ubuntu input/output error

The system is having severe trouble reading off of your hard disk. It's likely that the disk is dead (almost certain), but it could be something as simple as a loose/disconnected cable (don't count on it). There isn't anything you can do to troubleshoot it from here. Just power it off.

Check for loose connections on your hard disk. If everything is fine there boot from a rescue disk and run fsck or badblocks from there.

I hope you have a back up.

If you're using a VM it's quite likely that there was some interruption in the filesystem mounts, and linux switch the mounts to read only as a failsafe measure.

Unfortunately, it leaves your system practically unusable.

If you check /proc/mounts, and look for the root filesystem, there should be a line like this:

/dev/dm-0 / ext4 ro,relatime,errors=remount-ro,data=ordered 0 0

You'll see that the root filesystem has been mounted readonly.

Basically the only thing to do at this point (assuming this is the problem) is to reboot (via a KVM or other console power-off switch).