When restarting a VPS on your node, you will receive the error. The VPS won’t start from command prompt as well as GUI.
Error: required UB parameter swappages not set
This is because swappages are not set for that particular VPS. You will need to set it with command
vzctl set VEID –swappages=100:100 –save
Now, try starting the VPS, it should work.
Note: Replace VEID with your actual VPS ID.