tested on Ubuntu/xenial and Devuan/ascii
Warning: if running Linux as a dom0 on top of a XEN micro-kernel, some specific steps need to be taken: https://xenbits.xen.org/docs/4.10-testing/misc/kexec_and_kdump.txt.
This is usually available,
less /boot/config-4.9.0-6-amd64 CONFIG_RELOCATABLE=y CONFIG_KEXEC=y CONFIG_CRASH_DUMP=y CONFIG_DEBUG_INFO=y CONFIG_MAGIC_SYSRQ=y CONFIG_PROC_VMCORE=y
On Ubuntu,
locale apt install linux-crashdump apt install linux-image-generic linux-headers-generic linux-tools-generic Should kexec-tools handle reboots? ==> Yes Should kdump-tools be enabled by default? ==> Yes
On Devuan,
apt install crash kexec-tools makedumpfile apt install linux-image-amd64 linux-headers-amd64 linux-tools
On both,
vi /dev/default/kdump-tools vi /dev/default/kexec uname -a dpkg -l | grep linux-image ls -alhF /lib/modules poweroff
restart the guest/system adding this to the kernel boot arguments,
#crashkernel=auto #crashkernel=128M@16M #crashkernel=0M-2G:128M,2G-6G:256M,6G-8G:512M,8G-:768M #crashkernel=256M crashkernel=128M
shutdown the system, otherwise if you reboot it might just reload the kernel already,
poweroff #dpkg-reconfigure kdump-tools #dpkg-reconfigure kexec-tools
physically power on and check,
#ubuntu systemctl status kdump-tools #devuan service kdump-tools status dmesg | grep -i crash cat /proc/cmdline cat /proc/sys/kernel/sysrq #should be >0 kdump-config status kdump-config show kdump-config test sysctl -a | grep oops ls -lhF /var/lib/kdump/initrd.img ls -lhF /var/lib/kdump/vmlinuz ls -alhF /var/crash
Let’s proceed with a crash dump,
cat /sys/kernel/kexec_crash_loaded echo c > /proc/sysrq-trigger #cat /sys/kernel/kexec_loaded
cd /var/crash/201804292156 crash /usr/lib/debug/vmlinux-4.9.0-6-amd64 dump.201804292156