Hello Friends,
In this post, I would explain to you how to resolve one of the most intreseting issue on linux servers "Kernel Panic". I think the linux lovers much awaited such issue while they are working on Unix troubleshooting part.
As everyone knows Kernel are most importent part of any operating system and if it is crashed that's means your system crashed.
Normally kernel panic occur when you upgrade the server or upgrade the packages on the server. Here, you can find one of the Kernel panic issue as describe below.
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
Pid: 1, comm: swapper Not tainted 2.6.32-502.el6.x86_64 #1
Call Trace:
[<ffffffff815292bc>] ? panic+0xa7/0x16f
[<ffffffff81c2b432>] ? mount_block_root+0x216/0x2cb
[<ffffffff81002930>] ? bstat+0x2b0/0x980
[<ffffffff81c2b53d>] ? mount_root+0x56/0x5a
[<ffffffff81c2b6b1>] ? prepare_namespace+0x170/0x1a9
[<ffffffff81c2a92a>] ? kernel_init+0x2e1/0x2f7
[<ffffffff8100c20a>] ? child_rip+0xa/0x20
[<ffffffff81c2a649>] ? kernel_init+0x0/0x2f7
[<ffffffff8100c200>] ? child_rip+0x0/0x20
Solution : Normally this issue occur while you upgrade your server using yum and after reboot server is not boot due to kernel panic problem. This problem occur while kernel version has not been changed properly.
You can boot your linux server in grup mode and check the kernel and initrd paramtere. Match both the parameter if they are using same kernel version. During upgrade the initrd version normally not changed so you can manually change the correct kernel version entry in this file.
Once you modified the initrd files boot the server and make a same changes in grub.conf file too, otherwise once you take a reboot or shutdown the machine same kerenl panic error will occur.
[root@localhost]# vi /etc/grub.conf
#boot=/dev/sda
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title CentOS 6 (2.6.32-504.el6.x86_64)
root (hd0,0)
kernel /vmlinuz-2.6.32-504.el6.x86_64 ro root=/dev/mapper/vstorage-root rd_NO_LUKS LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=auto rd_LVM_LV=vstorage/root KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM rhgb quiet
initrd /initramfs-2.6.32-504.el6.x86_64.img
In above example, the default value 0 identifies the first title option to be used as default, the corresponding kernel version in title option line as 2.6.32-504.el6.x86_64 and the initramfs image file as initramfs-2.6.32-504.el6.x86_64.img.
Before changing thing please take a backup of grub.conf file. now you can rename the kernel version in the initrd line and matched the same version at both the line and reboot the server, after reboot your linux machine will boot normally.
Hope your kernel panic issue will be resolved after reading this post. Please let me know if you are still facing this issue, I would try to help you.
