VMware ESXi Error: “ramdisk ‘root’ is full”

During the cleanup from a recent DR test at work, I ran into an issue where I couldn’t migrate guests between different hosts. We have three hosts in a HA/DRS cluster, so if I couldn’t move the guests around there is no way that VMware could automatically do this either.

Not exactly sure why I couldn’t do this, I figured I would reboot each host one at a time. The first host was not able to be put into maintenance mode, since the guest vMotions failed. I also realized that this was the host I was trying to get guests off of when the vMotions failed earlier. Other hosts seemed to vMotion guests between them fine, it was only an issue with “host 1.” I also noticed that I could not open the console for any guest on this particular host.

I checked in the Event Logs in vCenter and found an error similar to (I forgot to document the EXACT error message wording): RAMDISK root is full on host1. I didn’t find much on the Internet regarding this error, other than the actual ESXi OS must have a full partition and I should clean it. I wasn’t quite sure what to delete, but I did find a command to identify what part of the host was full (vdf -h). I called VMware for support and, while helpful, they didn’t show me anything I didn’t already find on my own.

I found the partition that was full was only 32 MB and there was a 30 MB /var/log/hpHelper.log (we have HP hosts) file. I copied the log file using WinSCP, then deleted it from the host, and restarted the host services. After that, vMotions to/from that host were successful and I could put it in maintenance mode to reboot it.

Summary –

–  I couldn’t vMotion guests between hosts at one of our datacenter locations.
–  The event log in the vSphere client showed that ramdisk root is full on host1.
–  SSHing into host1 and running `vdf -h` shows that ramdisk root has 0% free space out of 32 MB.
–  I looked around and found that /var/log was very large.
–  I found a 30 MB file in /var/log called hpHelper.log.
–  I used WinSCP to copy that file to my desktop and read it, it’s just a log file.
–  I ran `rm /var/log/hpHelper.log` and `touch hpHelper.log` to delete and re-create the log file.
–  I restarted the management services on the host – `./sbin/services.sh restart`
–  Now I can open the console on various guests and I can vMotion between hosts.