Solution to: Getting Kernel Panic After Update of Virtual Machine

If you recently updated your Centos VM you may started getting the error below:

Kernel panic -- not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

unknown-block may change depending on your configuration, but symptoms stay same: Kernel panic after the update, and this error message.

Solution is:

yum remove kernel
yum update

That fixed my problem. Hopefully it fixes yours.



System Sleep States

When you put your computer to suspend, it will turn some of its devices to power saving mode to preserve energy consumption. But computers have many sleep states from deeper to shallow just like humans. The most shallow one is the freeze (or S0-idle) which only puts CPU to idle and if possible turn other devices to less power consuming mode. The most deeper one is the “Sleep-to-Memory” (or S3) in which CPU is turned off, and nearly only memory and some critical devices uses energy. It is also possible to suspend-to-disk (S4, S5), with STD current state of computer saved to disk. STD is called hibernate. In hibernate cold reboot will be performed so, it will take longer to restore the state.

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