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
$ ~; D' [. [$ p* X" B/ _4 b  UNIT          LOAD   ACTIVE SUB    DESCRIPTION
1 }" t9 O. b) s' c& ^5 C6 o● httpd.service loaded failed failed The Apache HTTP Server

LOAD   = Reflects whether the unit definition was properly loaded.
6 |( z; ]9 ]1 w9 U) VACTIVE = The high-level unit activation state, i.e. generalization of SUB.
; d0 K2 T8 C& R& X5 h5 \6 k$ C, mSUB    = The low-level unit activation state, values depend on unit type.
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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。

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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
failed
[root@localhost ~]# systemctl is-failed vsftpd
active

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检查服务的状态

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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.
- o8 l1 g- U+ k% V! R% w3 w[root@localhost ~]# systemctl status httpd
● httpd.service - The Apache HTTP Server
  ?/ r; r6 c! [- @   Loaded: loaded (/usr/lib/systemd/system/httpd.service; disabled; vendor preset: disabled)
8 p# o" U% G( I, a1 K   Active: failed (Result: exit-code) since Tue 2020-05-26 09:22:05 CST; 18min ago
     Docs: man:httpd(8)
           man:apachectl(8)
! u( j  H- \( `) Y5 A1 d+ P Main PID: 2958 (code=exited, status=1/FAILURE)

May 26 09:22:05 localhost systemd[1]: Starting The Apache HTTP Server...
. R7 y! Y. L/ [- \$ ^& W2 `May 26 09:22:05 localhost httpd[2958]: httpd: Syntax error on line 354 of /etc/httpd/conf/httpd.conf: /...osed.
% k: i; ~' M3 W: \- iMay 26 09:22:05 localhost systemd[1]: httpd.service: main process exited, code=exited, status=1/FAILURE
: h! ^0 R, G- O" M) I  rMay 26 09:22:05 localhost kill[2959]: kill: cannot find process ""
+ f6 Z, k' o! u* oMay 26 09:22:05 localhost systemd[1]: httpd.service: control process exited, code=exited status=1
0 z1 P$ P  C, f% [  @  N8 J7 PMay 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'
, @/ `1 ^" q& {& oMay 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. --
& m1 V. ]# e/ k2 a" cMay 26 09:22:05 localhost systemd[1]: Starting The Apache HTTP Server...
& o1 T+ x% w% X; cMay 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.
) O1 N+ O, j. H+ w, W6 N) Q6 _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
) Q7 }4 D+ T# \1 A: d( a3 aMay 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.
1 o0 M) Z' K8 s1 lMay 26 09:22:05 localhost systemd[1]: httpd.service failed.
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) g6 D8 g" ^5 M& H[root@localhost ~]# journalctl -u httpd.service |grep 'error'
% p3 v- t" _% p" L# X! h8 Y5 XMay 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

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。