infra-docs-fpo/modules/sysadmin_guide/pages/virt-image.adoc

= Fedora Infrastructure Kpartx Notes

== How to mount virtual partitions

There can be multiple reasons you need to work with the contents of a
virtual machine without that machine running.

[arabic]
. You have decommisioned the system and found you need to get something
  that was not backed up.
. The system is for some reason unbootable and you need to change some
  file to make it work.
. Forensics work of some sort.

In the case of 1 and 2 the following commands and tools are invaluable.
In the case of 3, you should work with the Fedora Security Team and
follow their instructions completely.

== Steps to Work With Virtual System

[arabic]
. Find out what physical server the virtual machine image is on.
+
____
[upperalpha]
.. Log into _batcave01.rdu3.fedoraproject.org_
.. search for the hostname in the file `/var/log/virthost-lists.out`:
+
....
$ grep proxy01.phx2.fedoraproject.org /var/log/virthost-lists.out
virthost05.phx2.fedoraproject.org:proxy01.phx2.fedoraproject.org:running:1
....
.. If the image does not show up in the list then most likely it is an
image which has been decommissioned. You will need to search the virtual
hosts more directly:
+
....
# for i in `awk -F: '{print $1}' /var/log/virthost-lists.out |
        sort -u`; do
            ansible $i -m shell -a 'lvs | grep proxy01.phx2'
        done
....
____

. Log into the virtual server and make sure the image is shutdown. Even
in cases where the system is not working correctly it may have still
have a running qemu on the physical server. It is best to confirm that
the box is dead.
+
....
# virsh destroy <hostname>
....
. We will be using the kpartx command to make the guest image ready for
mounting.
+
....
# lvs | grep <hostname>
# kpartx -l /dev/mapper/<volume>-<hostname>
# kpartx -a /dev/mapper/<volume>-<hostname>
# vgscan
# vgchange -ay /dev/mapper/<new volume-name>
# mount /dev/mapper/<partition we want> /mnt
....
. Edit the files as needed.
. Tear down the tree.
+
....
# umount /mnt
# vgchange -an <volume-name>
# vgscan
# kpartx -d /dev/mapper/<volume>-<hostname>
....