Using Apache HTTP Server on Microsoft Windows

Operating System Requirements

The primary Windows platform for running Apache httpd 2.4 is Windows 2000 or later. Always obtain and install the current service pack to avoid operating system bugs.

Downloading httpd for Windows

The Apache HTTP Server Project itself does not provide binary releases of software, only source code. Individual committers may provide binary packages as a convenience, but it is not a release deliverable.

If you cannot compile the Apache HTTP Server yourself, you can obtain a binary package from numerous binary distributions available on the Internet.

Popular options for deploying Apache httpd, and, optionally, PHP and MySQL, on Microsoft Windows, include:

• Apache Lounge
• WampServer

Customizing httpd for Windows

Apache httpd is configured by the files in the conf subdirectory. These are the same files used to configure the Unix version, but there are a few different directives for httpd on Windows. See the directive index for all the available directives.

The default configuration of the source distribution expects the server to be installed into \Apache24. This can be customized at compilation time, but it's important that ultimately the ServerRoot in httpd.conf match the actual installation root. Binary distributions may customize either the default installation root or the overall layout of the initial configuration.

The main differences in httpd for Windows are:

• Because httpd for Windows is multithreaded, it does not use a separate process for each request, as httpd can on Unix. Instead there are usually only two httpd processes running: a parent process, and a child which handles the requests. Within the child process each request is handled by a separate thread.

  The process management directives are also different:

  MaxConnectionsPerChild: Like the Unix directive, this controls how many connections a single child process will serve before exiting. However, unlike on Unix, a replacement process is not instantly available. Use the default MaxConnectionsPerChild 0, unless instructed to change the behavior to overcome a memory leak in third party modules or in-process applications.

  Warning: The server configuration file is reread when a new child process is started. If you have modified httpd.conf, the new child may not start or you may receive unexpected results.

  ThreadsPerChild: This directive is new. It tells the server how many threads it should use. This is the maximum number of connections the server can handle at once, so be sure to set this number high enough for your site if you get a lot of hits. The recommended default is ThreadsPerChild 150, but this must be adjusted to reflect the greatest anticipated number of simultaneous connections to accept.

• The directives that accept filenames as arguments must use Windows filenames instead of Unix ones. However, because httpd may interpret backslashes as an "escape character" sequence, you should consistently use forward slashes in path names, not backslashes.

• While filenames are generally case-insensitive on Windows, URLs are still treated internally as case-sensitive before they are mapped to the filesystem. For example, the <Location>, Alias, and ProxyPass directives all use case-sensitive arguments. For this reason, it is particularly important to use the <Directory> directive when attempting to limit access to content in the filesystem, since this directive applies to any content in a directory, regardless of how it is accessed. If you wish to assure that only lowercase is used in URLs, you can use something like:

  RewriteEngine On
  RewriteMap lowercase int:tolower
  RewriteCond "%{REQUEST_URI}" "[A-Z]"
  RewriteRule "(.*)" "${lowercase:$1}" [R,L]

• When running, httpd needs write access only to the logs directory and any configured cache directory tree. Due to the issue of case insensitive and short 8.3 format names, httpd must validate all path names given. This means that each directory which httpd evaluates, from the drive root up to the directory leaf, must have read, list and traverse directory permissions. If Apache2.4 is installed at C:\Program Files, then the root directory, Program Files and Apache2.4 must all be visible to httpd.

• httpd for Windows contains the ability to load modules at runtime, without recompiling the server. If httpd is compiled normally, it will install a number of optional modules in the \Apache2.4\modules directory. To activate these or other modules, the LoadModule directive must be used. For example, to activate the status module, use the following (in addition to the status-activating directives in access.conf):

  LoadModule status_module "modules/mod_status.so"

  Information on creating loadable modules is also available.

• httpd can also load ISAPI (Internet Server Application Programming Interface) extensions such as those used by Microsoft IIS and other Windows servers. More information is available. Note that httpd cannot load ISAPI Filters, and ISAPI Handlers with some Microsoft feature extensions will not work.

• When running CGI scripts, the method httpd uses to find the interpreter for the script is configurable using the ScriptInterpreterSource directive.

• Since it is often difficult to manage files with names like .htaccess in Windows, you may find it useful to change the name of this per-directory configuration file using the AccessFilename directive.

• Any errors during httpd startup are logged into the Windows event log when running on Windows NT. This mechanism acts as a backup for those situations where httpd is not yet prepared to use the error.log file. You can review the Windows Application Event Log by using the Event Viewer, e.g. Start - Settings - Control Panel - Administrative Tools - Event Viewer.

Running httpd as a Service

Apache httpd comes with a utility called the Apache Service Monitor. With it you can see and manage the state of all installed httpd services on any machine on your network. To be able to manage an httpd service with the monitor, you have to first install the service (either automatically via the installation or manually).

You can install httpd as a Windows NT service as follows from the command prompt at the httpd bin subdirectory:

If you need to specify the name of the service you want to install, use the following command. You have to do this if you have several different service installations of httpd on your computer. If you specify a name during the install, you have to also specify it during any other -k operation.

If you need to have specifically named configuration files for different services, you must use this:

If you use the first command without any special parameters except -k install, the service will be called Apache2.4 and the configuration will be assumed to be conf\httpd.conf.

Removing an httpd service is easy. Just use:

The specific httpd service to be uninstalled can be specified by using:

Normal starting, restarting and shutting down of an httpd service is usually done via the Apache Service Monitor, by using commands like NET START Apache2.4 and NET STOP Apache2.4 or via normal Windows service management. Before starting httpd as a service by any means, you should test the service's configuration file by using:

You can control an httpd service by its command line switches, too. To start an installed httpd service you'll use this:

To stop an httpd service via the command line switches, use this:

or

You can also restart a running service and force it to reread its configuration file by using:

By default, all httpd services are registered to run as the system user (the LocalSystem account). The LocalSystem account has no privileges to your network via any Windows-secured mechanism, including the file system, named pipes, DCOM, or secure RPC. It has, however, wide privileges locally.

It is recommended that users create a separate account for running httpd service(s). If you have to access network resources via httpd, this is required.

1. Create a normal domain user account, and be sure to memorize its password.
2. Grant the newly-created user a privilege of Log on as a service and Act as part of the operating system. On Windows NT 4.0 these privileges are granted via User Manager for Domains, but on Windows 2000 and XP you probably want to use Group Policy for propagating these settings. You can also manually set these via the Local Security Policy MMC snap-in.
3. Confirm that the created account is a member of the Users group.
4. Grant the account read and execute (RX) rights to all document and script folders (htdocs and cgi-bin for example).
5. Grant the account change (RWXD) rights to the httpd logs directory.
6. Grant the account read and execute (RX) rights to the httpd.exe binary executable.

If you allow the account to log in as a user and as a service, then you can log on with that account and test that the account has the privileges to execute the scripts, read the web pages, and that you can start httpd in a console window. If this works, and you have followed the steps above, httpd should execute as a service with no problems.

When starting httpd as a service you may encounter an error message from the Windows Service Control Manager. For example, if you try to start httpd by using the Services applet in the Windows Control Panel, you may get the following message:

You will get this generic error if there is any problem with starting the httpd service. In order to see what is really causing the problem you should follow the instructions for Running httpd for Windows from the Command Prompt.

If you are having problems with the service, it is suggested you follow the instructions below to try starting httpd.exe from a console window, and work out the errors before struggling to start it as a service again.

Running httpd as a Console Application

Running Apache httpd as a service is usually the recommended way to use it, but it is sometimes easier to work from the command line, especially during initial configuration and testing.

To run httpd from the command line as a console application, use the following command:

httpd will execute, and will remain running until it is stopped by pressing Control-C.

You can also run httpd via the shortcut Start Apache in Console placed to Start Menu --> Programs --> Apache HTTP Server 2.4.xx --> Control Apache Server during the installation. This will open a console window and start httpd inside it. If you don't have httpd installed as a service, the window will remain visible until you stop httpd by pressing Control-C in the console window where httpd is running in. The server will exit in a few seconds. However, if you do have httpd installed as a service, the shortcut starts the service. If the httpd service is running already, the shortcut doesn't do anything.

If httpd is running as a service, you can tell it to stop by opening another console window and entering:

Running as a service should be preferred over running in a console window because this lets httpd end any current operations and clean up gracefully.

But if the server is running in a console window, you can only stop it by pressing Control-C in the same window.

You can also tell httpd to restart. This forces it to reread the configuration file. Any operations in progress are allowed to complete without interruption. To restart httpd, either press Control-Break in the console window you used for starting httpd, or enter

if the server is running as a service.

If the httpd console window closes immediately or unexpectedly after startup, open the Command Prompt from the Start Menu --> Programs. Change to the folder to which you installed httpd, type the command httpd.exe, and read the error message. Then change to the logs folder, and review the error.log file for configuration mistakes. Assuming httpd was installed into C:\Program Files\Apache Software Foundation\Apache2.4\, you can do the following:

Then wait for httpd to stop, or press Control-C. Then enter the following:

When working with httpd it is important to know how it will find the configuration file. You can specify a configuration file on the command line in two ways:

• -f specifies an absolute or relative path to a particular configuration file:

  httpd.exe -f "c:\my server files\anotherconfig.conf"

  or

  httpd.exe -f files\anotherconfig.conf

• -n specifies the installed httpd service whose configuration file is to be used:

  httpd.exe -n "MyServiceName"

In both of these cases, the proper ServerRoot should be set in the configuration file.

If you don't specify a configuration file with -f or -n, httpd will use the file name compiled into the server, such as conf\httpd.conf. This built-in path is relative to the installation directory. You can verify the compiled file name from a value labelled as SERVER_CONFIG_FILE when invoking httpd with the -V switch, like this:

httpd will then try to determine its ServerRoot by trying the following, in this order:

1. A ServerRoot directive via the -C command line switch.
2. The -d switch on the command line.
3. Current working directory.
4. A registry entry which was created if you did a binary installation.
5. The server root compiled into the server. This is /apache by default, you can verify it by using httpd.exe -V and looking for a value labelled as HTTPD_ROOT.

If you did not do a binary install, httpd will in some scenarios complain about the missing registry key. This warning can be ignored if the server was otherwise able to find its configuration file.

The value of this key is the ServerRoot directory which contains the conf subdirectory. When httpd starts it reads the httpd.conf file from that directory. If this file contains a ServerRoot directive which contains a different directory from the one obtained from the registry key above, httpd will forget the registry key and use the directory from the configuration file. If you copy the httpd directory or configuration files to a new location it is vital that you update the ServerRoot directive in the httpd.conf file to reflect the new location.

Testing the Installation

After starting Apache httpd (either in a console window or as a service) it will be listening on port 80 (unless you changed the Listen directive in the configuration files or installed httpd only for the current user). To connect to the server and access the default page, launch a browser and enter this URL:

httpd should respond with a welcome page and you should see "It Works!". If nothing happens or you get an error, look in the error.log file in the logs subdirectory. If your host is not connected to the net, or if you have serious problems with your DNS (Domain Name Service) configuration, you may have to use this URL:

If you happen to be running httpd on an alternate port, you need to explicitly put that in the URL:

Once your basic installation is working, you should configure it properly by editing the files in the conf subdirectory. Again, if you change the configuration of the Windows NT service for httpd, first attempt to start it from the command line to make sure that the service starts with no errors.

Because httpd cannot share the same port with another TCP/IP application, you may need to stop, uninstall or reconfigure certain other services before running httpd. These conflicting services include other WWW servers, some firewall implementations, and even some client applications (such as Skype) which will use port 80 to attempt to bypass firewall issues.

Configuring Access to Network Resources

Access to files over the network can be specified using two mechanisms provided by Windows:

Mapped drive letters

e.g., Alias "/images/" "Z:/"

UNC paths

e.g., Alias "/images/" "//imagehost/www/images/"

Mapped drive letters allow the administrator to maintain the mapping to a specific machine and path outside of the Apache httpd configuration. However, these mappings are associated only with interactive sessions and are not directly available to Apache httpd when it is started as a service. Use only UNC paths for network resources in httpd.conf so that the resources can be accessed consistently regardless of how Apache httpd is started. (Arcane and error prone procedures may work around the restriction on mapped drive letters, but this is not recommended.)

  UNCList dochost
  DocumentRoot "//dochost/www/html/"

  UNCList 192.168.1.50
  DocumentRoot "//192.168.1.50/docs/"

UNCList imagehost1 imagehost2
Alias "/images/" "//imagehost/www/images/"
Alias "/images2/" "//imagehost2/www/images/"

<Directory "//imagehost/www/images/">
#...
</Directory>
<Directory "//imagehost2/www/images/">
#...
</Directory>

When running Apache httpd as a service, you must create a separate account in order to access network resources, as described above.

Windows Tuning

• If more than a few dozen piped loggers are used on an operating system instance, scaling up the "desktop heap" is often necessary. For more detailed information, refer to the piped logging documentation.