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并确定当前安装的版本

1. # systemd --version
2. systemd@H_403_31@215
3. +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

1. # whereis systemd
2. systemd:/usr/lib/systemd/etc/systemd/usr/share/systemd/usr/share/man/man1/systemd.@H_403_31@1.gz
3. # whereis systemctl
4. systemctl:/usr/bin/systemctl/usr/share/man/man1/systemctl.@H_403_31@1.gz

3. 检查systemd是否运行

1. # ps -eaf | grep [s]ystemd
2. root@H_403_31@1@H_403_31@0@H_403_31@0@H_403_31@16:@H_403_31@27?@H_403_31@00:@H_403_31@00:@H_403_31@00/usr/lib/systemd/systemd--switched-root--system--deserialize@H_403_31@23
3. root@H_403_31@444@H_403_31@1@H_403_31@0@H_403_31@16:@H_403_31@27?@H_403_31@00:@H_403_31@00:@H_403_31@00/usr/lib/systemd/systemd-journald
4. root@H_403_31@469@H_403_31@1@H_403_31@0@H_403_31@16:@H_403_31@27?@H_403_31@00:@H_403_31@00:@H_403_31@00/usr/lib/systemd/systemd-udevd
5. root@H_403_31@555@H_403_31@1@H_403_31@0@H_403_31@16:@H_403_31@27?@H_403_31@00:@H_403_31@00:@H_403_31@00/usr/lib/systemd/systemd-logind
6. dbus@H_403_31@556@H_403_31@1@H_403_31@0@H_403_31@16:@H_403_31@27?@H_403_31@00:@H_403_31@00:@H_403_31@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

1. # systemd-analyze
2. Startupfinishedin@H_403_31@487ms(kernel)+@H_403_31@2.776s(initrd)+@H_403_31@20.229s(userspace)=@H_403_31@23.493s

5. 分析启动时各个进程花费的时间

1. # systemd-analyze blame
2. @H_403_31@8.565smariadb.service
3. @H_403_31@7.991swebmin.service
4. @H_403_31@6.095spostfix.service
5. @H_403_31@4.311shttpd.service
6. @H_403_31@3.926sfirewalld.service
7. @H_403_31@3.780skdump.service
8. @H_403_31@3.238stuned.service
9. @H_403_31@1.712snetwork.service
10. @H_403_31@1.394slvm2-monitor.service
11. @H_403_31@1.126ssystemd-logind.service
12. ....

6. 分析启动时的关键链

1. # systemd-analyze critical-chain
2. Thetime after the unitisactiveorstartedisprinted after the"@"character.
3. Thetime the unit takes to startisprinted after the"+"character.
4. multi-user.target@@H_403_31@20.222s
5. └─mariadb.service@@H_403_31@11.657s+@H_403_31@8.565s
6. └─network.target@@H_403_31@11.168s
7. └─network.service@@H_403_31@9.456s+@H_403_31@1.712s
8. └─NetworkManager.service@@H_403_31@8.858s+@H_403_31@596ms
9. └─firewalld.service@@H_403_31@4.931s+@H_403_31@3.926s
10. └─basic.target@@H_403_31@4.916s
11. └─sockets.target@@H_403_31@4.916s
12. └─dbus.socket@@H_403_31@4.916s
13. └─sysinit.target@@H_403_31@4.905s
14. └─systemd-update-utmp.service@@H_403_31@4.864s+@H_403_31@39ms
15. └─auditd.service@@H_403_31@4.563s+@H_403_31@301ms
16. └─systemd-tmpfiles-setup.service@@H_403_31@4.485s+@H_403_31@69ms
17. └─rhel-import-state.service@@H_403_31@4.342s+@H_403_31@142ms
18. └─local-fs.target@@H_403_31@4.324s
19. └─boot.mount@@H_403_31@4.286s+@H_403_31@31ms
20. └─systemd-fsck@dev-disk-by\x@H_403_31@2duuid-@H_403_31@79f594ad\x@H_403_31@2da332\x@H_403_31@2d4730\x@H_403_31@2dbb5f\x@H_403_31@2d85d19608096
21. └─dev-disk-by\x@H_403_31@2duuid-@H_403_31@79f594ad\x@H_403_31@2da332\x@H_403_31@2d4730\x@H_403_31@2dbb5f\x@H_403_31@2d85d196080964.device@@H_403_31@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

1. # systemctl list-unit-files
2. UNIT FILE STATE
3. proc-sys-fs-binfmt_misc.automountstatic
4. dev-hugepages.mountstatic
5. dev-mqueue.mountstatic
6. proc-sys-fs-binfmt_misc.mountstatic
7. sys-fs-fuse-connections.mountstatic
8. sys-kernel-config.mountstatic
9. sys-kernel-debug.mountstatic
10. tmp.mount disabled
11. brandbot.path disabled
12. .....

8. 列出所有运行中单元

1. # systemctl list-units
2. UNIT LOAD ACTIVE SUB DESCRIPTION
3. proc-sys-fs-binfmt_misc.automount loaded active waitingArbitraryExecutableFileFormatsFileSyste
4. sys-devices-pc...@H_403_31@0-@H_403_31@1:@H_403_31@0:@H_403_31@0:@H_403_31@0-block-sr0.device loaded active plugged VBox_CD-ROM
5. sys-devices-pc...:@H_403_31@00:@H_403_31@03.0-net-enp0s3.device loaded active plugged PRO/@H_403_31@1000MTDesktopAdapter
6. sys-devices-pc...@H_403_31@00:@H_403_31@05.0-sound-card0.device loaded active plugged@H_403_31@82801AAAC'97 Audio Controller
7. sys-devices-pc...:0:0-block-sda-sda1.device loaded active plugged VBox_HARDDISK
8. sys-devices-pc...:0:0-block-sda-sda2.device loaded active plugged LVM PV Qzyo3l-qYaL-uRUa-Cjuk-pljo-qKtX-VgBQ8
9. sys-devices-pc...0-2:0:0:0-block-sda.device loaded active plugged VBox_HARDDISK
10. sys-devices-pl...erial8250-tty-ttyS0.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS0
11. sys-devices-pl...erial8250-tty-ttyS1.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS1
12. sys-devices-pl...erial8250-tty-ttyS2.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS2
13. sys-devices-pl...erial8250-tty-ttyS3.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS3
14. sys-devices-virtual-block-dm\x2d0.device loaded active plugged /sys/devices/virtual/block/dm-0
15. sys-devices-virtual-block-dm\x2d1.device loaded active plugged /sys/devices/virtual/block/dm-1
16. sys-module-configfs.device loaded active plugged /sys/module/configfs
17. ...

9. 列出所有失败单元

1. # systemctl --Failed
2. UNIT LOAD ACTIVE SUB DESCRIPTION
3. kdump.service loaded Failed FailedCrashrecovery kernel arming
4. LOAD=Reflectswhether the unit definition was properly loaded.
5. ACTIVE=Thehigh-level unit activation state,i.e.generalization of SUB.
6. SUB=Thelow-level unit activation state,values depend on unit type.
7. @H_403_31@1loaded units listed.Pass--all to see loaded but inactive units,too.
8. Toshow all installed unit filesuse'systemctl list-unit-files'.

10. 检查某个单元（如 cron.service）是否启用

1. # systemctl is-enabled crond.service
2. enabled

11. 检查某个单元或服务是否运行

1. # systemctl status firewalld.service
2. firewalld.service-firewalld-dynamicfirewall daemon
3. Loaded:loaded(/usr/lib/systemd/system/firewalld.service;enabled)
4. Active:active(running)sinceTue@H_403_31@2015-@H_403_31@04-@H_403_31@28@H_403_31@16:@H_403_31@27:@H_403_31@55IST;@H_403_31@34minago
5. MainPID:@H_403_31@549(firewalld)
6. CGroup:/system.slice/firewalld.service
7. └─@H_403_31@549/usr/bin/python-Es/usr/sbin/firewalld--nofork--nopid
8. Apr@H_403_31@28@H_403_31@16:@H_403_31@27:@H_403_31@51tecmint systemd[@H_403_31@1]:Startingfirewalld-dynamicfirewall daemon...
9. Apr@H_403_31@28@H_403_31@16:@H_403_31@27:@H_403_31@55tecmint systemd[@H_403_31@1]:Startedfirewalld-dynamicfirewall 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）

1. # systemctl list-unit-files --type=service
2. UNIT FILE STATE
3. arp-ethers.service disabled
4. auditd.service enabled
5. autovt@.service disabled
6. blk-availability.service disabled
7. brandbot.servicestatic
8. collectd.service disabled
9. console-getty.service disabled
10. console-shell.service disabled
11. cpupower.service disabled
12. crond.service enabled
13. dbus-org.Fedoraproject.FirewallD1.service enabled
14. ....

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

1. # systemctl start httpd.service
2. # systemctl restart httpd.service
3. # systemctl stop httpd.service
4. # systemctl reload httpd.service
5. # systemctl status httpd.service
6. httpd.service-TheApacheHTTPServer
7. Loaded:loaded(/usr/lib/systemd/system/httpd.service;enabled)
8. Active:active(running)sinceTue@H_403_31@2015-@H_403_31@04-@H_403_31@28@H_403_31@17:@H_403_31@21:@H_403_31@30IST;@H_403_31@6sago
9. Process:@H_403_31@2876ExecStop=/bin/kill-WINCH ${MAINPID}(code=exited,status=@H_403_31@0/SUCCESS)
10. MainPID:@H_403_31@2881(httpd)
11. Status:"Processing requests..."
12. CGroup:/system.slice/httpd.service
13. ├─@H_403_31@2881/usr/sbin/httpd-DFOREGROUND
14. ├─@H_403_31@2884/usr/sbin/httpd-DFOREGROUND
15. ├─@H_403_31@2885/usr/sbin/httpd-DFOREGROUND
16. ├─@H_403_31@2886/usr/sbin/httpd-DFOREGROUND
17. ├─@H_403_31@2887/usr/sbin/httpd-DFOREGROUND
18. └─@H_403_31@2888/usr/sbin/httpd-DFOREGROUND
19. Apr@H_403_31@28@H_403_31@17:@H_403_31@21:@H_403_31@30tecmint systemd[@H_403_31@1]:StartingTheApacheHTTPServer...
20. Apr@H_403_31@28@H_403_31@17:@H_403_31@21:@H_403_31@30tecmint httpd[@H_403_31@2881]:AH00558:httpd:Couldnotreliably determine the server's fully q...ssage
21. Apr 28 17:21:30 tecmint systemd[1]: Started The Apache HTTP Server.
22. 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）

1. # systemctl is-active httpd.service
2. # systemctl enable httpd.service
3. # systemctl disable httpd.service

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

1. # systemctl mask httpd.service
2. ln-s'/dev/null''/etc/systemd/system/httpd.service'
3. # systemctl unmask httpd.service
4. rm'/etc/systemd/system/httpd.service'

16. 使用systemctl命令杀死服务

1. # systemctl kill httpd
2. # systemctl status httpd
3. httpd.service-TheApacheHTTPServer
4. Loaded:loaded(/usr/lib/systemd/system/httpd.service;enabled)
5. Active:Failed(Result:exit-code)sinceTue@H_403_31@2015-@H_403_31@04-@H_403_31@28@H_403_31@18:@H_403_31@01:@H_403_31@42IST;@H_403_31@28minago
6. MainPID:@H_403_31@2881(code=exited,status=@H_403_31@0/SUCCESS)
7. Status:"Total requests: 0; Current requests/sec: 0; Current traffic: 0 B/sec"
8. Apr@H_403_31@28@H_403_31@17:@H_403_31@37:@H_403_31@29tecmint systemd[@H_403_31@1]:httpd.service:Gotnotification messagefromPID@H_403_31@2881,but recepti...bled.
9. Apr@H_403_31@28@H_403_31@17:@H_403_31@37:@H_403_31@29tecmint systemd[@H_403_31@1]:httpd.service:Gotnotification messagefromPID@H_403_31@2881,but recepti...bled.
10. Apr@H_403_31@28@H_403_31@17:@H_403_31@37:@H_403_31@39tecmint systemd[@H_403_31@1]:httpd.service:Gotnotification messagefromPID@H_403_31@2881,but recepti...bled.
11. Apr@H_403_31@28@H_403_31@17:@H_403_31@37:@H_403_31@39tecmint systemd[@H_403_31@1]:httpd.service:Gotnotification messagefromPID@H_403_31@2881,but recepti...bled.
12. Apr@H_403_31@28@H_403_31@17:@H_403_31@37:@H_403_31@49tecmint systemd[@H_403_31@1]:httpd.service:Gotnotification messagefromPID@H_403_31@2881,but recepti...bled.
13. Apr@H_403_31@28@H_403_31@17:@H_403_31@37:@H_403_31@49tecmint systemd[@H_403_31@1]:httpd.service:Gotnotification messagefromPID@H_403_31@2881,but recepti...bled.
14. Apr@H_403_31@28@H_403_31@17:@H_403_31@37:@H_403_31@59tecmint systemd[@H_403_31@1]:httpd.service:Gotnotification messagefromPID@H_403_31@2881,but recepti...bled.
15. Apr@H_403_31@28@H_403_31@17:@H_403_31@37:@H_403_31@59tecmint systemd[@H_403_31@1]:httpd.service:Gotnotification messagefromPID@H_403_31@2881,but recepti...bled.
16. Apr@H_403_31@28@H_403_31@18:@H_403_31@01:@H_403_31@42tecmint systemd[@H_403_31@1]:httpd.service:control process exited,code=exited status=@H_403_31@226
17. Apr@H_403_31@28@H_403_31@18:@H_403_31@01:@H_403_31@42tecmint systemd[@H_403_31@1]:Unithttpd.service entered Failed state.
18. Hint:Somelines were ellipsized,use-l to showinfull.

使用Systemctl控制并管理挂载点

17. 列出所有系统挂载点

1. # systemctl list-unit-files --type=mount
2. UNIT FILE STATE
3. dev-hugepages.mountstatic
4. dev-mqueue.mountstatic
5. proc-sys-fs-binfmt_misc.mountstatic
6. sys-fs-fuse-connections.mountstatic
7. sys-kernel-config.mountstatic
8. sys-kernel-debug.mountstatic
9. 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

1. # systemctl start tmp.mount
2. # systemctl stop tmp.mount
3. # systemctl restart tmp.mount
4. # systemctl reload tmp.mount
5. # systemctl status tmp.mount
6. tmp.mount-TemporaryDirectory
7. Loaded:loaded(/usr/lib/systemd/system/tmp.mount;disabled)
8. Active:active(mounted)sinceTue@H_403_31@2015-@H_403_31@04-@H_403_31@28@H_403_31@17:@H_403_31@46:@H_403_31@06IST;@H_403_31@2min@H_403_31@48sago
9. Where:/tmp
10. What:tmpfs
11. Docs:man:hier(@H_403_31@7)
12. http://www.freedesktop.org/wiki/Software/systemd/APIFileSystems
13. Process:@H_403_31@3908ExecMount=/bin/mount tmpfs/tmp-t tmpfs-o mode=@H_403_31@1777,strictatime(code=exited,status=@H_403_31@0/SUCCESS)
14. Apr@H_403_31@28@H_403_31@17:@H_403_31@46:@H_403_31@06tecmint systemd[@H_403_31@1]:MountingTemporaryDirectory...
15. Apr@H_403_31@28@H_403_31@17:@H_403_31@46:@H_403_31@06tecmint systemd[@H_403_31@1]:tmp.mount:Directory/tmp to mount overisnotempty,mounting anyway.
16. Apr@H_403_31@28@H_403_31@17:@H_403_31@46:@H_403_31@06tecmint systemd[@H_403_31@1]:MountedTemporaryDirectory.

19. 在启动时激活、启用或禁用挂载点（系统启动时自动挂载）

1. # systemctl is-active tmp.mount
2. # systemctl enable tmp.mount
3. # systemctl disable tmp.mount

20. 在Linux中屏蔽（让它不能启用）或可见挂载点

1. # systemctl mask tmp.mount
2. ln-s'/dev/null''/etc/systemd/system/tmp.mount'
3. # systemctl unmask tmp.mount
4. 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

1. # systemctl list-unit-files --type=socket
2. UNIT FILE STATE
3. dbus.socketstatic
4. dm-event.socket enabled
5. lvm2-lvMetad.socket enabled
6. rsyncd.socket disabled
7. sshd.socket disabled
8. syslog.socketstatic
9. systemd-initctl.socketstatic
10. systemd-journald.socketstatic
11. systemd-shutdownd.socketstatic
12. systemd-udevd-control.socketstatic
13. systemd-udevd-kernel.socketstatic
14. @H_403_31@11unit files listed.

22. 在Linux中启动、重启、停止、重载套接口并检查其状态

1. # systemctl start cups.socket
2. # systemctl restart cups.socket
3. # systemctl stop cups.socket
4. # systemctl reload cups.socket
5. # systemctl status cups.socket
6. cups.socket-CUPSPrintingServiceSockets
7. Loaded:loaded(/usr/lib/systemd/system/cups.socket;enabled)
8. Active:active(listening)sinceTue@H_403_31@2015-@H_403_31@04-@H_403_31@28@H_403_31@18:@H_403_31@10:@H_403_31@59IST;@H_403_31@8sago
9. Listen:/var/run/cups/cups.sock(Stream)
10. Apr@H_403_31@28@H_403_31@18:@H_403_31@10:@H_403_31@59tecmint systemd[@H_403_31@1]:StartingCUPSPrintingServiceSockets.
11. Apr@H_403_31@28@H_403_31@18:@H_403_31@10:@H_403_31@59tecmint systemd[@H_403_31@1]:Listeningon CUPSPrintingServiceSockets.

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）

1. # systemctl is-active cups.socket
2. # systemctl enable cups.socket
3. # systemctl disable cups.socket

24. 屏蔽（使它不能启动）或显示套接口

1. # systemctl mask cups.socket
2. ln-s'/dev/null''/etc/systemd/system/cups.socket'
3. # systemctl unmask cups.socket
4. 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）

1. # systemctl show -p cpuShares httpd.service
2. cpuShares=@H_403_31@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/

1. # systemctl set-property httpd.service cpuShares=2000
2. # systemctl show -p cpuShares httpd.service
3. cpuShares=@H_403_31@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：

1. # vi /etc/systemd/system/httpd.service.d/90-cpuShares.conf
2. [Service]
3. cpuShares=@H_403_31@2000

27. 检查某个服务的所有配置细节

1. # systemctl show httpd
2. Id=httpd.service
3. Names=httpd.service
4. Requires=basic.target
5. Wants=system.slice
6. WantedBy=multi-user.target
7. Conflicts=shutdown.target
8. Before=shutdown.target multi-user.target
9. After=network.target remote-fs.target nss-lookup.target systemd-journald.socket basic.target system.slice
10. Description=TheApacheHTTPServer
11. LoadState=loaded
12. ActiveState=active
13. SubState=running
14. FragmentPath=/usr/lib/systemd/system/httpd.service
15. ....

28. 分析某个服务（httpd）的关键链

1. # systemd-analyze critical-chain httpd.service
2. Thetime after the unitisactiveorstartedisprinted after the"@"character.
3. Thetime the unit takes to startisprinted after the"+"character.
4. httpd.service+@H_403_31@142ms
5. └─network.target@@H_403_31@11.168s
6. └─network.service@@H_403_31@9.456s+@H_403_31@1.712s
7. └─NetworkManager.service@@H_403_31@8.858s+@H_403_31@596ms
8. └─firewalld.service@@H_403_31@4.931s+@H_403_31@3.926s
9. └─basic.target@@H_403_31@4.916s
10. └─sockets.target@@H_403_31@4.916s
11. └─dbus.socket@@H_403_31@4.916s
12. └─sysinit.target@@H_403_31@4.905s
13. └─systemd-update-utmp.service@@H_403_31@4.864s+@H_403_31@39ms
14. └─auditd.service@@H_403_31@4.563s+@H_403_31@301ms
15. └─systemd-tmpfiles-setup.service@@H_403_31@4.485s+@H_403_31@69ms
16. └─rhel-import-state.service@@H_403_31@4.342s+@H_403_31@142ms
17. └─local-fs.target@@H_403_31@4.324s
18. └─boot.mount@@H_403_31@4.286s+@H_403_31@31ms
19. └─systemd-fsck@dev-disk-by\x@H_403_31@2duuid-@H_403_31@79f594ad\x@H_403_31@2da332\x@H_403_31@2d4730\x@H_403_31@2dbb5f\x@H_403_31@2d85d196080964.service@@H_403_31@4.092s+@H_403_31@149ms
20. └─dev-disk-by\x@H_403_31@2duuid-@H_403_31@79f594ad\x@H_403_31@2da332\x@H_403_31@2d4730\x@H_403_31@2dbb5f\x@H_403_31@2d85d196080964.device@@H_403_31@4.092s

29. 获取某个服务（httpd）的依赖性列表

1. # systemctl list-dependencies httpd.service
2. httpd.service
3. ├─system.slice
4. └─basic.target
5. ├─firewalld.service
6. ├─microcode.service
7. ├─rhel-autorelabel-mark.service
8. ├─rhel-autorelabel.service
9. ├─rhel-configure.service
10. ├─rhel-dmesg.service
11. ├─rhel-loadmodules.service
12. ├─paths.target
13. ├─slices.target
14. │├─-.slice
15. │└─system.slice
16. ├─sockets.target
17. │├─dbus.socket
18. ....

30. 按等级列出控制组

1. # systemd-cgls
2. ├─@H_403_31@1/usr/lib/systemd/systemd--switched-root--system--deserialize@H_403_31@23
3. ├─user.slice
4. │└─user-@H_403_31@0.slice
5. │└─session-@H_403_31@1.scope
6. │├─@H_403_31@2498sshd:root@pts/@H_403_31@0
7. │├─@H_403_31@2500-bash
8. │├─@H_403_31@4521systemd-cgls
9. │└─@H_403_31@4522systemd-cgls
10. └─system.slice
11. ├─httpd.service
12. │├─@H_403_31@4440/usr/sbin/httpd-DFOREGROUND
13. │├─@H_403_31@4442/usr/sbin/httpd-DFOREGROUND
14. │├─@H_403_31@4443/usr/sbin/httpd-DFOREGROUND
15. │├─@H_403_31@4444/usr/sbin/httpd-DFOREGROUND
16. │├─@H_403_31@4445/usr/sbin/httpd-DFOREGROUND
17. │└─@H_403_31@4446/usr/sbin/httpd-DFOREGROUND
18. ├─polkit.service
19. │└─@H_403_31@721/usr/lib/polkit-@H_403_31@1/polkitd--no-debug
20. ....

31. 按cpu、内存、输入和输出列出控制组

1. # systemd-cgtop
2. PathTasks%cpuMemoryInput/sOutput/s
3. /@H_403_31@83@H_403_31@1.0@H_403_31@437.8M--
4. /system.slice-@H_403_31@0.1---
5. /system.slice/mariadb.service@H_403_31@2@H_403_31@0.1---
6. /system.slice/tuned.service@H_403_31@1@H_403_31@0.0---
7. /system.slice/httpd.service@H_403_31@6@H_403_31@0.0---
8. /system.slice/NetworkManager.service@H_403_31@1----
9. /system.slice/atop.service@H_403_31@1----
10. /system.slice/atopacct.service@H_403_31@1----
11. /system.slice/auditd.service@H_403_31@1----
12. /system.slice/crond.service@H_403_31@1----
13. /system.slice/dbus.service@H_403_31@1----
14. /system.slice/firewalld.service@H_403_31@1----
15. /system.slice/lvm2-lvMetad.service@H_403_31@1----
16. /system.slice/polkit.service@H_403_31@1----
17. /system.slice/postfix.service@H_403_31@3----
18. /system.slice/rsyslog.service@H_403_31@1----
19. /system.slice/system-getty.slice/getty@tty1.service@H_403_31@1----
20. /system.slice/systemd-journald.service@H_403_31@1----
21. /system.slice/systemd-logind.service@H_403_31@1----
22. /system.slice/systemd-udevd.service@H_403_31@1----
23. /system.slice/webmin.service@H_403_31@1----
24. /user.slice/user-@H_403_31@0.slice/session-@H_403_31@1.scope@H_403_31@3----

@H_502_6370@ 控制系统运行等级

32. 启动系统救援模式

1. # systemctl rescue
2. Broadcastmessagefromroot@tecmint on pts/@H_403_31@0(Wed@H_403_31@2015-@H_403_31@04-@H_403_31@29@H_403_31@11:@H_403_31@31:@H_403_31@18IST):
3. Thesystemisgoing down torescuemode NOW!

33. 进入紧急模式

1. # systemctl emergency
2. Welcometo emergency mode!Afterloggingin,type"journalctl -xb"to view
3. system logs,"systemctl reboot"to reboot,"systemctl default"totryagain
4. to bootintodefaultmode.

34. 列出当前使用的运行等级

1. # systemctl get-default
2. multi-user.target

35. 启动运行等级5，即图形模式

1. # systemctl isolate runlevel5.target
2. 或
3. # systemctl isolate graphical.target

36. 启动运行等级3，即多用户模式（命令行）

1. # systemctl isolate runlevel3.target
2. 或
3. # systemctl isolate multiuser.target

36. 设置多用户模式或图形模式为默认运行等级

1. # systemctl set-default runlevel3.target
2. # 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

1. # systemctl reboot
2. # systemctl halt
3. # systemctl suspend
4. # systemctl hibernate
5. # 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。

本文永久更新链接地址：http://www.linuxidc.com/Linux/2015-07/120833.htm

原文链接：https://www.f2er.com/centos/380781.html