systemctl 命令完全指南
Systemctl是一个systemd工具，主要负责控制systemd系统和服务管理器。 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，但并非总是如此。  使用Systemctl管理Linux服务 本文旨在阐明在运行systemd的系统上如何控制系统和服务。 Systemd初体验和Systemctl基础 1. 首先检查你的系统中是否安装有systemd并确定当前安
systemd systemctl
210.36.46.238
Linux中国出品，必属精品。
XYJK1002 [Chrome 42.0|Windows 7]
2015-07-31T08:24:36.000
114.245.8.240
哇！太赞誉了，感谢本文译者 GOLinux ！欢迎更多的兄弟姐妹加入LCTT ： http://lctt.github.io/ ~
linux [Chrome 43.0|Mac 10.10]
2015-08-01T21:26:05.000
171.8.201.207
谢谢分享，谢谢LC！
netb2c [Chrome 44.0|Fedora]
2015-08-01T22:08:46.000
36.47.2.82
第一条命令应该是 systemctl --version 吧
来自陕西西安的 Chrome 43.0|Windows 8.1 用户
2015-08-04T17:56:01.000
223.64.63.72
Linux中国出品，必属精品。
夜域诡士 [Chrome 31.0|Windows 7]
2015-08-04T18:36:29.000
123.120.50.14
您说的对，已经修改。
linux [Chrome 44.0|Mac 10.10]
2015-08-04T20:33:23.000
15.211.153.80
希望增加 控制reboot时启动顺序等相关说明 谢谢！
来自美国的 Chrome 54.0|Windows 7 用户
2016-12-07T17:08:24.000
36.47.163.188
感谢楼主分享！
来自陕西西安的 Chrome 55.0|Windows 7 用户
2017-01-11T11:17:33.000
125.69.124.51
感谢楼主分享！
来自四川成都的 Firefox 54.0|Windows 7 用户
2017-06-15T12:29:08.000
211.138.190.245
感谢，学到了很多！
amwuje [Microsoft Edge 14.14393|Windows 10]
2017-07-04T14:47:44.000
116.231.19.31
17. 列出所有系统挂载点<br />
<br />
tmp.mount&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;disabled<br />
<br />
tmp.mount&nbsp;&nbsp;是什么东西？怎么得来的？
来自上海的 Chrome 74.0|Windows 10 用户
2019-06-08T06:12:41.000
116.231.19.31
17. 列出所有系统挂载点<br />
<br />
tmp.mount&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;disabled<br />
<br />
tmp.mount&nbsp;&nbsp;是什么东西？怎么得来的？
来自上海的 Chrome 74.0|Windows 10 用户
2019-06-08T06:12:47.000
116.231.19.31
17. 列出所有系统挂载点<br />
<br />
tmp.mount&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;disabled<br />
<br />
tmp.mount&nbsp;&nbsp;是什么东西？怎么得来的？
来自上海的 Chrome 74.0|Windows 10 用户
2019-06-08T06:12:49.000
116.231.19.31
17. 列出所有系统挂载点<br />
<br />
tmp.mount&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;disabled<br />
<br />
tmp.mount&nbsp;&nbsp;是什么东西？怎么得来的？
来自上海的 Chrome 74.0|Windows 10 用户
2019-06-08T06:12:50.000
116.231.19.31
17. 列出所有系统挂载点<br />
<br />
tmp.mount&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;&nbsp; &nbsp;disabled<br />
<br />
<br />
tmp.mount&nbsp;&nbsp;是什么东西？怎么得来的？
来自上海的 Chrome 74.0|Windows 10 用户
2019-06-08T06:14:09.000
110.184.114.34
14、19、23中的 systemctl is-active 并不是用于激活，而是查询运行状态。和 systemctl enable、systemctl disable 配对的应该是 systemctl is-enabled
来自四川成都的 Chrome 39.0|Windows 10 用户
2020-06-24T15:49:00.000
211.141.83.125
66666
来自江西赣州的 Chrome 81.0|Windows 10 用户
2020-07-22T15:31:01.000
122.235.252.161
学习了，很详细
来自浙江杭州的 Chrome 69.0|Windows 7 用户
2020-08-24T11:27:32.000
114.88.179.92
我是哪的用户？
来自上海的 Chrome 86.0|Windows 10 用户
2021-03-19T17:36:53.000
114.88.179.92
你是上海的用户
来自上海的 Chrome 86.0|Windows 10 用户
2021-03-22T15:36:31.000
114.88.179.92
yes
来自上海的 Chrome 86.0|Windows 10 用户
2021-03-22T15:38:37.000
183.134.218.234
我是哪里的？
来自浙江宁波的 Chrome 78.0|Mac 10.16 用户
2021-06-01T14:27:11.000
121.35.102.247
666
来自广东深圳的 Chrome 104.0|Windows 10 用户
2022-08-17T14:24:39.000
120.199.32.90
不得不说，讲得清晰又不浮于表面，真好。
来自浙江杭州的 Chrome 103.0|Windows 10 用户
2022-10-25T20:41:39.000
120.199.32.90
不得不说，讲得清晰又不浮于表面，真好。
来自浙江杭州的 Chrome 103.0|Windows 10 用户
2022-10-25T20:41:42.000
120.199.32.90
w w w . c n b l o g s . c o m / i s m e - z j h / p / 1 1 6 8 5 2 3 3 . h t m l<br />
这个更不错
来自浙江杭州的 Chrome 103.0|Windows 10 用户
2022-10-25T21:14:58.000
153.0.156.89
https://www.cnblogs.com/isme-zjh/p/11685233.html
linux [Chrome 106.0|Mac 10.15]
2022-10-25T22:55:08.000
Systemctl是一个systemd工具，主要负责控制systemd系统和服务管理器。 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，但并非总是如此。  使用Systemctl管理Linux服务 本文旨在阐明在运行systemd的系统上如何控制系统和服务。 Systemd初体验和Systemctl基础 1. 首先检查你的系统中是否安装有systemd并确定当前安
Systemctl是一个systemd工具，主要负责控制systemd系统和服务管理器。


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，但并非总是如此。


![Manage Linux Services Using Systemctl](/data/attachment/album/201507/30/210221zg6czg8yogegegay.jpg)


*使用Systemctl管理Linux服务*


本文旨在阐明在运行systemd的系统上“如何控制系统和服务”。


### Systemd初体验和Systemctl基础


#### 1. 首先检查你的系统中是否安装有systemd并确定当前安装的版本



```
# systemctl --version

systemd 215
+PAM +AUDIT +SELINUX +IMA +SYSVINIT +LIBCRYPTSETUP +GCRYPT +ACL +XZ -SECCOMP -APPARMOR

```

上例中很清楚地表明，我们安装了215版本的systemd。


#### 2. 检查systemd和systemctl的二进制文件和库文件的安装位置



```
# whereis systemd 
systemd: /usr/lib/systemd /etc/systemd /usr/share/systemd /usr/share/man/man1/systemd.1.gz


# whereis systemctl
systemctl: /usr/bin/systemctl /usr/share/man/man1/systemctl.1.gz

```

#### 3. 检查systemd是否运行



```
# ps -eaf | grep [s]ystemd

root         1     0  0 16:27 ?        00:00:00 /usr/lib/systemd/systemd --switched-root --system --deserialize 23
root       444     1  0 16:27 ?        00:00:00 /usr/lib/systemd/systemd-journald
root       469     1  0 16:27 ?        00:00:00 /usr/lib/systemd/systemd-udevd
root       555     1  0 16:27 ?        00:00:00 /usr/lib/systemd/systemd-logind
dbus       556     1  0 16:27 ?        00:00:00 /bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation

```

**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



```
# systemd-analyze
Startup finished in 487ms (kernel) + 2.776s (initrd) + 20.229s (userspace) = 23.493s

```

#### 5. 分析启动时各个进程花费的时间



```
# systemd-analyze blame

8.565s mariadb.service
7.991s webmin.service
6.095s postfix.service
4.311s httpd.service
3.926s firewalld.service
3.780s kdump.service
3.238s tuned.service
1.712s network.service
1.394s lvm2-monitor.service
1.126s systemd-logind.service
....

```

#### 6. 分析启动时的关键链



```
# 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.

multi-user.target @20.222s
└─mariadb.service @11.657s +8.565s
  └─network.target @11.168s
    └─network.service @9.456s +1.712s
      └─NetworkManager.service @8.858s +596ms
        └─firewalld.service @4.931s +3.926s
          └─basic.target @4.916s
            └─sockets.target @4.916s
              └─dbus.socket @4.916s
                └─sysinit.target @4.905s
                  └─systemd-update-utmp.service @4.864s +39ms
                    └─auditd.service @4.563s +301ms
                      └─systemd-tmpfiles-setup.service @4.485s +69ms
                        └─rhel-import-state.service @4.342s +142ms
                          └─local-fs.target @4.324s
                            └─boot.mount @4.286s +31ms
                              └─systemd-fsck@dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d19608096
                                └─dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d196080964.device @4

```

**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



```
# systemctl list-unit-files

UNIT FILE                                   STATE   
proc-sys-fs-binfmt_misc.automount           static  
dev-hugepages.mount                         static  
dev-mqueue.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
brandbot.path                               disabled
.....

```

#### 8. 列出所有运行中单元



```
# systemctl list-units

UNIT                                        LOAD   ACTIVE SUB       DESCRIPTION
proc-sys-fs-binfmt_misc.automount           loaded active waiting   Arbitrary Executable File Formats File Syste
sys-devices-pc...0-1:0:0:0-block-sr0.device loaded active plugged   VBOX_CD-ROM
sys-devices-pc...:00:03.0-net-enp0s3.device loaded active plugged   PRO/1000 MT Desktop Adapter
sys-devices-pc...00:05.0-sound-card0.device loaded active plugged   82801AA AC'97 Audio Controller
sys-devices-pc...:0:0-block-sda-sda1.device loaded active plugged   VBOX_HARDDISK
sys-devices-pc...:0:0-block-sda-sda2.device loaded active plugged   LVM PV Qzyo3l-qYaL-uRUa-Cjuk-pljo-qKtX-VgBQ8
sys-devices-pc...0-2:0:0:0-block-sda.device loaded active plugged   VBOX_HARDDISK
sys-devices-pl...erial8250-tty-ttyS0.device loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS0
sys-devices-pl...erial8250-tty-ttyS1.device loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS1
sys-devices-pl...erial8250-tty-ttyS2.device loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS2
sys-devices-pl...erial8250-tty-ttyS3.device loaded active plugged   /sys/devices/platform/serial8250/tty/ttyS3
sys-devices-virtual-block-dm\x2d0.device    loaded active plugged   /sys/devices/virtual/block/dm-0
sys-devices-virtual-block-dm\x2d1.device    loaded active plugged   /sys/devices/virtual/block/dm-1
sys-module-configfs.device                  loaded active plugged   /sys/module/configfs
...

```

#### 9. 列出所有失败单元



```
# systemctl --failed

UNIT          LOAD   ACTIVE SUB    DESCRIPTION
kdump.service loaded failed failed Crash recovery kernel arming

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.

1 loaded units listed. Pass --all to see loaded but inactive units, too.
To show all installed unit files use 'systemctl list-unit-files'.

```

#### 10. 检查某个单元（如 cron.service）是否启用



```
# systemctl is-enabled crond.service

enabled

```

#### 11. 检查某个单元或服务是否运行



```
# systemctl status firewalld.service

firewalld.service - firewalld - dynamic firewall daemon
   Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled)
   Active: active (running) since Tue 2015-04-28 16:27:55 IST; 34min ago
 Main PID: 549 (firewalld)
   CGroup: /system.slice/firewalld.service
           └─549 /usr/bin/python -Es /usr/sbin/firewalld --nofork --nopid

Apr 28 16:27:51 tecmint systemd[1]: Starting firewalld - dynamic firewall daemon...
Apr 28 16:27:55 tecmint systemd[1]: Started firewalld - dynamic firewall daemon.

```

### 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）



```
# systemctl list-unit-files --type=service

UNIT FILE                                   STATE   
arp-ethers.service                          disabled
auditd.service                              enabled 
autovt@.service                             disabled
blk-availability.service                    disabled
brandbot.service                            static  
collectd.service                            disabled
console-getty.service                       disabled
console-shell.service                       disabled
cpupower.service                            disabled
crond.service                               enabled 
dbus-org.fedoraproject.FirewallD1.service   enabled 
....

```

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



```
# systemctl start httpd.service
# systemctl restart httpd.service
# systemctl stop httpd.service
# systemctl reload httpd.service
# systemctl status httpd.service

httpd.service - The Apache HTTP Server
   Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled)
   Active: active (running) since Tue 2015-04-28 17:21:30 IST; 6s ago
  Process: 2876 ExecStop=/bin/kill -WINCH ${MAINPID} (code=exited, status=0/SUCCESS)
 Main PID: 2881 (httpd)
   Status: "Processing requests..."
   CGroup: /system.slice/httpd.service
           ├─2881 /usr/sbin/httpd -DFOREGROUND
           ├─2884 /usr/sbin/httpd -DFOREGROUND
           ├─2885 /usr/sbin/httpd -DFOREGROUND
           ├─2886 /usr/sbin/httpd -DFOREGROUND
           ├─2887 /usr/sbin/httpd -DFOREGROUND
           └─2888 /usr/sbin/httpd -DFOREGROUND

Apr 28 17:21:30 tecmint systemd[1]: Starting The Apache HTTP Server...
Apr 28 17:21:30 tecmint httpd[2881]: AH00558: httpd: Could not reliably determine the server's fully q...ssage
Apr 28 17:21:30 tecmint systemd[1]: Started The Apache HTTP Server.
Hint: Some lines were ellipsized, use -l to show in full.

```

**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）



```
# systemctl is-active httpd.service
# systemctl enable httpd.service
# systemctl disable httpd.service

```

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



```
# systemctl mask httpd.service
ln -s '/dev/null' '/etc/systemd/system/httpd.service'

# systemctl unmask httpd.service
rm '/etc/systemd/system/httpd.service'

```

#### 16. 使用systemctl命令杀死服务



```
# systemctl kill httpd
# systemctl status httpd

httpd.service - The Apache HTTP Server
   Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled)
   Active: failed (Result: exit-code) since Tue 2015-04-28 18:01:42 IST; 28min ago
 Main PID: 2881 (code=exited, status=0/SUCCESS)
   Status: "Total requests: 0; Current requests/sec: 0; Current traffic:   0 B/sec"

Apr 28 17:37:29 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
Apr 28 17:37:29 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
Apr 28 17:37:39 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
Apr 28 17:37:39 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
Apr 28 17:37:49 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
Apr 28 17:37:49 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
Apr 28 17:37:59 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
Apr 28 17:37:59 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
Apr 28 18:01:42 tecmint systemd[1]: httpd.service: control process exited, code=exited status=226
Apr 28 18:01:42 tecmint systemd[1]: Unit httpd.service entered failed state.
Hint: Some lines were ellipsized, use -l to show in full.

```

### 使用Systemctl控制并管理挂载点


#### 17. 列出所有系统挂载点



```
# systemctl list-unit-files --type=mount

UNIT FILE                     STATE   
dev-hugepages.mount           static  
dev-mqueue.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

```

#### 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



```
# systemctl start tmp.mount
# systemctl stop tmp.mount
# systemctl restart tmp.mount
# systemctl reload tmp.mount
# systemctl status tmp.mount

tmp.mount - Temporary Directory
   Loaded: loaded (/usr/lib/systemd/system/tmp.mount; disabled)
   Active: active (mounted) since Tue 2015-04-28 17:46:06 IST; 2min 48s ago
    Where: /tmp
     What: tmpfs
     Docs: man:hier(7)

http://www.freedesktop.org/wiki/Software/systemd/APIFileSystems

  Process: 3908 ExecMount=/bin/mount tmpfs /tmp -t tmpfs -o mode=1777,strictatime (code=exited, status=0/SUCCESS)

Apr 28 17:46:06 tecmint systemd[1]: Mounting Temporary Directory...
Apr 28 17:46:06 tecmint systemd[1]: tmp.mount: Directory /tmp to mount over is not empty, mounting anyway.
Apr 28 17:46:06 tecmint systemd[1]: Mounted Temporary Directory.

```

#### 19. 在启动时激活、启用或禁用挂载点（系统启动时自动挂载）



```
# systemctl is-active tmp.mount
# systemctl enable tmp.mount
# systemctl disable  tmp.mount

```

#### 20. 在Linux中屏蔽（让它不能启用）或可见挂载点



```
# systemctl mask tmp.mount

ln -s '/dev/null' '/etc/systemd/system/tmp.mount'

# 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



```
# systemctl list-unit-files --type=socket

UNIT FILE                    STATE   
dbus.socket                  static  
dm-event.socket              enabled 
lvm2-lvmetad.socket          enabled 
rsyncd.socket                disabled
sshd.socket                  disabled
syslog.socket                static  
systemd-initctl.socket       static  
systemd-journald.socket      static  
systemd-shutdownd.socket     static  
systemd-udevd-control.socket static  
systemd-udevd-kernel.socket  static  

11 unit files listed.

```

#### 22. 在Linux中启动、重启、停止、重载套接口并检查其状态



```
# systemctl start cups.socket
# systemctl restart cups.socket
# systemctl stop cups.socket
# systemctl reload cups.socket
# systemctl status cups.socket

cups.socket - CUPS Printing Service Sockets
   Loaded: loaded (/usr/lib/systemd/system/cups.socket; enabled)
   Active: active (listening) since Tue 2015-04-28 18:10:59 IST; 8s ago
   Listen: /var/run/cups/cups.sock (Stream)

Apr 28 18:10:59 tecmint systemd[1]: Starting CUPS Printing Service Sockets.
Apr 28 18:10:59 tecmint systemd[1]: Listening on CUPS Printing Service Sockets.

```

#### 23. 在启动时激活套接口，并启用或禁用它（系统启动时自启动）



```
# systemctl is-active cups.socket
# systemctl enable cups.socket
# systemctl disable cups.socket

```

#### 24. 屏蔽（使它不能启动）或显示套接口



```
# systemctl mask cups.socket
ln -s '/dev/null' '/etc/systemd/system/cups.socket'

# systemctl unmask cups.socket
rm '/etc/systemd/system/cups.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）



```
# systemctl show -p CPUShares httpd.service

CPUShares=1024

```

**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/



```
# 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：



```
# 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



```
# systemctl show httpd

Id=httpd.service
Names=httpd.service
Requires=basic.target
Wants=system.slice
WantedBy=multi-user.target
Conflicts=shutdown.target
Before=shutdown.target multi-user.target
After=network.target remote-fs.target nss-lookup.target systemd-journald.socket basic.target system.slice
Description=The Apache HTTP Server
LoadState=loaded
ActiveState=active
SubState=running
FragmentPath=/usr/lib/systemd/system/httpd.service
....

```

#### 28. 分析某个服务（httpd）的关键链



```
# systemd-analyze critical-chain httpd.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.

httpd.service +142ms
└─network.target @11.168s
  └─network.service @9.456s +1.712s
    └─NetworkManager.service @8.858s +596ms
      └─firewalld.service @4.931s +3.926s
        └─basic.target @4.916s
          └─sockets.target @4.916s
            └─dbus.socket @4.916s
              └─sysinit.target @4.905s
                └─systemd-update-utmp.service @4.864s +39ms
                  └─auditd.service @4.563s +301ms
                    └─systemd-tmpfiles-setup.service @4.485s +69ms
                      └─rhel-import-state.service @4.342s +142ms
                        └─local-fs.target @4.324s
                          └─boot.mount @4.286s +31ms
                            └─systemd-fsck@dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d196080964.service @4.092s +149ms
                              └─dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d196080964.device @4.092s

```

#### 29. 获取某个服务（httpd）的依赖性列表



```
# systemctl list-dependencies httpd.service

httpd.service
├─system.slice
└─basic.target
  ├─firewalld.service
  ├─microcode.service
  ├─rhel-autorelabel-mark.service
  ├─rhel-autorelabel.service
  ├─rhel-configure.service
  ├─rhel-dmesg.service
  ├─rhel-loadmodules.service
  ├─paths.target
  ├─slices.target
  │ ├─-.slice
  │ └─system.slice
  ├─sockets.target
  │ ├─dbus.socket
....

```

#### 30. 按等级列出控制组



```
# systemd-cgls

├─1 /usr/lib/systemd/systemd --switched-root --system --deserialize 23
├─user.slice
│ └─user-0.slice
│   └─session-1.scope
│     ├─2498 sshd: root@pts/0    
│     ├─2500 -bash
│     ├─4521 systemd-cgls
│     └─4522 systemd-cgls
└─system.slice
  ├─httpd.service
  │ ├─4440 /usr/sbin/httpd -DFOREGROUND
  │ ├─4442 /usr/sbin/httpd -DFOREGROUND
  │ ├─4443 /usr/sbin/httpd -DFOREGROUND
  │ ├─4444 /usr/sbin/httpd -DFOREGROUND
  │ ├─4445 /usr/sbin/httpd -DFOREGROUND
  │ └─4446 /usr/sbin/httpd -DFOREGROUND
  ├─polkit.service
  │ └─721 /usr/lib/polkit-1/polkitd --no-debug
....

```

#### 31. 按CPU、内存、输入和输出列出控制组



```
# systemd-cgtop

Path                                                              Tasks   %CPU   Memory  Input/s Output/s

/                                                                    83    1.0   437.8M        -        -
/system.slice                                                         -    0.1        -        -        -
/system.slice/mariadb.service                                         2    0.1        -        -        -
/system.slice/tuned.service                                           1    0.0        -        -        -
/system.slice/httpd.service                                           6    0.0        -        -        -
/system.slice/NetworkManager.service                                  1      -        -        -        -
/system.slice/atop.service                                            1      -        -        -        -
/system.slice/atopacct.service                                        1      -        -        -        -
/system.slice/auditd.service                                          1      -        -        -        -
/system.slice/crond.service                                           1      -        -        -        -
/system.slice/dbus.service                                            1      -        -        -        -
/system.slice/firewalld.service                                       1      -        -        -        -
/system.slice/lvm2-lvmetad.service                                    1      -        -        -        -
/system.slice/polkit.service                                          1      -        -        -        -
/system.slice/postfix.service                                         3      -        -        -        -
/system.slice/rsyslog.service                                         1      -        -        -        -
/system.slice/system-getty.slice/getty@tty1.service                   1      -        -        -        -
/system.slice/systemd-journald.service                                1      -        -        -        -
/system.slice/systemd-logind.service                                  1      -        -        -        -
/system.slice/systemd-udevd.service                                   1      -        -        -        -
/system.slice/webmin.service                                          1      -        -        -        -
/user.slice/user-0.slice/session-1.scope                              3      -        -        -        -

```

### 控制系统运行等级


#### 32. 启动系统救援模式



```
# systemctl rescue

Broadcast message from root@tecmint on pts/0 (Wed 2015-04-29 11:31:18 IST):

The system is going down to rescue mode NOW!

```

#### 33. 进入紧急模式



```
# 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 into default mode.

```

#### 34. 列出当前使用的运行等级



```
# systemctl get-default

multi-user.target

```

#### 35. 启动运行等级5，即图形模式



```
# systemctl isolate runlevel5.target
或
# systemctl isolate graphical.target

```

#### 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



```
# systemctl reboot

# systemctl halt

# systemctl suspend

# systemctl hibernate

# systemctl hybrid-sleep

```

对于不知运行等级为何物的人，说明如下。


* Runlevel 0 : 关闭系统
* Runlevel 1 : 救援？维护模式
* Runlevel 3 : 多用户，无图形系统
* Runlevel 4 : 多用户，无图形系统
* Runlevel 5 : 多用户，图形化系统
* Runlevel 6 : 关闭并重启机器


到此为止吧。保持连线，进行评论。别忘了在下面的评论中为我们提供一些有价值的反馈哦。喜欢我们、与我们分享，求扩散。




---


via: <http://www.tecmint.com/manage-services-using-systemd-and-systemctl-in-linux/>


作者：[Avishek Kumar](http://www.tecmint.com/author/avishek/) 译者：[GOLinux](https://github.com/GOLinux) 校对：[wxy](https://github.com/wxy)


本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](https://linux.cn/) 荣誉推出

