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从0到1一步一步玩转openEuler--21 openEuler 管理服务-改变运行级别

21 管理服务-改变运行级别

21.1 Target和运行级别

systemd用目标(target)替代了运行级别的概念,提供了更大的灵活性,如您可以继承一个已有的目标,并添加其他服务,来创建自己的目标。表7列举了systemd下的目标和常见runlevel的对应关系。

表 7 运行级别和systemd目标

运行级别 systemd目标(target) 描述
runlevel0.target,poweroff.target 关闭系统。
1, s, single runlevel1.target,rescue.target 单用户模式。
2, 4 runlevel2.target,runlevel4.target,multi-user.target 用户定义/域特定运行级别。默认等同于3。
3 runlevel3.target,multi-user.target 多用户,非图形化。用户可以通过多个控制台或网络登录。
5 runlevel5.target,graphical.target 多用户,图形化。通常为所有运行级别3的服务外加图形化登录。
6 runlevel6.target,reboot.target 重启系统。
emergency emergency.target 紧急Shell

21.2 查看系统默认启动目标

查看当前系统默认的启动目标,命令如下:

# systemctl get-default

例如示例命令如下:

[root@superman-21 ~]# systemctl get-default
multi-user.target
[root@superman-21 ~]# 

21.3 查看当前系统所有的启动目标

查看当前系统所有的启动目标,命令如下:

# systemctl list-units --type=target

例如示例命令如下:

[root@superman-21 ~]# systemctl list-units --type=target
  UNIT                  LOAD   ACTIVE SUB    DESCRIPTION                        
  basic.target          loaded active active Basic System
  bluetooth.target      loaded active active Bluetooth Support
  getty.target          loaded active active Login Prompts
  local-fs-pre.target   loaded active active Preparation for Local File Systems
  local-fs.target       loaded active active Local File Systems
  multi-user.target     loaded active active Multi-User System
  network-online.target loaded active active Network is Online
  network-pre.target    loaded active active Preparation for Network
  network.target        loaded active active Network
  nfs-client.target     loaded active active NFS client services
  paths.target          loaded active active Path Units
  remote-fs-pre.target  loaded active active Preparation for Remote File Systems
  remote-fs.target      loaded active active Remote File Systems
  rpc_pipefs.target     loaded active active rpc_pipefs.target
  rpcbind.target        loaded active active RPC Port Mapper
  slices.target         loaded active active Slice Units
  sockets.target        loaded active active Socket Units
  sound.target          loaded active active Sound Card
  sshd-keygen.target    loaded active active sshd-keygen.target
  swap.target           loaded active active Swaps
  sysinit.target        loaded active active System Initialization
  timers.target         loaded active active Timer Units

LOAD   = Reflects whether the unit definition was properly loaded.
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
SUB    = The low-level unit activation state, values depend on unit type.
22 loaded units listed. Pass --all to see loaded but inactive units, too.
To show all installed unit files use 'systemctl list-unit-files'.
[root@superman-21 ~]# 

21.4 改变默认目标

改变系统默认的目标,在root权限下执行如下命令:

# systemctl set-default name.target

例如示例命令如下:

[root@superman-21 ~]# systemctl set-default multi-user.target
[root@superman-21 ~]# 

21.5 改变当前目标

改变当前系统的目标,在root权限下执行如下命令:

# systemctl isolate name.target

例如示例命令如下:

[root@superman-21 ~]# systemctl isolate rescue.target
[root@superman-21 ~]#

21.6 切换到救援模式

改变当前系统为救援模式,在root权限下执行如下命令:

# systemctl rescue

例如示例命令如下:

[root@superman-21 ~]# systemctl rescue
[root@superman-21 ~]# 

这条命令和“systemctl isolate rescue.target”类似。命令执行后会在串口有如下打印信息:

You are in rescue mode. After logging in, type "journalctl -xb" to viewsystem logs, systemctl reboot" to reboot, "systemctl default" or "exit"to boot into default mode.
Give root password for maintenance
(or press Control-D to continue):

image-20221211195017526说明: 用户需要重启系统,从救援模式进入正常模式。

21.7 切换到紧急模式

改变当前系统为紧急模式,在root权限下执行如下命令:

# systemctl emergency

这条命令和“systemctl isolate emergency.target”类似。命令执行后会在串口有如下打印信息:

You are in emergency mode. After logging in, type "journalctl -xb" to viewsystem logs, systemctl reboot" to reboot, "systemctl default" or "exit"to boot into default mode.
Give root password for maintenance
(or press Control-D to continue):

例如示例命令如下:

[root@superman-21 ~]# systemctl emergency
[root@superman-21 ~]# 

image-20221211195017526 说明: 用户需要重启系统,从紧急模式进入正常模式。

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