Using systemctl to Manage Services
Note: For
in all examples below, the format of may also be used instead - though it is not required in recent versions of systemd, and is therefore not shown.
Several examples of widely used services are: httpd (Apache Web server), sshd (SSH server), nfs (NFS server), autofs (AutoFS service), vsftpd (the "Very Secure FTP" server), and many more...
Start a Service
#
systemctl start
Stop a Service
#
systemctl stop
Restart a Service
#
systemctl restart
A Conditional Restart of a Service (Restarts a service only if it's already running)
#
systemctl try-restart
Reload a Service
#
systemctl reload
Check whether a Service is Running
#
systemctl status
( Or: #
systemctl is-active )
List all Available Services and Show their Running Status
Note: may be "piped" through grep, to find a specific service: | grep
#
systemctl list-units --type service --all
or
systemctl list-units -t service
Enable a Service (this makes it start automatically at start up)
does what
chkconfig on used to do.
#
systemctl enable
Disable a Service (this stops the service from starting at startup)
does what
chkconfig off used to do.
#
systemctl disable
Check whether a Service is Enabled
#
systemctl is-enabled
( Also mentioned in: # systemctl status
, under "Loaded:" )
List all Available Services, and check whether they are Enabled
Note: may be piped through grep, to find a specific service: | grep
#
systemctl list-unit-files --type service
Kill all Running Processes Related to a Service
#
systemctl kill
Available unit types.
Service unit
.service
A system service.
Target unit
.target
A group of systemd units.
Automount unit
.automount
A file system automount point.
Device unit
.device
A device file recognized by the kernel.
Mount unit
.mount
A file system mount point.
Path unit
.path
A file or directory in a file system.
Scope unit
.scope
An externally created process.
Slice unit
.slice
A group of organized units that manage system processes.
Snapshot unit
.snapshot
A saved state of the systemd manager.
Socket unit
.socket
An inter-process communication socket.
Swap unit
.swap
A swap device or a swap file.
Timer unit
.timer
A systemd timer.
Boot process
Systemd primary task is to manage the boot process and provides information about it.
To get the boot process duration, type:
#
systemd-analyze
To get the time spent by each task during the boot process, type:
#
systemd-analyze blame
To get the list of the dependencies, type:
#
systemctl list-dependencies
More examples
To move to single user mode, type:
#
systemctl rescue
To move to the level 3 (equivalent to the previous level 3), type:
#
systemctl isolate runlevel3.target
Or:
#
systemctl isolate multi-user.target
To move to the graphical level (equivalent to the previous level 5), type:
#
systemctl isolate graphical.target
To set the default run level to non-graphical mode, type:
#
systemctl set-default multi-user.target
To set the default run level to graphical mode, type:
#
systemctl set-default graphical.target
To get the current default run level, type:
#
systemctl get-default
To stop a server, type:
#
systemctl poweroff
Note: You can still use the poweroff command, a link to the systemctl command has been created (the same thing is true for the halt and reboot commands).
To reboot , suspend it or put your machine into hibernation, type:
#
systemctl reboot
#
systemctl suspend
#
systemctl hibernate
Journal analysis
In addition, Systemd handles the system event log, a syslog daemon is not mandatory any more.
To get the content of the Systemd journal, type:
#
journalctl
To get all the events related to the crond process in the journal, type:
#
journalctl /sbin/crond
Note: You can replace /sbin/crond by `which crond`.
To get all the events since the last boot, type:
#
journalctl -b
To get all the events that appeared today in the journal, type:
#
journalctl --since=today
To get all the events with a syslog priority of err, type:
#
journalctl -p err
To get the 10 last events and wait for any new one (like “tail -f /var/log/messages“), type:
#
journalctl -f
