DMESG(8) System Manager's Manual DMESG(8)
dmesg - collect system diagnostic messages to form error log
/etc/dmesg [ - ]
Dmesg looks in a system buffer for recently printed diagnostic messages
and prints them on the standard output. The messages are those printed
by the system when device (hardware) errors occur and (occasionally)
when system tables overflow non-fatally. If the - flag is given, then
dmesg computes (incrementally) the new messages since the last time it
was run and places these on the standard output. This is typically
used with cron(8) to produce the error log /usr/adm/messages by running
/etc/dmesg - >> /usr/adm/messages
every 10 minutes.
/usr/adm/messages error log (conventional location)
/usr/adm/msgbuf scratch file for memory of - option
The system error message buffer is of small finite size. As dmesg is
run only every few minutes, not all error messages are guaranteed to be
logged. This can be construed as a blessing rather than a curse.
Error diagnostics generated immediately before a system crash will
never get logged.
4th Berkeley Distribution 4 February 1983 DMESG(8)