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I'm looking for a command that checks the validity of the config files in Apache server on both Debian and RHEL distros. I need to do this prior to restart, so there will be no downtime.

6 Answers 6

364

Check: http://httpd.apache.org/docs/2.2/programs/apachectl.html

apachectl configtest
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  • I am getting this message running the above command AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1. Set the 'ServerName' directive globally to suppress this message Sep 15, 2016 at 16:18
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    Add a line "ServerName whateveryoulike" to your apache config. Replace whateveryoulike with what ever you like to name your server.
    – Pit
    Sep 26, 2016 at 6:48
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    might require sudo ?
    – Miguel
    Mar 29, 2017 at 10:29
53

Another way is httpd -t. Therefore, it's available in Windows-version of Apache. Check http://httpd.apache.org/docs/2.4/programs/httpd.html

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    Oddly, on Ubuntu, when I run apachectl configtest I get Syntax OK, but when I run apache2 -t I get AH00526: Syntax error on line 74 of /etc/apache2/apache2.conf (among other errors) Dec 8, 2018 at 2:02
  • @ButtleButkus but the server when you systemctl restart apache2 is ok right? Oct 6, 2021 at 4:16
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apachectl configtest is the correct answer. Unfortunately I've got a windows installation where apachectl is missing. Here calling httpd also helps.

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The Apache config test (apachectl configtest, or its equivalents) only tests the config file (and the files it recursively includes) for valid syntax. However, the original question asked for preventing downtime. Even when apachectl configtest does not return an error, an actual restart may still fail, causing downtime.

Common causes for such failures include missing or inaccessible SSL certificates, missing directories for log files or a missing website root directory. Often, such errors are caused by removing a vhost's directory without removing the vhost Apache config file. It is highly recommended to use a tool like puppet or ansible to prevent such inconsistencies.

Seeing that this question is the number one hit when googling "apache config lint" I thought I'd mention this little detail...

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  • Is there a way to test for common causes of failure per above?
    – Vishal
    Sep 22, 2020 at 0:59
  • That would require a script, that parses the apache config and implements the missing checks. I'm not aware of any freely available scripts that does so.
    – BertD
    Sep 22, 2020 at 12:26
  • I have written such a script. If I took the time to put it on github, would anyone use it? It specifically checks SSL configurations, that the files are in the correct location and that the modulos match using openssl, among other things. Sep 27, 2021 at 19:09
  • I would! Putting it on github definitely is a bonus.
    – BertD
    Sep 28, 2021 at 20:40
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What I usually do is

apache2ctl -t && apache2ctl graceful
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    Your answer would be more useful if you explained why this works.
    – crafter
    Jul 30, 2021 at 10:56
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    I'll hazard a guess. The "-t" runs a syntax test for configuration files only. If that fails, the && prevents the next command from running. The next command, 'apache2ctl graceful' will restart the httpd service in a way that won't disconnect existing connections (hence, graceful). Jan 27 at 16:06
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I have actually tried before:

apachectl configtest

We can actually see the status code to know the error:

/etc/init.d/apache2 restart; systemctl status apache2.service

● apache2.service - The Apache HTTP Server Loaded: loaded (/lib/systemd/system/apache2.service; disabled; vendor preset: disabled) Active: failed (Result: exit-code) since Sun 2021-05-30 17:16:45 +08; 41ms ago Docs: https://httpd.apache.org/docs/2.4/ Process: 168391 ExecStart=/usr/sbin/apachectl start (code=exited, status=1/FAILURE) CPU: 67ms

May 30 17:16:45 kali systemd[1]: Starting The Apache HTTP Server... May 30 17:16:45 kali apachectl[168394]: AH00526: Syntax error on line 13 of /etc/apache2/mods-enabled/security2.conf

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