Log Locations

Common Log Locations:

Apache

Domain access logs:
  /usr/local/apache/domlogs/<DOMAIN>

Site and service error logs:
  /usr/local/apache/logs/error_log

SuExec audit log:
  /usr/local/apache/logs/suexec_log

SuPHP audit log:
  /usr/local/apache/logs/suphp_log

cPanel

Service status:
  /var/log/chkservd.log

Service status:
  /var/log/chkservd.log

Access and user actions:
  /usr/local/cpanel/logs/access_log

Exim

(see exim )

Fatal errors:
  /var/log/exim_paniclog

Incoming mail queue:
  /var/spool/exim/input

Exim Messages rejected based on ACLs or other policies:
  /var/log/exim_rejectlog

Exim Delivery and receipt:
  /var/log/exim_mainlog

IMAP, POP login attempts, transactions, fatal errors and spam scoring:
  /var/log/maillog
  /var/log/messages

System

Cron:
  /var/log/cron

Most other logs:
  /var/log/messages

MySQL database logs:
/var/log/mysqld.log

References

cPanel Log Locations Poster:

cPanel Log Locations Poster