what happened to dmesg.log?

Discussion:

(too old to reply)

William Unruh

2022-05-04 17:41:42 UTC

It used to be that the dmesg were written to the log file
/var/log/dmesg.log. However in Mageia 8 this seems to have disappeared.
How can I get it back?

William Unruh

2022-05-04 18:09:20 UTC

Permalink

Post by William Unruh
It used to be that the dmesg were written to the log file
/var/log/dmesg.log. However in Mageia 8 this seems to have disappeared.
How can I get it back?

Sorry, just /var/log/dmesg , not dmesg.log but it has still disappeared.

David W. Hodgins

2022-05-04 18:37:04 UTC

Permalink

Post by William Unruh
It used to be that the dmesg were written to the log file
/var/log/dmesg.log. However in Mageia 8 this seems to have disappeared.
How can I get it back?

It was dropped with the switch to systemd. It was used to capture as much of the
boot log as could be captured before rsyslog started. As there was no way to feed
those messages to the syslog daemon, they were kept in a separate file.

With systemd and it's journal, those messages (and more that were previously being
lost at boot) are all included in the journal. You can still use the dmesg command
to see those messages using a timestamp instead of date/time.

Regards, Dave Hodgins

William Unruh

2022-05-04 21:30:10 UTC

Permalink

Post by David W. Hodgins

Post by William Unruh
It used to be that the dmesg were written to the log file
/var/log/dmesg.log. However in Mageia 8 this seems to have disappeared.
How can I get it back?

It was dropped with the switch to systemd. It was used to capture as much of the
boot log as could be captured before rsyslog started. As there was no way to feed
those messages to the syslog daemon, they were kept in a separate file.
With systemd and it's journal, those messages (and more that were previously being
lost at boot) are all included in the journal. You can still use the dmesg command
to see those messages using a timestamp instead of date/time.

Hm, /var/log/dmesg was still there even after syslogd was implimented.
The problem with the journal is that some of the dmesg messages seem to
not be there if one for example does journalctl -k which is claimed in
some places to be the equivalent of dmesg.
dmesg -T will also produce a date/time which is definitely more useful
than "seconds since 1970"

David W. Hodgins

2022-05-04 22:25:52 UTC

Permalink

Post by William Unruh
Hm, /var/log/dmesg was still there even after syslogd was implimented.
The problem with the journal is that some of the dmesg messages seem to
not be there if one for example does journalctl -k which is claimed in
some places to be the equivalent of dmesg.
dmesg -T will also produce a date/time which is definitely more useful
than "seconds since 1970"

You're right it wasn't the switch to systemd. My mistake.

The log file doesn't automatically get deleted on an upgrade. The install I'm using
right now started as a Mageia 3 install, and has been upgraded each release,
currently running Mageia 8.
# ll /var/log/dmesg
-rw-r--r-- 1 root root 71781 Oct 26 2019 /var/log/dmesg

The first line show the kernel used was 5.5.0-1.mga6, so it was the upgrade to
Mageia 7 when the file stopped getting updated.

journalctl -k is intended to be similar to dmesg, but not identical.

Without -T, dmesg shows time since the kernel started counting, not since the
linux epoch.

I recommend forgetting about dmesg. Just use "journalctl -b --no-h", or
"journalctl -b -1 --no-h", etc.

Regards, Dave Hodgins

Bit Twister

2022-05-05 00:20:12 UTC

Permalink

Post by William Unruh
Hm, /var/log/dmesg was still there even after syslogd was implimented.

I am going to guess some systemd update did away /var/log/dmesg .
Clean mga8 install.

# cat /var/log/dmesg
cat: /var/log/dmesg: No such file or directory

I remember is was there because I had opened a mga7 bug report about its contents
did not show up in the journal.

Post by William Unruh
The problem with the journal is that some of the dmesg messages seem to
not be there if one for example does journalctl -k which is claimed in
some places to be the equivalent of dmesg.

Looking pretty close to me.
$ journalctl -k
-- Logs begin at Fri 2022-04-29 06:33:13 CDT, end at Wed 2022-05-04 19:02:05 CD>
May 03 02:36:37 wb.home.test kernel: Linux version 5.15.35-desktop-2.mga8 (iurt>
May 03 02:36:37 wb.home.test kernel: Command line: BOOT_IMAGE=/boot/vmlinuz roo>
May 03 02:36:37 wb.home.test kernel: x86/fpu: x87 FPU will use FXSAVE
May 03 02:36:37 wb.home.test kernel: signal: max sigframe size: 1440
May 03 02:36:37 wb.home.test kernel: BIOS-provided physical RAM map:
May 03 02:36:37 wb.home.test kernel: BIOS-e820: [mem 0x0000000000000000-0x00000>

need a little less noise
$ journalctl -k --no-hostname
-- Logs begin at Fri 2022-04-29 06:33:13 CDT, end at Wed 2022-05-04 19:02:05 CD>
May 03 02:36:37 kernel: Linux version 5.15.35-desktop-2.mga8 (***@ecosse.magei>
May 03 02:36:37 kernel: Command line: BOOT_IMAGE=/boot/vmlinuz root=LABEL=mga8 >
May 03 02:36:37 kernel: x86/fpu: x87 FPU will use FXSAVE
May 03 02:36:37 kernel: signal: max sigframe size: 1440
May 03 02:36:37 kernel: BIOS-provided physical RAM map:
May 03 02:36:37 kernel: BIOS-e820: [mem 0x0000000000000000-0x0000000000098bff] >

Note to lurkers, if you are in the systemd-journal group you do not have
to get to a root prompt to view the system jounal.

David W. Hodgins

2022-05-05 02:35:43 UTC

Permalink

Post by William Unruh
Hm, /var/log/dmesg was still there even after syslogd was implimented.

Now I'm more confused. I was looking to see where it was being created, to
figure out exactly when it was dropped. It wasn't dropped.

/lib/systemd/system/mandriva-save-dmesg.service still exists and is enabled.

Running "systemctl start mandriva-save-dmesg.service" causes the file to
get updated.

I don't know why it isn't being run automatically. I'll ask around and open
a bug report, if it's not intentional.

Regards, Dave Hodgins

Bit Twister

2022-05-05 03:06:08 UTC

Permalink

Post by David W. Hodgins

Post by William Unruh
Hm, /var/log/dmesg was still there even after syslogd was implimented.

Now I'm more confused. I was looking to see where it was being created, to
figure out exactly when it was dropped. It wasn't dropped.
/lib/systemd/system/mandriva-save-dmesg.service still exists and is enabled.
Running "systemctl start mandriva-save-dmesg.service" causes the file to
get updated.
I don't know why it isn't being run automatically. I'll ask around and open
a bug report, if it's not intentional.

# systemctl status mandriva-save-dmesg.service

● mandriva-save-dmesg.service - Save boot dmesg content
Loaded: loaded (/usr/lib/systemd/system/mandriva-save-dmesg.service; enabled; vendor preset: enabled)
Active: inactive (dead)

journalctl | grep save-dmesg

May 01 05:40:01 drakscanner[659325]: running: /bin/systemctl --quiet is-enabled mandriva-save-dmesg.service
May 01 05:40:08 drakscanner[659325]: running: /bin/systemctl --quiet is-enabled mandriva-save-dmesg.service
May 04 20:16:13 drakscanner[705679]: running: /bin/systemctl --quiet is-enabled mandriva-save-dmesg.service
May 04 20:16:19 drakscanner[705679]: running: /bin/systemctl --quiet is-enabled mandriva-save-dmesg.service

faeychild

2022-05-05 04:16:49 UTC

Permalink

Post by Bit Twister
# systemctl status mandriva-save-dmesg.service
● mandriva-save-dmesg.service - Save boot dmesg content
Loaded: loaded (/usr/lib/systemd/system/mandriva-save-dmesg.service; enabled; vendor preset: enabled)
Active: inactive (dead)
journalctl | grep save-dmesg
May 01 05:40:01 drakscanner[659325]: running: /bin/systemctl --quiet is-enabled mandriva-save-dmesg.service
May 01 05:40:08 drakscanner[659325]: running: /bin/systemctl --quiet is-enabled mandriva-save-dmesg.service
May 04 20:16:13 drakscanner[705679]: running: /bin/systemctl --quiet is-enabled mandriva-save-dmesg.service
May 04 20:16:19 drakscanner[705679]: running: /bin/systemctl --quiet is-enabled mandriva-save-dmesg.service

~]$ systemctl status mandriva-save-dmesg.service
● mandriva-save-dmesg.service - Save boot dmesg content
Loaded: loaded
(/usr/lib/systemd/system/mandriva-save-dmesg.service; enabled; vendor pres>
Active: inactive (dead)
[***@unimatrix ~]$ journalctl | grep save-dmesg

I got a long pause here (4-5) seconds before the prompt returned with
nothing

[***@unimatrix ~]$

--
faeychild
Running plasmashell 5.20.4 on 5.15.35-desktop-2.mga8 kernel.
Mageia release 8 (Official) for x86_64 installed via Mageia-8-x86_64-DVD.iso

David W. Hodgins

2022-05-05 04:30:58 UTC

Permalink

Post by faeychild
~]$ systemctl status mandriva-save-dmesg.service
● mandriva-save-dmesg.service - Save boot dmesg content
Loaded: loaded
(/usr/lib/systemd/system/mandriva-save-dmesg.service; enabled; vendor pres>
Active: inactive (dead)
I got a long pause here (4-5) seconds before the prompt returned with
nothing

Use "journalctl -b" to limit the search to only the current boot.

I strongly recommend setting limits on the size of the journal.
# grep -v -e ^$ -e ^'#' /etc/systemd/journald.conf
[Journal]
SystemMaxUse=200M
RuntimeMaxUse=200M
ForwardToSyslog=yes
ForwardToConsole=yes
TTYPath=/dev/tty12

See "man journald.conf" for details. The defaults for the MaxUse are 10% and 15%
of the size of the filesystem where /var/log/journal/ is stored.

With 200M my system keeps around a month of data, though it varies depending on
what I've been doing.

Regards, Dave Hodgins

Bit Twister

2022-05-05 05:32:17 UTC

Permalink

Post by faeychild

~]$ systemctl status mandriva-save-dmesg.service
● mandriva-save-dmesg.service - Save boot dmesg content
Loaded: loaded
(/usr/lib/systemd/system/mandriva-save-dmesg.service; enabled; vendor pres>
Active: inactive (dead)
I got a long pause here (4-5) seconds before the prompt returned with
nothing

Depends on size of journal and speed of system.
I have a new_boot_logs script to clear/truncate/delete log/journal files and reboot system.

# ls -l --all --escape --human-readable --color=auto' /var/log/journal/$(cat /etc/machine-id)
total 153M
drwxr-sr-x+ 2 root systemd-journal 24K May 4 22:08 .
drwxr-sr-x+ 3 root systemd-journal 4.0K Jan 14 14:01 ..
-rw-r-----+ 1 root systemd-journal 8.0M May 4 22:08 ***@688d8b538b6949b397c6928df9bf4ee2-0000000001953c37-0005de3b0c47acc3.journal
-rw-r-----+ 1 root systemd-journal 8.0M May 5 00:17 system.journal
-rw-r-----+ 1 root systemd-journal 8.0M May 5 00:16 user-1500.journal
-rw-r-----+ 1 root systemd-journal 8.0M May 4 22:08 user-1501.journal
-rw-r-----+ 1 root systemd-journal 8.0M May 4 22:08 user-1504.journal
-rw-r-----+ 1 root systemd-journal 8.0M May 5 00:14 user-1508.journal
-rw-r-----+ 1 root systemd-journal 8.0M May 4 22:08 user-1510.journal
-rw-r-----+ 1 root systemd-journal 8.0M May 5 00:14 user-1511.journal
-rw-r-----+ 1 root systemd-journal 8.0M May 4 22:08 user-1512.journal
-rw-r-----+ 1 root systemd-journal 8.0M May 4 22:08 user-1513.journal
-rw-r-----+ 1 root systemd-journal 8.0M May 4 22:08 user-1515.journal
-rw-r-----+ 1 root systemd-journal 8.0M May 4 22:08 user-1522.journal
-rw-r-----+ 1 root systemd-journal 8.0M May 4 22:08 user-1526.journal
-rw-r-----+ 1 root systemd-journal 8.0M May 4 22:08 user-1527.journal
-rw-r-----+ 1 root systemd-journal 8.0M May 4 22:08 user-1528.journal
-rw-r-----+ 1 root systemd-journal 8.0M May 4 22:08 user-1530.journal
-rw-r-----+ 1 root systemd-journal 8.0M May 4 22:08 user-1531.journal
-rw-r-----+ 1 root systemd-journal 8.0M May 4 22:08 user-1534.journal
-rw-r-----+ 1 root systemd-journal 8.0M May 4 22:08 user-1535.journal

Note no size limits set
# grep -v -e ^$ -e ^'#' /etc/systemd/journald.conf
[Journal]
ForwardToConsole=yes
TTYPath=/dev/tty12

new_boot_logs calls my new_journal script

# cat local/bin/new_journal
#!/bin/bash
#*******************************************************************************
#* new_journal - empty boot/application logs.
#*
#*
#* http://www.freedesktop.org/software/systemd/man/systemd-journald.service
#* flush logs and request immediate rotation of the journal files
#* then delete rotated files and all user logs.
#*
#* Usage: new_journal
#*
#*******************************************************************************

PATH=/usr/local/sbin:/sbin:/bin:/usr/sbin:/usr/bin

#**********************************
#* remove any editor backup files
#**********************************

rm --force /etc/modprobe.d/*~
rm --force /etc/sysconfig/network-scripts/ifcfg-*~

type dovecot > /dev/null 2>&1
if [ $? -eq 0 ] ; then
systemctl --quiet is-active dovecot 2> /dev/null
if [ $? -eq 0 ] ; then
systemctl stop dovecot
fi
truncate -s 0 /var/log/dovecot/errors.log
fi

_log_dir=/var/log/journal/$(cat /etc/machine-id)
if [ -e $_log_dir ] ; then
echo "Wiping journal logs"
journalctl --rotate > /dev/null 2>&1
journalctl --vacuum-time=1s
sleep 2
rm --force $_log_dir/user-*.journal
rm --force $_log_dir/*@*
fi

type dovecot > /dev/null 2>&1
if [ $? -eq 0 ] ; then
systemctl --quiet is-enabled dovecot 2> /dev/null
if [ $? -eq 0 ] ; then
systemctl start dovecot
truncate -s 0 /var/log/dovecot/errors.log
fi
fi

pkill --full "fa --no-pager"

#************************ end new_journal ******************************

David W. Hodgins

2022-05-05 06:37:17 UTC

Permalink

See https://bugs.mageia.org/show_bug.cgi?id=30380

Regards, Dave Hodgins

William Unruh

2022-05-05 06:37:48 UTC

Permalink

Post by Bit Twister

Post by William Unruh
Hm, /var/log/dmesg was still there even after syslogd was implimented.

I am going to guess some systemd update did away /var/log/dmesg .
Clean mga8 install.
# cat /var/log/dmesg
cat: /var/log/dmesg: No such file or directory
I remember is was there because I had opened a mga7 bug report about its contents
did not show up in the journal.

Looking pretty close to me.
$ journalctl -k
-- Logs begin at Fri 2022-04-29 06:33:13 CDT, end at Wed 2022-05-04 19:02:05 CD>
May 03 02:36:37 wb.home.test kernel: Linux version 5.15.35-desktop-2.mga8 (iurt>
May 03 02:36:37 wb.home.test kernel: Command line: BOOT_IMAGE=/boot/vmlinuz roo>
May 03 02:36:37 wb.home.test kernel: x86/fpu: x87 FPU will use FXSAVE
May 03 02:36:37 wb.home.test kernel: signal: max sigframe size: 1440
May 03 02:36:37 wb.home.test kernel: BIOS-e820: [mem 0x0000000000000000-0x00000>
need a little less noise
$ journalctl -k --no-hostname
-- Logs begin at Fri 2022-04-29 06:33:13 CDT, end at Wed 2022-05-04 19:02:05 CD>
May 03 02:36:37 kernel: Command line: BOOT_IMAGE=/boot/vmlinuz root=LABEL=mga8 >
May 03 02:36:37 kernel: x86/fpu: x87 FPU will use FXSAVE
May 03 02:36:37 kernel: signal: max sigframe size: 1440
May 03 02:36:37 kernel: BIOS-e820: [mem 0x0000000000000000-0x0000000000098bff] >

In my case I was looking at the debugging of wpa_supplicant and a number
of dmesg messages came from the wireless card number. They were not in
journalctl -k, which I think just give you the kernel messages, and
dmesg has more than just kernel messages.

(for example on one of my machine it also has a bunch of shorewall Drop
messages as well.)

Post by Bit Twister
Note to lurkers, if you are in the systemd-journal group you do not have
to get to a root prompt to view the system jounal.

Bit Twister

2022-05-05 14:02:48 UTC

Permalink

Post by William Unruh
In my case I was looking at the debugging of wpa_supplicant and a number
of dmesg messages came from the wireless card number. They were not in
journalctl -k, which I think just give you the kernel messages,

man journalctl suggests you are correct.

Post by William Unruh
and dmesg has more than just kernel messages.

Up to a point in time, has been my experience. I have converted my brain
to always use journalctl for hunting info/messages.

It greatly helps to have a wrapper script to take any number of keyword
arguments to search with.

Example: $ ujctl enp3s0
# looking in journalctl
May 04 22:08:02 systemd-networkd[508]: enp3s0: Failed to send DHCP RELEASE, ignoring: Operation not permitted
May 04 22:08:02 systemd-networkd[508]: enp3s0: DHCP lease lost
May 04 22:11:43 kernel: r8169 0000:03:00.0 enp3s0: renamed from eth0
May 04 22:11:43 systemd-networkd[507]: eth0: Interface name change detected, eth0 has been renamed to enp3s0.
May 04 22:11:44 systemd-networkd[507]: enp3s0: Link UP
May 04 22:11:44 kernel: r8169 0000:03:00.0 enp3s0: Link is Down
May 04 22:11:46 kernel: r8169 0000:03:00.0 enp3s0: Link is Up - 1Gbps/Full - flow control rx/tx
May 04 22:11:46 systemd-networkd[507]: enp3s0: Gained carrier
May 04 22:11:49 systemd-networkd[507]: enp3s0: DHCPv4 address 192.168.50.132/24 via 192.168.50.1

I also automagically launch two xterms upon login.
One is a 5 line I pin to the desktop and the other in window 0 is a 24
line I can scroll back to see what went on.

xterm -title wb_mga8_8_o0_xtail journalctl --no-hostname -fa --no-pager \
-fn 9x15 -fg black -bg SpringGreen3 -geom 135x5+20+0

xterm -title wb_mga8_8_o0_xcon journalctl --no-hostname -fa --no-pager \
-fn 9x15 -fg black -bg SpringGreen3 -geom 135x24+20+130

Doug Laidlaw

2022-05-05 09:19:47 UTC

Permalink

Post by William Unruh
It used to be that the dmesg were written to the log file
/var/log/dmesg.log. However in Mageia 8 this seems to have disappeared.
How can I get it back?

I didn't know that it even existed. dmesg|tail and the systemd journal
are all that I have ever needed. On BT's advice, I added my username to
the "journalctl" group, allowing me to view the journal as an ordinary user.