= Systemd =

'''systemd''' is an amalgamation of init processes and service managers.

First and foremost, it is the server daemon `systemd(1)`. It is also the userland interfaces `systemctl(1)` and `journalctl(1)`.

The systemd project also encompasses [[Linux/SystemdNetworkd|systemd-networkd]], [[Linux/SystemdResolved|systemd-resolved]], [[Linux/SystemdTimerd|systemd-timerd]], [[Linux/SystemdLogind|systemd-logind]], [[Linux/SystemdHomed|systemd-homed]], [[Linux/SystemdFirewalld|systemd-firewalld]], among a few others.

<<TableOfContents>>

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== Usage ==

A service is configured with a '''unit file'''. A unit file's functionality is hinted by its file extension:

 * services (`.service`)
 * mount points (`.mount`)
 * devices (`.device`)
 * sockets (`.socket`)

Operating system unit files are located in `/usr/lib/systemd` and symlinked to `/etc/systemd` to enable them. User process unit files are located in `$HOME/.config/systemd/user` and symlinked to `/etc/systemd/user` to enable them.



=== Overwriting Unit Files ===

To overwrite a unit file, try:

{{{
systemctl edit --full foo
}}}

Alternatively but not recommended: to overwrite `/usr/lib/systemd/system/foo`, create an editted copy at `/etc/systemd/system/foo`.

In either case, reloading the service will cause the new configuration to be used.



=== Editing Unit Files ===

A '''drop-in file''' is a partial unit file that is patched over the primary unit file at load time.

To create a drop-in file, try:

{{{
systemctl edit foo
}}}

Alternatively but not recommended: to edit `/usr/lib/systemd/system/foo`, create the directory `/etc/systemd/system/foo.d/` and place `.conf` files within it.

To revert edits to a unit file, try:

{{{
systemctl revert foo
}}}

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== Configuration ==

If a unit file takes too long to start at boot, `systemd(1)` switches to verbose mode and prints information that may help in diagnosing issues. This setting can be explicitly disabled in `/etc/systemd/system.conf`.

{{{
[Manager]
ShowStatus=no
}}}

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== See also ==

[[https://man.archlinux.org/man/systemd.1|systemd(1)]]



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