How to Force Apache to Use Custom Log Format

Force Apache to Use Custom Log Format

By default, Apache web server uses a specific log format to record access logs. However, you can customize this format to suit your needs. This article explains how to force Apache to use a custom log format, providing detailed context and covering key concepts related to log formatting.

Understanding Apache Log Formats

Apache log formats are defined using the %-based syntax. The log format specifies the fields that are recorded in the log files, such as virtual host, request protocol, request line, and various headers. For example, the default log format %v %p %h %l %u %t "%r" %>s %b records the following fields:

• %v: The virtual host
• %p: The request protocol
• %h: The remote host
• %l: The remote logname
• %u: The authenticated user
• %t: The time that the server finished processing the request
• "%r": The first line of the request
• %>s: The status code
• %b: The bytes sent, excluding the headers

Creating a Custom Log Format

To create a custom log format, you need to define a new format using the LogFormat directive. For example, to create a custom log format that records the requested URL, the HTTP referer, and the user agent, you can use the following directive:

In this example, the %U field records the requested URL, while the %{Referer}i and %{User-Agent}i fields record the referer and the user agent, respectively.

Forcing Apache to Use the Custom Log Format

To force Apache to use the custom log format, you need to set the CustomLog directive to use the custom format. For example, to use the custom log format defined in the previous section, you can use the following directive:

This directive tells Apache to use the custom\_format log format when writing access logs to the /var/log/apache2/access\_log file.

Example Custom Log Format

Here's an example custom log format that includes various fields, such as the virtual host, the request method, the request URI, the response status code, the response size, the user agent, and the referer:

In this example, the %v field records the virtual host, while the %m field records the request method. The %U field records the requested URI, while the %>s field records the response status code. The %O field records the response size, while the %{User-Agent}i and %{Referer}i fields record the user agent and the referer, respectively.

Forcing Apache to use a custom log format allows you to record the information that's important to you. By understanding the log format syntax and creating a custom log format that includes the fields you need, you can ensure that your Apache logs are as useful as possible. In this article, we've covered key concepts related to log formatting and provided an example custom log format that includes various fields.

References

• Apache Module mod\_log\_config
• Apache Logs