On 2021-03-19 11:24, D. Hugh Redelmeier via talk wrote:
[One reason for this message is to test if the mailing list is working.
I
haven't seen a new message in a 10 days.]
dmseg command
=============
The dmesg command shows you the kernel log. It takes the log from the
kernel itself. It is stored in a circular RAM buffer, so you can still
read it if the normal logging system isn't working. This buffer is a
fixed size so older messages can get pushed out by newer ones if there
is
enough logging going on.
You can get more info on Fedora by
journalctl -b
but it isn't limited to kernel messages. It does colour-code messages
based on severity, so that's a nice plus. Since this log typically
goes
to disk, it tends to be complete. Oh: the -b flag means: start from
the
most recent boot -- logs can go back months and years.
As an old timer, my first instinct is to use dmesg.
looking at kernel messages
==========================
dmesg | less -i
dmesg pours out a lot of lines. less is a good way of navigating this
log. The -i makes searches within less case-insensitive.
A good read. Thanks for sharing!
Small note: On Debian (and other distros?) if a non-root user runs dmesg
to read the contents of the kernel message buffer they will see ...
dmesg: read kernel buffer failed: Operation not permitted
Turns out it is a security feature -
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=842226#15
To allow users to read the kernel log without being prompted for a
password, modify /etc/sysctl.conf by adding ...
kernel.dmesg_restrict = 0
... and reload the configuration ...
$ sudo sysctl -p
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