systemctl parameter description
1. Use syntax
Usage: systemctl [OPTIONS…] {COMMAND}…
2, parameter description
| parameter | parameter description |
|---|---|
| start | immediately start the following unit |
| stop | immediately close the following unit |
| restart | Close immediately and start the following unit, that is, execute stop and start again |
| reload | Do not close and then follow In the case of the unit, reload the configuration file to make the setting take effect |
| enable | Setting the next time the unit is turned on, the following unit will be disabled Start |
| disable | Set the following unit will not be started when the next boot |
| status | The status of the following unit will list information such as whether it is running, whether it is powered on, etc. |
| is-active | Is it currently running |
| is-enable | Is there a preset to enable this unit when booting? |
| kill | Don’t be scared by the name kill, it is actually to run The process of the unit sends a signal |
| show | Lists the configuration of the unit. |
| mask | Log out the unit, you will not be able to start this unit after logout |
| unmask | Cancel logout of unit |
| list-units | List the currently activated units according to the unit. If you add –all, the ones that are not started will be listed. (equivalent to no parameters) |
| list-unit-files | List all the units to install and their startup status (enabled, disabled, static, mask). |
| –type=TYPE is the unit type, mainly service, socket, target, etc. | |
| get-default | Get the current target |
| set-default | The target after setting becomes the default operation mode |
| isolate | Switch to the following mode |
systemctl description
| Task | Old Instructions | New Instructions |
|---|---|---|
| Make a service start automatically | chkconfig –level 3 | httpd on systemctl enable httpd.service |
| Make a service Do not start automatically | chkconfig –level 3 httpd off | systemctl disable httpd.service |
| Check service status | service httpd status systemctl status httpd.service (service details) | systemctl is-enabled httpd.service (only shows whether Active) |
| Show all started services | chkconfig –list | systemctl list-units –type=service |
| Start a service | service httpd start | systemctl start httpd.service |
| Stop a service | service httpd stop | systemctl stop httpd.service |
| Restart a service | service httpd restart | systemctl restart httpd.service |
| A service reloads the configuration file | service httpd reload | systemctl reload httpd.service |
systemctl example
List all available units
systemctl list-unit-files |more systemctl list-units --type=target
List all loaded units
systemctl list-units |more
View all services that can be managed by systemctl
systemctl list-units --type=service
There are many kinds of management units available for systemctl. In daily work, we only use them to manage services. The common types of units are:
Service unit: file extension .service, used to define system services;
Target unit: file extension .target, used to simulate the realization of “running level”;
Device unit: file extension .device, used to define the device recognized by the kernel;
Mount unit: file extension .mount, used to define the mount point of the file system;
Socket unit: file extension .socket, used to identify the socket file used for inter-process communication;
Snapshot unit: file extension .snapshot, used to manage system snapshots;
Swap unit: file extension .swap, used to identify the swap device;
Automount unit: file extension .automount, used to define the automatic point device of the file system;
Path unit: file extension .path, used to define a file or directory in the file system;
Logout service
After the service is deregistered, the service cannot be started and stopped through systemctl.
[root@s153 system]# systemctl mask firewalld Created symlink from /etc/systemd/system/firewalld.service to /dev/null. [root@s153 system]# systemctl start firewalld Failed to start firewalld.service: Unit is masked.
Cancel logout service
[root@s153 system]# systemctl unmask firewalld Removed symlink /etc/systemd/system/firewalld.service. [root@s153 system]# systemctl start firewalld
Set the service to start automatically at boot
[root@s153 system]# systemctl enable xinetd.service Created symlink from /etc/systemd/system/multi-user.target.wants/xinetd.service to /usr/lib/systemd/system/xinetd.service.
Cancel the service from starting at boot
[root@s153 system]# systemctl disable xinetd.service Removed symlink /etc/systemd/system/multi-user.target.wants/xinetd.service.
View machine information
[root@s153 system]# systemctl list-machines NAME STATE FAILED JOBS s153 (host) running 0 0 1 machines listed.
View system environment variables
[root@s153 system]# systemctl show-environment LANG=zh_CN.UTF-8 PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin
Reload unit file
If you manually modified the unit file, you can use this command to reload it.
[root@s153 system]# systemctl daemon-reload
Create a system snapshot
[root@s153 system]# systemctl snapshot wuhs wuhs.snapshot
Delete the specified snapshot
[root@s153 system]# systemctl delete wuhs
Check whether the service starts automatically at boot
[root@s153 system]# systemctl is-enabled xinetd.service enabled
Kill the service
[root@s153 system]# systemctl kill xinetd [root@s153 system]# systemctl is-failed xinetd inactive
Enter rescue mode
[root@s153 system]# systemctl rescue Broadcast message from root@s153 on pts/1 (Wed 2022-07-20 13:08:30 CST): The system is going down to rescue mode NOW! #Switch to default mode in rescue mode [root@s153 ~]# systemctl default
Shut down the system
[root@s153 ~]# systemctl poweroff
Restart the machine
[root@s153 ~]# systemctl reboot
System Sleep
suspend suspend mode, similar to the sleep mode of the window environment, will save the state data of the system to the memory, and then shut down most of the system hardware, of course, there is no actual shutdown. When the user presses the button to wake up the machine, the system data will be restored in the memory, and then the hardware that is mostly shut down will be re-driven, and it will start to work normally! Wake up faster.
[root@s153 ~]# systemctl suspend
View system startup mode
[root@s153 boot]# systemctl get-default multi-user.target
Set the system to start with a graphical interface
[root@s153 system]# systemctl set-default graphical.target Removed symlink /etc/systemd/system/default.target. Created symlink from /etc/systemd/system/default.target to /usr/lib/systemd/system/graphical.target.