Installing Apache 2.0

Editor's note: Ryan Bloom has been one of the core developers of Apache 2.0. We spotted him at the Covalent booth during Linux World in New York last January and asked him to write a series of columns explaining the new version of Apache to O'Reilly Network readers. Here's his first column, covering what's new in Apache 2.0 and how to install it.

The Apache developers have been working on Apache 2.0 for the last two years, and on April 4, the first public beta of Apache 2.0 was released. This is the first in a series of six monthly columns in which we'll explain how Apache 2.0 differs from Apache 1.3, and why Apache users should care.

Why upgrade?

One of the most important changes is the added multi-threading support to Apache 2.0. Version 1.3 relied on processes to serve requests, and that was a performance hit on many operating systems. Threads combined with processes make Apache 2.0 more scalable.

The second advantage over Apache 1.3 is filtered input/output (I/O), which allows one module to modify the output of another module. An often-requested feature of Apache 1.3 was for CGI scripts to output SSI tags. This wasn't possible in version 1.3, however filtered I/O allows this to work in Apache 2.0.

Apache 2.0 will also provide support for SSL without any modifications to the core. There is already a mod_tls, which although minimal currently, will be extended in time to provide full SSL support.

The first hurdle to using Apache 2.0 is configuration and installation of Apache. There are two forms of configuration -- compile-time and run-time. This article will focus on getting a tarball, compiling it, and then installing it.

Installing and configuring Apache 2.0

Before we can begin, download the latest version of Apache 2.0. The best place to get a stable copy of Apache, is from the Apache web server home page.

If you are a developer who wants to download the latest development version, you should go to the Apache developers page, and read through the relevant links about getting code from CVS.

This article will assume that you are using the Apache 2.0.15 tarball, although future versions of Apache should be very similar. Once you have the tarball, unzip and untar it with the command

tar -xvzf httpd-2*.tar.gz .

Now we can get to work configuring Apache itself. In previous versions of Apache, there were two different models for configuring Apache, each of which had been rolled by the Apache Group itself. The first method was to use a text file that controlled which components were built. The second was an "autoconf-like" system, which in reality just modified the text file for you.

With Apache 2.0, the Apache developers decided they were more interested in writing a web server than maintaining a configuration system. So, Apache 2.0 uses autoconf and libtool to determine which components of Apache are built. Tarballs downloaded from the Apache site already have the configure script created, but for those who have downloaded a development version to generate the configure script, run the command ./buildconf. This will traverse all of the required directories to ensure that you have all of the software components required by Apache.

At this point, you should have a configure script at the top-level of the Apache 2.0 tree. This is the script that actually configures Apache. However, configure script has many options that allow users to control every aspect of how Apache is built. A complete list of options can be found by running:

./configure --help

• --prefix. Specifies where to install Apache
• --with-maintainer-mode. Compiles with full debugging options. This will be an important option, at least until the server reaches a stable release.
• --with-mpm. Specifies which multiprocessing module will be used. MPMs are an integral part of Apache 2.0, and I will discuss them briefly below. A more in-depth discussion can be found online.
• --enable-module. Specifies which modules should be compiled into Apache. This can be either a list of modules, or the keyword most, which configures a hard-coded list of modules.
• --enable-mods-shared. Specifies which modules should be compiled as shared modules.

Multiprocessing Modules (MPMs) let you tune Apache 2.0 for any site. What works on one site or operating system may not work well on another. To solve this problem, system administrators can specify how their Apache server runs. Some OSes have more options than others. For example, on Unix there are three standard MPMs:

• Prefork -- Same model as Apache 1.3. The parent process creates a set of child processes that are ready to serve a request. Each child process has one thread, and can serve one request at a time. When the server gets busy, it spawns a new child process to increase the number of requests that can be handled.
• Threaded -- Similar to Prefork, except each child has a static number of threads. The exact number is specified at run-time in the httpd.conf file.
• Perchild -- The parent process creates a specified number of child processes, each with a minimal number of threads. As the server gets busy, the processes create more threads to handle heavier traffic.

Windows, on the other hand, has only one option:

• Winnt -- A model similar to Apache 1.3, where there are two process, the parent is responsible for monitoring the child and ensuring there is always a process serving requests.

Building the server

Once the configure script has run, we must build the server. This is done by running make in the top-level of the Apache source directory. The final step is to actually install the new server, which is done by running make install. This command will copy the server binaries and support files into the directory specified with the --prefix option to the configure script. If no prefix is specified, then /usr/local/apache is used by default.

We are almost done now. If the install succeeded, you should be able to change to the installation directory and run ./bin/apachectl start. However, we need to know which port the server is listening on. If you installed as root, it should use port 80, the default HTTP port, however if you installed as some other user Apache defaults to port 8080. This can be modified by editing the httpd.conf file, and searching for the Port directive. Now, start up your favorite browser and request the page, either http://localhost/ or http://localhost:8080/, depending on the port. You should see the default Apache web page. If you don't, the error log should tell you what happened.

You have just set up your first Apache 2.0 web server, and should now be serving pages. Remember that this server is not a released product yet, so there are likely to be some bugs. If you find any, please report them through the Apache bug database.

Next month, I will focus more on the run-time configuration as I discuss how to how to migrate your servers from Apache 1.3 to Apache 2.0.

Ryan Bloom is a member of the Apache Software Foundation, and the Vice President of the Apache Portable Run-time project.

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An Amble Through Apache Configuration

Read more Apache 2.0 Basics columns.

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