libvirt/docs/manpages/virtxend.rst
Martin Kletzander 59d30adacd libvirt-guests: Fix dependency ordering in service file
After some debugging and discussion with systemd team it turns out we
are misusing the ordering in libvirt-guests.service.  That happened
because we want to support both monolithic and modular daemon setups and
on top of that we also want to support socket activation and services
without socket activation.  Unfortunately this is impossible to express
in the unit file because of how transactions are handled in systemd when
dependencies are resolved and multiple actions (jobs) are queued.  For
explanation from Michal Sekletar see comment #7 in the BZ this patch is
fixing:

https://bugzilla.redhat.com/show_bug.cgi?id=1964855#c7

In order to support all the scenarios this patch also amends the
manpages so that users that are changing the default can also read how
to correct the dependency ordering in libvirt-guests unit file.

Ideally we would also keep the existing configuration during upgrade,
but due to our huge support matrix this seems hardly feasible as it
could introduce even more problems.

Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2022-09-26 13:04:48 +02:00

5.3 KiB

virtxend

libvirt Xen management daemon

Manual section

8

Manual group

Virtualization Support

SYNOPSIS

virtxend [OPTION]...

DESCRIPTION

The virtxend program is a server side daemon component of the libvirt virtualization management system.

It is one of a collection of modular daemons that replace functionality previously provided by the monolithic libvirtd daemon.

This daemon runs on virtualization hosts to provide management for Xen virtual machines.

The virtxend daemon only listens for requests on a local Unix domain socket. Remote off-host access and backwards compatibility with legacy clients expecting libvirtd is provided by the virtproxy daemon.

Restarting virtxend does not interrupt running guests. Guests continue to operate and changes in their state will generally be picked up automatically during startup. None the less it is recommended to avoid restarting with running guests whenever practical.

SYSTEM SOCKET ACTIVATION

The virtxend daemon is capable of starting in two modes.

In the traditional mode, it will create and listen on UNIX sockets itself.

In socket activation mode, it will rely on systemd to create and listen on the UNIX sockets and pass them as pre-opened file descriptors. In this mode most of the socket related config options in /etc/libvirt/virtxend.conf will no longer have any effect.

Socket activation mode is generally the default when running on a host OS that uses systemd. To revert to the traditional mode, all the socket unit files must be masked:

$ systemctl mask virtxend.socket virtxend-ro.socket \
   virtxend-admin.socket

If using libvirt-guests service then the ordering for that service needs to be adapted so that it is ordered after the service unit instead of the socket unit. Since dependencies and ordering cannot be changed with drop-in overrides, the whole libvirt-guests unit file needs to be changed. In order to preserve such change copy the installed /usr/lib/systemd/system/libvirt-guests.service to /etc/systemd/system/libvirt-guests.service and make the change there, specifically make sure the After= ordering mentions virtxend.service and not virtxend.socket:

[Unit]
After=virtxend.service

OPTIONS

-h, --help

Display command line help usage then exit.

-d, --daemon

Run as a daemon & write PID file.

-f, --config *FILE*

Use this configuration file, overriding the default value.

-p, --pid-file *FILE*

Use this name for the PID file, overriding the default value.

-t, --timeout *SECONDS*

Exit after timeout period (in seconds), provided there are neither any client connections nor any running domains.

-v, --verbose

Enable output of verbose messages.

--version

Display version information then exit.

SIGNALS

On receipt of SIGHUP virtxend will reload its configuration.

FILES

The virtxend program must be ran as root. Trying to start the program under a different user results in error.

  • @SYSCONFDIR@/libvirt/virtxend.conf

The default configuration file used by virtxend, unless overridden on the command line using the -f | --config option.

In addition to the default configuration file, virtxend reads configuration for the libxl driver from:

  • @SYSCONFDIR@/libvirt/libxl.conf

This file contains various knobs and default values for virtual machines created within libxl driver, and offers a way to override the built in defaults, Location of this file can't be overridden by any command line switch.

  • @RUNSTATEDIR@/libvirt/virtxend-sock
  • @RUNSTATEDIR@/libvirt/virtxend-sock-ro
  • @RUNSTATEDIR@/libvirt/virtxend-admin-sock

The sockets virtxend will use.

The TLS Server private key virtxend will use.

  • @RUNSTATEDIR@/virtxend.pid

The PID file to use, unless overridden by the -p | --pid-file option.

EXAMPLES

To retrieve the version of virtxend:

# virtxend --version
virtxend (libvirt) @VERSION@

To start virtxend, instructing it to daemonize and create a PID file:

# virtxend -d
# ls -la @RUNSTATEDIR@/virtxend.pid
-rw-r--r-- 1 root root 6 Jul  9 02:40 @RUNSTATEDIR@/virtxend.pid

BUGS

Please report all bugs you discover. This should be done via either:

  1. the mailing list

    https://libvirt.org/contact.html

  2. the bug tracker

    https://libvirt.org/bugs.html

Alternatively, you may report bugs to your software distributor / vendor.

AUTHORS

Please refer to the AUTHORS file distributed with libvirt.

Copyright (C) 2006-2020 Red Hat, Inc., and the authors listed in the libvirt AUTHORS file.

LICENSE

virtxend is distributed under the terms of the GNU LGPL v2.1+. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE

SEE ALSO

virsh(1), libvirtd(8), https://www.libvirt.org/daemons.html, https://www.libvirt.org/drvxen.html