dmesg(8)

NAME

dmesg − collect system diagnostic messages to form error log

SYNTAX

/etc/dmesg [ − ] [ corefile [ namelist ] ]

DESCRIPTION

The dmesg command 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 every ten minutes running the command

/etc/dmesg − >> /usr/adm/messages

The ULTRIX-11 error logging system logs hardware related errors, dmesg is used to save other types of error messages.

The optional corefile and namelist options can be used for postmortem debugging. If corefile is specified, it will be used instead of /dev/mem; if namelist is also specified, it will be used instead of /unix.

RESTRICTIONS

Referring to dmesg as the error log is a misnomer.

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. If this happens, dmesg prints “...” before printing the buffer.

Error diagnostics generated immediately before a system crash will never get logged.

FILES

/usr/adm/messageserror log (conventional location)
/usr/adm/msgbufscratch file for memory of − option
/dev/memdefault corefile
/unixdefault namelist