The sysrq mechanism allows someone with physical access to the system to
easily cause it to boot by just pressing some keys. That's why the sysrq
default allows only very few commands to be issued. kdump is for real
crashes. kdump testing may require using the sysrq-trigger mechanism,
but that could just as well write to /proc/sys/kernel/sysrq before
causing the crash. In fact, that's just what kdump-tools autopkgtest
does.
echo 1 > /proc/sys/kernel/sysrq
echo c > /proc/sysrq-trigger
So, not a bug here.
** Also affects: systemd (Ubuntu)
Importance: Undecided
Status: New
** Changed in: systemd (Ubuntu Cosmic)
Status: New => Won't Fix
** Changed in: linux (Ubuntu Cosmic)
Status: Triaged => Invalid
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https://bugs.launchpad.net/bugs/1793369
Title:
Ubuntu18.10:ppc64:s390x - Sysrq trigger disabled when writing to /proc
/sysrq-trigger
Status in The Ubuntu-power-systems project:
Triaged
Status in linux package in Ubuntu:
Invalid
Status in systemd package in Ubuntu:
New
Status in linux source package in Cosmic:
Invalid
Status in systemd source package in Cosmic:
Won't Fix
Bug description:
== Comment: #0 - Praveen K. Pandey <praveen.pan...@in.ibm.com> - 2018-09-19
04:49:39 ==
---Problem Description---
[Witherspoon-DD2.2][Ubu 18.10] [4.18.0-7-generic ] : Sysrq trigger disabled
when writing to /proc/sysrq-trigger
while testing kdump trying trigger kdump panic via /proc/sysrq-trigger it
failed as : SysRq : This sysrq operation is disabled
LOG:
root@test:~# cat /proc/sys/kernel/sysrq
176
root@test:~# echo c > /proc/sysrq-trigger
root@test:~# dmesg
[ 380.340051] mlx5_core 0000:01:00.1 enp1s0f1: Self test out: status
flags(0x2)
[ 389.404239] sysrq: SysRq : This sysrq operation is disabled.
root@test~# cat /boot/config-4.18.0-7-generic | grep CONFIG_MAGIC_SYSRQ
CONFIG_MAGIC_SYSRQ=y
CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE=0x01b6
CONFIG_MAGIC_SYSRQ_SERIAL=y
root@test:~# cat /etc/sysctl.conf | grep kernel.sysrq
#kernel.sysrq=438
root@test:~# kdump-config show
DUMP_MODE: kdump
USE_KDUMP: 1
KDUMP_SYSCTL: kernel.panic_on_oops=1
KDUMP_COREDIR: /var/crash
crashkernel addr:
/var/lib/kdump/vmlinuz: symbolic link to /boot/vmlinux-4.18.0-7-generic
kdump initrd:
/var/lib/kdump/initrd.img: symbolic link to
/var/lib/kdump/initrd.img-4.18.0-7-generic
current state: ready to kdump
kexec command:
/sbin/kexec -p
--command-line="root=UUID=c0302064-c5a3-49a7-8bd4-402283e6fcbe ro quiet splash
nr_cpus=1 systemd.unit=kdump-tools.service irqpoll noirqdistrib nousb"
--initrd=/var/lib/kdump/initrd.img /var/lib/kdump/vmlinuz
root@test:~#
Regards
Praveen
== Comment: #2 - Praveen K. Pandey <praveen.pan...@in.ibm.com> - 2018-09-19
05:16:11 ==
when i enable in /etc/sysctl.conf it works . i append below value in
sysctl.conf
echo "kernel.sysrq = 1" >> /etc/sysctl.conf
I think this is should be enable by default in ubuntu 18.10 as
earlier ubuntu distro it has , not sure why it got removed as kdump
mechanism require this .
Praveen
Regards
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