I installed an operative system inside of Xen Virtual Box. The space was 25 GB, I would need to increase it but I haven’t found the way to do it. Is it possible to make bigger this virtual machine?. My Opensuse has more than enough free space so I can use more for virtual machine, the problem is that I don’t know how to do it.
You need to define what you mean by “bigger.”
You can increase your virtual RAM.
You can increase the number of virtual CPU <if> it makes a difference to your software (usually today’s software doesn’t care).
If you’re talking about the size of your virtual disk, you first start with the disk format (not the file system). Depending on the existing disk format, you then look for the documentation and tools which might be used to expand the disk. If the existing format has limited capability to do what you want, you can look for tools to convert to a different disk format.
How have you set up the virtual hard drive?
Did you put it into a file? In this case you should double-check whether or not the image format supports size changes (in this case you should be able to modify the file size - however, you may still be required to repartition the virtual hard disk).
If the image format does NOT support resizing, you may have to create a second disk image, assign it to the VM and copy the contents from the old drive to the new one, then remove the original virtual drive.
In case you have used a physical partition for your virtual drive you are required to repartition your physical hd to accommodate the increased image size.