ServerAlias falcot.org
DocumentRoot /srv/www/www.falcot.org
</VirtualHost>
The Apache server, as configured so far, uses the same log files for all virtual hosts (although this could be changed by adding CustomLog directives in the definitions of the virtual hosts). It therefore makes good sense to customize the format of this log file to have it include the name of the virtual host. This can be done by creating a /etc/apache2/conf.d/customlog file that defines a new format for all log files (with the LogFormat directive). The CustomLog line must also be removed (or commented out) from the /etc/apache2/sites-available/default file.
Example 11.17. The /etc/apache2/conf.d/customlog file
# New log format including (virtual) host name
LogFormat "%v %h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" vhost
# Now let's use this "vhost" format by default
CustomLog /var/log/apache2/access.log vhost
11.2.3. Common Directives
This section briefly reviews some of the commonly-used Apache configuration directives.
The main configuration file usually includes several Directory blocks; they allow specifying different behaviors for the server depending on the location of the file being served. Such a block commonly includes Options and AllowOverride directives.
Example 11.18. Directory block
<Directory /var/www>
Options Includes FollowSymlinks
AllowOverride All
DirectoryIndex index.php index.html index.htm
</Directory>
The DirectoryIndex directive contains a list of files to try when the client request matches a directory. The first existing file in the list is used and sent as a response.
The Options directive is followed by a list of options to enable. The None value disables all options; correspondingly, All enables them all except MultiViews. Available options include:
ExecCGI indicates that CGI scripts can be executed.
FollowSymlinks tells the server that symbolic links can be followed, and that the response should contain the contents of the target of such links.
SymlinksIfOwnerMatch also tells the server to follow symbolic links, but only when the link and the its target have the same owner.
Includes enables Server Side Includes (SSI for short). These are directives embedded in HTML pages and executed on the fly for each request.
Indexes tells the server to list the contents of a directory if the HTTP request sent by the client points at a directory without an index file (ie, when no files mentioned by the DirectoryIndex directive exists in this directory).
MultiViews enables content negociation; this can be used by the server to return a web page matching the preferred language as configured in the browser.
BACK TO BASICS .htaccess file
The .htaccess file contains Apache configuration directives enforced each time a request concerns an element of the directory where it is stored. The scope of these directives also recurses to all the subdirectories within.
Most of the directives that can occur in a Directory block are also legal in a .htaccess file.
The AllowOverride directive lists all the options that can be enabled or disabled by way of a .htaccess file. A common use of this option is to restrict ExecCGI, so that the administrator chooses which users are allowed to run programs under the web server's identity (the www-data user).
11.2.3.1. Requiring an Authentication
In some circumstances, access to part of a website needs to be restricted, so only legitimate users who provide a username and a password are granted access to the contents.
Example 11.19. .htaccess file requiring an authentication
Require valid-user
AuthName "Private directory"
AuthType Basic
AuthUserFile /etc/apache2/authfiles/htpasswd-private
SECURITY No security
The authentication system used in the above example (Basic) has minimal security as the password is sent in clear text (it is only encoded as base64, which is a simple encoding rather than an encryption method). It should also be noted that the documents “protected” by this mechanism also go over the network in the clear. If security is important, the whole HTTP connection should be encrypted with SSL.
The /etc/apache2/authfiles/htpasswd-private file contains a list of users and passwords; it is commonly manipulated with the htpasswd command. For example, the following command is used to add a user or change their password:
# htpasswd /etc/apache2/authfiles/htpasswd-private user
New password:
Re-type new password:
Adding password for user user
11.2.3.2. Restricting Access
The Allow from and Deny from directives control access restrictions for a directory (and its subdirectories, recursively).
The Order directive tells the server of the order in which the Allow from and Deny from directives are applied; the last one that matches takes precedence. In concrete terms, Order deny,allow allows access if no Deny from applies, or if an Allow from directive does. Conversely, Order allow,deny rejects access if no Allow from directive matches (or if a Deny from directive applies).
The Allow from and Deny from directives can be followed by an IP address, a network (such as 192.168.0.0/255.255.255.0, 192.168.0.0/24 or even 192.168.0), a hostname or a domain name, or the all keyword, designating everyone.
Example 11.20. Reject by default but allow from the local network
Order deny,allow
Allow from 192.168.0.0/16
Deny from all
11.2.4. Log Analyzers
A log analyzer is frequently installed on a web server; since the former provides the administrators with a precise idea of the usage patterns of the latter.
The Falcot Corp administrators selected AWStats (Advanced Web Statistics) to analyze their Apache log files.
The first configuration step is the creation of the /etc/awstats/awstats.conf file. The /usr/share/doc/awstats/examples/awstats.model.conf.gz template is a recommended starting point, and the Falcot administrators keep it unchanged apart from the following parameters:
LogFile="/var/log/apache2/access.log"
LogFormat = "%virtualname %host %other %logname %time1 %methodurl %code %bytesd %refererquot %uaquot"
SiteDomain="www.falcot.com"
HostAliases="falcot.com REGEX[^.*\.falcot\.com$]"
DNSLookup=1
DirData="/var/lib/awstats"
DirIcons="/awstats-icon"
DirLang="/usr/share/awstats/lang"
LoadPlugin="tooltips"
All these parameters are documented by comments in the template file. In particular, the LogFile and LogFormat parameters describe the location and format of the log file and the information it contains; SiteDomain and HostAliases list the various names under which the main web site is known.
For high traffic sites, DNSLookup should usually not be set to 1; for smaller sites, such as the Falcot one described above, this setting allows getting more readable reports that include full machine names instead of raw IP addresses.