coredns/man/coredns-secondary.7

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.TH "COREDNS-SECONDARY" 7 "June 2020" "CoreDNS" "CoreDNS Plugins"

.SH "NAME"
.PP
\fIsecondary\fP - enables serving a zone retrieved from a primary server.

.SH "DESCRIPTION"
.PP
With \fIsecondary\fP you can transfer (via AXFR) a zone from another server. The retrieved zone is
\fInot committed\fP to disk (a violation of the RFC). This means restarting CoreDNS will cause it to
retrieve all secondary zones.

.SH "SYNTAX"
.PP
.RS

.nf
secondary [ZONES...]

.fi
.RE

.IP \(bu 4
\fBZONES\fP zones it should be authoritative for. If empty, the zones from the configuration block
are used. Note that without a remote address to \fIget\fP the zone from, the above is not that useful.


.PP
A working syntax would be:

.PP
.RS

.nf
secondary [zones...] {
    transfer from ADDRESS
    transfer to ADDRESS
}

.fi
.RE

.IP \(bu 4
\fB\fCtransfer from\fR specifies from which address to fetch the zone. It can be specified multiple times;
if one does not work, another will be tried.
.IP \(bu 4
\fB\fCtransfer to\fR can be enabled to allow this secondary zone to be transferred again.


.PP
When a zone is due to be refreshed (Refresh timer fires) a random jitter of 5 seconds is
applied, before fetching. In the case of retry this will be 2 seconds. If there are any errors
during the transfer the transfer fails; this will be logged.

.SH "EXAMPLES"
.PP
Transfer \fB\fCexample.org\fR from 10.0.1.1, and if that fails try 10.1.2.1.

.PP
.RS

.nf
example.org {
    secondary {
        transfer from 10.0.1.1
        transfer from 10.1.2.1
    }
}

.fi
.RE

.PP
Or re-export the retrieved zone to other secondaries.

.PP
.RS

.nf
\&. {
    secondary example.net {
        transfer from 10.1.2.1
        transfer to *
    }
}

.fi
.RE

.SH "BUGS"
.PP
Only AXFR is supported and the retrieved zone is not committed to disk.