# 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:

- These modules have been removed: mod_authn_default, mod_authz_default, mod_mem_cache. If you were using mod_mem_cache in 2.2, look at mod_cache_disk in 2.4.
- All load balancing implementations have been moved to individual, self-contained mod_proxy submodules, e.g. mod_lbmethod_bybusyness. You might need to build and load any of these that your configuration uses.
- Platform support has been removed for BeOS, TPF, and even older platforms such as A/UX, Next, and Tandem. These were believed to be broken anyway.
- configure: dynamic modules (DSO) are built by default
- configure: By default, only load those modules that are either required or explicitly selected by a configure `--enable-foo` argument.
- configure: the "most" module set gets built by default
- configure: the "reallyall" module set adds developer modules to the "all" set

# 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.
- FileETag
  now defaults to "MTime Size" (without INode).
- 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.
- mod_substitute
  : The maximum line length is now limited to 1MB.
- mod_reqtimeout
  : If the module is loaded, it will now set some default timeouts.

# Misc Changes

- mod_autoindex
  : will now extract titles and display descriptions for .xhtml files, which were previously ignored.
- mod_ssl
  : The default format of the `*_DN` variables has changed. The old format can still be used with the new `LegacyDNStringFormat` argument to SSLOptions. The SSLv2 protocol is no longer supported.
- htpasswd
  now uses MD5 hash by default on all platforms.
- The NameVirtualHost directive no longer has any effect, other than to emit a warning. Any address/port combination appearing in multiple virtual hosts is implicitly treated as a name-based virtual host.
- mod_deflate
  will now skip compression if it knows that the size overhead added by the compression is larger than the data to be compressed.
- Multi-language error documents from 2.2.x may not work unless they are adjusted to the new syntax of mod_include's `#if expr=` element or the directive SSILegacyExprParser is enabled for the directory containing the error documents.

# 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

- Startup errors:
  - `Invalid command 'User', perhaps misspelled or defined by a module not included in the server configuration` - load module mod_unixd
  - `Invalid command 'Require', perhaps misspelled or defined by a module not included in the server configuration`, or `Invalid command 'Order', perhaps misspelled or defined by a module not included in the server configuration` - load module mod_access_compat, or update configuration to 2.4 authorization directives.
  - `Ignoring deprecated use of DefaultType in line NN of /path/to/httpd.conf` - remove DefaultType and replace with other configuration settings.
- Errors serving requests:
  - `configuration error: couldn't check user: /path` - load module mod_authn_core.