[Bug 1793369] Re: Ubuntu18.10:ppc64:s390x - Sysrq trigger disabled when writing to /proc/sysrq-trigger

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** Tags removed: targetmilestone-inin---
** Tags added: targetmilestone-inin1810

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Title:
  Ubuntu18.10:ppc64:s390x - Sysrq trigger disabled when writing to /proc
  /sysrq-trigger

Status in The Ubuntu-power-systems project:
  Invalid
Status in linux package in Ubuntu:
  Invalid
Status in systemd package in Ubuntu:
  Invalid
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.Pandey at 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 at test:~# cat /proc/sys/kernel/sysrq 
  176
  root at test:~# echo c > /proc/sysrq-trigger
  root at 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 at 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 at test:~# cat /etc/sysctl.conf | grep kernel.sysrq
  #kernel.sysrq=438
  root at 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 at test:~# 

  Regards
  Praveen

  == Comment: #2 - Praveen K. Pandey <Praveen.Pandey at 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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