Most Linux logs are located under /var/log/ and can be viewed using
any text editor
/var/log/wtmp: Contains the logs of all logged in and logged out users. Can be analyzed using 'last' command on linux
/var/log/btmp: Contains only failed login attempts. Can be analyzed using 'last' command on linux
/var/log/messages or /var/log/syslog: Contains generic system activity logs
/var/log/auth.log or /var/log/secure: All authentication related events in are logged here.
/var/log/boot.log: Contains related information and messages logged during system startup process.
/var/log/dmesg: Contains Information related to hardware devices and their drivers are logged here.
/var/log/kern.log: Contains information logged by the kernel.
/var/log/faillog: Contains information on failed login attempts.
/var/log/cron: Contains information on cron jobs.
/var/lg/yum: Contains the information that is logged when a new package is installed using the yum command.
/var/log/mail.log or /var/log/maillog: All mail server related logs are stored here.
/var/log/httpd/ or /var/log/apache2: Contains the logs recorded by the Apache server. Logging information are stored in two different log files – error_log and access_log.
/var/log/mysqld.log or /var/log/mysql.log or /var/log/mysql/: All debug, failure and success messages related to the [mysqld] and [mysqld_safe] daemon are logged to this file.
/var/log/apt/: Contains information related to Advance package tool (apt). Loggin information are stored in history.log and term.log
/var/log/lastlog: Contains information about the successful logins to the host