I installed the mod_qos module using the steps found here, every step went perfectly fine without any problems, however, when attempting to restart the apache service it returned the following error:

apache2: Syntax error on line 203 of /etc/apache2/apache2.conf: Syntax error on line 1 of /etc/apache2/mods-enabled/qos.load: Cannot load /usr/lib/apache2/modules/mod_qos.so into server: /usr/lib/apache2/modules/mod_qos.so: undefined symbol: EVP_DecryptFinal

The contents of the qos.load file is just this line:

LoadModule qos_module /usr/lib/apache2/modules/mod_qos.so

How do I solve this error?


This means that mod_qos is trying to use a part of a library that is not (yet) loaded or available. EVP_DecryptFinal should be a part of openSSL, so provided that you've got mod_ssl installed, try loading it before you load qos.

  • mod_ssl is installed and working, how can I make sure it's loaded before loading mod_qos? would renaming ssl.load -> 0.load and qos.load -> 1.load work? – xorinzor Feb 20 '13 at 16:58
  • that actually seems to have solved the problem – xorinzor Feb 20 '13 at 17:10

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