# Compiling and Installing

This document covers compilation and installation of Apache on Unix and Unix-like systems only. For compiling and installation on Windows, see Using Apache with Microsoft Windows. For other platforms, see the platform documentation.

Apache 2.0's configuration and installation environment has changed completely from Apache 1.3. Apache 1.3 used a custom set of scripts to achieve easy installation. Apache 2.0 now uses `libtool` and `autoconf` to create an environment that looks like many other Open Source projects.

If you are upgrading from one minor version to the next (for example, 2.0.50 to 2.0.51), please skip down to the upgrading section.

Configure the source tree
Starting Apache
Stopping and Restarting

# Overview for the impatient

Download | `$ lynx http://httpd.apache.org/download.cgi`
Extract | `$ gzip -d httpd-2_1_NN.tar.gz $ tar xvf httpd-2_1_NN.tar`
Configure | `$ ./configure --prefix=PREFIX`
Compile | `$ make`
Install | `$ make install`
Customize | `$ vi PREFIX/conf/httpd.conf`
Test | `$ PREFIX/bin/apachectl start`

NN must be replaced with the current minor version number, and PREFIX must be replaced with the filesystem path under which the server should be installed. If PREFIX is not specified, it defaults to `/usr/local/apache2`.

Each section of the compilation and installation process is described in more detail below, beginning with the requirements for compiling and installing Apache HTTPD.

# Requirements

The following requirements exist for building Apache:

Disk Space
  Make sure you have at least 50 MB of temporary free disk space available. After installation Apache occupies approximately 10 MB of disk space. The actual disk space requirements will vary considerably based on your chosen configuration options and any third-party modules.
ANSI-C Compiler and Build System
  Make sure you have an ANSI-C compiler installed. The GNU C compiler (GCC) from the Free Software Foundation (FSF) is recommended (version 2.7.2 is fine). If you don't have GCC then at least make sure your vendor's compiler is ANSI compliant. In addition, your `PATH` must contain basic build tools such as `make`.
Accurate time keeping
  Elements of the HTTP protocol are expressed as the time of day. So, it's time to investigate setting some time synchronization facility on your system. Usually the `ntpdate` or `xntpd` programs are used for this purpose which are based on the Network Time Protocol (NTP). See the Usenet newsgroup comp.protocols.time.ntp and the NTP homepage for more details about NTP software and public time servers.
Perl 5 [OPTIONAL]
  For some of the support scripts like apxs or dbmmanage (which are written in Perl) the Perl 5 interpreter is required (versions 5.003 or newer are sufficient). If no such interpreter is found by the configure script there is no harm. Of course, you still can build and install Apache 2.0. Only those support scripts cannot be used. If you have multiple Perl interpreters installed (perhaps a Perl 4 from the vendor and a Perl 5 from your own), then it is recommended to use the `--with-perl` option (see below) to make sure the correct one is selected by configure.

# Download

Apache can be downloaded from the Apache HTTP Server download site which lists several mirrors. Most users of Apache on unix-like systems will be better off downloading and compiling a source version. The build process (described below) is easy, and it allows you to customize your server to suit your needs. In addition, binary releases are often not up to date with the latest source releases. If you do download a binary, follow the instructions in the `INSTALL.bindist` file inside the distribution.

After downloading, it is important to verify that you have a complete and unmodified version of the Apache HTTP Server. This can be accomplished by testing the downloaded tarball against the PGP signature. Details on how to do this are available on the download page and an extended example is available describing the use of PGP.

# Extract

Extracting the source from the Apache HTTPD tarball is a simple matter of uncompressing, and then untarring:

$ gzip -d httpd-2_1_NN.tar.gz
$ tar xvf httpd-2_1_NN.tar

This will create a new directory under the current directory containing the source code for the distribution. You should `cd` into that directory before proceeding with compiling the server.

# Configuring the source tree

The next step is to configure the Apache source tree for your particular platform and personal requirements. This is done using the script configure included in the root directory of the distribution. (Developers downloading the CVS version of the Apache source tree will need to have `autoconf` and `libtool` installed and will need to run `buildconf` before proceeding with the next steps. This is not necessary for official releases.)

To configure the source tree using all the default options, simply type `./configure`. To change the default options, configure accepts a variety of variables and command line options.

The most important option is the location `--prefix` where Apache is to be installed later, because Apache has to be configured for this location to work correctly. More fine-tuned control of the location of files is possible with additional configure options.

Also at this point, you can specify which features you want included in Apache by enabling and disabling modules. Apache comes with a Base set of modules included by default. Other modules are enabled using the `--enable-module` option, where module is the name of the module with the `mod_` string removed and with any underscore converted to a dash. You can also choose to compile modules as shared objects (DSOs) -- which can be loaded or unloaded at runtime -- by using the option `--enable-module=shared`. Similarly, you can disable Base modules with the `--disable-module` option. Be careful when using these options, since configure cannot warn you if the module you specify does not exist; it will simply ignore the option.

In addition, it is sometimes necessary to provide the configure script with extra information about the location of your compiler, libraries, or header files. This is done by passing either environment variables or command line options to configure. For more information, see the configure manual page.

For a short impression of what possibilities you have, here is a typical example which compiles Apache for the installation tree `/sw/pkg/apache` with a particular compiler and flags plus the two additional modules mod_rewrite and mod_speling for later loading through the DSO mechanism:

$ CC="pgcc" CFLAGS="-O2" \
./configure --prefix=/sw/pkg/apache \
--enable-rewrite=shared \
--enable-speling=shared

When configure is run it will take several minutes to test for the availability of features on your system and build Makefiles which will later be used to compile the server.

Details on all the different configure options are available on the configure manual page.

# Build

Now you can build the various parts which form the Apache package by simply running the command:

$ make

Please be patient here, since a base configuration takes approximately 3 minutes to compile under a Pentium III/Linux 2.2 system, but this will vary widely depending on your hardware and the number of modules which you have enabled.

# Install

Now it's time to install the package under the configured installation PREFIX (see `--prefix` option above) by running:

$ make install

If you are upgrading, the installation will not overwrite your configuration files or documents.

# Customize

Next, you can customize your Apache HTTP server by editing the configuration files under `PREFIX/conf/`.

$ vi PREFIX/conf/httpd.conf

Have a look at the Apache manual under docs/manual/ or consult http://httpd.apache.org/docs-2.1/ for the most recent version of this manual and a complete reference of available configuration directives.

# Test

Now you can start your Apache HTTP server by immediately running:

$ PREFIX/bin/apachectl start

and then you should be able to request your first document via URL `http://localhost/`. The web page you see is located under the DocumentRoot which will usually be `PREFIX/htdocs/`. Then stop the server again by running:

$ PREFIX/bin/apachectl stop

# Upgrading

The first step in upgrading is to read the release announcement and the file `CHANGES` in the source distribution to find any changes that may affect your site. When changing between major releases (for example, from 1.3 to 2.0 or from 2.0 to 2.2), there will likely be major differences in the compile-time and run-time configuration that will require manual adjustments. All modules will also need to be upgraded to accomodate changes in the module API.

Upgrading from one minor version to the next (for example, from 2.0.55 to 2.0.57) is easier. The `make install` process will not overwrite any of your existing documents, log files, or configuration files. In addition, the developers make every effort to avoid incompatible changes in the configure options, run-time configuration, or the module API between minor versions. In most cases you should be able to use an identical configure command line, an identical configuration file, and all of your modules should continue to work. (This is only valid for versions after 2.0.41; earlier versions have incompatible changes.)

If you kept the source tree from your last installation, upgrading is even easier. The file `config.nice` in the root of the old source tree contains the exact configure command line that you used to configure the source tree. Then to upgrade from one version to the next, you need only copy the `config.nice` file to the source tree of the new version, edit it to make any desired changes, and then run:

$ ./config.nice
$ make
$ make install
$ PREFIX/bin/apachectl stop
$ PREFIX/bin/apachectl start

You should always test any new version in your environment before putting it into production. For example, you can install and run the new version along side the old one by using a different `--prefix` and a different port (by adjusting the Listen directive) to test for any incompatibilities before doing the final upgrade.