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Services are programs that can be run without user intervention. On ubuntu, they
are managed by systemd.
systemd provides a standardized way to manage (start,
stop, getting status, …) services.
Most services are provided by their installation pacakges, but it’s possible to create custom services, as explained in this post.
systemctl (man page)
systemctl is the tool to manage services. It is typically used when service
or /etc/init.d/SERVICENAME was used in sysvinit
based systems.
Getting the status
Example for the ssh service:
● ssh.service - OpenBSD Secure Shell server
Loaded: loaded (/lib/systemd/system/ssh.service; enabled; vendor preset: enabled)
Active: active (running) since Tue 2018-06-26 19:28:22 CEST; 17min ago
Main PID: 950 (sshd)
Tasks: 1 (limit: 4630)
CGroup: /system.slice/ssh.service
└─950 /usr/sbin/sshd -D
Jun 26 19:28:22 server systemd[1]: Starting OpenBSD Secure Shell server...
Jun 26 19:28:22 server sshd[950]: Server listening on 0.0.0.0 port 22.
Jun 26 19:28:22 server sshd[950]: Server listening on :: port 22.
Jun 26 19:28:22 server systemd[1]: Started OpenBSD Secure Shell server.
Jun 26 19:28:55 server sshd[1182]: Accepted publickey for pim from X.X.X.X port X ssh2: RSA SHA256:X/X
Jun 26 19:28:55 server sshd[1182]: pam_unix(sshd:session): session opened for user pim by (uid=0)
Start/stop/enable/disable/…
| Command | Effect |
|---|---|
sudo systemctl daemon-reload |
Reload systemd configuration, MUST be done after each .service file change |
sudo systemctl start SERVICE |
Start a service |
sudo systemctl stop SERVICE |
Stop a service |
sudo systemctl enable SERVICE |
Enable a service, the service will be automatically started |
sudo systemctl disable SERVICE |
Disable a service |
sudo systemctl enable SERVICE --now |
Enable and start a service, the service will be automatically started |
sudo systemctl disable SERVICE --now |
Disable and stop a service |
sudo systemctl restart SERVICE |
Restart a service |
sudo systemctl reload SERVICE |
Reload a service (only if reload is implemented) |
sudo systemctl reload-or-restart SERVICE |
Reload a service if reload is implemented, restart otherwise |
Listing services
systemctl list-units --type=service
UNIT LOAD ACTIVE SUB DESCRIPTION
accounts-daemon.service loaded active running Accounts Service
apparmor.service loaded active exited AppArmor initialization
apport.service loaded active exited LSB: automatic crash report generation
atd.service loaded active running Deferred execution scheduler
blk-availability.service loaded active exited Availability of block devices
...
Listing enabled services
systemctl list-units --type=service --state=active
UNIT LOAD ACTIVE SUB DESCRIPTION
accounts-daemon.service loaded active running Accounts Service
apparmor.service loaded active exited AppArmor initialization
apport.service loaded active exited LSB: automatic crash report generation
atd.service loaded active running Deferred execution scheduler
blk-availability.service loaded active exited Availability of block devices
...
Listing running services
systemctl list-units --type=service --state=running
UNIT LOAD ACTIVE SUB DESCRIPTION
accounts-daemon.service loaded active running Accounts Service
atd.service loaded active running Deferred execution scheduler
cron.service loaded active running Regular background program processing daemon
dbus.service loaded active running D-Bus System Message Bus
...
The next post is about custom services.
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Question, remark, bug? Don't hesitate to contact me or report a bug.