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.TH "UNBOUND-ANCHOR" "8" "Nov 26, 2025" "1.24.2" "Unbound"
.SH NAME
unbound-anchor \- Unbound 1.24.2 anchor utility.
.SH SYNOPSIS
.sp
\fBunbound\-anchor\fP [\fBopts\fP]
.SH DESCRIPTION
.sp
\fBunbound\-anchor\fP performs setup or update of the root trust anchor for DNSSEC
validation.
The program fetches the trust anchor with the method from \fI\%RFC 7958\fP when
regular \fI\%RFC 5011\fP update fails to bring it up to date.
It can be run (as root) from the commandline, or run as part of startup
scripts.
Before you start the \fI\%unbound(8)\fP DNS server.
.sp
Suggested usage:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
# in the init scripts.
# provide or update the root anchor (if necessary)
unbound\-anchor \-a \(dq@UNBOUND_ROOTKEY_FILE@\(dq
# Please note usage of this root anchor is at your own risk
# and under the terms of our LICENSE (see source).
#
# start validating resolver
# the unbound.conf contains:
# auto\-trust\-anchor\-file: \(dq@UNBOUND_ROOTKEY_FILE@\(dq
unbound \-c unbound.conf
.ft P
.fi
.UNINDENT
.UNINDENT
.sp
This tool provides builtin default contents for the root anchor and root update
certificate files.
.sp
It tests if the root anchor file works, and if not, and an update is possible,
attempts to update the root anchor using the root update certificate.
It performs a https fetch of
\fI\%root\-anchors.xml\fP
and checks the results (\fI\%RFC 7958\fP); if all checks are successful, it updates
the root anchor file.
Otherwise the root anchor file is unchanged.
It performs \fI\%RFC 5011\fP tracking if the DNSSEC information available via the
DNS makes that possible.
.sp
It does not perform an update if the certificate is expired, if the network is
down or other errors occur.
.sp
The available options are:
.INDENT 0.0
.TP
.B \-a <file>
The root anchor key file, that is read in and written out.
Default is \fB@UNBOUND_ROOTKEY_FILE@\fP\&.
If the file does not exist, or is empty, a builtin root key is written
to it.
.UNINDENT
.INDENT 0.0
.TP
.B \-c <file>
The root update certificate file, that is read in.
Default is \fB@UNBOUND_ROOTCERT_FILE@\fP\&.
If the file does not exist, or is empty, a builtin certificate is used.
.UNINDENT
.INDENT 0.0
.TP
.B \-l
List the builtin root key and builtin root update certificate on stdout.
.UNINDENT
.INDENT 0.0
.TP
.B \-u <name>
The server name, it connects to \fBhttps://name\fP\&.
Specify without \fBhttps://\fP prefix.
The default is \fB\(dqdata.iana.org\(dq\fP\&.
It connects to the port specified with \fI\%\-P\fP\&.
You can pass an IPv4 address or IPv6 address (no brackets) if you want.
.UNINDENT
.INDENT 0.0
.TP
.B \-S
Do not use SNI for the HTTPS connection.
Default is to use SNI.
.UNINDENT
.INDENT 0.0
.TP
.B \-b <address>
The source address to bind to for domain resolution and contacting the
server on https.
May be either an IPv4 address or IPv6 address (no brackets).
.UNINDENT
.INDENT 0.0
.TP
.B \-x <path>
The pathname to the root\-anchors.xml file on the server.
(forms URL with \fI\%\-u\fP).
The default is \fB/root\-anchors/root\-anchors.xml\fP\&.
.UNINDENT
.INDENT 0.0
.TP
.B \-s <path>
The pathname to the root\-anchors.p7s file on the server.
(forms URL with \fI\%\-u\fP).
The default is \fB/root\-anchors/root\-anchors.p7s\fP\&.
This file has to be a PKCS7 signature over the xml file, using the pem
file (\fI\%\-c\fP) as trust anchor.
.UNINDENT
.INDENT 0.0
.TP
.B \-n <name>
The emailAddress for the Subject of the signer\(aqs certificate from the
p7s signature file.
Only signatures from this name are allowed.
The default is \fBdnssec@iana.org\fP\&.
If you pass \fB\(dq\(dq\fP then the emailAddress is not checked.
.UNINDENT
.INDENT 0.0
.TP
.B \-4
Use IPv4 for domain resolution and contacting the server on
https.
Default is to use IPv4 and IPv6 where appropriate.
.UNINDENT
.INDENT 0.0
.TP
.B \-6
Use IPv6 for domain resolution and contacting the server on https.
Default is to use IPv4 and IPv6 where appropriate.
.UNINDENT
.INDENT 0.0
.TP
.B \-f <resolv.conf>
Use the given resolv.conf file.
Not enabled by default, but you could try to pass
\fB/etc/resolv.conf\fP on some systems.
It contains the IP addresses of the recursive nameservers to use.
However, since this tool could be used to bootstrap that very recursive
nameserver, it would not be useful (since that server is not up yet,
since we are bootstrapping it).
It could be useful in a situation where you know an upstream cache is
deployed (and running) and in captive portal situations.
.UNINDENT
.INDENT 0.0
.TP
.B \-r <root.hints>
Use the given root.hints file (same syntax as the BIND and Unbound root
hints file) to bootstrap domain resolution.
By default a list of builtin root hints is used.
unbound\-anchor goes to the network itself for these roots, to resolve
the server (\fI\%\-u\fP option) and to check the root DNSKEY records.
It does so, because the tool when used for bootstrapping the recursive
resolver, cannot use that recursive resolver itself because it is
bootstrapping that server.
.UNINDENT
.INDENT 0.0
.TP
.B \-R
Allow fallback from \fI\%\-f\fP \fB<resolv.conf>\fP file to direct root
servers query.
It allows you to prefer local resolvers, but fallback automatically to
direct root query if they do not respond or do not support DNSSEC.
.UNINDENT
.INDENT 0.0
.TP
.B \-v
More verbose.
Once prints informational messages, multiple times may enable large
debug amounts (such as full certificates or byte\-dumps of downloaded
files).
By default it prints almost nothing.
It also prints nothing on errors by default; in that case the original
root anchor file is simply left undisturbed, so that a recursive server
can start right after it.
.UNINDENT
.INDENT 0.0
.TP
.B \-C <unbound.conf>
Debug option to read \fB<unbound.conf>\fP into the resolver process
used.
.UNINDENT
.INDENT 0.0
.TP
.B \-P <port>
Set the port number to use for the https connection.
The default is 443.
.UNINDENT
.INDENT 0.0
.TP
.B \-F
Debug option to force update of the root anchor through downloading the
xml file and verifying it with the certificate.
By default it first tries to update by contacting the DNS, which uses
much less bandwidth, is much faster (200 msec not 2 sec), and is nicer
to the deployed infrastructure.
With this option, it still attempts to do so (and may verbosely tell
you), but then ignores the result and goes on to use the xml fallback
method.
.UNINDENT
.INDENT 0.0
.TP
.B \-h
Show the version and commandline option help.
.UNINDENT
.SH EXIT CODE
.sp
This tool exits with value 1 if the root anchor was updated using the
certificate or if the builtin root\-anchor was used.
It exits with code 0 if no update was necessary, if the update was possible
with \fI\%RFC 5011\fP tracking, or if an error occurred.
.sp
You can check the exit value in this manner:
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
unbound\-anchor \-a \(dqroot.key\(dq || logger \(dqPlease check root.key\(dq
.ft P
.fi
.UNINDENT
.UNINDENT
.sp
Or something more suitable for your operational environment.
.SH TRUST
.sp
The root keys and update certificate included in this tool are provided for
convenience and under the terms of our license (see the LICENSE file in the
source distribution or \fI\%https://github.com/NLnetLabs/unbound/blob/master/LICENSE\fP
and might be stale or not suitable to your purpose.
.sp
By running \fI\%unbound\-anchor \-l\fP the keys and certificate that are
configured in the code are printed for your convenience.
.sp
The built\-in configuration can be overridden by providing a root\-cert file and
a rootkey file.
.SH FILES
.INDENT 0.0
.TP
.B @UNBOUND_ROOTKEY_FILE@
The root anchor file, updated with 5011 tracking, and read and written
to.
The file is created if it does not exist.
.TP
.B @UNBOUND_ROOTCERT_FILE@
The trusted self\-signed certificate that is used to verify the
downloaded DNSSEC root trust anchor.
You can update it by fetching it from
\fI\%https://data.iana.org/root\-anchors/icannbundle.pem\fP (and validate it).
If the file does not exist or is empty, a builtin version is used.
.TP
.B \fI\%https://data.iana.org/root\-anchors/root\-anchors.xml\fP
Source for the root key information.
.TP
.B \fI\%https://data.iana.org/root\-anchors/root\-anchors.p7s\fP
Signature on the root key information.
.UNINDENT
.SH SEE ALSO
.sp
\fI\%unbound.conf(5)\fP,
\fI\%unbound(8)\fP\&.
.SH AUTHOR
Unbound developers are mentioned in the CREDITS file in the distribution.
.SH COPYRIGHT
1999-2025, NLnet Labs
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