Ubuntu Logs – Where is /var/log/messages?

Ubuntu no longer uses the /var/log/messages file by default. The same information is available in the file /var/log/syslog. You can re-enable logging to /var/log/messages if you would like.

Syslog is a standard logging facility. It collects messages from various programs, including the kernel. It is usually configured to store these messages by default. How it stores these messages is generally distribution-dependant. /var/log/messages is generally used to store non-critical messages while /var/log/syslog stores everything, including critical and non-critical messages.