systemd replaces upstart and init

The systemd daemon replaces Upstart for managing system run levels and services. Replacing init, systemd is the first process that starts after the system boots, and is the final process that is running when the system shuts down. systemd controls the final stages of booting and prepares the system for use. systemd also speeds up booting by loading services concurrently.

systemctl Command Equivalents

The following table shows the nearest equivalent Oracle Linux 7 systemctl command for various system management commands used in Oracle Linux 6.

Table 1 — systemctl Command equivalents
OL6 CommandOL7 EquivalentDescription
chkconfig --list name systemctl is-enabled name Check whether a service is enabled to start at boot time.
chkcondig name off systemctl disable name Disable a service from starting at boot time.
chkconfig name on systemctl enable name Enable a service to start at boot time.
halt systemctl halt Halt the system
pm-hibernate systemctl hibernate Put the system into hiberation
pm-suspend systemctl suspend Suspend the system
pm-suspend-hybrid systemctl hybrid-sleep Put the system into hibernation and suspend its operation
poweroff systemctl poweroff Power off the system
reboot systemctl reboot Reboot the system
runlevel systemctl list-units --type target Display the currently active targets, which taken as a group constitute the nearest equivalent that systemd has to a run level.
service name start systemctl start name Start a service
service namestatus systemctl status name Display the status of a service
service name stop systemctl stop name Stop a service
telinit runlevel systemctl isolate name.target Change the systemd target

As well as services (name.service) and targets (name.target), other types of unit that you can manage in systemd include devices (name.device), file system mount points (name.mount), and sockets (name.socket).

For example, the following command instructs the system to mount the temporary file system (tmpfs) on /tmp at boot time:

root@ol7# systemctl enable tmp.mount

systemd Target Equivalents

The following table shows the nearest equivalent systemd targets to the run levels that are used in Oracle Linux 6.

Table 2 — systemd Target Eqivalents
OL6 Run LevelOL7 EqivalentDescription
0 poweroff.target
runlevel0.target
Shutdown and power off the system.
1 rescue.target
runlevel1.target
Set up a rescue shell.
2 multi-user.target
runlevel2.target
Set up a non-graphical, multi-user system.
3 multi-user.target
runlevel3.target
Set up a non-graphical, multi-user system with networking.
4 multi-user.target
runlevel4.target
User defined (or not used).
5 graphical.target
runlevel5.target
Set up a multi-user system with networking and display manager.
6 reboot.system
runlevel6.target
Shut down and reboot the system.

The runlevel* targets are implemented as symbolic links.

The nearest equivalent systemd target to the Oracle Linux 6 run levels 2, 3, and 4 is multi-user.target.

You can use the following commands to display the current default systemd target and to configure a new default target:

root@ol7# systemctl get-default
root@ol7# systemctl set-default name.target

If required, you can create customized versions of the targets that are defined in /usr/lib/systemd/system.

For more information, see the systemctl(1) and systemd.unit(5) manual pages and http:// freedesktop.org/wiki/Software/systemd/.