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。文内含长段代码可复制可往左滑，希望对大家有帮助！

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列出启动失败的服务

[root@localhost ~]# systemctl list-units --state failed
3 x* `% |) L9 y2 K; I' Q3 k6 f  UNIT          LOAD   ACTIVE SUB    DESCRIPTION
● httpd.service loaded failed failed The Apache HTTP Server
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5 u/ `, E8 O+ ALOAD   = Reflects whether the unit definition was properly loaded.
2 @* p- `6 F% P: K- J, |) M1 xACTIVE = The high-level unit activation state, i.e. generalization of SUB.
& x0 p+ W7 o8 K. d  ^+ ~7 zSUB    = The low-level unit activation state, values depend on unit type.

5 `0 X+ |3 ]+ ?! b& T' ~, U9 O1 loaded units listed. Pass --all to see loaded but inactive units, too.
! B  O" N: ^$ Y4 }- A. BTo 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

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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 httpd
0 ^. e+ y8 T) B" Hfailed
" y# W" A, w. O[root@localhost ~]# systemctl is-failed vsftpd
& k. E- X2 V( G0 r" h! q% l( @4 gactive

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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
' u6 b" f3 g" U1 I# B● httpd.service - The Apache HTTP Server
+ X, M( c8 W" m) A! N   Loaded: loaded (/usr/lib/systemd/system/httpd.service; disabled; vendor preset: disabled)
2 |- T  W& P% A" c   Active: failed (Result: exit-code) since Tue 2020-05-26 09:22:05 CST; 18min ago
     Docs: man:httpd(8)
           man:apachectl(8)
0 |  Z  f8 k$ ?9 y: c$ n Main PID: 2958 (code=exited, status=1/FAILURE)

& ?- [/ ~! i; k3 C& O4 ]) VMay 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 ""
. e2 f6 a! Q9 kMay 26 09:22:05 localhost systemd[1]: httpd.service: control process exited, code=exited status=1
2 t1 O3 C3 p0 k, ^) ]6 }. k) I* [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.
1 J) n* \. |1 r/ Z' ~: cHint: 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.

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
4 ?  ?3 c+ r5 A9 f-- 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.
+ |/ q2 ~" H) z! ]. BMay 26 09:22:05 localhost systemd[1]: Unit httpd.service entered failed state.
May 26 09:22:05 localhost systemd[1]: httpd.service failed.

' V) o, h! k- `; M* K8 |( q#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。

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总    结

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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。