After dist-upgrade Apache was upgraded from 2.2 to 2.4, Apache and cannot start

Symptoms

Note: the article is related to the issue that occurs after Apache upgrade (during dist-upgrade for example).

• After failed Plesk upgrade on Debian OS with Apache version 2.4 installed, web server is not starting.

• The following error messages appears:

  apache2: Syntax error on line 234 of /etc/apache2/apache2.conf: Syntax error on line 5 of /etc/apache2/conf.d/zz010_psa_httpd.conf: Syntax error on line 72 of /etc/apache2/plesk.conf.d/server.conf: No matches for the wildcard '*.conf' in '/etc/apache2/plesk.conf.d/ip_default', failing (use IncludeOptional if required)
  Action 'configtest' failed.
  The Apache error log may have more information.

  Invalid command 'Order', perhaps misspelled or defined by a module not included in the server configuration

  SSLSessionCache: 'shmcb' session cache not supported (known names: dbm,memcache). Maybe you need to load the appropriate socache module (mod_socache_shmcb?).

  The apache2 instance did not start within 20 seconds. Please read the log files to discover problems.

  [proxy_balancer:emerg] [pid 25870] AH01177: Failed to lookup provider 'shm' for 'slotmem': is mod_slotmem_shm loaded?

  Invalid command 'Require', perhaps misspelled or defined by a module not included in the server configuration

  Invalid command 'User', perhaps misspelled or defined by a module not included in the server configuration1.

  Invalid command 'DirectoryIndex', perhaps misspelled or defined by a module not included in the server configuration

  ERROR: Config file dir.conf not properly enabled: /etc/apache2/mods-enabled/dir.conf is a real file, not touching it

Cause

Configuration files were not completely switched to the new Apache 2.4

Resolution

1. Check if custom templates exist in /usr/local/psa/admin/conf/templates folder. If so review all of them and change Include to IncludeOptional in every line what contain wildcard.

2. If there are no custom templates change Include to IncludeOptional in every line what contain wildcard in the following files:

   /etc/apache2/conf.d/zz010_psa_httpd.conf
   /etc/apache2/plesk.conf.d/server.conf
   /etc/apache2/plesk.conf.d/horde.conf

3. Enable and activate the following Apache modules

   # a2enmod authz_core authz_host access_compat socache_shmcb slotmem_shm mpm_worker unixd php5 dir