I have just pushed an experimental User-Mode Linux (UML) backend for libguestfs ≥ 1.23.15. What this means is you can now try using UML instead of KVM, which may be more lightweight and/or faster for you.
Update: The User Mode Linux book is available as a free PDF download from the publisher here.
If your distro doesn’t ship UML, you will need to compile UML from source. This was very straightforward and took me only 5 minutes following these instructions.
You will also need to install
uml_utilities (specifically we need the
uml_mkcow program to work around a bug in UML).
LIBGUESTFS_BACKEND=uml and LIBGUESTFS_QEMU to point to the UML “linux” or “vmlinux” program that you compiled. (Note that we’re just reusing the “qemu” variable name for convenience; when using UML, qemu/KVM is not involved).
You can try using guestfish or other virt tools as normal (being an experimental backend, they may not work quite right …)
$ export LIBGUESTFS_BACKEND=uml $ export LIBGUESTFS_QEMU=/home/rjones/d/linux/vmlinux $ guestfish -a /tmp/test1.img Welcome to guestfish, the guest filesystem shell for editing virtual machine filesystems and disk images. Type: 'help' for help on commands 'man' to read the manual 'quit' to quit the shell ><fs> run ><fs> list-filesystems /dev/ubda1: ext2 ><fs> mount /dev/ubda1 / ><fs> ll / total 17 drwxr-xr-x 3 root root 1024 Aug 11 20:46 . drwxr-xr-x 23 1000 1000 4096 Aug 11 20:54 .. -rw-r--r-- 1 root root 0 Aug 11 18:31 foobar -rw-r--r-- 1 root root 0 Aug 11 18:35 foobarbar -rw-r--r-- 1 root root 0 Aug 11 20:46 foobarbarbar drwx------ 2 root root 12288 Aug 9 22:47 lost+found
The main restriction of the UML backend is that only raw format disks are supported, no qcow2, no NBD or other remote storage.