The default sysctl setting for kernel.sysrq in Ubuntu is 176 (and was in bionic and xenial) and it is shipped in /etc/sysctl.d/10-magic- sysrq.conf file. This file is provided by a required package from the minimal task, called `procps`.
176 enables: 128 - allow reboot/poweroff 32 - enable remount read-only 16 - enable sync command Do you have `procps` package installed on your system? Is anything else overriding that setting? If that setting is not suitable for you, I recommend to either modify /etc/sysctl.d/10-magic-sysrq.conf or to add another .conf drop in, with a higher number in /etc/sysctl.d directory to suit your system better. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. 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: 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.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 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-power-systems/+bug/1793369/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
