VCenter Server: Shell.set command not found

Mitigation

1. Reboot of the VM / vCenter Server Appliance

2. While booting and showing the bootloder, Press "e" to edit the entry

3. Append "/bin/bash" to the line ending with ""

4. Press Enter to boot the modified boot entry

5. Enjoy the shell, fix the problem (Most likely 100% space used ; confirm with df -h ; find directories that are big with du -sh