depending on your OS, you can grep something from either /var/log/syslog or /var/log/messages or through journalctl.
to see older messages, check for /var/log/syslog.1 or /var/log/messages.1 or /var/log/syslog.1.gz or...
type
to see all these logs
to read a log you can use
(if the log ends with .gz you can use
) . in there, type '/' to enter a search string. in there, type '-i' to change case (in)sensitive search.
at all times, you can use