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！

列出启动失败的服务

[root@localhost ~]# systemctl list-units --state failed
  UNIT          LOAD   ACTIVE SUB    DESCRIPTION
+ k7 [  K. }5 \  s8 s& T  n6 d  b● httpd.service loaded failed failed The Apache HTTP Server
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LOAD   = Reflects whether the unit definition was properly loaded.
ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
0 Q0 v- r5 C) Q& g+ t) v: d8 j" \SUB    = The low-level unit activation state, values depend on unit type.
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8 }1 O" P$ x( e2 v/ M8 X1 loaded units listed. Pass --all to see loaded but inactive units, too.
+ z+ {$ S( O9 N! @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。

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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。

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[root@localhost ~]# systemctl is-failed httpd
+ P1 m; B- `8 @; R, ]+ Wfailed
[root@localhost ~]# systemctl is-failed vsftpd
active
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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。

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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
: Z7 e6 I; p' _: z. B& T● 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
" W4 J. S0 J0 N/ i6 p     Docs: man:httpd(8)
           man:apachectl(8)
0 v- g( u* _( p0 h9 _% s' e* K Main PID: 2958 (code=exited, status=1/FAILURE)
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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.
% p5 b  n9 T. y" gMay 26 09:22:05 localhost systemd[1]: httpd.service: main process exited, code=exited, status=1/FAILURE
) u+ o/ x7 J3 Z" K+ BMay 26 09:22:05 localhost kill[2959]: kill: cannot find process ""
1 l. d) @5 `, L" Z& {& LMay 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.
- g+ v4 A, k2 z9 MMay 26 09:22:05 localhost systemd[1]: Unit httpd.service entered failed state.
8 H9 @+ D( n! X1 sMay 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。

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[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
0 Z: {/ t" p1 H-- Logs begin at Sun 2020-05-24 06:52:52 CST, end at Tue 2020-05-26 09:48:03 CST. --
: w# b3 H% E0 _* @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.
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#过滤出有错误的信息。
: O! J; j( t& N3 {4 s* V' O8 H[root@localhost ~]# journalctl -u httpd.service |grep 'error'
2 C2 W( {/ H8 K9 U* l/ z1 pMay 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

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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。

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