CentOS7中使用systemctl列出启动失败的服务

LinuxProbe

本教程介绍如何使用systemctl工具列出启动失败的systemd管理的各个服务

列出启动失败的服务
[root@localhost ~]# systemctl list-units --state failed  UNIT          LOAD   ACTIVE SUB    DESCRIPTION● httpd.service loaded failed failed The Apache HTTP ServerLOAD   = 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'.

                               
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可以发现，有个一个服务启动失败了。

is-failed选项

可以使用is-failed选项检查指定的服务是否启动失败。如果启动失败，结果是failed。如果启动没有问题，结果是active。

[root@localhost ~]# systemctl is-failed httpdfailed[root@localhost ~]# systemctl is-failed vsftpdactive

                               
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检查服务的状态

可以使用status选项，查看服务启动失败的原因，下面状态信息里面告诉我们，是httpd.conf配置文件354行有语法错误。

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/FAILUREMay 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=1May 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.

                               
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使用journalctl查看服务的启动日志

如果使用systemctl status [unit]没有找到服务启动失败的原因，可以使用journalctl查看更多的启动日志。

下面操作是过滤出所有带有error的行，可以找到启动失败的服务。

[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.

                               
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也可以使用journalctl -u [unit]只查看某一个服务的启动日志：

[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/FAILUREMay 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=1May 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.#过滤出有错误的信息。[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.

                               
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发现 /etc/httpd/conf/httpd.conf配置文件的354行，Directory标签没有关闭，返现原因了，就马上修改吧。

总结

我们学习了如何使用systemctl命令显示在Linux上运行失败的服务/单元。有关详细信息，请查看systemctl手册。

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