To enable /var/log/messages is disabled in the beta-1 version of Ubuntu Precise Pangolin (download here), do the following:
Edit /etc/rsyslog.d/50-default.conf and uncomment the lines
*.=info;*.=notice;*.=warn;\
auth,authpriv.none;\
cron,daemon.none;\
mail,news.none -/var/log/messages
auth,authpriv.none;\
cron,daemon.none;\
mail,news.none -/var/log/messages
Then restart the rsyslog daemon:
# service rsyslog restart
(Reference: Ubuntu forums)
