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dracut Warning: No root device “block:/dev/disk/by-label/root” found – CentOS 6 19 May 2013

Posted by Maulvi Bakar in : Linux,System,Work , trackback

I’ve been on GE-mode for the past few months. In effort to maintain stability, I resisted upgrading the KVM-host machine to the latest kernel. Sorry guys, I’m still on CentOS, not on OEL, so no Ksplice!

To cut story short, the kernel upgrades results in the infamous CentOS/RHEL depmod bug! –

dracut Warning: No root device "block:/dev/disk/by-label/root" found
dracut Warning: Boot has failed. To debug this issue add "rdshell" to the kernel command line.
dracut Warning: Signal caught!
dracut Warning: Boot has failed. To debug this issue add "rdshell" to the kernel command line.
Kernel panic - not syncing: Attempted to kill init!
Pid: 1, comm: init Not tainted 2.6.32-358.6.2.el6.x86_64 #1
Call Trace:
[] ? panic+0x78/0x143
[] ? do_exit+0x852/0x860
[] ? fput+0x25/0x30
[] ? do_group_exit+0x58/0xd0
[] ? sys_exit_group+0x17/0x20
[] ? system_call_fastpath+0x16/0x1b

The system kernel-panics!

Even the built-in kernel fallback options in GRUB did not activate!!

Canvassing the net suggests that the kernel modules did not install properly and the solution is to install manually via the commands below –

# depmod -ae -F /boot/System.map-2.6.32-358.6.2.el6.x86_64 2.6.32-358.6.2.el6.x86_64
# dracut --force '' 2.6.32-358.6.2.el6.x86_64

I tried that via CentOS Rescue Mode and ‘chroot /mnt/sysimage’. This too was fun, KVM Console ISO Image redirection from your local PC to a site on the far side of the galaxy is something you should only attempt on a high-bandwidth! UniFi is crap!

Luckily the KVM Console supports mounting ISO Image from a SAMBA Share. A small tiny low-end-box serves the purpose nicely and being much closer in peering to the main KVM-host site makes it even better!

Unfortunately, that doesn’t seem to work for me.

But what does work – instead of ‘yum update’, I did a ‘yum localinstall’. Downloaded the kernel and kernel-devel RPMs onto the local disk and installed it after removing the broken kernel before that.

That seems to do the trick!

Hope it solves someone else issue with this.

God willing!

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