Linux systemctl 命令完全指南
Systemctl是一個systemd工具，主要負責控制systemd系統和服務管理器。
Systemd是一個系統管理守護進程、工具和庫的集合，用于取代System V初始進程。Systemd的功能是用于集中管理和配置類UNIX系統。
在Linux生態系統中，Systemd被部署到了大多數的標準Linux發行版中，只有為數不多的幾個發行版尚未部署。Systemd通常是所有其它守護進程的父進程，但并非總是如此。
使用Systemctl管理Linux服務
本文旨在闡明在運行systemd的系統上“如何控制系統和服務”。
Systemd初體驗和Systemctl基礎
1. 首先檢查你的系統中是否安裝有systemd并確定當前安裝的版本
# systemd --versionsystemd 215 +PAM +AUDIT +SELINUX +IMA +SYSVINIT +LIBCRYPTSETUP +GCRYPT +ACL +XZ -SECCOMP -APPARMOR</pre>
上例中很清楚地表明，我們安裝了215版本的systemd。
2. 檢查systemd和systemctl的二進制文件和庫文件的安裝位置
# whereis systemd systemd: /usr/lib/systemd /etc/systemd /usr/share/systemd /usr/share/man/man1/systemd.1.gzwhereis systemctl
systemctl: /usr/bin/systemctl /usr/share/man/man1/systemctl.1.gz</pre>
3. 檢查systemd是否運行
# ps -eaf | grep [s]ystemdroot 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 ? 00:00:00 /usr/lib/systemd/systemd-logind dbus 556 1 0 16:27 ? 00:00:00 /bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation</pre>
注意：systemd是作為父進程（PID=1）運行的。在上面帶（-e）參數的ps命令輸出中，選擇所有進程，（-a）選擇除會話前導外的所有進程，并使用（-f）參數輸出完整格式列表（即 -eaf）。
也請注意上例中后隨的方括號和例子中剩余部分。方括號表達式是grep的字符類表達式的一部分。
4. 分析systemd啟動進程
# systemd-analyze Startup finished in 487ms (kernel) + 2.776s (initrd) + 20.229s (userspace) = 23.493s5. 分析啟動時各個進程花費的時間
# systemd-analyze blame8.565s 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 ....</pre>
6. 分析啟動時的關鍵鏈
# systemd-analyze critical-chainThe 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</pre>
重要：Systemctl接受服務（.service），掛載點（.mount），套接口（.socket）和設備（.device）作為單元。
7. 列出所有可用單元
# systemctl list-unit-filesUNIT 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 .....</pre>8. 列出所有運行中單元
# systemctl list-unitsUNIT 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 ...</pre>
9. 列出所有失敗單元
# systemctl --failedUNIT 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'.</pre>
10. 檢查某個單元（如 cron.service）是否啟用
# systemctl is-enabled crond.serviceenabled</pre>
11. 檢查某個單元或服務是否運行
# systemctl status firewalld.servicefirewalld.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.</pre>
使用Systemctl控制并管理服務
12. 列出所有服務（包括啟用的和禁用的）
# systemctl list-unit-files --type=serviceUNIT 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 ....</pre>13. Linux中如何啟動、重啟、停止、重載服務以及檢查服務（如 httpd.service）狀態
# systemctl start httpd.servicesystemctl 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.</pre>
注意：當我們使用systemctl的start，restart，stop和reload命令時，我們不會從終端獲取到任何輸出內容，只有status命令可以打印輸出。
14. 如何激活服務并在啟動時啟用或禁用服務（即系統啟動時自動啟動服務）
# systemctl is-active httpd.servicesystemctl enable httpd.service
systemctl disable httpd.service</pre>
15. 如何屏蔽（讓它不能啟動）或顯示服務（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'</pre>
16. 使用systemctl命令殺死服務
# systemctl kill httpdsystemctl 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.</pre>
使用Systemctl控制并管理掛載點
17. 列出所有系統掛載點
# systemctl list-unit-files --type=mountUNIT 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</pre>18. 掛載、卸載、重新掛載、重載系統掛載點并檢查系統中掛載點狀態
# systemctl start tmp.mountsystemctl 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.</pre>
19. 在啟動時激活、啟用或禁用掛載點（系統啟動時自動掛載）
# systemctl is-active tmp.mountsystemctl enable tmp.mount
systemctl disable tmp.mount</pre>
20. 在Linux中屏蔽（讓它不能啟用）或可見掛載點
# systemctl mask tmp.mountln -s '/dev/null' '/etc/systemd/system/tmp.mount'
systemctl unmask tmp.mount
rm '/etc/systemd/system/tmp.mount'</pre>
使用Systemctl控制并管理套接口
21. 列出所有可用系統套接口
# systemctl list-unit-files --type=socketUNIT 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 static11 unit files listed.</pre>
22. 在Linux中啟動、重啟、停止、重載套接口并檢查其狀態
# systemctl start cups.socketsystemctl 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.</pre>
23. 在啟動時激活套接口，并啟用或禁用它（系統啟動時自啟動）
# systemctl is-active cups.socketsystemctl enable cups.socket
systemctl disable cups.socket</pre>
24. 屏蔽（使它不能啟動）或顯示套接口
# systemctl mask cups.socket ln -s '/dev/null' '/etc/systemd/system/cups.socket'systemctl unmask cups.socket
rm '/etc/systemd/system/cups.socket'</pre>
服務的CPU利用率（分配額）
25. 獲取當前某個服務的CPU分配額（如httpd）
# systemctl show -p CPUShares httpd.serviceCPUShares=1024</pre>
注意：各個服務的默認CPU分配份額=1024，你可以增加/減少某個進程的CPU分配份額。
26. 將某個服務（httpd.service）的CPU分配份額限制為2000 CPUShares/
# systemctl set-property httpd.service CPUShares=2000systemctl show -p CPUShares httpd.service
CPUShares=2000</pre>
注意：當你為某個服務設置CPUShares，會自動創建一個以服務名命名的目錄（如 httpd.service），里面包含了一個名為90-CPUShares.conf的文件，該文件含有CPUShare限制信息，你可以通過以下方式查看該文件：
# vi /etc/systemd/system/httpd.service.d/90-CPUShares.conf[Service] CPUShares=2000</pre>
27. 檢查某個服務的所有配置細節
# systemctl show httpdId=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 ....</pre>
28. 分析某個服務（httpd）的關鍵鏈
# systemd-analyze critical-chain httpd.serviceThe 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</pre>
29. 獲取某個服務（httpd）的依賴性列表
# systemctl list-dependencies httpd.servicehttpd.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 ....</pre>
30. 按等級列出控制組
# 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 ....</pre>31. 按CPU、內存、輸入和輸出列出控制組
# systemd-cgtopPath 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 - - - -</pre>
控制系統運行等級
32. 啟動系統救援模式
# systemctl rescueBroadcast message from root@tecmint on pts/0 (Wed 2015-04-29 11:31:18 IST):
The system is going down to rescue mode NOW!</pre>
33. 進入緊急模式
# systemctl emergencyWelcome 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.</pre>
34. 列出當前使用的運行等級
# systemctl get-defaultmulti-user.target</pre>
35. 啟動運行等級5，即圖形模式
# systemctl isolate runlevel5.target 或systemctl isolate graphical.target</pre>
36. 啟動運行等級3，即多用戶模式（命令行）
# systemctl isolate runlevel3.target 或systemctl isolate multiuser.target</pre>
36. 設置多用戶模式或圖形模式為默認運行等級
# systemctl set-default runlevel3.targetsystemctl set-default runlevel5.target</pre>
37. 重啟、停止、掛起、休眠系統或使系統進入混合睡眠
# systemctl rebootsystemctl halt
systemctl suspend
systemctl hibernate
systemctl hybrid-sleep</pre>
對于不知運行等級為何物的人，說明如下。
- Runlevel 0 : 關閉系統
- Runlevel 1 : 救援？維護模式
- Runlevel 3 : 多用戶，無圖形系統
- Runlevel 4 : 多用戶，無圖形系統
- Runlevel 5 : 多用戶，圖形化系統
- Runlevel 6 : 關閉并重啟機器 </ul>
到此為止吧。保持連線，進行評論。別忘了在下面的評論中為我們提供一些有價值的反饋哦。喜歡我們、與我們分享，求擴散。
來源： linux.cn