systemctl 命令完全指南

编译自：http://www.tecmint.com/manage-services-using-systemd-and-systemctl-in-linux/
作者： Avishek Kumar
原创：LCTT
https://linux.cn/article-5926-1.html
译者：
GOLinux

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 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<
4000
/span>: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

原文章链接：https://linux.cn/article-5926-1.html