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Matthew Miller
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en-US/systemd.adoc
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en-US/systemd.adoc
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= Systemd
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'''
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[NOTE]
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======
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This page was automatically converted from https://fedoraproject.org/wiki/Systemd
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It is probably
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* Badly formatted
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* Missing graphics and tables that do not covert well from mediawiki
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* Out-of-date
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* In need of other love
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Please fix it, remove this notice, and then add to `_topic_map.yml`
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Pull requests accepted at https://pagure.io/fedora-docs/fedora-howto
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Once that is live, go to the original wiki page and add an `{{old}}`
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tag, followed by a note like
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....
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{{admon/note|This page has a new home!|
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This wiki page is no longer maintained. Please find the up-to-date
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version at: https://docs.fedoraproject.org/whatever-the-url
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}}
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....
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======
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'''
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systemd is a system and service manager for Linux, compatible with SysV
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and LSB init scripts. systemd provides aggressive parallelization
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capabilities, uses socket and D-Bus activation for starting services,
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offers on-demand starting of daemons, keeps track of processes using
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Linux cgroups, supports snapshotting and restoring of the system state,
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maintains mount and automount points and implements an elaborate
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transactional dependency-based service control logic. It can work as a
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drop-in replacement for sysvinit. For more information, watch the video
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at http://www.youtube.com/watch?v=TyMLi8QF6sw
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[[why-systemd]]
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Why systemd?
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~~~~~~~~~~~~
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http://0pointer.de/blog/projects/why.html
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[[systemd-documentation]]
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systemd documentation
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~~~~~~~~~~~~~~~~~~~~~
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systemd has very comprehensive documentation. Refer to
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http://0pointer.de/blog/projects/systemd-docs.html
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[[boot-kernel-command-line]]
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Boot Kernel Command Line
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~~~~~~~~~~~~~~~~~~~~~~~~
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On boot *systemd* activates (by default), the target unit
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_default.target_ whose job is to activate services and other units by
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pulling them in via dependencies.
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To override the unit to activate, *systemd* parses its own kernel
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command line arguments via the `systemd.unit=` command line option. This
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may be used to temporarily boot into a different boot unit. The
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classical run-levels are replaced as following:
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`systemd.unit=rescue.target` is a special target unit for setting up the
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base system and a rescue shell (similar to run level 1);
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`systemd.unit=emergency.target`, is very similar to passing
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`init=/bin/sh` but with the option to boot the full system from there;
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`systemd.unit=multi-user.target` for setting up a non-graphical
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multi-user system; `systemd.unit=graphical.target` for setting up a
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graphical login screen.
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For details about these special systemd boot units, view the man
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`systemd.special` page. it scripts
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[[what-is-the-tool-to-manage-services-with-systemd]]
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What is the tool to manage services with systemd?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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systemctl is the primary tool to use. It combines the functionality of
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both service and chkconfig into a single tool that you can use for
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instance to enable/disable services permanently or only for the current
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session.
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list all running services etc:
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....
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systemctl
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....
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Refer to man systemctl for more details. systemd-cgls lists the running
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process in a tree format. It can recursively show the content of any
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given control group. Refer to man systemd-cgls for more details.
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[[how-do-i-startstop-or-enabledisable-services]]
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How do I start/stop or enable/disable services?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Activates a service immediately:
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....
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systemctl start foo
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....
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Deactivates a service immediately:
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....
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systemctl stop foo
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....
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Restarts a service:
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....
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systemctl restart foo
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....
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Shows status of a service including whether it is running or not:
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....
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systemctl status foo
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....
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Enables a service to be started on bootup:
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....
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systemctl enable foo
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....
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Disables a service to not start during bootup:
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....
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systemctl disable foo
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....
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Prevent a service from starting dynamically or even manually unless
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unmasked:
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....
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systemctl mask foo
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....
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Check whether a service is already enabled or not:
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....
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systemctl is-enabled foo
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....
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Refer to man systemctl for more details.
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[[how-do-i-change-the-target-runlevel]]
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How do I change the target (runlevel)?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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systemd has the concept of targets which is a more flexible replacement
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for runlevels in sysvinit.
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Run level 3 is emulated by multi-user.target. Run level 5 is emulated by
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graphical.target. runlevel3.target is a symbolic link to
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multi-user.target and runlevel5.target is a symbolic link to
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graphical.target.
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You can switch to 'runlevel 3' by running
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....
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systemctl isolate multi-user.target
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....
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You can switch to 'runlevel 5' by running
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....
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systemctl isolate graphical.target
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....
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[[how-do-i-change-the-default-target]]
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How do I change the default target?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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....
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systemctl set-default <name of target>.target
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....
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graphical.target is the default. You might want multi-user.target for
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the equivalent of non graphical (runlevel 3) from sysv init. The full
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list of targets can be accessed via systemctl list-units --type=target
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systemd does not use /etc/inittab file.
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[[how-do-i-know-the-current-target]]
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How do I know the current target?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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....
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systemctl get-default
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....
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[[how-to-power-off-the-machine]]
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How to power off the machine?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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You can use
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....
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poweroff
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....
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Some more possibilities are: `halt -p`, `init 0`, `shutdown -P now`
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Note that `halt` used to work the same as `poweroff` in previous Fedora
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releases, but systemd distinguishes between the two, so `halt` without
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parameters now does exactly what it says - it merely stops the system
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without turning it off.
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[[does-service-command-work-with-systemd]]
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Does service command work with systemd?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Yes. It has been modified to call systemctl automatically when dealing
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with systemd service files. So either of the following commands does the
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same thing
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....
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systemctl stop NetworkManager
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....
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(or)
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....
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service NetworkManager stop
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....
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[[does-chkconfig-command-work-with-systemd]]
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Does chkconfig command work with systemd?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Yes, for turning on/off services, compatibility has been provided both
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ways. chkconfig has been modified to call systemctl when dealing with
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systemd service files. Also systemctl automatically calls chkconfig when
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dealing with a traditional sysv init file.
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So either of the following commands does the same thing
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....
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systemctl disable NetworkManager
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....
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(or)
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....
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chkconfig NetworkManager off
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....
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chkconfig --list doesn't list systemd services, only Sys V services. The
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output of chkconfig takes note of this, along with supplying additional
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information.
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[[does-system-config-services-work-with-systemd]]
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Does system-config-services work with systemd?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Yes. It does.
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[[how-do-i-change-the-number-of-gettys-running-by-default]]
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How do I change the number of gettys running by default?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The simplest way is to edit /etc/systemd/logind.conf
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([http://www.freedesktop.org/software/systemd/man/logind.conf.html#NAutoVTs=
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man page]):
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....
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[Login]
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...
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NAutoVTs=8
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....
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This setting will take effect after reboot.
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Alternatively, getty@.services which open the login prompt can be
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enabled and started individually.
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To add another getty:
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....
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systemctl enable getty@tty8
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systemctl start getty@tty8
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....
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To remove a getty:
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....
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systemctl disable getty@tty8
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systemctl stop getty@tty8
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....
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systemd does not use /etc/inittab file.
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[[how-do-i-set-automatic-login-on-a-virtual-console-terminal]]
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How do I set automatic login on a virtual console terminal?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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First create a new service similar to getty@.service:
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....
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# cp /lib/systemd/system/getty@.service \
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/etc/systemd/system/autologin@.service
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# ln -s /etc/systemd/system/autologin@.service \
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/etc/systemd/system/getty.target.wants/getty@tty8.service
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....
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then edit ExecStart, Restart and Alias values, like this:
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....
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...
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ExecStart=-/sbin/mingetty --autologin USERNAME %I
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Restart=no
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...
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Alias=getty.target.wants/getty@tty8.service
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....
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and finally reload daemon and start the service:
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....
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systemctl daemon-reload
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systemctl start getty@tty8.service
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....
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Note that if you exit tty8 session, you wont be able to use it until
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next reboot or manual start by systemctl, except if you leave Restart as
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‘always’, but I highly recommend to avoid this according to security
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reasons.
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[[how-do-i-customize-a-unit-file-add-a-custom-unit-file]]
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How do I customize a unit file/ add a custom unit file?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The best way to customize unit files is to add
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/etc/systemd/system/foobar.service.d/*.conf where foobar.service is the
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name of the service you want to customize. If a directory doesn't
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already exist, create one and drop a conf file with the settings you
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want to override. For example,
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/etc/systemd/system/httpd.service.d/restart.conf
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....
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[Service]
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Restart=always
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RestartSec=30
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....
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Refer to man
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http://www.freedesktop.org/software/systemd/man/systemd.unit.html[systemd.unit]
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page for more details.
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Special care must be taken when overriding options which can be set
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muliple times (`ExecStart`, `ExecStartPre`, `ExecStartPost` are a common
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example). Assigning some value to the option _appends_ to the existing
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list, while assiging the _empty_ value _resets_ the list.
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For example, let's say we have a service file like this:
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....
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[Service]
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ExecStart=/bin/echo execstart1
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ExecStart=
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ExecStart=/bin/echo execstart2
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ExecStartPost=/bin/echo post1
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ExecStartPost=/bin/echo post2
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....
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When started, this service will print
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....
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execstart2
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post1
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post2
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....
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The same rules apply to snippets in `.d` directories. This means that
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snippets which override `ExecStart` and similar settings, often should
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start with the empty assignment `ExecStart=`, followed by the new
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setting.
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[[how-do-i-debug-systemd-issues]]
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How do I debug systemd issues?
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Refer to How_to_debug_Systemd_problems
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[[man-pages]]
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Man pages
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---------
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systemd comes with extensive documentation including several man pages.
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On the web: http://www.freedesktop.org/software/systemd/man/[list of all
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systemd man pages],
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http://www.freedesktop.org/software/systemd/man/systemd.directives.html[index
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of all settings].
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[[references]]
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References
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----------
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* http://www.freedesktop.org/wiki/Software/systemd[Project homepage]
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* http://0pointer.de/blog/projects/ - Lennart's blog has lots of
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information about systemd. Lennart is the primary systemd developer
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* http://www.freedesktop.org/wiki/Software/systemd/FrequentlyAskedQuestions
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* http://www.freedesktop.org/wiki/Software/systemd/TipsAndTricks
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* link:Features/systemd[ Features Fedora 15:systemd]
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* http://fosdem.org/2011/interview/lennart-poettering.html[Interview
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with the developer]
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'''
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See a typo, something missing or out of date, or anything else which can be
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||||
improved? Edit this document at https://pagure.io/fedora-docs/fedora-howto.
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