Before the guest domain may be started, the Xen hypervisor must have enough free memory for the new guest. First, check the amount of memory used:

xm list
Name              Id  Mem(MB)  CPU  State  Time(s)  Console
Domain-0           0      458    0  r----    181.8

If this is a computer with 512 MB, the Xen hypervisor takes away 64 MB and Domain-0 occupies the rest. To free some of the memory for the new guest, the command xm balloon is used. To set the size of Domain-0 to 330 MB, enter the following as root:

xm balloon 0 330

In the next xm list, the memory usage of Domain-0 should have dropped to 330 MB. Now there is enough memory available to start a guest with 128 MB. The command xm start guest1 -c starts the guest and links the console of the starting guest to the current terminal. If this is the first time that this guest starts, finish the installation with YaST.

It is always possible to detach this console or reattach it from another terminal. To detach, use Ctrl-]. To reattach, first check the ID of the needed guest with xm list and attach to that ID with xm console ID.

The xm tool of Xen has many possible parameters. View a list with a short explanation by entering xm help. Table 37.1, “xm Commands” provides some of the most important commands as a starting point.