linux命令学习之：systemctl

待我称王封你为后i 2022-03-21 08:52 786阅读 0赞

转载: [https://www.cnblogs.com/jing99/p/7895860.html][https_www.cnblogs.com_jing99_p_7895860.html]

systemctl命令是系统服务管理器指令，主要负责控制systemd系统和服务管理器，它实际上将 service 和 chkconfig 这两个命令组合到一起。

CentOS 7.x开始，CentOS开始使用systemd服务来代替daemon，原来管理系统启动和管理系统服务的相关命令全部由systemctl命令来代替。

Systemd是一个系统管理守护进程、工具和库的集合，用于取代System V初始进程。Systemd的功能是用于集中管理和配置类UNIX系统。

在Linux生态系统中，Systemd被部署到了大多数的标准Linux发行版中，只有为数不多的几个发行版尚未部署。Systemd通常是所有其它守护进程的父进程，但并非全是如此。

**1、原来的 service 命令与 systemctl 命令对比**

<table> 
 <thead> 
  <tr> 
   <th>daemon命令</th> 
   <th>systemctl命令</th> 
   <th>说明</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>service [服务] start</td> 
   <td>systemctl start [unit type]</td> 
   <td>启动服务</td> 
  </tr> 
  <tr> 
   <td>service [服务] stop</td> 
   <td>systemctl stop [unit type]</td> 
   <td>停止服务</td> 
  </tr> 
  <tr> 
   <td>service [服务] restart</td> 
   <td>systemctl restart [unit type]</td> 
   <td>重启服务</td> 
  </tr> 
 </tbody> 
</table>

此外还是二个systemctl参数没有与service命令参数对应

*  status：参数来查看服务运行情况
 *  reload：重新加载服务，加载更新后的配置文件（并不是所有服务都支持这个参数，比如network.service）

**　　示例：**

![复制代码][copycode.gif]

#启动网络服务
    systemctl start network.service
    
    #停止网络服务
    systemctl stop network.service
    
    #重启网络服务
    systemctl restart network.service
    
    #查看网络服务状态
    systemctl status network.serivce

![复制代码][copycode.gif]

**2、原来的chkconfig 命令与 systemctl 命令对比**

<table> 
 <thead> 
  <tr> 
   <th>daemon命令</th> 
   <th>systemctl命令</th> 
   <th>说明</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>chkconfig [服务] on</td> 
   <td>systemctl enable [unit type]</td> 
   <td>设置服务开机启动</td> 
  </tr> 
  <tr> 
   <td>chkconfig [服务] off</td> 
   <td>systemctl disable [unit type]</td> 
   <td>设备服务禁止开机启动<br> &nbsp;</td> 
  </tr> 
 </tbody> 
</table>

**　　示例：**

![复制代码][copycode.gif]

#停止cup电源管理服务
    systemctl stop cups.service
    
    #禁止cups服务开机启动
    systemctl disable cups.service
    
    #查看cups服务状态
    systemctl status cups.service
    
    #重新设置cups服务开机启动
    systemctl enable cups.service

![复制代码][copycode.gif]

**3、查看系统上上所有的服务**

**命令格式：**`systemctl [command] [–type=TYPE] [–all]`

**参数详解：**

`　　command` - list-units：依据unit列出所有启动的unit。加上 –all 才会列出没启动的unit; - list-unit-files:依据/usr/lib/systemd/system/ 内的启动文件，列出启动文件列表

`–type=TYPE` - 为unit type, 主要有service, socket, target

**　　应用举例：**

<table> 
 <thead> 
  <tr> 
   <th>systemctl命令</th> 
   <th>说明</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>systemctl</td> 
   <td>列出所有的系统服务</td> 
  </tr> 
  <tr> 
   <td>systemctl list-units</td> 
   <td>列出所有启动unit</td> 
  </tr> 
  <tr> 
   <td>systemctl list-unit-files</td> 
   <td>列出所有启动文件</td> 
  </tr> 
  <tr> 
   <td>systemctl list-units –type=service –all</td> 
   <td>列出所有service类型的unit</td> 
  </tr> 
  <tr> 
   <td>systemctl list-units –type=service –all grep cpu</td> 
   <td>列出 cpu电源管理机制的服务</td> 
  </tr> 
  <tr> 
   <td>systemctl list-units –type=target –all</td> 
   <td>列出所有target</td> 
  </tr> 
 </tbody> 
</table>

**4、systemctl特殊的用法**

<table> 
 <thead> 
  <tr> 
   <th>systemctl命令</th> 
   <th>说明</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>systemctl is-active [unit type]</td> 
   <td>查看服务是否运行</td> 
  </tr> 
  <tr> 
   <td>systemctl is-enable [unit type]</td> 
   <td>查看服务是否设置为开机启动</td> 
  </tr> 
  <tr> 
   <td>systemctl mask [unit type]</td> 
   <td>注销指定服务</td> 
  </tr> 
  <tr> 
   <td>systemctl unmask [unit type]</td> 
   <td>取消注销指定服务</td> 
  </tr> 
 </tbody> 
</table>

**　　应用举例：**

![复制代码][copycode.gif]

#查看网络服务是否启动
    systemctl is-active network.service
    
    #检查网络服务是否设置为开机启动
    systemctl is-enable network.service
    
    #停止cups服务
    systemctl stop cups.service
    
    #注销cups服务
    systemctl mask cups.service
    
    #查看cups服务状态
    systemctl status cups.service
    
    #取消注销cups服务
    systemctl unmask cups.service

![复制代码][copycode.gif]

**5、常用示例：**

**Systemctl基础、体验**

1. 检查系统中是否安装有systemctl并确定当前安装的版本

[root@CTU1000094955 ~]# systemctl --version
    systemd 219
    +PAM +AUDIT +SELINUX +IMA -APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ -LZ4 -SECCOMP +BLKID +ELFUTILS +KMOD +IDN

上例中很清楚地表明，我们安装了219版本的systemctl。

2. 检查systemd和systemctl的二进制文件和库文件的安装位置

[root@CTU1000094955 ~]# whereis systemd
    systemd: /usr/lib/systemd /etc/systemd /usr/share/systemd /usr/share/man/man1/systemd.1.gz
    [root@CTU1000094955 ~]# whereis systemctl
    systemctl: /usr/bin/systemctl /usr/share/man/man1/systemctl.1.gz

3. 检查systemd是否运行

[root@CTU1000094955 ~]# ps -eaf | grep [s]ystemd
    root          1      0  0 16:15 ?        00:00:04 /usr/lib/systemd/systemd --switched-root --system --deserialize 21
    root        631      1  0 16:15 ?        00:00:24 /usr/lib/systemd/systemd-journald
    root        661      1  0 16:15 ?        00:00:00 /usr/lib/systemd/systemd-udevd
    dbus        813      1  0 16:15 ?        00:00:02 /bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation
    root        841      1  0 16:15 ?        00:00:00 /usr/lib/systemd/systemd-logind

**　　注意**：systemd是作为父进程（PID=1）运行的。在上面带（-e）参数的ps命令输出中，选择所有进程，（-a）选择除会话前导外的所有进程，并使用（-f）参数输出完整格式列表（即 -eaf）。

也请注意上例中后随的方括号和例子中剩余部分。方括号表达式是grep的字符类表达式的一部分。

4. 分析systemd启动进程

[root@CTU1000094955 ~]# systemd-analyze
    Startup finished in 743ms (kernel) + 6.959s (initrd) + 17.696s (userspace) = 25.399s

5. 分析启动时各个进程花费的时间

![复制代码][copycode.gif]

[root@CTU1000094955 ~]# systemd-analyze blame
             11.859s dev-xvda1.device
              5.670s NetworkManager-wait-online.service
              4.610s plymouth-quit-wait.service
              3.757s systemd-udev-settle.service
              3.078s kdump.service
              2.257s mysql.service
              1.451s libvirtd.service
              1.228s postfix.service
               751ms uvp-monitor.service
               675ms spesserviced.service
               675ms messageserviced.service
               660ms tuned.service
               586ms network.service
               525ms accounts-daemon.service
               467ms NetworkManager.service
               457ms systemd-udevd.service
               416ms abrt-ccpp.service
               397ms firewalld.service
               365ms ModemManager.service

![复制代码][copycode.gif]

6. 分析启动时的关键链

![复制代码][copycode.gif]

[root@CTU1000094955 ~]# systemd-analyze critical-chain
    The time after the unit is active or started is printed after the "@" character.
    The time the unit takes to start is printed after the "+" character.
    
    graphical.target @17.682s
    ?..multi-user.target @17.682s
      ?..getty.target @17.682s
        ?..serial-getty@hvc0.service @17.681s
          ?..systemd-user-sessions.service @12.929s +18ms
            ?..remote-fs.target @12.921s
              ?..remote-fs-pre.target @12.921s
                ?..iscsi-shutdown.service @12.907s +12ms
                  ?..network.target @12.900s
                    ?..network.service @12.311s +586ms
                      ?..NetworkManager.service @6.166s +467ms
                        ?..basic.target @5.903s
                          ?..sockets.target @5.903s
                            ?..rpcbind.socket @5.903s
                              ?..sysinit.target @5.895s
                                ?..systemd-update-utmp.service @5.877s +16ms
                                  ?..auditd.service @5.738s +135ms
                                    ?..systemd-tmpfiles-setup.service @5.661s +73ms
                                      ?..rhel-import-state.service @5.526s +134ms
                                        ?..local-fs.target @5.525s
                                          ?..run-user-0.mount @14.041s
                                            ?..local-fs-pre.target @1.615s
                                              ?..systemd-tmpfiles-setup-dev.service @
                                                ?..kmod-static-nodes.service @1.473s 
                                                  ?..systemd-journald.socket
                                                    ?..-.slice

![复制代码][copycode.gif]

**　　重要**：Systemctl接受服务（.service），挂载点（.mount），套接口（.socket）和设备（.device）作为单元。

7. 列出所有可用单元

![复制代码][copycode.gif]

[root@CTU1000094955 ~]# systemctl list-unit-files
    UNIT FILE                                   STATE   
    proc-sys-fs-binfmt_misc.automount           static  
    dev-hugepages.mount                         static  
    dev-mqueue.mount                            static  
    proc-fs-nfsd.mount                          static  
    proc-sys-fs-binfmt_misc.mount               static  
    sys-fs-fuse-connections.mount               static  
    sys-kernel-config.mount                     static  
    sys-kernel-debug.mount                      static  
    tmp.mount                                   disabled
    var-lib-nfs-rpc_pipefs.mount                static  
    brandbot.path                               disabled
    cups.path                                   enabled 
    systemd-ask-password-console.path           static

![复制代码][copycode.gif]

8. 列出所有运行中单元

![复制代码][copycode.gif]

[root@CTU1000094955 ~]# systemctl list-units
      UNIT                                                                               LOAD   ACTIVE SUB       DESCRIPTION
      proc-sys-fs-binfmt_misc.automount                                                  loaded active waiting   Arbitrary Executable File Formats File System Automount Point
      sys-devices-pci0000:00-0000:00:01.1-ata2-host1-target1:0:1-1:0:1:0-block-sr0.device loaded active plugged   QEMU_DVD-ROM
      sys-devices-platform-serial8250-tty-ttyS2.device                                   loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS2
      sys-devices-platform-serial8250-tty-ttyS3.device                                   loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS3
      sys-devices-pnp0-00:08-tty-ttyS0.device                                            loaded active plugged   /sys/devices/pnp0/00:08/tty/ttyS0
      sys-devices-pnp0-00:09-tty-ttyS1.device                                            loaded active plugged   /sys/devices/pnp0/00:09/tty/ttyS1
      sys-devices-vbd\x2d51712-block-xvda-xvda1.device                                   loaded active plugged   /sys/devices/vbd-51712/block/xvda/xvda1
      sys-devices-vbd\x2d51712-block-xvda-xvda2.device                                   loaded active plugged   /sys/devices/vbd-51712/block/xvda/xvda2
      sys-devices-vbd\x2d51712-block-xvda.device                                         loaded active plugged   /sys/devices/vbd-51712/block/xvda
      sys-devices-vbd\x2d51776-block-xvde.device                                         loaded active plugged   LVM PV I2rhCm-www3-J79i-r3ei-1XCb-a1qS-3OWSg9 on /dev/xvde
      sys-devices-vif\x2d0-net-eth0.device                                               loaded active plugged   /sys/devices/vif-0/net/eth0

![复制代码][copycode.gif]

9. 列出所有失败单元

![复制代码][copycode.gif]

[root@CTU1000094955 ~]# systemctl --failed
      UNIT              LOAD   ACTIVE SUB    DESCRIPTION
    ?.bluetooth.service loaded failed failed Bluetooth service
    ?.rc-local.service  loaded failed failed /etc/rc.d/rc.local Compatibility
    
    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.
    
    2 loaded units listed. Pass --all to see loaded but inactive units, too.
    To show all installed unit files use 'systemctl list-unit-files'.

![复制代码][copycode.gif]

10. 检查某个单元（如 cron.service）是否启用

\[root@CTU1000094955 ~\]\# **systemctl is-enabled firewalld.service**  
disabled

11. 检查某个单元或服务是否运行

![复制代码][copycode.gif]

[root@CTU1000094955 ~]# systemctl status firewalld.service
    ?.firewalld.service - firewalld - dynamic firewall daemon
       Loaded: loaded (/usr/lib/systemd/system/firewalld.service; disabled; vendor preset: enabled)
       Active: active (running) since Sat 2017-11-25 16:20:44 CST; 1h 29min ago
     Main PID: 7677 (firewalld)
       CGroup: /system.slice/firewalld.service
               ?..7677 /usr/bin/python -Es /usr/sbin/firewalld --nofork --nopid
    
    Nov 25 16:20:43 CTU1000094955 systemd[1]: Starting firewalld - dynamic firewall daemon...
    Nov 25 16:20:44 CTU1000094955 systemd[1]: Started firewalld - dynamic firewall daemon.

![复制代码][copycode.gif]

**使用Systemctl控制并管理服务**

12. 列出所有服务（包括启用的和禁用的）

![复制代码][copycode.gif]

[root@CTU1000094955 ~]# systemctl list-unit-files --type=service
    UNIT FILE                                   STATE   
    abrt-ccpp.service                           enabled 
    abrt-oops.service                           enabled 
    abrt-pstoreoops.service                     disabled
    abrt-vmcore.service                         enabled 
    abrt-xorg.service                           enabled 
    abrtd.service                               enabled 
    accounts-daemon.service                     enabled 
    alsa-restore.service                        static  
    alsa-state.service                          static  
    alsa-store.service                          static  
    anaconda-direct.service                     static  
    anaconda-nm-config.service                  static  
    anaconda-noshell.service                    static  
    anaconda-shell@.service                     static

![复制代码][copycode.gif]

13. Linux中如何启动、重启、停止、重载服务以及检查服务（如 firewalld.service）状态

![复制代码][copycode.gif]

[root@CTU1000094955 ~]# systemctl start httpd.service
    Failed to start httpd.service: Unit httpd.service failed to load: No such file or directory.
    [root@CTU1000094955 ~]# systemctl start firewalld.service
    [root@CTU1000094955 ~]# systemctl restart firewalld.service
    [root@CTU1000094955 ~]# systemctl stop firewalld.service
    [root@CTU1000094955 ~]# systemctl reload firewalld.service
    Job for firewalld.service invalid.
    [root@CTU1000094955 ~]# systemctl status firewalld.service
    ?.firewalld.service - firewalld - dynamic firewall daemon
       Loaded: loaded (/usr/lib/systemd/system/firewalld.service; disabled; vendor preset: enabled)
       Active: inactive (dead)
    
    Nov 25 16:18:11 CTU1000094955 systemd[1]: Stopped firewalld - dynamic firewall daemon.
    Nov 25 16:20:43 CTU1000094955 systemd[1]: Starting firewalld - dynamic firewall daemon...
    Nov 25 16:20:44 CTU1000094955 systemd[1]: Started firewalld - dynamic firewall daemon.
    Nov 25 17:52:25 CTU1000094955 systemd[1]: Started firewalld - dynamic firewall daemon.
    Nov 25 17:52:38 CTU1000094955 systemd[1]: Stopping firewalld - dynamic firewall daemon...
    Nov 25 17:52:40 CTU1000094955 systemd[1]: Starting firewalld - dynamic firewall daemon...
    Nov 25 17:52:40 CTU1000094955 systemd[1]: Started firewalld - dynamic firewall daemon.
    Nov 25 17:52:53 CTU1000094955 systemd[1]: Stopping firewalld - dynamic firewall daemon...
    Nov 25 17:52:55 CTU1000094955 systemd[1]: Stopped firewalld - dynamic firewall daemon.
    Nov 25 17:53:07 CTU1000094955 systemd[1]: Unit firewalld.service cannot be reloaded because it is inactive.
    [root@CTU1000094955 ~]# systemctl restart firewalld.service
    [root@CTU1000094955 ~]# systemctl reload firewalld.service
    [root@CTU1000094955 ~]# systemctl status firewalld.service
    ?.firewalld.service - firewalld - dynamic firewall daemon
       Loaded: loaded (/usr/lib/systemd/system/firewalld.service; disabled; vendor preset: enabled)
       Active: active (running) since Sat 2017-11-25 17:53:40 CST; 8s ago
      Process: 31721 ExecReload=/bin/kill -HUP $MAINPID (code=exited, status=0/SUCCESS)
     Main PID: 31008 (firewalld)
       CGroup: /system.slice/firewalld.service
               ?..31008 /usr/bin/python -Es /usr/sbin/firewalld --nofork --nopid
    
    Nov 25 17:53:39 CTU1000094955 systemd[1]: Starting firewalld - dynamic firewall daemon...
    Nov 25 17:53:40 CTU1000094955 systemd[1]: Started firewalld - dynamic firewall daemon.
    Nov 25 17:53:43 CTU1000094955 systemd[1]: Reloaded firewalld - dynamic firewall daemon.

![复制代码][copycode.gif]

**　　注意**：当我们使用systemctl的start，restart，stop和reload命令时，我们不会从终端获取到任何输出内容，只有status命令可以打印输出。

14. 如何激活服务并在启动时启用或禁用服务（即系统启动时自动启动服务）

![复制代码][copycode.gif]

[root@CTU1000094955 ~]# systemctl is-active firewalld.service
    active
    [root@CTU1000094955 ~]# systemctl enable firewalld.service
    Created symlink from /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service to /usr/lib/systemd/system/firewalld.service.
    Created symlink from /etc/systemd/system/basic.target.wants/firewalld.service to /usr/lib/systemd/system/firewalld.service.
    [root@CTU1000094955 ~]# systemctl list-unit-files |grep firewall
    firewalld.service                           enabled 
    [root@CTU1000094955 ~]# systemctl status firewalld.service
    ?.firewalld.service - firewalld - dynamic firewall daemon
       Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled; vendor preset: enabled)
       Active: active (running) since Sat 2017-11-25 17:53:40 CST; 4min 6s ago
     Main PID: 31008 (firewalld)
       CGroup: /system.slice/firewalld.service
               ?..31008 /usr/bin/python -Es /usr/sbin/firewalld --nofork --nopid
    
    Nov 25 17:53:39 CTU1000094955 systemd[1]: Starting firewalld - dynamic firewall daemon...
    Nov 25 17:53:40 CTU1000094955 systemd[1]: Started firewalld - dynamic firewall daemon.
    Nov 25 17:53:43 CTU1000094955 systemd[1]: Reloaded firewalld - dynamic firewall daemon.
    [root@CTU1000094955 ~]# systemctl disable firewalld.service
    Removed symlink /etc/systemd/system/basic.target.wants/firewalld.service.
    Removed symlink /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service.
    [root@CTU1000094955 ~]# systemctl list-unit-files |grep firewall
    firewalld.service                           disabled

![复制代码][copycode.gif]

15. 如何屏蔽（让它不能启动）或显示服务（如 httpd.service）

[root@CTU1000094955 ~]# systemctl mask firewalld.service
    Created symlink from /etc/systemd/system/firewalld.service to /dev/null.
    [root@CTU1000094955 ~]# systemctl unmask firewalld.service
    Removed symlink /etc/systemd/system/firewalld.service.

16. 使用systemctl命令杀死服务

![复制代码][copycode.gif]

[root@CTU1000094955 ~]# systemctl kill httpd
    Failed to kill unit httpd.service: Unit httpd.service is not loaded.
    [root@CTU1000094955 ~]# systemctl kill firewalld.service
    [root@CTU1000094955 ~]# systemctl status firewalld.service
    ?.firewalld.service - firewalld - dynamic firewall daemon
       Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled; vendor preset: enabled)
       Active: inactive (dead) since Sat 2017-11-25 18:05:17 CST; 7s ago
     Main PID: 31008 (code=exited, status=0/SUCCESS)
    
    Nov 25 17:53:39 CTU1000094955 systemd[1]: Starting firewalld - dynamic firewall daemon...
    Nov 25 17:53:40 CTU1000094955 systemd[1]: Started firewalld - dynamic firewall daemon.
    Nov 25 17:53:43 CTU1000094955 systemd[1]: Reloaded firewalld - dynamic firewall daemon.

![复制代码][copycode.gif]

**使用Systemctl控制并管理挂载点**

17. 列出所有系统挂载点

![复制代码][copycode.gif]

[root@CTU1000094955 ~]# systemctl list-unit-files --type=mount
    UNIT FILE                     STATE   
    dev-hugepages.mount           static  
    dev-mqueue.mount              static  
    proc-fs-nfsd.mount            static  
    proc-sys-fs-binfmt_misc.mount static  
    sys-fs-fuse-connections.mount static  
    sys-kernel-config.mount       static  
    sys-kernel-debug.mount        static  
    tmp.mount                     disabled
    var-lib-nfs-rpc_pipefs.mount  static  
    
    9 unit files listed.

![复制代码][copycode.gif]

18. 挂载、卸载、重新挂载、重载系统挂载点并检查系统中挂载点状态

![复制代码][copycode.gif]

[root@CTU1000094955 ~]# systemctl start tmp.mount
    [root@CTU1000094955 ~]# systemctl stop tmp.mount
    [root@CTU1000094955 ~]# systemctl reload tmp.mount
    Job for tmp.mount invalid.
    [root@CTU1000094955 ~]# systemctl status tmp.mount
    ?.tmp.mount - Temporary Directory
       Loaded: loaded (/usr/lib/systemd/system/tmp.mount; disabled; vendor preset: disabled)
       Active: inactive (dead) since Sat 2017-11-25 18:09:06 CST; 25s ago
        Where: /tmp
         What: tmpfs
         Docs: man:hier(7)
               http://www.freedesktop.org/wiki/Software/systemd/APIFileSystems
      Process: 40649 ExecUnmount=/bin/umount /tmp -n (code=exited, status=0/SUCCESS)
      Process: 40271 ExecMount=/bin/mount tmpfs /tmp -n -t tmpfs -o mode=1777,strictatime (code=exited, status=0/SUCCESS)
    
    Nov 25 18:08:58 CTU1000094955 systemd[1]: Mounting Temporary Directory...
    Nov 25 18:08:58 CTU1000094955 systemd[1]: Mounted Temporary Directory.
    Nov 25 18:09:06 CTU1000094955 systemd[1]: Unmounting Temporary Directory...
    Nov 25 18:09:06 CTU1000094955 systemd[1]: Unmounted Temporary Directory.
    Nov 25 18:09:21 CTU1000094955 systemd[1]: Unit tmp.mount cannot be reloaded because it is inactive.
    [root@CTU1000094955 ~]# systemctl restart tmp.mount
    [root@CTU1000094955 ~]# systemctl status tmp.mount
    ?.tmp.mount - Temporary Directory
       Loaded: loaded (/usr/lib/systemd/system/tmp.mount; disabled; vendor preset: disabled)
       Active: active (mounted) since Sat 2017-11-25 18:09:53 CST; 2s ago
        Where: /tmp
         What: tmpfs
         Docs: man:hier(7)
               http://www.freedesktop.org/wiki/Software/systemd/APIFileSystems
      Process: 40649 ExecUnmount=/bin/umount /tmp -n (code=exited, status=0/SUCCESS)
      Process: 41410 ExecMount=/bin/mount tmpfs /tmp -n -t tmpfs -o mode=1777,strictatime (code=exited, status=0/SUCCESS)
    
    Nov 25 18:09:53 CTU1000094955 systemd[1]: tmp.mount: Directory /tmp to mount over is not empty, mounting anyway.
    Nov 25 18:09:53 CTU1000094955 systemd[1]: Mounting Temporary Directory...
    Nov 25 18:09:53 CTU1000094955 systemd[1]: Mounted Temporary Directory.
    [root@CTU1000094955 ~]# systemctl reload tmp.mount

![复制代码][copycode.gif]

19. 在启动时激活、启用或禁用挂载点（系统启动时自动挂载）

![复制代码][copycode.gif]

[root@CTU1000094955 ~]# systemctl is-active tmp.mount
    active
    [root@CTU1000094955 ~]# systemctl disable tmp.mount
    Removed symlink /etc/systemd/system/local-fs.target.wants/tmp.mount.
    [root@CTU1000094955 ~]# systemctl is-active tmp.mount
    active
    [root@CTU1000094955 ~]# systemctl enable tmp.mount
    Failed to execute operation: Access denied

![复制代码][copycode.gif]

20. 在Linux中屏蔽（让它不能启用）或可见挂载点

[root@CTU1000094955 ~]# systemctl mask tmp.mount
    ln -s '/dev/null''/etc/systemd/system/tmp.mount'
    [root@CTU1000094955 ~]# systemctl unmask tmp.mount
    rm '/etc/systemd/system/tmp.mount'

**使用Systemctl控制并管理套接口**

21. 列出所有可用系统套接口

![复制代码][copycode.gif]

[root@CTU1000094955 ~]# systemctl list-unit-files --type=socket
    UNIT FILE                    STATE   
    avahi-daemon.socket          enabled 
    cups.socket                  enabled 
    dbus.socket                  static  
    dm-event.socket              enabled 
    iscsid.socket                enabled 
    iscsiuio.socket              enabled 
    libvirtd.socket              static  
    lldpad.socket                disabled
    lvm2-lvmetad.socket          enabled 
    lvm2-lvmpolld.socket         enabled 
    rpcbind.socket               enabled 
    rsyncd.socket                disabled
    sshd.socket                  disabled
    syslog.socket                static  
    systemd-initctl.socket       static  
    systemd-journald.socket      static  
    systemd-networkd.socket      disabled
    systemd-shutdownd.socket     static  
    systemd-udevd-control.socket static  
    systemd-udevd-kernel.socket  static  
    virtlockd.socket             disabled
    
    21 unit files listed.

![复制代码][copycode.gif]

22. 在Linux中启动、重启、停止、重载套接口并检查其状态

![复制代码][copycode.gif]

[root@CTU1000094955 ~]# systemctl start sshd.socket
    [root@CTU1000094955 ~]# systemctl restart sshd.socket
    Failed to restart sshd.socket: Transaction contains conflicting jobs 'restart' and 'stop' for sshd-keygen.service. Probably contradicting requirement dependencies configured.
    [root@CTU1000094955 ~]# systemctl status sshd.socket
    ?.sshd.socket - OpenSSH Server Socket
       Loaded: loaded (/usr/lib/systemd/system/sshd.socket; disabled; vendor preset: disabled)
       Active: active (listening) since Sat 2017-11-25 18:28:12 CST; 22s ago
         Docs: man:sshd(8)
               man:sshd_config(5)
       Listen: [::]:22 (Stream)
     Accepted: 0; Connected: 0
    
    Nov 25 18:28:12 CTU1000094955 systemd[1]: Listening on OpenSSH Server Socket.
    Nov 25 18:28:12 CTU1000094955 systemd[1]: Starting OpenSSH Server Socket.
    [root@CTU1000094955 ~]# systemctl stop sshd.socket
    [root@CTU1000094955 ~]# systemctl reload sshd.socket
    Failed to reload sshd.socket: Job type reload is not applicable for unit sshd.socket.
    [root@CTU1000094955 ~]# systemctl status sshd.socket
    ?.sshd.socket - OpenSSH Server Socket
       Loaded: loaded (/usr/lib/systemd/system/sshd.socket; disabled; vendor preset: disabled)
       Active: inactive (dead) since Sat 2017-11-25 18:28:46 CST; 19s ago
         Docs: man:sshd(8)
               man:sshd_config(5)
       Listen: [::]:22 (Stream)
     Accepted: 0; Connected: 0
    
    Nov 25 18:28:12 CTU1000094955 systemd[1]: Listening on OpenSSH Server Socket.
    Nov 25 18:28:12 CTU1000094955 systemd[1]: Starting OpenSSH Server Socket.
    Nov 25 18:28:46 CTU1000094955 systemd[1]: Closed OpenSSH Server Socket.
    Nov 25 18:28:46 CTU1000094955 systemd[1]: Stopping OpenSSH Server Socket.

![复制代码][copycode.gif]

24. 屏蔽（使它不能启动）或显示套接口

[root@CTU1000094955 ~]# systemctl mask sshd.socket
    Created symlink from /etc/systemd/system/sshd.socket to /dev/null.
    [root@CTU1000094955 ~]# systemctl unmask sshd.socket
    Removed symlink /etc/systemd/system/sshd.socket.

**服务的CPU利用率（分配额）**

25. 获取当前某个服务的CPU分配额（如httpd）

[root@CTU1000094955 ~]# systemctl show -p CPUShares httpd.service
    CPUShares=18446744073709551615

**　　注意**：各个服务的默认CPU分配份额=1024，你可以增加/减少某个进程的CPU分配份额。

26. 将某个服务（httpd.service）的CPU分配份额限制为2000 CPUShares/

[root@CTU1000094955 ~]# systemctl set-property httpd.service CPUShares=2000 
    # systemctl show -p CPUShares httpd.service 
    CPUShares=2000

**　　注意**：当你为某个服务设置CPUShares，会自动创建一个以服务名命名的目录（如 httpd.service），里面包含了一个名为90-CPUShares.conf的文件，该文件含有CPUShare限制信息，你可以通过以下方式查看该文件：

[root@CTU1000094955 ~]# vi /etc/systemd/system/httpd.service.d/90-CPUShares.conf 
    [Service] 
    CPUShares=2000

27. 检查某个服务的所有配置细节

![复制代码][copycode.gif]

[root@CTU1000094955 ~]# systemctl show httpd
    Restart=no
    NotifyAccess=none
    RestartUSec=100ms
    TimeoutStartUSec=1min 30s
    TimeoutStopUSec=1min 30s
    WatchdogUSec=0
    WatchdogTimestampMonotonic=0
    StartLimitInterval=10000000
    StartLimitBurst=5
    StartLimitAction=none
    FailureAction=none
    ... ...  中间省略部分内容

![复制代码][copycode.gif]

28. 分析某个服务（httpd）的关键链

![复制代码][copycode.gif]

[root@CTU1000094955 ~]# systemd-analyze critical-chain firewalld.service
    The time after the unit is active or started is printed after the "@" character.
    The time the unit takes to start is printed after the "+" character.
    
    firewalld.service +380ms
    ?..basic.target @5.903s
      ?..sockets.target @5.903s
        ?..rpcbind.socket @5.903s
          ?..sysinit.target @5.895s
            ?..systemd-update-utmp.service @5.877s +16ms
              ?..auditd.service @5.738s +135ms
                ?..systemd-tmpfiles-setup.service @5.661s +73ms
                  ?..rhel-import-state.service @5.526s +134ms
                    ?..local-fs.target @5.525s
                      ?..run-user-0.mount @14.041s
                        ?..local-fs-pre.target @1.615s
                          ?..systemd-tmpfiles-setup-dev.service @1.519s +92ms
                            ?..kmod-static-nodes.service @1.473s +44ms
                              ?..systemd-journald.socket
                                ?..-.slice

![复制代码][copycode.gif]

29. 获取某个服务（httpd）的依赖性列表

![复制代码][copycode.gif]

[root@CTU1000094955 ~]# systemctl list-dependencies firewalld.service
    firewalld.service
    ?.?..system.slice
    ?.?..basic.target
    ?.  ?..alsa-restore.service
    ?.  ?..alsa-state.service
      ?.?.....
    ?.  ?..microcode.service
    ?.  ?..rhel-autorelabel-mark.service
    ?.  ?..rhel-autorelabel.service
    ?.  ?..rhel-configure.service
    ?.  ?..rhel-dmesg.service
    ?.  ?..rhel-loadmodules.service
    ?.  ?..paths.target
    ?.  ?..slices.target
    ... ....  后面省略部分内容

![复制代码][copycode.gif]

30. 按等级列出控制组

![复制代码][copycode.gif]

[root@CTU1000094955 ~]# systemd-cgls
    ?..1 /usr/lib/systemd/systemd --switched-root --system --deserialize 21
    ?..user.slice
    ?.?..user-988.slice
    ?.?.?..session-c1.scope
    ?.?.  ?..3150 gdm-session-worker [pam/gdm-launch-environment]
    ?.?.  ?..3187 /usr/bin/gnome-session --autostart /usr/share/gdm/greeter/autostart --session gnome-initial-setup
    ?.?.  ?..3190 /usr/bin/dbus-launch --exit-with-session /usr/bin/gnome-session --autostart /usr/share/gdm/greeter/autostart --session gnome-initial-setup
    ?.?.  ?..3199 /bin/dbus-daemon --fork --print-pid 4 --print-address 6 --session
    ?.?.  ?..3288 /usr/libexec/at-spi-bus-launcher
    ?.?.  ?..3305 /bin/dbus-daemon --config-file=/etc/at-spi2/accessibility.conf --nofork --print-address 3
    ?.?.  ?..3309 /usr/libexec/at-spi2-registryd --use-gnome-session
    ?.?.  ?..3410 gnome-shell --mode=initial-setup
    ...  ...  中间省略部分内容
    ?.?.  ?..3767 /usr/libexec/ibus-engine-simple
    ?.?.  ?..3879 gnome-keyring-daemon --unlock
    ?.?..user-0.slice

![复制代码][copycode.gif]

31. 按CPU、内存、输入和输出列出控制组

![复制代码][copycode.gif]

[root@CTU1000094955 ~]# systemd-cgtop
    Path                                                                                                                                                    Tasks   %CPU   Memory  Input/s Output/s
    
    /                                                                                                                                                         418      -     2.8G        -        -
    /system.slice/ModemManager.service                                                                                                                          1      -        -        -        -
    /system.slice/NetworkManager.service                                                                                                                        1      -        -        -        -
    /system.slice/abrt-oops.service                                                                                                                             1      -        -        -        -
    /system.slice/abrt-xorg.service                                                                                                                             1      -        -        -        -
    /system.slice/abrtd.service                                                                                                                                 1      -        -        -        -
    /system.slice/accounts-daemon.service                                                                                                                       1      -        -        -        -
    /system.slice/alsa-state.service                                                                                                                            1      -        -        -        -
    /system.slice/atd.service                                                                                                                                   1      -        -        -        -
    /system.slice/auditd.service                                                                                                                                3      -        -        -        -

![复制代码][copycode.gif]

**控制系统运行等级**

32. 启动系统救援模式

[root@CTU1000094955 ~]# systemctl rescue
    Broadcast message from root@tecmint on pts/0(Wed2015-04-2911:31:18 IST):
    The system is going down to rescue mode NOW!

33. 进入紧急模式

[root@CTU1000094955 ~]# systemctl emergency
    Welcome to emergency mode!After logging in, type "journalctl -xb" to view
    system logs,"systemctl reboot" to reboot,"systemctl default" to try again
    to boot intodefault mode.

34. 列出当前使用的运行等级

运行等级说明如下。

*  Runlevel 0 : 关闭系统　　shutdown.target　　
 *  Runlevel 1 : 紧急？维护模式　　emergency.target
 *  Runlevel 2 : 救援？维护模式　　rescure.target
 *  Runlevel 3 : 多用户，无图形系统　　multi-user.target
 *  Runlevel 4 : 多用户，无图形系统　　无
 *  Runlevel 5 : 多用户，图形化系统　　graphical.target
 *  Runlevel 6 : 关闭并重启机器　　无

[root@CTU1000094955 ~]# systemctl get-default
    graphical.target

35. 启动运行等级5，即图形模式

![复制代码][copycode.gif]

# systemctl isolate runlevel5.target
    或
    # systemctl isolate graphical.target
     
    
    [root@CTU1000094955 ~]# systemctl isolate runlevel5.target
    PolicyKit daemon disconnected from the bus.
    We are no longer a registered authentication agent.

![复制代码][copycode.gif]

36. 启动运行等级3，即多用户模式（命令行）

# systemctl isolate runlevel3.target
    或
    # systemctl isolate multiuser.target

36. 设置多用户模式或图形模式为默认运行等级

# systemctl set-default runlevel3.target
    # systemctl set-default runlevel5.target

37. 重启、停止、挂起、休眠系统或使系统进入混合睡眠

![复制代码][copycode.gif]

# systemctl reboot　　重新启动
    # systemctl halt
    # systemctl suspend　　进入睡眠模式
    # systemctl hibernate　　进入休眠模式
    # systemctl hybrid-sleep
    # systemctl rescue　　强制进入救援模式
    # systemctl emergency　　强制进入紧急救援模式
    # systemctl poweroff　　系统关机

![复制代码][copycode.gif]

[https_www.cnblogs.com_jing99_p_7895860.html]: https://www.cnblogs.com/jing99/p/7895860.html
[copycode.gif]: /images/20220321/ccb182e701954200a463492066997bf9.png