Upgrading to 2.4 from 2.2

In order to assist folks upgrading, we maintain a document describing information critical to existing Apache HTTP Server users. These are intended to be brief notes, and you should be able to find more information in either the New Features document, or in the src/CHANGES file. Application and module developers can find a summary of API changes in the API updates overview.

This document describes changes in server behavior that might require you to change your configuration or how you use the server in order to continue using 2.4 as you are currently using 2.2. To take advantage of new features in 2.4, see the New Features document.

This document describes only the changes from 2.2 to 2.4. If you are upgrading from version 2.0, you should also consult the 2.0 to 2.2 upgrading document.

 Overview of new features in Apache HTTP Server 2.4
Compile-Time Configuration Changes

The compilation process is very similar to the one used in version 2.2. Your old configure command line (as found in build/config.nice in the installed server directory) can be used in most cases. There are some changes in the default settings. Some details of changes:

Run-Time Configuration Changes

There have been significant changes in authorization configuration, and other minor configuration changes, that could require changes to your 2.2 configuration files before using them for 2.4.

Authorization

Any configuration file that uses authorization will likely need changes.

You should review the Authentication, Authorization and Access Control Howto, especially the section Beyond just authorization which explains the new mechanisms for controlling the order in which the authorization directives are applied.

Access control

In 2.2, access control based on client hostname, IP address, and other characteristics of client requests was done using the directives Order, Allow, Deny, and Satisfy.

In 2.4, such access control is done in the same way as other authorization checks, using the new module mod_authz_host. The old access control idioms should be replaced by the new authentication mechanisms, although for compatibility with old configurations, the new module mod_access_compat is provided.

Here are some examples of old and new ways to do the same access control.

In this example, all requests are denied.

2.2 configuration: Order deny,allow
Deny from all 2.4 configuration: Require all denied

In this example, all requests are allowed.

2.2 configuration: Order allow,deny
Allow from all 2.4 configuration: Require all granted

In the following example, all hosts in the example.org domain are allowed access; all other hosts are denied access.

2.2 configuration: Order Deny,Allow
Deny from all
Allow from example.org 2.4 configuration: Require host example.org
Other configuration changes

Some other small adjustments may be necessary for particular configurations as discussed below.

  • MaxRequestsPerChild has been renamed to MaxConnectionsPerChild, describes more accurately what it does. The old name is still supported.
  • MaxClients has been renamed to MaxRequestWorkers, which describes more accurately what it does. For async MPMs, like event, the maximum number of clients is not equivalent than the number of worker threads. The old name is still supported.
  • The DefaultType directive no longer has any effect, other than to emit a warning if it's used with any value other than none. You need to use other configuration settings to replace it in 2.4.
  • EnableSendfile now defaults to Off.
  • mod_log_config: ${cookie}C matches whole cookie names. Previously any substring would match.
  • mod_dav_fs: The format of the DavLockDB file has changed for systems with inodes. The old DavLockDB file must be deleted on upgrade.
  • KeepAlive only accepts values of On or Off. Previously, any value other than "Off" or "0" was treated as "On".
  • Directives AcceptMutex, LockFile, RewriteLock, SSLMutex, SSLStaplingMutex, and WatchdogMutexPath have been replaced with a single Mutex directive. You will need to evaluate any use of these removed directives in your 2.2 configuration to determine if they can just be deleted or will need to be replaced using Mutex.
  • mod_cache: CacheIgnoreURLSessionIdentifiers now does an exact match against the query string instead of a partial match. If your configuration was using partial strings, e.g. using sessionid to match /someapplication/image.gif;jsessionid=123456789, then you will need to change to the full string jsessionid.
  • mod_ldap: LDAPTrustedClientCert is now consistently a per-directory setting only. If you use this directive, review your configuration to make sure it is present in all the necessary directory contexts.
  • mod_filter: FilterProvider syntax has changed and now uses a boolean expression to determine if a filter is applied.
  • mod_include:
    • The #if expr element now uses the new expression parser. The old syntax can be restored with the new directive SSILegacyExprParser.
    • An SSI* config directive in directory scope no longer causes all other per-directory SSI* directives to be reset to their default values.
  • mod_charset_lite: The DebugLevel option has been removed in favour of per-module LogLevel configuration.
  • mod_ext-filter: The DebugLevel option has been removed in favour of per-module LogLevel configuration.
  • mod_ssl: CRL based revocation checking now needs to be explicitly configured through SSLCARevocationCheck.
Misc Changes
Third Party Modules

All modules must be recompiled for 2.4 before being loaded.

Many third-party modules designed for version 2.2 will otherwise work unchanged with the Apache HTTP Server version 2.4. Some will require changes; see the API update overview.

Common problems when upgrading