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.\"
.IX Title "nbdkit-service 1"
.TH nbdkit-service 1 "2019-01-26" "nbdkit-1.10.3" "NBDKIT"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
nbdkit\-service \- running nbdkit as a service, and systemd socket activation
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Most people start nbdkit from the command line or run it from another
program (see \fBnbdkit\-captive\fR\|(1).  It is also possible to run nbdkit
as a standalone service, which is what this page describes.
.SH "SOCKET ACTIVATION"
.IX Header "SOCKET ACTIVATION"
nbdkit supports socket activation (sometimes called systemd socket
activation).  This is a simple protocol where instead of nbdkit itself
opening the listening socket(s), the parent process (typically
systemd) passes in pre-opened file descriptors.  Socket activation
lets you serve infrequent \s-1NBD\s0 requests using a superserver without
needing nbdkit to be running the whole time.
.PP
Socket activation is triggered when both the \f(CW\*(C`LISTEN_FDS\*(C'\fR and
\&\f(CW\*(C`LISTEN_PID\*(C'\fR environment variables are set.  In this mode using
\&\fI\-i\fR, \fI\-p\fR, \fI\-\-run\fR, \fI\-s\fR or \fI\-U\fR flags on the command line is
illegal and will cause an error.  Also in this mode nbdkit does not
fork into the background (ie. \fI\-f\fR is implied).
.SS "Using socket activation with systemd"
.IX Subsection "Using socket activation with systemd"
To use nbdkit with socket activation from systemd, create a unit file
ending in \f(CW\*(C`.socket\*(C'\fR (eg. \f(CW\*(C`/etc/systemd/system/nbdkit.socket\*(C'\fR)
containing:
.PP
.Vb 2
\& [Unit]
\& Description=NBDKit Network Block Device server
\& 
\& [Socket]
\& ListenStream=10809
\& 
\& [Install]
\& WantedBy=sockets.target
.Ve
.PP
There are various formats for the \f(CW\*(C`ListenStream\*(C'\fR key.  See
\&\fBsystemd.socket\fR\|(5) for more information.
.PP
Also create a service unit (eg. \f(CW\*(C`/etc/systemd/system/nbdkit.service\*(C'\fR)
containing:
.PP
.Vb 2
\& [Service]
\& ExecStart=/usr/sbin/nbdkit file /path/to/serve
.Ve
.PP
For more information on systemd and socket activation, see
http://0pointer.de/blog/projects/socket\-activation.html
.SH "LOGGING"
.IX Header "LOGGING"
Error messages from nbdkit can be sent to either standard error
(\fI\-\-log=stderr\fR) or to the system log (\fI\-\-log=syslog\fR).
.PP
The default, if \fI\-\-log\fR is not specified on the command line, is to
send error messages to stderr, unless nbdkit forks into the background
in which case they are sent to syslog.
.PP
In detail:
.IP "Messages go to standard error (stderr):" 4
.IX Item "Messages go to standard error (stderr):"
When running from the command line in the foreground.
.Sp
When using systemd socket activation.
.Sp
Using \fI\-\-log=stderr\fR forces all messages to go to standard error.
.IP "Messages go to the system log (syslog):" 4
.IX Item "Messages go to the system log (syslog):"
When running from the command line, forked into the background.
.Sp
Using \fI\-\-log=syslog\fR forces all messages to go to the system log.
.PP
Debug messages (\fI\-v\fR/\fI\-\-verbose\fR) always go to standard error and
are never sent to the system log.
.SH "ENVIRONMENT VARIABLES"
.IX Header "ENVIRONMENT VARIABLES"
.ie n .IP """LISTEN_FDS""" 4
.el .IP "\f(CWLISTEN_FDS\fR" 4
.IX Item "LISTEN_FDS"
.PD 0
.ie n .IP """LISTEN_PID""" 4
.el .IP "\f(CWLISTEN_PID\fR" 4
.IX Item "LISTEN_PID"
.PD
If present in the environment when nbdkit starts up, these trigger
\&\*(L"\s-1SOCKET ACTIVATION\*(R"\s0.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBnbdkit\fR\|(1),
\&\fBsystemd\fR\|(1),
\&\fBsystemd.socket\fR\|(5),
\&\fBsyslog\fR\|(3),
\&\fBrsyslogd\fR\|(8),
\&\fBjournalctl\fR\|(1).
.SH "AUTHORS"
.IX Header "AUTHORS"
Eric Blake
.PP
Richard W.M. Jones
.PP
Pino Toscano
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright (C) 2013\-2018 Red Hat Inc.
.SH "LICENSE"
.IX Header "LICENSE"
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
.IP "\(bu" 4
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
.IP "\(bu" 4
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
.IP "\(bu" 4
Neither the name of Red Hat nor the names of its contributors may be
used to endorse or promote products derived from this software without
specific prior written permission.
.PP
\&\s-1THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS\s0 ''\s-1AS IS\s0'' \s-1AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES\s0 (\s-1INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES\s0; \s-1LOSS OF
USE, DATA, OR PROFITS\s0; \s-1OR BUSINESS INTERRUPTION\s0) \s-1HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT\s0 (\s-1INCLUDING NEGLIGENCE OR OTHERWISE\s0) \s-1ARISING IN ANY WAY OUT
OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.\s0