>From my notes:
===== OK, I did the following and made some forward progress: /etc/default/grub: added console=ttyS0 update-grub reboot virsh console vm843 echo 8 > /proc/sys/kernel/printk rm -fr /var/crash/* sync echo c > /proc/sysrq-trigger I now see the capture kernel panic messages. ===== The important item here is the additional serial console which allowed me to view the messages in an xterm and scroll back (on a vnc console, there is no such ability). eric ________________________________ From: boun...@canonical.com <boun...@canonical.com> on behalf of norman shen <1908...@bugs.launchpad.net> Sent: Wednesday, June 16, 2021 1:57 AM To: Eric DeVolder <eric.devol...@oracle.com> Subject: [Bug 1908090] Re: ubuntu 20.04 kdump fails hello, may I ask how did you capture the log? My kdump also stuck but unfortunately does not print anything. the system looks dead though. the vm got a memory size of 4GiB -- You received this bug notification because you are subscribed to the bug report. https://bugs.launchpad.net/bugs/1908090 Title: ubuntu 20.04 kdump fails Status in kexec-tools package in Ubuntu: New Bug description: When linux-crashdump (5.4.0.58.61) is enabled on Ubuntu 20.04 LTS, everything appears to be in good working order, according to "systemctl status kdump-tools" and "kdump-config status". However, upon an actual crash, the system hangs, and no crash files are produced. I've investigated and have learned that the capture kernel does indeed start, but it is unable to unpack the rootfs/initrd, and thus fails and hangs. [ 1.070469] Trying to unpack rootfs image as initramfs... [ 1.333182] swapper/0 invoked oom-killer: gfp_mask=0x100cc2(GFP_HIGHUSER), order=0, oom_score_adj=0 [ 1.335074] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.4.0-26-generic #30-Ubuntu [ 1.336396] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014 [ 1.336396] Call Trace: [ 1.336396] dump_stack+0x6d/0x9a [ 1.336396] dump_header+0x4f/0x1eb [ 1.336396] out_of_memory.part.0.cold+0x39/0x83 [ 1.336396] out_of_memory+0x6d/0xd0 ... [ 1.413202] ---[ end Kernel panic - not syncing: System is deadlocked on memory ]--- On this system with 8G of memory, the crash memory as specified on the kernel command line is "crashkernel=512M-:192M". I changed the 192M to 256M, and now kdump works. Not sure how the 192M value is chosen, but it does not work. I think this used value used to work for 16.04 and maybe 18.04 (I didn't try), but is no longer useful for 20.04. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/kexec-tools/+bug/1908090/+subscriptions -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1908090 Title: ubuntu 20.04 kdump fails To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/kexec-tools/+bug/1908090/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
