'/proc/sys/kernel/core_pattern': Permission denied

[Uwe Mintermann <uwe.mintermann@googlemail.com>]

Hi,

I am facing the problem that no core files are written on my server
(Debian GNU/Linux buster/sid).

root:~# sysctl kernel.core_pattern
kernel.core_pattern = |/usr/libexec/abrt-hook-ccpp %s %c %p %u %g %t e
root:~# ls /usr/libexec/abrt-hook-ccpp
ls: cannot access '/usr/libexec/abrt-hook-ccpp': No such file or directory

Ok problem is clear. abrt should handle segment faults but abrt is not
installed. So I am trying to change the sysctl kernel.core_pattern to
"core" as root (no sudo).

root:~# sysctl -w kernel.core_pattern=core
sysctl: permission denied on key 'kernel.core_pattern'


root:~# echo "core" > /proc/sys/kernel/core_pattern
bash: /proc/sys/kernel/core_pattern: Permission denied

root:~# rm /proc/sys/kernel/core_pattern
rm: cannot remove '/proc/sys/kernel/core_pattern': Permission denied

Whats wrong? I have no access as root even though the file system is
mounted as writable.

-rw-r--r-- 1 root root 0 Oct  3 21:01 /proc/sys/kernel/core_pattern
proc on /proc type proc (rw,relatime)


Can anyone help? I have installed some debian testing packages a few
months ago and reverted it.

Thanks!
Uwe