Enable kdump on a compiled linux kernel

2
votes

Ho to get a core dump on a changed Linux kernel ?

I am running a Ubuntu 14.04 VM with 4G ram, 4 cores, compiled and installed a 3.18 kernel.

BOOT_IMAGE=/boot/vmlinuz-3.18.7+ root=UUID=4a45cb37-0577-4307-bfc5-da80ee9097db ro crashkernel=384M-:128M

user@dhcp194:~/source/nfs4tc$ sudo kdump-config test USE_KDUMP:
1 KDUMP_SYSCTL: kernel.panic_on_oops=1 KDUMP_COREDIR:
/var/crash crashkernel addr: 0x30000000 kdump kernel addr: relocatable kdump kernel: /boot/vmlinuz-3.18.7+ kdump initrd: /boot/initrd.img-3.18.7+ kexec command to be used: /sbin/kexec -p --command-line="BOOT_IMAGE=/boot/vmlinuz-3.18.7+ root=UUID=4a45cb37-0577-4307-bfc5-da80ee9097db ro irqpoll maxcpus=1 nousb" --initrd=/boot/initrd.img-3.18.7+ /boot/vmlinuz-3.18.7+

kdump-load throws an error.

user@dhcp194:~/source/nfs4tc$ sudo kdump-config load Could not find a free area of memory of 0x9521000 bytes... locate_hole failed * failed to load kdump kernel

syslog snippet:

/var/log/syslog.1:Apr 3 17:30:23 dhcp194 kdump-tools: failed to load kdump kernel /var/log/syslog.1:Apr 3 17:58:12 dhcp194 kdump-tools: failed to load kdump kernel /var/log/syslog.1:Apr 3 19:39:09 dhcp194 kdump-tools: failed to load kdump kernel

It works in a fresh installed VM, but after changing the kernel it wont. I use default .config file for kernel compilation. Any help ?

1
ccompilationlinux-kernelkernelcrash-dumps

1 Answers

0
votes

Let's call a crash kernel - the one kdump must load, and system kernel - your host kernel.

  1. Enable CONFIG_KEXEC in your system kernel
  2. In your system kernel bootloader must pass crashkernel=YM@X string to your system kernel cmd line (possibly in your case through atags) where Y is a reserved space for your crash kernel (in MBs) and X is a physical address where crashkernel will be located.

To check 2. you could review /proc/iomem. If there is no "crash kernel" section in it, then something is going wrong. And next ... use -d option in kexec utility for verbose mode