So it was actually trivial, looking at the very last message from the bug report:
Part of the changelog from the aforementioned kernel:
- security,printk: Enable SECURITY_DMESG_RESTRICT, preventing non-root users reading the kernel log by default (sysctl:
kernel.dmesg_restrict)
So the solution is simply to run once:
% sudo sysctl kernel.dmesg_restrict=0
kernel.dmesg_restrict = 0
Then your local user can start using dmesg
again. This apply to any user, instead of a group which I initially assumed.
Everything is back to what I wanted:
% dmesg|wc
1307 11745 93652
and
% cat /dev/kmsg|head|wc
10 82 857
And to make it persists across reboots, simply save it as conf file:
$ echo kernel.dmesg_restrict = 0 | sudo tee -a /etc/sysctl.d/10-local.conf >/dev/null
$ cat /etc/sysctl.d/10-local.conf
kernel.dmesg_restrict = 0
If you are on Ubuntu, for release 20.10 onwards there is already a line to persist this setting in /etc/sysctl.d/10-kernel-hardening.conf
. After changing the file, to make the changes effective the user either needs to reboot or run sudo service procps restart
.