libguestfs notes

Libguestfs basics.

# apt-get install libguestfs-tools 
# apt-get install guestfish


The libguestfs Filesystem Interactive SHell.

An example: explore, read and write to disk image file within the libguestfs VM.
# guestfish --rw -a /home/vm/anaxagoras.qcow2
> run
 100% ⟦▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓⟧ 00:00
> list-filesystems
/dev/vda1: ext4
/dev/vda2: unknown
/dev/vda5: swap
> mount /dev/vda1 /

Add a file to the disk image file system.
> touch /etc/guestfish_play
> edit /etc/guestfish_play
> quit


Display files in a virtual machine.

# virsh list
 Id    Name                           State
 9     anaxagoras                     running

# virt-cat anaxagoras /etc/issue
Debian GNU/Linux 7 \n \l
# virt-cat anaxagoras /etc/hostname


Mount a guest filesystem on the host using FUSE and libguestfs

# apt-get install guestmount

Mount rw a filesystem contained in a disk image file.
# mkdir /mnt/anax
# guestmount -a /home/vm/anaxagoras.qcow2 -m /dev/vda1 --rw /mnt/anax/

# cat /mnt/anax/etc/guestfish_play
# echo "hi kosme" > /mnt/anax/etc/guestfish_play
# mv /mnt/anax/etc/guestfish_play /mnt/anax/etc/guestmount_play
# umount /mnt/anax

guestmount is and looks traditionally-scriptable. However, guestfish is as or more scriptable. Also, libguestfs has cute C , Perl and Python APIs.


List free space on virtual filesystems.
# virt-df anaxagoras
Filesystem                           1K-blocks       Used  Available  Use%
anaxagoras:/dev/sda1                  19751804     840608   17907832    5%


List filesystems, partitions, block devices, LVM in a virtual machine or a disk image file.

# virt-filesystems --long --parts --blkdevs -a /home/vm/anaxagoras.qcow2 -h
Name       Type       MBR  Size  Parent
/dev/sda1  partition  83   19G   /dev/sda
/dev/sda2  partition  05   1.0K  /dev/sda
/dev/sda5  partition  82   880M  /dev/sda
/dev/sda   device     -    20G   -


# virt-filesystems --long -h --all -a anaxagoras.qcow2 
Name       Type        VFS      Label  MBR  Size  Parent
/dev/sda1  filesystem  ext4     -      -    19G   -
/dev/sda2  filesystem  unknown  -      -    1.0K  -
/dev/sda5  filesystem  swap     -      -    880M  -
/dev/sda1  partition   -        -      83   19G   /dev/sda
/dev/sda2  partition   -        -      05   1.0K  /dev/sda
/dev/sda5  partition   -        -      82   880M  /dev/sda
/dev/sda   device      -        -      -    20G   -


List filesystems in a virtual machine or disk image.

# virt-list-filesystems anaxagoras.qcow2 
# virt-list-filesystems anaxagoras


Resize a virtual disk image file.

Eg: Expand the 20GB anaxagoras qcow2 disk image file to a 30GB qcow2 disk image file.
# truncate -r anaxagoras.qcow2 anaxagoras30G.qcow2
# truncate -s +10G anaxagoras30G.qcow2
# virt-resize --expand /dev/sda1 anaxagoras.qcow2 anaxagoras30G.qcow2 
Examining anaxagoras.qcow2 ...

Summary of changes:

/dev/sda1: This partition will be resized from 19.1G to 29.1G.  The 
    filesystem ext4 on /dev/sda1 will be expanded using the 'resize2fs' 

/dev/sda2: This partition will be left alone.

Setting up initial partition table on anaxagoras30G.qcow2 ...
Copying /dev/sda1 ...
 100% ⟦▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓⟧ 00:00
Copying /dev/sda2 ...
 100% ⟦▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓⟧ 00:00
Expanding /dev/sda1 using the 'resize2fs' method ...

Resize operation completed with no errors.  Before deleting the old 
disk, carefully check that the resized disk boots and works correctly.

Test resized image.
# cd /etc/libvirt/qemu/
# stor anaxagoras.xml
# virsh
virsh # edit anaxagoras
virsh # define anaxagoras.xml
virsh # start anaxagoras
virsh # quit
# ssh anaxagoras
root@anaxagoras:~# df -h
Filesystem                                              Size  Used Avail Use% Mounted on
rootfs                                                   29G  822M   27G   3% /
udev                                                     10M     0   10M   0% /dev
tmpfs                                                   202M  172K  202M   1% /run
/dev/disk/by-uuid/8ca4bd34-120c-45ff-bd0b-86d8de552d10   29G  822M   27G   3% /
tmpfs                                                   5.0M     0  5.0M   0% /run/lock
tmpfs                                                   579M     0  579M   0% /run/shm

More virt-.* tools.
virt-alignment-scan    virt-filesystems       virt-ls                virt-tar-in
virt-cat               virt-format            virt-make-fs           virt-tar-out
virt-clone             virt-host-validate     virt-pki-validate      virt-viewer
virt-convert           virt-image             virt-rescue            virt-win-reg
virt-copy-in           virt-inspector         virt-resize            virt-xml-validate
virt-copy-out          virt-install           virt-sparsify          
virt-df                virt-list-filesystems  virt-sysprep           
virt-edit              virt-list-partitions   virt-tar               

The system used.
# cat /etc/debian_version /etc/issue
Debian GNU/Linux 7 \n \l

libguestfs basics