Apache HTTP Server Version 2.4

Apache > HTTP Server > Documentation > Version 2.4

# Upgrading to 2.4 from 2.2

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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.

### See also

- Overview of new features in Apache HTTP Server 2.4
- Comments

## 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 a basic set of modules is loaded. The other `LoadModule` directives are commented out in the configuration file.
- 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.

Directives that control how authorization modules respond when they don't match the authenticated user have been removed: This includes AuthzLDAPAuthoritative, AuthzDBDAuthoritative, AuthzDBMAuthoritative, AuthzGroupFileAuthoritative, AuthzUserAuthoritative, and AuthzOwnerAuthoritative. These directives have been replaced by the more expressive `RequireAny`, `RequireNone`, and `RequireAll`.

If you use `mod_authz_dbm`, you must port your configuration to use `Require dbm-group ...` in place of `Require group ...`.

#### 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.

### Mixing old and new directives

Mixing old directives like `Order`, `Allow` or `Deny` with new ones like `Require` is technically possible but discouraged. `mod_access_compat` was created to support configurations containing only old directives to facilitate the 2.4 upgrade. Please check the examples below to get a better idea about issues that might arise.

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

In the following example, mixing old and new directives leads to unexpected results.

### Mixing old and new directives: NOT WORKING AS EXPECTED

    DocumentRoot "/var/www/html"

    <Directory "/">
        AllowOverride None
        Order deny,allow
        Deny from all
    </Directory>

    <Location "/server-status">
        SetHandler server-status
        Require 127.0.0.1
    </Location>

    access.log - GET /server-status 403 127.0.0.1
    error.log - AH01797: client denied by server configuration: /var/www/html/server-status

Why httpd denies access to servers-status even if the configuration seems to allow it? Because `mod_access_compat` directives take precedence over the `mod_authz_host` one in this configuration merge scenario.

This example conversely works as expected:

### Mixing old and new directives: WORKING AS EXPECTED

    DocumentRoot "/var/www/html"

    <Directory "/">
        AllowOverride None
        Require all denied
    </Directory>

    <Location "/server-status">
        SetHandler server-status
        Order deny,allow
        Deny from all
        Allow From 127.0.0.1
    </Location>

    access.log - GET /server-status 200 127.0.0.1

So even if mixing configuration is still possible, please try to avoid it when upgrading: either keep old directives and then migrate to the new ones on a later stage or just migrate everything in bulk.

### 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.
- `AllowOverride` now defaults to `None`.
- `EnableSendfile` now defaults to Off.
- `FileETag` now defaults to "MTime Size" (without INode).
- `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_cache`: The second parameter to `CacheEnable` only matches forward proxy content if it begins with the correct protocol. In 2.2 and earlier, a parameter of '/' matched all content.
- `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_proxy_scgi`: The default setting for `PATH_INFO` has changed from httpd 2.2, and some web applications will no longer operate properly with the new `PATH_INFO` setting. The previous setting can be restored by configuring the `proxy-scgi-pathinfo` variable.
- `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.
- `mod_dumpio`: `DumpIOLogLevel` is no longer supported. Data is always logged at `LogLevel` `trace7`.
- On Unix platforms, piped logging commands configured using either `ErrorLog` or `CustomLog` were invoked using `/bin/sh -c` in 2.2 and earlier. In 2.4 and later, piped logging commands are executed directly. To restore the old behaviour, see the piped logging documentation.

## 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. `SSLProxyCheckPeerCN` and `SSLProxyCheckPeerExpire` now default to On, causing proxy requests to HTTPS hosts with bad or outdated certificates to fail with a 502 status code (Bad gateway)
- `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.
- The functionality provided by `mod_authn_alias` in previous versions (i.e., the `AuthnProviderAlias` directive) has been moved into `mod_authn_core`.
- The RewriteLog and RewriteLogLevel directives have been removed. This functionality is now provided by configuring the appropriate level of logging for the `mod_rewrite` module using the `LogLevel` directive. See also the mod_rewrite logging section.

## 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.
  - `Invalid command 'AddOutputFilterByType', perhaps misspelled or defined by a module not included in the server configuration` - `AddOutputFilterByType` has moved from the core to mod_filter, which must be loaded.
- Errors serving requests:
  - `configuration error: couldn't check user: /path` - load module `mod_authn_core`.
  - `.htaccess` files aren't being processed - Check for an appropriate `AllowOverride` directive; the default changed to `None` in 2.4.

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