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并确定当前安装的版本

1. # systemd --version
2. systemd 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.1.gz
3. # whereis systemctl
4. systemctl:/usr/bin/systemctl /usr/share/man/man1/systemctl.1.gz

 

3. 检查systemd是否运行

1. # ps -eaf | grep [s]ystemd
2. root 10016:27?00:00:00/usr/lib/systemd/systemd --switched-root --system --deserialize 23
3. root 4441016:27?00:00:00/usr/lib/systemd/systemd-journald
4. root 4691016:27?00:00:00/usr/lib/systemd/systemd-udevd
5. root 5551016:27?00:00:00/usr/lib/systemd/systemd-logind
6. dbus 5561016:27?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

1. # systemd-analyze
2. Startup finished in487ms(kernel)+2.776s(initrd)+20.229s(userspace)=23.493s

 

5. 分析启动时各个进程花费的时间

1. # systemd-analyze blame
2. 8.565s mariadb.service
3. 7.991s webmin.service
4. 6.095s postfix.service
5. 4.311s httpd.service
6. 3.926s firewalld.service
7. 3.780s kdump.service
8. 3.238s tuned.service
9. 1.712s network.service
10. 1.394s lvm2-monitor.service
11. 1.126s systemd-logind.service
12. ....

 

6. 分析启动时的关键链

1. # systemd-analyze critical-chain
2. The time after the unit is active or started is printed after the "@"character.
3. The time the unit takes to start is printed after the "+" character.
4. multi-user.target @20.222s
5. └─mariadb.service @11.657s+8.565s
6. └─network.target @11.168s
7. └─network.service @9.456s+1.712s
8. └─NetworkManager.service @8.858s+596ms
9. └─firewalld.service @4.931s+3.926s
10. └─basic.target @4.916s
11. └─sockets.target @4.916s
12. └─dbus.socket @4.916s
13. └─sysinit.target @4.905s
14. └─systemd-update-utmp.service @4.864s+39ms
15. └─auditd.service @4.563s+301ms
16. └─systemd-tmpfiles-setup.service @4.485s+69ms
17. └─rhel-import-state.service @4.342s+142ms
18. └─local-fs.target @4.324s
19. └─boot.mount @4.286s+31ms
20. └─systemd-fsck@dev-disk-byx2duuid-79f594adx2da332x2d4730x2dbb5fx2d85d19608096
21. └─dev-disk-byx2duuid-79f594adx2da332x2d4730x2dbb5fx2d85d196080964.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

1. # systemctl list-unit-files
2. UNIT FILE STATE
3. proc-sys-fs-binfmt_misc.automount static
4. dev-hugepages.mount static
5. dev-mqueue.mount static
6. proc-sys-fs-binfmt_misc.mount static
7. sys-fs-fuse-connections.mount static
8. sys-kernel-config.mount static
9. sys-kernel-debug.mount static
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 waiting ArbitraryExecutableFileFormatsFileSyste
4. sys-devices-pc...0-1:0:0:0-block-sr0.device loaded active plugged VBOX_CD-ROM
5. sys-devices-pc...:00:03.0-net-enp0s3.device loaded active plugged PRO/1000 MT DesktopAdapter
6. sys-devices-pc...00:05.0-sound-card0.device loaded active plugged 82801AA AC'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-dmx2d0.device loaded active plugged /sys/devices/virtual/block/dm-0
15. sys-devices-virtual-block-dmx2d1.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 failed Crash recovery kernel arming
4. LOAD =Reflects whether the unit definition was properly loaded.
5. ACTIVE =The high-level unit activation state, i.e. generalization of SUB.
6. SUB =The low-level unit activation state, values depend on unit type.
7. 1 loaded units listed.Pass--all to see loaded but inactive units, too.
8. 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

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 -dynamic firewall daemon
3. Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled)
4. Active: active (running) since Tue2015-04-2816:27:55 IST;34min ago
5. Main PID:549(firewalld)
6. CGroup:/system.slice/firewalld.service
7. └─549/usr/bin/python -Es/usr/sbin/firewalld --nofork --nopid
8. Apr2816:27:51 tecmint systemd[1]:Starting firewalld -dynamic firewall daemon...
9. Apr2816:27:55 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）

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.service static
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 -TheApache HTTP Server
7. Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled)
8. Active: active (running) since Tue2015-04-2817:21:30 IST;6s ago
9. Process:2876ExecStop=/bin/kill -WINCH ${MAINPID}(code=exited, status=0/SUCCESS)
10. Main PID:2881(httpd)
11. Status:"Processing requests..."
12. CGroup:/system.slice/httpd.service
13. ├─2881/usr/sbin/httpd -DFOREGROUND
14. ├─2884/usr/sbin/httpd -DFOREGROUND
15. ├─2885/usr/sbin/httpd -DFOREGROUND
16. ├─2886/usr/sbin/httpd -DFOREGROUND
17. ├─2887/usr/sbin/httpd -DFOREGROUND
18. └─2888/usr/sbin/httpd -DFOREGROUND
19. Apr2817:21:30 tecmint systemd[1]:StartingTheApache HTTP Server...
20. Apr2817:21:30 tecmint httpd[2881]: AH00558: httpd:Couldnot reliably 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 -TheApache HTTP Server
4. Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled)
5. Active: failed (Result:exit-code) since Tue2015-04-2818:01:42 IST;28min ago
6. Main PID:2881(code=exited, status=0/SUCCESS)
7. Status:"Total requests: 0; Current requests/sec: 0; Current traffic: 0 B/sec"
8. Apr2817:37:29 tecmint systemd[1]: httpd.service:Got notification message from PID 2881, but recepti...bled.
9. Apr2817:37:29 tecmint systemd[1]: httpd.service:Got notification message from PID 2881, but recepti...bled.
10. Apr2817:37:39 tecmint systemd[1]: httpd.service:Got notification message from PID 2881, but recepti...bled.
11. Apr2817:37:39 tecmint systemd[1]: httpd.service:Got notification message from PID 2881, but recepti...bled.
12. Apr2817:37:49 tecmint systemd[1]: httpd.service:Got notification message from PID 2881, but recepti...bled.
13. Apr2817:37:49 tecmint systemd[1]: httpd.service:Got notification message from PID 2881, but recepti...bled.
14. Apr2817:37:59 tecmint systemd[1]: httpd.service:Got notification message from PID 2881, but recepti...bled.
15. Apr2817:37:59 tecmint systemd[1]: httpd.service:Got notification message from PID 2881, but recepti...bled.
16. Apr2818:01:42 tecmint systemd[1]: httpd.service: control process exited, code=exited status=226
17. Apr2818:01:42 tecmint systemd[1]:Unit httpd.service entered failed state.
18. 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

1. # systemctl list-unit-files --type=mount
2. UNIT FILE STATE
3. dev-hugepages.mount static
4. dev-mqueue.mount static
5. proc-sys-fs-binfmt_misc.mount static
6. sys-fs-fuse-connections.mount static
7. sys-kernel-config.mount static
8. sys-kernel-debug.mount static
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) since Tue2015-04-2817:46:06 IST;2min48s ago
9. Where:/tmp
10. What: tmpfs
11. Docs: man:hier(7)
12. http://www.freedesktop.org/wiki/Software/systemd/APIFileSystems
13. Process:3908ExecMount=/bin/mount tmpfs /tmp -t tmpfs -o mode=1777,strictatime (code=exited, status=0/SUCCESS)
14. Apr2817:46:06 tecmint systemd[1]:MountingTemporaryDirectory...
15. Apr2817:46:06 tecmint systemd[1]: tmp.mount:Directory/tmp to mount over isnot empty, mounting anyway.
16. Apr2817:46:06 tecmint systemd[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.socket static
4. dm-event.socket enabled
5. lvm2-lvmetad.socket enabled
6. rsyncd.socket disabled
7. sshd.socket disabled
8. syslog.socket static
9. systemd-initctl.socket static
10. systemd-journald.socket static
11. systemd-shutdownd.socket static
12. systemd-udevd-control.socket static
13. systemd-udevd-kernel.socket static
14. 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

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 - CUPS PrintingServiceSockets
7. Loaded: loaded (/usr/lib/systemd/system/cups.socket; enabled)
8. Active: active (listening) since Tue2015-04-2818:10:59 IST;8s ago
9. Listen:/var/run/cups/cups.sock (Stream)
10. Apr2818:10:59 tecmint systemd[1]:Starting CUPS PrintingServiceSockets.
11. Apr2818:10:59 tecmint systemd[1]:Listening on CUPS PrintingServiceSockets.

 

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=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=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=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=TheApache HTTP Server
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. The time after the unit is active or started is printed after the "@"character.
3. The time the unit takes to start is printed after the "+" character.
4. httpd.service +142ms
5. └─network.target @11.168s
6. └─network.service @9.456s+1.712s
7. └─NetworkManager.service @8.858s+596ms
8. └─firewalld.service @4.931s+3.926s
9. └─basic.target @4.916s
10. └─sockets.target @4.916s
11. └─dbus.socket @4.916s
12. └─sysinit.target @4.905s
13. └─systemd-update-utmp.service @4.864s+39ms
14. └─auditd.service @4.563s+301ms
15. └─systemd-tmpfiles-setup.service @4.485s+69ms
16. └─rhel-import-state.service @4.342s+142ms
17. └─local-fs.target @4.324s
18. └─boot.mount @4.286s+31ms
19. └─systemd-fsck@dev-disk-byx2duuid-79f594adx2da332x2d4730x2dbb5fx2d85d196080964.service@4.092s+149ms
20. └─dev-disk-byx2duuid-79f594adx2da332x2d4730x2dbb5fx2d85d196080964.device@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. ├─1/usr/lib/systemd/systemd --switched-root --system --deserialize 23
3. ├─user.slice
4. │└─user-0.slice
5. │└─session-1.scope
6. │├─2498 sshd: root@pts/0
7. │├─2500-bash
8. │├─4521 systemd-cgls
9. │└─4522 systemd-cgls
10. └─system.slice
11. ├─httpd.service
12. │├─4440/usr/sbin/httpd -DFOREGROUND
13. │├─4442/usr/sbin/httpd -DFOREGROUND
14. │├─4443/usr/sbin/httpd -DFOREGROUND
15. │├─4444/usr/sbin/httpd -DFOREGROUND
16. │├─4445/usr/sbin/httpd -DFOREGROUND
17. │└─4446/usr/sbin/httpd -DFOREGROUND
18. ├─polkit.service
19. │└─721/usr/lib/polkit-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%CPU MemoryInput/s Output/s
3. /831.0437.8M--
4. /system.slice -0.1---
5. /system.slice/mariadb.service 20.1---
6. /system.slice/tuned.service 10.0---
7. /system.slice/httpd.service 60.0---
8. /system.slice/NetworkManager.service 1----
9. /system.slice/atop.service 1----
10. /system.slice/atopacct.service 1----
11. /system.slice/auditd.service 1----
12. /system.slice/crond.service 1----
13. /system.slice/dbus.service 1----
14. /system.slice/firewalld.service 1----
15. /system.slice/lvm2-lvmetad.service 1----
16. /system.slice/polkit.service 1----
17. /system.slice/postfix.service 3----
18. /system.slice/rsyslog.service 1----
19. /system.slice/system-getty.slice/getty@tty1.service 1----
20. /system.slice/systemd-journald.service 1----
21. /system.slice/systemd-logind.service 1----
22. /system.slice/systemd-udevd.service 1----
23. /system.slice/webmin.service 1----
24. /user.slice/user-0.slice/session-1.scope3----

 

控制系统运行等级

 

32. 启动系统救援模式

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

 

33. 进入紧急模式

1. # systemctl emergency
2. Welcome to emergency mode!After logging in, type "journalctl -xb" to view
3. system logs,"systemctl reboot" to reboot,"systemctl default" to try again
4. to boot intodefault mode.

 

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