Werk #18156: Prevent site Apache stopped with syntax error due to undefined symbol

Component Other components
Title Prevent site Apache stopped with syntax error due to undefined symbol
Date Sep 12, 2025
Level Prominent Change
Class Bug Fix
Compatibility Compatible - no manual interaction needed
Checkmk versions & editions
2.5.0b1
Not yet released
Checkmk Raw (CRE), Checkmk Enterprise (CEE), Checkmk Cloud (CCE), Checkmk MSP (CME)
2.4.0p14
Not yet released
Checkmk Raw (CRE), Checkmk Enterprise (CEE), Checkmk Cloud (CCE), Checkmk MSP (CME)
2.3.0p39
Not yet released
Checkmk Raw (CRE), Checkmk Enterprise (CEE), Checkmk Cloud (CCE), Checkmk MSP (CME)

In previous versions of Checkmk, an update of the packages apache2 or apache2-bin would cause the site Apache to crash on the next reload. This crash commonly occured at midnight, when a site rotates the Apache logs. In such an instance, omd status would show that the site is partially running. Moreover, the following error could be found in /omd/sites/cmk/var/log/apache/error_log:

[mpm_prefork:notice] [pid 2364] AH00171: Graceful restart requested, doing restart apache2: Syntax error on line 126 of /omd/sites/cmk/etc/apache/apache.conf: Cannot load /omd/sites/cmk/lib/apache/modules/mod_headers.so into server: /omd/sites/cmk/lib/apache/modules/mod_headers.so: undefined symbol: ap_set_content_type_ex

With this change, all OMD sites will be restarted after an update of the apache2 or apache2-bin packages. This prevents the crash.

Background

The active Apache process is not able to gracefully reload after the apache or apache2-bin packages have been updated. For this reason, distributions include post update triggers, e.g., /var/lib/dpkg/info/apache2.postinst. These ensure that the system Apache is restarted after the update. Checkmk now also includes these triggers to restart the site Apache.

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