to the verbosity (if any) from the config file.
.TP
.B \-V
Show the version number and build options, and exit.
.SH "SEE ALSO"
\fIunbound.conf\fR(5),
\fIunbound\-checkconf\fR(8),
\fInsd\fR(8).
.SH "AUTHORS"
.B Unbound
developers are mentioned in the CREDITS file in the distribution.
