Apache server is an open source web server or HTTP server widely used not only in Linux and Unix-based operating system but nowadays in Windows as well. Apache is known for it's stability and highly configurable with support of many add on modules for customization. In Linux, Apache, PHP and MySql work greats together and always be a perfect web server solution for many organizations around the world.

Ubuntu web server installation

We must first check apache2 package in Ubuntu to make sure it's already installed using dpkg and ps command. Here are dpkg and ps command usage examples:

luzar@ubuntu:~$ sudo dpkg -l | grep apache
[sudo] password for luzar:
ii  apache2     2.2.8-1ubuntu0.3     Next generation, scalable, extendable web server
ii  apache2-mpm-prefork  2.2.8-1ubuntu0.3    Traditional model for Apache HTTPD
ii  apache2-utils        2.2.8-1ubuntu0.3    utility programs for webservers
ii  apache2.2-common     2.2.8-1ubuntu0.3    Next generation, scalable,
 extendable web server
ii  libapache2-mod-php5  5.2.4-2ubuntu5.4    server-side, HTML-embedded
 scripting language
luzar@ubuntu:~$

In the example above, we use | (pipe) grep with dpkg command to grab all apache package in our system. If we just use dpkg -l apache, dpkg won't find apache unless we specified the exact name, which is apache2.

This is an example of how to use ps command to check apache running service:

luzar@ubuntu:~$ ps aux | grep apache
root      4594  0.0  1.3  20460  6748 ?   Ss  Dec10   0:01 /usr/sbin/apache2 -k start
www-data  5247  0.0  0.6  20460  3376 ?   S   Dec10   0:00 /usr/sbin/apache2 -k start
www-data  5248  0.0  0.6  20460  3376 ?   S   Dec10   0:00 /usr/sbin/apache2 -k start
www-data  5249  0.0  0.6  20460  3376 ?   S   Dec10   0:00 /usr/sbin/apache2 -k start
www-data  5253  0.0  0.6  20460  3376 ?   S   Dec10   0:00 /usr/sbin/apache2 -k start
www-data  5255  0.0  0.6  20460  3376 ?   S   Dec10   0:00 /usr/sbin/apache2 -k start
luzar     8725  0.0  0.1   3004   752 pts/0    R+   02:32   0:00 grep apache
luzar@ubuntu:~$

If you don't have results like the example above, that means apache has not been installed in your system. You can install apache using apt-get command like an example below:

luzar@ubuntu:~$ sudo apt-get install apache2
Reading package lists... Done
Building dependency tree
Reading state information... Done
...
...

Apache2 start, stop and restart service

Now that apache2 already installed in your system, it's time to start the service. Here is the command to start apache2 service:

luzar@ubuntu:~$ sudo /etc/init.d/apache2 start
[sudo] password for luzar:
 * Starting web server apache2                                                                 [ OK ]

Here is a command to stop apache2 service:

luzar@ubuntu:~$ sudo /etc/init.d/apache2 stop
[sudo] password for luzar:
 * Stopping web server apache2                                                                 [ OK ]

Here is a command to restart apache2 service:

luzar@ubuntu:~$ sudo /etc/init.d/apache2 restart
 * Restarting web server apache2                                                               [ OK ]

Starting and stopping apache2 service is important when you are testing apache2 configuration and troubleshooting. All changes you made to the configuration file only be affected once you restart apache2 service.

At this point, you probably don't have any problem starting apache2 service. The apache2 still using default configuration. You can test your new web server using lynx web browser to open localhost default website in Ubuntu command line terminal. If you don't have lynx in your system, check lynx tutorial for installation and usage guide. Here is an example of a default apache2 website opened using lynx web browser:

luzar@ubuntu:~$ lynx localhost

Ubuntu apache2 configuration

All Apache2 configuration files are located in /etc/apache2 in Ubuntu. Other than apache2 main configuration file, apache2.conf, there are many other files and directory included in the package. In the past, httpd.conf is the apache main configuration file. Don't get confused. Ubuntu has made apache2 configuration easier though you might see it complicated. Here are the complete list of files and directories in apache2 directory:

luzar@ubuntu:/etc/apache2$ ls -l
total 40
-rw-r--r-- 1 root root 10587 2008-06-25 09:49 apache2.conf
drwxr-xr-x 2 root root  4096 2008-10-19 15:17 conf.d
-rw-r--r-- 1 root root   378 2008-06-25 09:49 envvars
-rw-r--r-- 1 root root     0 2008-10-19 15:17 httpd.conf
drwxr-xr-x 2 root root  4096 2008-12-11 20:46 mods-available
drwxr-xr-x 2 root root  4096 2008-10-19 15:17 mods-enabled
-rw-r--r-- 1 root root    59 2008-06-25 09:49 ports.conf
drwxr-xr-x 2 root root  4096 2008-10-19 15:17 sites-available
drwxr-xr-x 2 root root  4096 2008-10-19 15:17 sites-enabled
luzar@ubuntu:/etc/apache2$

Here are default configuration and brief explanation of files and directories above:

/etc/apache2/apache2.conf

Apache2 main configuration file.

### Section 1: Global Environment
#
# The directives in this section affect the overall operation of Apache,
# such as the number of concurrent requests it can handle or where it
# can find its configuration files.
#

#
# ServerRoot: The top of the directory tree under which the server's
# configuration, error, and log files are kept.
#
# NOTE!  If you intend to place this on an NFS (or otherwise network)
# mounted filesystem then please read the LockFile documentation (available
# at <URL:http://httpd.apache.org/docs-2.1/mod/mpm_common.html#lockfile>);
# you will save yourself a lot of trouble.
#
# Do NOT add a slash at the end of the directory path.
#
ServerRoot "/etc/apache2"

#
# The accept serialization lock file MUST BE STORED ON A LOCAL DISK.
#
...
...

/etc/apache2/httpd.conf

Add additional configuration parameters. By default, this file is empty.

/etc/apache2/envvars

Environment variables to tune the operation of Apache server.

# envvars - default environment variables for apache2ctl

# Since there is no sane way to get the parsed apache2 config in scripts, some
# settings are defined via environment variables and then used in apache2ctl,
# /etc/init.d/apache2, /etc/logrotate.d/apache2, etc.
export APACHE_RUN_USER=www-data
export APACHE_RUN_GROUP=www-data
export APACHE_PID_FILE=/var/run/apache2.pid

/etc/apache2/ports.conf

Port numbers that the Apache server will listen on.

Listen 80

<IfModule mod_ssl.c>
    Listen 443
</IfModule>

/etc/apache2/conf.d/

Put additional Apache configuration files in this directory. By default this directory only contains an example additional apache configuration file named charset . Here is charset default configuration.

# Read the documentation before enabling AddDefaultCharset.
# In general, it is only a good idea if you know that all your files
# have this encoding. It will override any encoding given in the files
# in meta http-equiv or xml encoding tags.

#AddDefaultCharset UTF-8

/etc/apache2/mods-available/

Contains all the modules installed for your server. This is the default modules came with Ubuntu 8.04 server. For additional modules, visit apache modules page in apache official website. Here are example of modules in /mod-available directory:

luzar@ubuntu:/etc/apache2$ ls mods-available/
actions.conf          authz_owner.load   dir.load           mem_cache.load       setenvif.load
actions.load          authz_user.load    disk_cache.conf    mime.conf            speling.load
alias.conf            autoindex.conf     disk_cache.load    mime.load            ssl.conf
alias.load            autoindex.load     dump_io.load       mime_magic.conf      ssl.load
asis.load             cache.load         env.load           mime_magic.load      status.conf
auth_basic.load       cern_meta.load     expires.load       negotiation.conf     status.load
auth_digest.load      cgid.conf          ext_filter.load    negotiation.load     substitute.load
authn_alias.load      cgid.load          file_cache.load    php5.conf            suexec.load
authn_anon.load       cgi.load           filter.load        php5.load            unique_id.load
authn_dbd.load        charset_lite.load  headers.load       proxy_ajp.load       userdir.conf
authn_dbm.load        dav_fs.conf        ident.load         proxy_balancer.load  userdir.load
authn_default.load    dav_fs.load        imagemap.load      proxy.conf           usertrack.load
authn_file.load       dav.load           include.load       proxy_connect.load   version.load
authnz_ldap.load      dav_lock.load      info.conf          proxy_ftp.load       vhost_alias.load
authz_dbm.load        dbd.load           info.load          proxy_http.load
authz_default.load    deflate.conf       ldap.load          proxy.load
authz_groupfile.load  deflate.load       log_forensic.load  rewrite.load
authz_host.load       dir.conf           mem_cache.conf     setenvif.conf

/etc/apache2/mods-enabled/

As you can see from mod-available above, there are 86 modules available by default. They are not enabled yet. Create a symbolic link in this directory that refers to the module file in /mods-available above to enable it. Below are the default enabled modules:

luzar@ubuntu:/etc/apache2$ ls -l mods-enabled/
total 0
lrwxrwxrwx 1 root root 28 2008-10-19 15:17 alias.conf -> ../mods-available/alias.conf
lrwxrwxrwx 1 root root 28 2008-10-19 15:17 alias.load -> ../mods-available/alias.load
lrwxrwxrwx 1 root root 33 2008-10-19 15:17 auth_basic.load -> ../mods-available/auth_basic.load
lrwxrwxrwx 1 root root 33 2008-10-19 15:17 authn_file.load -> ../mods-available/authn_file.load
lrwxrwxrwx 1 root root 36 2008-10-19 15:17 authz_default.load -> ../mods-available/authz_default.load
lrwxrwxrwx 1 root root 38 2008-10-19 15:17 authz_groupfile.load -> ../mods-available/authz_groupfile.load
lrwxrwxrwx 1 root root 33 2008-10-19 15:17 authz_host.load -> ../mods-available/authz_host.load
lrwxrwxrwx 1 root root 33 2008-10-19 15:17 authz_user.load -> ../mods-available/authz_user.load
lrwxrwxrwx 1 root root 32 2008-10-19 15:17 autoindex.conf -> ../mods-available/autoindex.conf
lrwxrwxrwx 1 root root 32 2008-10-19 15:17 autoindex.load -> ../mods-available/autoindex.load
lrwxrwxrwx 1 root root 26 2008-10-19 15:17 cgi.load -> ../mods-available/cgi.load
lrwxrwxrwx 1 root root 26 2008-10-19 15:17 dir.conf -> ../mods-available/dir.conf
lrwxrwxrwx 1 root root 26 2008-10-19 15:17 dir.load -> ../mods-available/dir.load
lrwxrwxrwx 1 root root 26 2008-10-19 15:17 env.load -> ../mods-available/env.load
lrwxrwxrwx 1 root root 27 2008-10-19 15:17 mime.conf -> ../mods-available/mime.conf
lrwxrwxrwx 1 root root 27 2008-10-19 15:17 mime.load -> ../mods-available/mime.load
lrwxrwxrwx 1 root root 34 2008-10-19 15:17 negotiation.conf -> ../mods-available/negotiation.conf
lrwxrwxrwx 1 root root 34 2008-10-19 15:17 negotiation.load -> ../mods-available/negotiation.load
lrwxrwxrwx 1 root root 27 2008-10-19 15:17 php5.conf -> ../mods-available/php5.conf
lrwxrwxrwx 1 root root 27 2008-10-19 15:17 php5.load -> ../mods-available/php5.load
lrwxrwxrwx 1 root root 31 2008-10-19 15:17 setenvif.conf -> ../mods-available/setenvif.conf
lrwxrwxrwx 1 root root 31 2008-10-19 15:17 setenvif.load -> ../mods-available/setenvif.load
lrwxrwxrwx 1 root root 29 2008-10-19 15:17 status.conf -> ../mods-available/status.conf
lrwxrwxrwx 1 root root 29 2008-10-19 15:17 status.load -> ../mods-available/status.load

Here is an example to enable another module:

luzar@ubuntu:/etc/apache2$ cd mods-enabled/
luzar@ubuntu:/etc/apache2/mods-enabled$ ln -s ../mods-available/rewrite.load 
rewrite.load
[sudo] password for luzar:
luzar@ubuntu:/etc/apache2/mods-enabled$ ls -l |grep rewrite.load
lrwxrwxrwx 1 root root 30 2008-12-12 03:37 rewrite.load -> 
../mods-available/rewrite.load

To disable a module, just delete the symbolic link.

/etc/apache2/sites-available/

Stores all the configuration files for the web sites serviced by Apache server. By default, only one file available, a default virtual host configuration file:

NameVirtualHost *
<VirtualHost * >
        ServerAdmin webmaster@localhost

        DocumentRoot /var/www/
        <Directory />
                Options FollowSymLinks
                AllowOverride None
        </Directory>
        <Directory /var/www/>
                Options Indexes FollowSymLinks MultiViews
                AllowOverride None
                Order allow,deny
                allow from all
        </Directory>

        ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/
        <Directory "/usr/lib/cgi-bin">
                AllowOverride None
                Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
                Order allow,deny
                Allow from all
        </Directory>

        ErrorLog /var/log/apache2/error.log

        # Possible values include: debug, info, notice, warn, error, crit,
        # alert, emerg.
        LogLevel warn

        CustomLog /var/log/apache2/access.log combined
        ServerSignature On

    Alias /doc/ "/usr/share/doc/"
    <Directory "/usr/share/doc/">
        Options Indexes MultiViews FollowSymLinks
        AllowOverride None
        Order deny,allow
        Deny from all
        Allow from 127.0.0.0/255.0.0.0 ::1/128
    </Directory>

</VirtualHost>

/etc/apache2/sites-enabled/

Create a symbolic link to enable sites in /etc/apache2/sites-available.

As you can see from the testing web server example previously, the default apache2 configuration is already working. Perhaps you want to change document root directory from /var/www to /srv/www because you want to keep certain server in a dedicated directory. Perhaps also because you want to avoid future problems where logs files taking all the available space. You can change the document root directory by editing /sites-available/default file configuration like an example below:

First you make a backup of the original file:

luzar@ubuntu:/etc/apache2/sites-available$ sudo cp default default.ori
[sudo] password for luzar:
luzar@ubuntu:/etc/apache2/sites-available$ ls
default  default.ori

Open /sites-available/default file with text editor and change document root directory like the example below:

luzar@ubuntu:/etc/apache2/sites-available$ sudo vim default
NameVirtualHost *
<VirtualHost *>
        ServerAdmin webmaster@localhost

        DocumentRoot /srv/www/
        <Directory />
                Options FollowSymLinks
                AllowOverride None
        </Directory>
        <Directory /srv/www/>
                Options Indexes FollowSymLinks MultiViews
                AllowOverride None
                Order allow,deny
                allow from all
        </Directory>
        ...
        ...

Then, copy the /var/www directory to /srv/ directory:

luzar@ubuntu:~$ sudo cp -r /var/www /srv/www

Create a new html file to test new document root directory. For example, I created a file named test.html in /srv/www directory. Here is the content:

<html>
<head>
<title>My testing website</title>
</head>

<body>
<h1>This is a testing website</h1>
<p>It works alright!</p>
</body>
</html>

Now we can restart apache2 service again before we test the new configuration. Here is the command:

luzar@ubuntu:~$ sudo /etc/init.d/apache2 restart

Finally we can test our new configuration. Here is the command:

luzar@ubuntu:~$ lynx localhost/test.html

Here is the result:

So our apache2 web server works fine. We can now put our website in /srv/www directory.