| 本教程介紹如何使用systemctl工具列出啟動失敗的systemd管理的各個服務 |
列出啟動失敗的服務
[root@localhost ~]# systemctl list-units --state failed UNIT LOAD ACTIVE SUB DESCRIPTION ● httpd.service loaded failed failed The Apache HTTP Server 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'.
可以發現，有個一個服務啟動失敗了。
is-failed選項
可以使用is-failed選項檢查指定的服務是否啟動失敗。如果啟動失敗，結果是failed。如果啟動沒有問題，結果是active。
[root@localhost ~]# systemctl is-failed httpd failed [root@localhost ~]# systemctl is-failed vsftpd active
檢查服務的狀態
可以使用status選項，查看服務啟動失敗的原因，下面狀態信息里面告訴我們，是httpd.conf配置文件354行有語法錯誤。
May 26 09:22:05 localhost httpd[2958]: httpd: Syntax error on line 354 of /etc/httpd/conf/httpd.conf: /...osed.
[root@localhost ~]# systemctl status httpd
● httpd.service - The Apache HTTP Server
Loaded: loaded (/usr/lib/systemd/system/httpd.service; disabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Tue 2020-05-26 09:22:05 CST; 18min ago
Docs: man:httpd(8)
man:apachectl(8)
Main PID: 2958 (code=exited, status=1/FAILURE)
May 26 09:22:05 localhost systemd[1]: Starting The Apache HTTP Server...
May 26 09:22:05 localhost httpd[2958]: httpd: Syntax error on line 354 of /etc/httpd/conf/httpd.conf: /...osed.
May 26 09:22:05 localhost systemd[1]: httpd.service: main process exited, code=exited, status=1/FAILURE
May 26 09:22:05 localhost kill[2959]: kill: cannot find process ""
May 26 09:22:05 localhost systemd[1]: httpd.service: control process exited, code=exited status=1
May 26 09:22:05 localhost systemd[1]: Failed to start The Apache HTTP Server.
May 26 09:22:05 localhost systemd[1]: Unit httpd.service entered failed state.
May 26 09:22:05 localhost systemd[1]: httpd.service failed.
Hint: Some lines were ellipsized, use -l to show in full.
使用journalctl查看服務的啟動日志
如果使用systemctl status [unit]沒有找到服務啟動失敗的原因，可以使用journalctl查看更多的啟動日志。
下面操作是過濾出所有帶有error的行，可以找到啟動失敗的服務。
[root@localhost ~]# journalctl |grep 'error' May 26 09:22:05 localhost httpd[2958]: httpd: Syntax error on line 354 of /etc/httpd/conf/httpd.conf: /etc/httpd/conf/httpd.conf:354: was not closed.
也可以使用journalctl -u [unit]只查看某一個服務的啟動日志：
[root@localhost ~]# journalctl -u httpd.service -- Logs begin at Sun 2020-05-24 06:52:52 CST, end at Tue 2020-05-26 09:48:03 CST. -- May 26 09:22:05 localhost systemd[1]: Starting The Apache HTTP Server... May 26 09:22:05 localhost httpd[2958]: httpd: Syntax error on line 354 of /etc/httpd/conf/httpd.conf: /etc/httpd/conf/httpd.conf:354: was not closed. May 26 09:22:05 localhost systemd[1]: httpd.service: main process exited, code=exited, status=1/FAILURE May 26 09:22:05 localhost kill[2959]: kill: cannot find process "" May 26 09:22:05 localhost systemd[1]: httpd.service: control process exited, code=exited status=1 May 26 09:22:05 localhost systemd[1]: Failed to start The Apache HTTP Server. May 26 09:22:05 localhost systemd[1]: Unit httpd.service entered failed state. May 26 09:22:05 localhost systemd[1]: httpd.service failed. #過濾出有錯誤的信息。 [root@localhost ~]# journalctl -u httpd.service |grep 'error' May 26 09:22:05 localhost httpd[2958]: httpd: Syntax error on line 354 of /etc/httpd/conf/httpd.conf: /etc/httpd/conf/httpd.conf:354: was not closed.
發現 /etc/httpd/conf/httpd.conf配置文件的354行，Directory標簽沒有關閉，返現原因了，就馬上修改吧。
總結
我們學習了如何使用systemctl命令顯示在Linux上運行失敗的服務/單元。有關詳細信息，請查看systemctl手冊。