mirror of https://gitlab.com/libvirt/libvirt.git synced 2024-12-24 22:55:23 +00:00

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

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libvirtd

libvirt management daemon

Manual section: 8
Manual group: Virtualization Support

SYNOPSIS

libvirtd [OPTION]...

DESCRIPTION

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

This daemon runs on host servers and performs required management tasks for virtualized guests. This includes activities such as starting, stopping and migrating guests between host servers, configuring and manipulating networking, and managing storage for use by guests.

The libvirt client libraries and utilities connect to this daemon to issue tasks and collect information about the configuration and resources of the host system and guests.

By default, the libvirtd daemon listens for requests on a local Unix domain socket. Using the -l | --listen command line option, the libvirtd daemon can be instructed to additionally listen on a TCP/IP socket. The TCP/IP socket to use is defined in the libvirtd configuration file.

Restarting libvirtd does not impact running guests. Guests continue to operate and will be picked up automatically if their XML configuration has been defined. Any guests whose XML configuration has not been defined will be lost from the configuration.

SYSTEM SOCKET ACTIVATION

The libvirtd daemon is capable of starting in two modes.

In the traditional mode, it will create and listen on UNIX sockets itself. If the --listen parameter is given, it will also listen on TCP/IP socket(s), according to the listen_tcp and listen_tls options in /etc/libvirt/libvirtd.conf

In socket activation mode, it will rely on systemd to create and listen on the UNIX, and optionally TCP/IP, sockets and pass them as pre-opened file descriptors. In this mode, it is not permitted to pass the --listen parameter, and most of the socket related config options in /etc/libvirt/libvirtd.conf will no longer have any effect. To enable TCP or TLS sockets use either

$ systemctl start libvirtd-tls.socket

$ systemctl start libvirtd-tcp.socket

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 libvirtd.socket libvirtd-ro.socket \
   libvirtd-admin.socket libvirtd-tls.socket libvirtd-tcp.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 libvirtd.service and not libvirtd.socket:

[Unit]
After=libvirtd.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.

-l, --listen

Listen for TCP/IP connections. This should not be set if using systemd socket activation. Instead activate the libvirtd-tls.socket or libvirtd-tcp.socket unit files.

-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 libvirtd will reload its configuration.

FILES

When run as root

@SYSCONFDIR@/libvirt/libvirtd.conf

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

Depending on what driver is installed, then the following files are also read:

@SYSCONFDIR@/libvirt/qemu.conf for the QEMU driver
@SYSCONFDIR@/libvirt/lxc.conf for the LXC driver
@SYSCONFDIR@/libvirt/libxl.conf for the libxl driver

These files contain various knobs and default values for virtual machines created within their respective drivers, and offer a way to override the built in defaults, for instance (but not limited to): paths to various supplementary binaries, TLS certificates location, graphical consoles configuration and others. Location of neither of these files can be overridden by any command line switch.

@RUNSTATEDIR@/libvirt/libvirt-sock
@RUNSTATEDIR@/libvirt/libvirt-sock-ro

The sockets libvirtd will use.

@SYSCONFDIR@/pki/CA/cacert.pem

The TLS Certificate Authority certificate libvirtd will use.

@SYSCONFDIR@/pki/libvirt/servercert.pem

The TLS Server certificate libvirtd will use.

@SYSCONFDIR@/pki/libvirt/private/serverkey.pem

The TLS Server private key libvirtd will use.

@RUNSTATEDIR@/libvirtd.pid

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

When run as non-root

$XDG_CONFIG_HOME/libvirt/libvirtd.conf

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

If QEMU driver is installed, then the following file is also read:

$XDG_CONFIG_HOME/libvirt/qemu.conf

If the file exists, it can contain various knobs and default values for virtual machines created within QEMU driver, and offers a way to override the built in defaults, for instance (but not limited to): paths to various supplementary binaries, TLS certificates location, graphical consoles configuration and others. Location of this file can't be overridden by any command line switch.

$XDG_RUNTIME_DIR/libvirt/libvirt-sock

The socket libvirtd will use.

$HOME/.pki/libvirt/cacert.pem

The TLS Certificate Authority certificate libvirtd will use.

$HOME/.pki/libvirt/servercert.pem

The TLS Server certificate libvirtd will use.

$HOME/.pki/libvirt/serverkey.pem

The TLS Server private key libvirtd will use.

$XDG_RUNTIME_DIR/libvirt/libvirtd.pid

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

If $XDG_CONFIG_HOME is not set in your environment, libvirtd will use $HOME/.config

If $XDG_RUNTIME_DIR is not set in your environment, libvirtd will use $HOME/.cache

EXAMPLES

To retrieve the version of libvirtd:

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

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

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

BUGS

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

the mailing list

https://libvirt.org/contact.html
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

LICENSE

libvirtd 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

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