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.  
3. systemd 215
4. +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.  
4.  
5. # whereis systemctl
6. 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.  
3. root 1 0 0 16:27 ? 00:00:00 /usr/lib/systemd/systemd --switched-root --system --deserialize 23
4. root 444 1 0 16:27 ? 00:00:00 /usr/lib/systemd/systemd-journald
5. root 469 1 0 16:27 ? 00:00:00 /usr/lib/systemd/systemd-udevd
6. root 555 1 0 16:27 ? 00:00:00 /usr/lib/systemd/systemd-logind
7. 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

1. # systemd-analyze
2. 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

1. # systemd-analyze blame
2.  
3. 8.565s mariadb.service
4. 7.991s webmin.service
5. 6.095s postfix.service
6. 4.311s httpd.service
7. 3.926s firewalld.service
8. 3.780s kdump.service
9. 3.238s tuned.service
10. 1.712s network.service
11. 1.394s lvm2-monitor.service
12. 1.126s systemd-logind.service
13. ....

6. 分析启动时的关键链

1. # systemd-analyze critical-chain
2.  
3. The time after the unit is active or started is printed after the "@" character.
4. The time the unit takes to start is printed after the "+" character.
5.  
6. multi-user.target @20.222s
7. └─mariadb.service @11.657s +8.565s
8. └─network.target @11.168s
9. └─network.service @9.456s +1.712s
10. └─NetworkManager.service @8.858s +596ms
11. └─firewalld.service @4.931s +3.926s
12. └─basic.target @4.916s
13. └─sockets.target @4.916s
14. └─dbus.socket @4.916s
15. └─sysinit.target @4.905s
16. └─systemd-update-utmp.service @4.864s +39ms
17. └─auditd.service @4.563s +301ms
18. └─systemd-tmpfiles-setup.service @4.485s +69ms
19. └─rhel-import-state.service @4.342s +142ms
20. └─local-fs.target @4.324s
21. └─boot.mount @4.286s +31ms
22. └─systemd-fsck@dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d19608096
23. └─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

1. # systemctl list-unit-files
2.  
3. UNIT FILE STATE
4. proc-sys-fs-binfmt_misc.automount static
5. dev-hugepages.mount static
6. dev-mqueue.mount static
7. proc-sys-fs-binfmt_misc.mount static
8. sys-fs-fuse-connections.mount static
9. sys-kernel-config.mount static
10. sys-kernel-debug.mount static
11. tmp.mount disabled
12. brandbot.path disabled
13. .....

8. 列出所有运行中单元

1. # systemctl list-units
2.  
3. UNIT LOAD ACTIVE SUB DESCRIPTION
4. proc-sys-fs-binfmt_misc.automount loaded active waiting Arbitrary Executable File Formats File Syste
5. sys-devices-pc...0-1:0:0:0-block-sr0.device loaded active plugged VBOX_CD-ROM
6. sys-devices-pc...:00:03.0-net-enp0s3.device loaded active plugged PRO/1000 MT Desktop Adapter
7. sys-devices-pc...00:05.0-sound-card0.device loaded active plugged 82801AA AC'97 Audio Controller
8. sys-devices-pc...:0:0-block-sda-sda1.device loaded active plugged VBOX_HARDDISK
9. sys-devices-pc...:0:0-block-sda-sda2.device loaded active plugged LVM PV Qzyo3l-qYaL-uRUa-Cjuk-pljo-qKtX-VgBQ8
10. sys-devices-pc...0-2:0:0:0-block-sda.device loaded active plugged VBOX_HARDDISK
11. sys-devices-pl...erial8250-tty-ttyS0.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS0
12. sys-devices-pl...erial8250-tty-ttyS1.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS1
13. sys-devices-pl...erial8250-tty-ttyS2.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS2
14. sys-devices-pl...erial8250-tty-ttyS3.device loaded active plugged /sys/devices/platform/serial8250/tty/ttyS3
15. sys-devices-virtual-block-dm\x2d0.device loaded active plugged /sys/devices/virtual/block/dm-0
16. sys-devices-virtual-block-dm\x2d1.device loaded active plugged /sys/devices/virtual/block/dm-1
17. sys-module-configfs.device loaded active plugged /sys/module/configfs
18. ...

9. 列出所有失败单元

1. # systemctl --failed
2.  
3. UNIT LOAD ACTIVE SUB DESCRIPTION
4. kdump.service loaded failed failed Crash recovery kernel arming
5.  
6. LOAD = Reflects whether the unit definition was properly loaded.
7. ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
8. SUB = The low-level unit activation state, values depend on unit type.
9.  
10. 1 loaded units listed. Pass --all to see loaded but inactive units, too.
11. 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.  
3. enabled

11. 检查某个单元或服务是否运行

1. # systemctl status firewalld.service
2.  
3. firewalld.service - firewalld - dynamic firewall daemon
4. Loaded: loaded (/usr/lib/systemd/system/firewalld.service; enabled)
5. Active: active (running) since Tue 2015-04-28 16:27:55 IST; 34min ago
6. Main PID: 549 (firewalld)
7. CGroup: /system.slice/firewalld.service
8. └─549 /usr/bin/python -Es /usr/sbin/firewalld --nofork --nopid
9.  
10. Apr 28 16:27:51 tecmint systemd[1]: Starting firewalld - dynamic firewall daemon...
11. 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）

1. # systemctl list-unit-files --type=service
2.  
3. UNIT FILE STATE
4. arp-ethers.service disabled
5. auditd.service enabled
6. autovt@.service disabled
7. blk-availability.service disabled
8. brandbot.service static
9. collectd.service disabled
10. console-getty.service disabled
11. console-shell.service disabled
12. cpupower.service disabled
13. crond.service enabled
14. dbus-org.fedoraproject.FirewallD1.service enabled
15. ....

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.  
7. httpd.service - The Apache HTTP Server
8. Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled)
9. Active: active (running) since Tue 2015-04-28 17:21:30 IST; 6s ago
10. Process: 2876 ExecStop=/bin/kill -WINCH ${MAINPID} (code=exited, status=0/SUCCESS)
11. Main PID: 2881 (httpd)
12. Status: "Processing requests..."
13. CGroup: /system.slice/httpd.service
14. ├─2881 /usr/sbin/httpd -DFOREGROUND
15. ├─2884 /usr/sbin/httpd -DFOREGROUND
16. ├─2885 /usr/sbin/httpd -DFOREGROUND
17. ├─2886 /usr/sbin/httpd -DFOREGROUND
18. ├─2887 /usr/sbin/httpd -DFOREGROUND
19. └─2888 /usr/sbin/httpd -DFOREGROUND
20.  
21. Apr 28 17:21:30 tecmint systemd[1]: Starting The Apache HTTP Server...
22. Apr 28 17:21:30 tecmint httpd[2881]: AH00558: httpd: Could not reliably determine the server's fully q...ssage
23. Apr 28 17:21:30 tecmint systemd[1]: Started The Apache HTTP Server.
24. 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.  
4. # systemctl unmask httpd.service
5. 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.  
4. httpd.service - The Apache HTTP Server
5. Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled)
6. Active: failed (Result: exit-code) since Tue 2015-04-28 18:01:42 IST; 28min ago
7. Main PID: 2881 (code=exited, status=0/SUCCESS)
8. Status: "Total requests: 0; Current requests/sec: 0; Current traffic: 0 B/sec"
9.  
10. Apr 28 17:37:29 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
11. Apr 28 17:37:29 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
12. Apr 28 17:37:39 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
13. Apr 28 17:37:39 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
14. Apr 28 17:37:49 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
15. Apr 28 17:37:49 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
16. Apr 28 17:37:59 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
17. Apr 28 17:37:59 tecmint systemd[1]: httpd.service: Got notification message from PID 2881, but recepti...bled.
18. Apr 28 18:01:42 tecmint systemd[1]: httpd.service: control process exited, code=exited status=226
19. Apr 28 18:01:42 tecmint systemd[1]: Unit httpd.service entered failed state.
20. 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.  
3. UNIT FILE STATE
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

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.  
7. tmp.mount - Temporary Directory
8. Loaded: loaded (/usr/lib/systemd/system/tmp.mount; disabled)
9. Active: active (mounted) since Tue 2015-04-28 17:46:06 IST; 2min 48s ago
10. Where: /tmp
11. What: tmpfs
12. Docs: man:hier(7)
13.  
14. http://www.freedesktop.org/wiki/Software/systemd/APIFileSystems
15.  
16. Process: 3908 ExecMount=/bin/mount tmpfs /tmp -t tmpfs -o mode=1777,strictatime (code=exited, status=0/SUCCESS)
17.  
18. Apr 28 17:46:06 tecmint systemd[1]: Mounting Temporary Directory...
19. Apr 28 17:46:06 tecmint systemd[1]: tmp.mount: Directory /tmp to mount over is not empty, mounting anyway.
20. 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）

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.  
3. ln -s '/dev/null' '/etc/systemd/system/tmp.mount'
4.  
5. # systemctl unmask tmp.mount
6.  
7. 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.  
3. UNIT FILE STATE
4. dbus.socket static
5. dm-event.socket enabled
6. lvm2-lvmetad.socket enabled
7. rsyncd.socket disabled
8. sshd.socket disabled
9. syslog.socket static
10. systemd-initctl.socket static
11. systemd-journald.socket static
12. systemd-shutdownd.socket static
13. systemd-udevd-control.socket static
14. systemd-udevd-kernel.socket static
15.  
16. 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.  
7. cups.socket - CUPS Printing Service Sockets
8. Loaded: loaded (/usr/lib/systemd/system/cups.socket; enabled)
9. Active: active (listening) since Tue 2015-04-28 18:10:59 IST; 8s ago
10. Listen: /var/run/cups/cups.sock (Stream)
11.  
12. Apr 28 18:10:59 tecmint systemd[1]: Starting CUPS Printing Service Sockets.
13. 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）

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.  
4. # systemctl unmask cups.socket
5. 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.  
3. 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.  
4. 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.  
3. [Service]
4. CPUShares=2000

27. 检查某个服务的所有配置细节

1. # systemctl show httpd
2.  
3. Id=httpd.service
4. Names=httpd.service
5. Requires=basic.target
6. Wants=system.slice
7. WantedBy=multi-user.target
8. Conflicts=shutdown.target
9. Before=shutdown.target multi-user.target
10. After=network.target remote-fs.target nss-lookup.target systemd-journald.socket basic.target system.slice
11. Description=The Apache HTTP Server
12. LoadState=loaded
13. ActiveState=active
14. SubState=running
15. FragmentPath=/usr/lib/systemd/system/httpd.service
16. ....

28. 分析某个服务（httpd）的关键链

1. # systemd-analyze critical-chain httpd.service
2.  
3. The time after the unit is active or started is printed after the "@" character.
4. The time the unit takes to start is printed after the "+" character.
5.  
6. httpd.service +142ms
7. └─network.target @11.168s
8. └─network.service @9.456s +1.712s
9. └─NetworkManager.service @8.858s +596ms
10. └─firewalld.service @4.931s +3.926s
11. └─basic.target @4.916s
12. └─sockets.target @4.916s
13. └─dbus.socket @4.916s
14. └─sysinit.target @4.905s
15. └─systemd-update-utmp.service @4.864s +39ms
16. └─auditd.service @4.563s +301ms
17. └─systemd-tmpfiles-setup.service @4.485s +69ms
18. └─rhel-import-state.service @4.342s +142ms
19. └─local-fs.target @4.324s
20. └─boot.mount @4.286s +31ms
21. └─systemd-fsck@dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d196080964.service @4.092s +149ms
22. └─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

1. # systemctl list-dependencies httpd.service
2.  
3. httpd.service
4. ├─system.slice
5. └─basic.target
6. ├─firewalld.service
7. ├─microcode.service
8. ├─rhel-autorelabel-mark.service
9. ├─rhel-autorelabel.service
10. ├─rhel-configure.service
11. ├─rhel-dmesg.service
12. ├─rhel-loadmodules.service
13. ├─paths.target
14. ├─slices.target
15. │ ├─-.slice
16. │ └─system.slice
17. ├─sockets.target
18. │ ├─dbus.socket
19. ....

30. 按等级列出控制组

1. # systemd-cgls
2.  
3. ├─1 /usr/lib/systemd/systemd --switched-root --system --deserialize 23
4. ├─user.slice
5. │ └─user-0.slice
6. │ └─session-1.scope
7. │ ├─2498 sshd: root@pts/0
8. │ ├─2500 -bash
9. │ ├─4521 systemd-cgls
10. │ └─4522 systemd-cgls
11. └─system.slice
12. ├─httpd.service
13. │ ├─4440 /usr/sbin/httpd -DFOREGROUND
14. │ ├─4442 /usr/sbin/httpd -DFOREGROUND
15. │ ├─4443 /usr/sbin/httpd -DFOREGROUND
16. │ ├─4444 /usr/sbin/httpd -DFOREGROUND
17. │ ├─4445 /usr/sbin/httpd -DFOREGROUND
18. │ └─4446 /usr/sbin/httpd -DFOREGROUND
19. ├─polkit.service
20. │ └─721 /usr/lib/polkit-1/polkitd --no-debug
21. ....

31. 按CPU、内存、输入和输出列出控制组

1. # systemd-cgtop
2.  
3. Path Tasks %CPU Memory Input/s Output/s
4.  
5. / 83 1.0 437.8M - -
6. /system.slice - 0.1 - - -
7. /system.slice/mariadb.service 2 0.1 - - -
8. /system.slice/tuned.service 1 0.0 - - -
9. /system.slice/httpd.service 6 0.0 - - -
10. /system.slice/NetworkManager.service 1 - - - -
11. /system.slice/atop.service 1 - - - -
12. /system.slice/atopacct.service 1 - - - -
13. /system.slice/auditd.service 1 - - - -
14. /system.slice/crond.service 1 - - - -
15. /system.slice/dbus.service 1 - - - -
16. /system.slice/firewalld.service 1 - - - -
17. /system.slice/lvm2-lvmetad.service 1 - - - -
18. /system.slice/polkit.service 1 - - - -
19. /system.slice/postfix.service 3 - - - -
20. /system.slice/rsyslog.service 1 - - - -
21. /system.slice/system-getty.slice/getty@tty1.service 1 - - - -
22. /system.slice/systemd-journald.service 1 - - - -
23. /system.slice/systemd-logind.service 1 - - - -
24. /system.slice/systemd-udevd.service 1 - - - -
25. /system.slice/webmin.service 1 - - - -
26. /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

1. # systemctl rescue
2.  
3. Broadcast message from root@tecmint on pts/0 (Wed 2015-04-29 11:31:18 IST):
4.  
5. The system is going down to rescue mode NOW!

33. 进入紧急模式

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

34. 列出当前使用的运行等级

1. # systemctl get-default
2.  
3. 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.  
3. # 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.  
3. # systemctl halt
4.  
5. # systemctl suspend
6.  
7. # systemctl hibernate
8.  
9. # 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 译者：GOLinux 校对：wxy

本文由 LCTT 原创翻译，Linux中国 荣誉推出

来源：https://linux.cn/article-5926-1.html