add swap to cloud host (KVM)

[Eliza]

Hi,

I have two cloud hosts both which are ubuntu, one has swap enabled:

$ free -m
               total        used        free      shared  buff/cache 
available
Mem:            991          88         233          29         670 
    684
Swap:           974         136         838

Another has none:

$ free -m
               total        used        free      shared  buff/cache 
available
Mem:            985         423         171          26         390 
    391
Swap:             0           0           0

So how to add swap to the system?

Thanks.