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28 .\" @(#)dmesg.8 8.1 (Berkeley) 6/5/93
36 .Nd "display the system message buffer"
40 .Op Fl M Ar core Op Fl N Ar system
44 utility displays the contents of the system message buffer.
47 option is not specified, the buffer is read from the currently running kernel
51 Otherwise, the buffer is read from the specified core file,
52 using the name list from the specified kernel image (or from
55 The options are as follows:
56 .Bl -tag -width indent
58 Show all data in the message buffer.
59 This includes any syslog records and
63 Clear the kernel buffer after printing.
65 Extract values associated with the name list from the specified core.
70 extract the name list from the specified system instead of the default,
71 which is the kernel image the system has booted from.
76 variables control how the kernel timestamps entries in the message buffer:
77 The default value is shown next to each variable.
78 .Bl -tag -width indent
79 .It kern.msgbuf_show_timestamp : No 0
80 If set to 0, no timetamps are added.
81 If set to 1, then a 1-second granularity timestamp will be added to most lines
82 in the message buffer.
83 If set to 2, then a microsecond granularity timestamp will be added.
84 This may also be set as a boot
87 The timestamps are placed at the start of most lines that the kernel generates.
88 Some multi-line messages will have only the first line tagged with a timestamp.
91 .Bl -tag -width ".Pa /var/run/dmesg.boot" -compact
92 .It Pa /var/run/dmesg.boot
93 usually a snapshot of the buffer contents
94 taken soon after file systems are mounted