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@(#)dmesg.8 6.1 (Berkeley) 04/27/85

C 4 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 the command /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.