PHReeK.oRG

I had a CentOS 5 Hyper-V VM running on Windows 2012 / Hyper-V 3.0 on which I mistakenly installed the Linux Integration Services 3.4 using the RHEL57 packages. The installation completed with some warnings and the initial reboot was OK, but after removing the "microsoft-hyper-v" and then "kmod-microsoft-hyper-v" packages the VM would no longer boot due to a kernel panic.

The kernel panic message was:

switchroot: mount failed: No such file or directory
Kernel panic - not syncing: Attempted to kill init!

1. I booted from the CentOS 5 installation CD #1 and entered "linux rescue" at the "boot:" prompt to enter rescue mode.
2. I selected the default language options.
3. I chose not to start networking services, as they were not required.
4. I selected the Continue button to mount the filesystem under /mnt/sysimage
5. I modified /mnt/sysimage/boot/grub/grub.conf
6. The existing kernel line was similar to

   kernel /vmlinuz-2.6.18-194.el5 ro root=/dev/VolGroup00/LogVol00 noprobe=hda1 noprobe=hda2

7. I modified it to

   kernel /vmlinuz-2.6.18-194.el5 ro root=/dev/VolGroup00/LogVol00

After rebooting, the server booted successfully.

The real solution for older CentOS 5 and RHEL 5 VMs is that you need to download Linux Integration Services 2.1 and install it.

If you didn't install the Development Tools group during initial installation, you'll likely need to remove the Hyper-V VM network adapter and add a Legacy Adapter to enable network connection.