【搬运】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

 # systemctl --version
 systemd
 +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..gz
 # whereis systemctl
 systemctl: /usr/bin/systemctl /usr/share/man/man1/systemctl..gz

3. 检查systemd是否运行

 # ps -eaf | grep [s]ystemd
 root    : ? :: /usr/lib/systemd/systemd --switched-root --system --deserialize
 root    : ? :: /usr/lib/systemd/systemd-journald
 root    : ? :: /usr/lib/systemd/systemd-udevd
 root    : ? :: /usr/lib/systemd/systemd-logind
 dbus    : ? :: /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) + .776s (initrd) + .229s (userspace) = .493s

5. 分析启动时各个进程花费的时间

# systemd-analyze blame
.565s mariadb.service
.991s webmin.service
.095s postfix.service
.311s httpd.service
.926s firewalld.service
.780s kdump.service
.238s tuned.service
.712s network.service
.394s lvm2-monitor.service
.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 @.222s
 └─mariadb.service @.657s +.565s
 └─network.target @.168s
 └─network.service @.456s +.712s
 └─NetworkManager.service @.858s +596ms
 └─firewalld.service @.931s +.926s
 └─basic.target @.916s
 └─sockets.target @.916s
 └─dbus.socket @.916s
 └─sysinit.target @.905s
 └─systemd-update-utmp.service @.864s +39ms
 └─auditd.service @.563s +301ms
 └─systemd-tmpfiles-setup.service @.485s +69ms
 └─rhel-import-state.service @.342s +142ms
 └─local-fs.target @.324s
 └─boot.mount @.286s +31ms
 └─systemd-fsck@dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d19608096
 └─dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d196080964.device @

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
    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...-:::-block-sr0.device loaded active plugged VBOX_CD-ROM
 sys-devices-pc...::03.0-net-enp0s3.device loaded active plugged PRO/ MT Desktop Adapter
 sys-devices-pc...:05.0-sound-card0.device loaded active plugged 82801AA AC'97 Audio Controller
 sys-devices-pc...::-block-sda-sda1.device loaded active plugged VBOX_HARDDISK
 sys-devices-pc...::-block-sda-sda2.device loaded active plugged LVM PV Qzyo3l-qYaL-uRUa-Cjuk-pljo-qKtX-VgBQ8
 sys-devices-pc...-:::-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-
 sys-devices-virtual-block-dm\x2d1.device loaded active plugged /sys/devices/virtual/block/dm-
 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.
  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 -- :: IST; 34min ago
 Main PID:  (firewalld)
 CGroup: /system.slice/firewalld.service
 └─ /usr/bin/python -Es /usr/sbin/firewalld --nofork --nopid
 Apr  :: tecmint systemd[]: Starting firewalld - dynamic firewall daemon...
 Apr  :: tecmint systemd[]: 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 -- :: IST; 6s ago
 Process:  ExecStop=/bin/kill -WINCH ${MAINPID} (code=exited, status=/SUCCESS)
 Main PID:  (httpd)
 Status: "Processing requests..."
 CGroup: /system.slice/httpd.service
 ├─ /usr/sbin/httpd -DFOREGROUND
 ├─ /usr/sbin/httpd -DFOREGROUND
 ├─ /usr/sbin/httpd -DFOREGROUND
 ├─ /usr/sbin/httpd -DFOREGROUND
 ├─ /usr/sbin/httpd -DFOREGROUND
 └─ /usr/sbin/httpd -DFOREGROUND
 Apr  :: tecmint systemd[]: Starting The Apache HTTP Server...
 Apr  :: tecmint httpd[]: AH00558: httpd: Could not reliably determine the server's fully q...ssage
 Apr  :: tecmint systemd[]: 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 -- :: IST; 28min ago
 Main PID:  (code=exited, status=/SUCCESS)
 Status: "Total requests: 0; Current requests/sec: 0; Current traffic: 0 B/sec"
 Apr  :: tecmint systemd[]: httpd.service: Got notification message from PID , but recepti...bled.
 Apr  :: tecmint systemd[]: httpd.service: Got notification message from PID , but recepti...bled.
 Apr  :: tecmint systemd[]: httpd.service: Got notification message from PID , but recepti...bled.
 Apr  :: tecmint systemd[]: httpd.service: Got notification message from PID , but recepti...bled.
 Apr  :: tecmint systemd[]: httpd.service: Got notification message from PID , but recepti...bled.
 Apr  :: tecmint systemd[]: httpd.service: Got notification message from PID , but recepti...bled.
 Apr  :: tecmint systemd[]: httpd.service: Got notification message from PID , but recepti...bled.
 Apr  :: tecmint systemd[]: httpd.service: Got notification message from PID , but recepti...bled.
 Apr  :: tecmint systemd[]: httpd.service: control process exited, code=exited status=
 Apr  :: tecmint systemd[]: 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 -- :: IST; 2min 48s ago
 Where: /tmp
 What: tmpfs
 Docs: man:hier()
 http://www.freedesktop.org/wiki/Software/systemd/APIFileSystems
 Process:  ExecMount=/bin/mount tmpfs /tmp -t tmpfs -o mode=,strictatime (code=exited, status=/SUCCESS)
 Apr  :: tecmint systemd[]: Mounting Temporary Directory...
 Apr  :: tecmint systemd[]: tmp.mount: Directory /tmp to mount over is not empty, mounting anyway.
 Apr  :: tecmint systemd[]: 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
  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 -- :: IST; 8s ago
 Listen: /var/run/cups/cups.sock (Stream)
 Apr  :: tecmint systemd[]: Starting CUPS Printing Service Sockets.
 Apr  :: tecmint systemd[]: 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=

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

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/-CPUShares.conf
 [Service]
 CPUShares=

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 @.168s
 └─network.service @.456s +.712s
 └─NetworkManager.service @.858s +596ms
 └─firewalld.service @.931s +.926s
 └─basic.target @.916s
 └─sockets.target @.916s
 └─dbus.socket @.916s
 └─sysinit.target @.905s
 └─systemd-update-utmp.service @.864s +39ms
 └─auditd.service @.563s +301ms
 └─systemd-tmpfiles-setup.service @.485s +69ms
 └─rhel-import-state.service @.342s +142ms
 └─local-fs.target @.324s
 └─boot.mount @.286s +31ms
 └─systemd-fsck@dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d196080964.service @.092s +149ms
 └─dev-disk-by\x2duuid-79f594ad\x2da332\x2d4730\x2dbb5f\x2d85d196080964.device @.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
 ├─ /usr/lib/systemd/systemd --switched-root --system --deserialize
 ├─user.slice
 │ └─user-.slice
 │ └─session-.scope
 │ ├─ sshd: root@pts/
 │ ├─ -bash
 │ ├─ systemd-cgls
 │ └─ systemd-cgls
 └─system.slice
 ├─httpd.service
 │ ├─ /usr/sbin/httpd -DFOREGROUND
 │ ├─ /usr/sbin/httpd -DFOREGROUND
 │ ├─ /usr/sbin/httpd -DFOREGROUND
 │ ├─ /usr/sbin/httpd -DFOREGROUND
 │ ├─ /usr/sbin/httpd -DFOREGROUND
 │ └─ /usr/sbin/httpd -DFOREGROUND
 ├─polkit.service
 │ └─ /usr/lib/polkit-/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
 /  1.0 437.8M - -
 /system.slice - 0.1 - - -
 /system.slice/mariadb.service  0.1 - - -
 /system.slice/tuned.service  0.0 - - -
 /system.slice/httpd.service  0.0 - - -
 /system.slice/NetworkManager.service  - - - -
 /system.slice/atop.service  - - - -
 /system.slice/atopacct.service  - - - -
 /system.slice/auditd.service  - - - -
 /system.slice/crond.service  - - - -
 /system.slice/dbus.service  - - - -
 /system.slice/firewalld.service  - - - -
 /system.slice/lvm2-lvmetad.service  - - - -
 /system.slice/polkit.service  - - - -
 /system.slice/postfix.service  - - - -
 /system.slice/rsyslog.service  - - - -
 /system.slice/system-getty.slice/[e-mail]  - - - -
 /system.slice/systemd-journald.service  - - - -
 /system.slice/systemd-logind.service  - - - -
 /system.slice/systemd-udevd.service  - - - -
 /system.slice/webmin.service  - - - -
 /user.slice/user-.slice/session-.scope  - - - -

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/ (Wed -- :: 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

---

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