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DMESG(8) NetBSD System Manager's Manual DMESG(8)
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dmesg -- display the system message buffer
dmesg [-dTt] [-M core] [-N system]
dmesg displays the contents of the system message buffer.
The options are as follows:
-d Show the timestamp deltas. Used together with -t only the deltas
-M Extract values associated with the name list from the specified
core instead of the default ``/dev/mem''.
-N Extract the name list from the specified system instead of the
-T Format uptime timestamps in a human readable form (using
ctime(3)) using output suitable for the local locale as set in
the environment. Repeating this option prints the uptime in ISO
8601 duration form, giving the duration since boot, in hours,
minutes, and seconds (to millisecond resolution). A third occur-
rence causes the duration to always be represented to millisecond
precision, even where that means trailing zeroes appear.
-t Quiet printing, don't print timestamps.
The system message buffer is a circular buffer of a fixed size. If the
buffer has been filled, the first line of the dmesg output may not be
complete. The size of the message buffer is configurable at compile-time
on most systems with the MSGBUFSIZE kernel option. Look for MSGBUFSIZE
in options(4) for details.
/var/run/dmesg.boot copy of dmesg at the time of last boot.
The dmesg command appeared in 3.0BSD.
The -T option will report nonsense when displaying lines from the message
buffer that were not added by the current running kernel.
When -TT is used, the duration is always given with maximum units of
hours, even when the number of hours is in the hundreds, thousands, or
more. This is because converting hours to days, over periods when ``time
skips'' occur, such as summer time beginning or ending, is not trivial.
A duration of 26 hours might be 1D3H or 1D1H at such events, rather than
the usual 1D2H, and when a time zone alters its offset, even more complex
calculations are needed. None of those calculations are done (even to
account for sub-hour time zone shifts), the duration indicated is always
calculated by simple division of seconds by 60 to produce minutes, and
again to produce hours. Most of the time [!] this is correct.
NetBSD 9.3 October 30, 2018 NetBSD 9.3