Commands that system administrators of Linux service management need to master

The main command-line tool for SYSTEMD is systemctl. Most Linux system administrators should already be familiar with system services and INIT system management, such as the use of Service,chkconfig and Telinit commands. SYSTEMD also accomplishes the same management tasks, but the syntax of the command tool Systemctl is different.

1. Sysvinit and Systemd's command comparison list

The following table helps system administrators understand the commands in SYSTEMD that can replace the original Sysvinit workflow. Note: Both the service and Chkconfig commands are still available in the SYSTEMD environment. Here is an example of the SSHD service:

Sysvinit command	SYSTEMD command	Note
Service sshd Start	Systemctl Start Sshd.service	Used to start a service (does not restart the existing service)
Service sshd Stop	Systemctl Stop Sshd.service	Used to stop a service (does not restart the existing service)
Service sshd Restart	Systemctl Restart Sshd.service	Used to stop and start a service
Service sshd Reload	Systemctl Reload Sshd.service	When supported, reloads the configuration file without interrupting the wait operation
Service sshd Condrestart	Systemctl Condrestart Sshd.service	If the service is running, restart it
Service sshd Status	Systemctl Status Sshd.service	Reporting whether the service is running
ls/etc/rc.d/init.d/	Systemctl List-unit-files--type=service Ls/lib/systemd/system/*.service /etc/systemd/system/*.service	Used to list the services that can be started or stopped
Chkconfig sshd on	Systemctl Enable Sshd.service	Set the service to start at the next startup or when other trigger conditions are met
Chkconfig sshd off	Systemctl Disable Sshd.service	Setting the service to disabled at the next startup or when other trigger conditions are met
Chkconfig sshd	Systemctl is-enabled Sshd.service	Used to check whether a service is configured to be enabled or disabled in the current environment
Chkconfig--list	Systemctl list-unit-files--type=service (recommended) Ls/etc/systemd/system/*.service	Output enabled and disabled for the service under each run level
Chkconfig sshd--list	Ls/etc/systemd/system/*.wants/sshd.service	Used to list which runlevel the service is enabled and disabled
Chkconfig sshd--add	Systemctl Daemon-reload	used when creating a new service file or changing settings

Note: All/sbin/service and/sbin/chkconfig listed above can still work in SYSTEMD environment and will be translated into native equivalent commands if necessary. The only exception is Chkconfig--list.

Sysvinit and Systemd Change the Run level command comparison table:

Sysvinit command	SYSTEMD command	Note
Telinit 3	Systemctl Isolate Multi-user.target Or Systemctl Isolate Runlevel3.target OR telinit 3	Changing the maximum user run level
Sed s/^id:.*:initdefault:/id:3:initdefault:/	Ln-sf/lib/systemd/system/multi-user.target/etc/systemd/system/default.target	Set the multi-user run level to be used at the next startup

Sysvinit and SYSTEMD Power management Command Comparison table:

Sysvinit command	SYSTEMD command	Operation
Reboot	Systemctl reboot	Restarting the machine
Halt-p	Systemctl Poweroff	Shutdown
echo Standby >/SYS/POWER/STATC	Systemctl suspend	Standby
echo Platform >/sys/power/dist; Echo Dist >/sys/power/state Or echo Shutdown >/sys/power/disk;echo dist >/sys/power/state	Systemctl Hibernate	Dormancy
	Systemctl Hybrid-sleep	Mixed sleep mode (simultaneously hibernate to hard drive and standby)

The shutdown command is not available to every logged-on user under any circumstances, and is generally only available to administrators.

2. Systemctl Command Instances

Basic usage of 2.1 systemctl

• systemctl--lists all loaded cells and their status (unit is the term for Task/service).

• Systemctl list-units--Lists all the units.

• Systemctl start [NAME ...] --Start (activate) one or more cells.

• Systemctl stop [NAME ...] --Stop (deactivate) one or more cells.

• systemctl disable [NAME ...] --Disables one or more cell files.

• Systemctl list-unit-files--displays all installed cell files and their status.

• Systemctl--failed--shows which units have failed during startup.

• Systemctl--type=xxx--type filter; type may be: Service, mount point, device, socket, and start target.

• Systemctl enable debug-shell.service--to start the shell on TTY 9 for debugging.

Commands that system administrators of Linux service management need to master