Ubuntu Version:
24.04.2
Desktop Environment (if applicable):
None (Ubuntu Server)
Problem Description:
I was going through the following documentation:
https://documentation.ubuntu.com/server/how-to/software/kernel-crash-dump/index.html
I am trying to set up Kernel Crash Dumps on my Ubuntu Server 24.04.2 setup. I believe I have it set up but I want to make sure I am not missing something as the documentation differs a bit from what I am seeing. Also for some reason when I test a kernel crash my system doesn’t reboot and a dump isn’t generated although everything else looks correct. Therefore I have a few questions:
Question 1:
According to the documentation you only need install sudo apt remove kdump-tools do we no longer need to install linux-crashdump too?
Question 2:
When installing or when you run dpkg-reconfigure kexec-tools according to the documentation you should get a prompt to use kexec-tools asking Should kexec-tools handle reboots (sysvinit only)? I did not. When I check /etc/default/kexec the following does not exist:
# Load a kexec kernel (true/false)
LOAD_KEXEC=true
Is this normal on 24.04.2 has the behavior changed or is something wrong on my end? I did find the following post from somebody else observing the same behavior so I am curious if the documentation is just not up to date:
https://askubuntu.com/questions/1517572/how-to-config-parameter-load-kexec-for-ubuntu24-04
The system is running systemd and not sysvinit so perhaps that’s normal and acceptable?
When verifying the install everything seems normal.
When I run cat /proc/cmdline I get:
BOOT_IMAGE=/vmlinuz-6.8.0-56-generic root=/dev/mapper/ubuntu--vg-ubuntu--lv ro crashkernel=2G-4G:320M,4G-32G:512M,32G-64G:1024M,64G-128G:2048M,128G-:4096M
When I run dmesg | grep -i crash I get:
...
[ 0.013007] crashkernel reserved: 0x0000000079000000 - 0x0000000099000000 (512 MB)
Last but not least kdump-config show gets me:
DUMP_MODE: kdump
USE_KDUMP: 1
KDUMP_COREDIR: /var/crash
crashkernel addr: 0x
/var/lib/kdump/vmlinuz: symbolic link to /boot/vmlinuz-6.8.0-56-generic
kdump initrd:
/var/lib/kdump/initrd.img: symbolic link to /var/lib/kdump/initrd.img-6.8.0-56-generic
current state: ready to kdump
crashkernel suggested size: 284M
kexec command:
/sbin/kexec -p --command-line="BOOT_IMAGE=/vmlinuz-6.8.0-56-generic root=/dev/mapper/ubuntu--vg-ubuntu--lv ro reset_devices systemd.unit=kdump-tools-dump.service nr_cpus=1 irqpoll usbcore.nousb" --initrd=/var/lib/kdump/initrd.img /var/lib/kdump/vmlinuz
Is everything looking normal here for 24.04.2? I did see that in the documentation kdump-config show has the following line which I am missing:
KDUMP_SYSCTL: kernel.panic_on_oops=1
However when I run cat /proc/sys/kernel/panic_on_oops I get a 1 so it should be set correctly.
Is all this normal 24.04.2 behavior?
Question 3:
When I trigger a kernel crash via echo c > /proc/sysrq-trigger my system never rebooted it would just hang/freeze so I manually restarted the server hours later. Any idea why that is? What else can I check to make sure my configurations are correct for things to reboot on an oops.