Knowing Apache Logs

LOG is the main friend of an Apache Administrator. We can see error_log , access_logs under LOG directory in Apache web server. It contain many things. Here I am briefly explaining what all the fields mean in a single line of Apache Log. CLF or Common Log Format is the core of logging in Apache. A module called mod_log_config is responsible for all these logging activities.

The CLF log file contains a separate line for each request. A line is composed of several tokens separated by spaces:

host ident authuser date request status bytes

host : The fully qualified domain name of the client, or its IP address

ident : If the IdentityCheck directive is enabled and the client machine runs
identd, then this is the identity information reported by the client

authuser :If the requested URL required a successful Basic HTTP authentication,
then the user name is the value of this token.

date : The date and time of the request. The date field can be [day/month/year:hour:minute:second zone]

request : The request line from the client, enclosed in double quotes (“).

status : The three-digit HTTP status code returned to the client.

bytes : The number of bytes in the object returned to the client, excluding all
HTTP headers.