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| The '''systemd project''' is an amalgamation of init processes and service managers. | '''systemd''' is an amalgamation of init processes and service managers. |
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| == Unit Files == | == Usage == |
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| The systemd project is configured using '''unit files'''. A unit file's functionality is hinted by its file extension: * services (.service) * mount points (.mount) * devices (.device) * sockets (.socket) |
A service is configured with a '''unit file'''. A unit file's functionality is hinted by its file extension: |
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| Server-level unit files are located in `/etc/systemd`. User-level unit files are located in | * 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. |
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| === Replacing Unit Files === | === Overwriting Unit Files === |
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| To replace the unit file `/usr/lib/systemd/system/foo`, create the file `/etc/systemd/system/foo` and re-enable. Alternatively, try: |
To overwrite a unit file, try: |
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| systemctl edit --full unit | systemctl edit --full foo |
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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. |
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| A '''drop-in file''' is a segment of a unit file that is parsed and applied over the pre-existing unit file. | A '''drop-in file''' is a partial unit file that is patched over the primary unit file at load time. |
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| To create drop-in files for the unit file `/usr/lib/systemd/system/foo`, create the directory `/etc/systemd/system/foo.d/` and place `.conf` files there to override or add new options. Alternatively, try: |
To create a drop-in file, try: |
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| systemctl edit unit | systemctl edit foo |
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| 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. | |
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=== Reverting Unit Files === To revert changes to a unit file, try: |
To revert edits to a unit file, try: |
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| systemctl revert unit | systemctl revert foo |
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| == Daemon Configuration == | == Configuration == |
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| If a unit file takes too long to start at boot, systemd switches to verbose mode and prints information that may help in diagnosing issues. This setting can be explicitly disabled in `/etc/systemd/system.conf`. | 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`. |
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 systemd-networkd, systemd-resolved, systemd-timerd, systemd-logind, systemd-homed, systemd-firewalld, among a few others.
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
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.
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