So, you've got a few Xen images around, and they are starting to fill up. How do you add a few more gigs to 'em?
root@tpe:/# xm shutdown vm01That's it, you just added a gig to your image called 'vm01.img'.
root@tpe:/# cd /xenimages
root@tpe:/xenimages# dd if=/dev/zero bs=1024 count=1000000 >> vm01.img
root@tpe:/path/to/images# resize2fs -f vm01.img