​--- Title: VirtualBox - Editing .vdi slug: VirtualBox - Editing .vdi Date: 2018-04-13 Category: Virtualization Tags: VirtualBox Authors: lucanuscervus Summary: ​---

How to mount and edit .vdi files with a LVM filesystem.

How to mount a vdi disk image?

#First, install the QEMU tools
sudo apt-get install qemu-utils

#Load the nbd kernel module
sudo modprobe nbd

#Next run qemu-nbd. This will connect the vdi file to the nbd0 device.
sudo qemu-nbd -c /dev/nbd0 /path/to/file.vdi

#Then create device maps from partition tables
sudo kpartx -a /dev/nbd0

#Finally mount the partition
sudo mount /dev/mapper/nbd0p1 /mnt

#When you’re done, unmount the filesystem and shut down the qemu-nbd service.
sudo umount /mnt
sudo qemu-nbd -d /dev/nbd0

How to Mount a Logical Volume

When I tried to mount /dev/nbd0, I got the following error:

lucanuscervus@omv:~$ sudo mount /dev/mapper/nbd0p1 /mnt
mount: unknown filesystem type 'LVM2_member'

So, first I uses the command pvs to find information about the physical volumes on the computer.

lucanuscervus@omv:~$ sudo pvs
  PV                 VG      Fmt  Attr PSize  PFree
  /dev/mapper/nbd0p1 vg-root lvm2 a--  25.00g    0

Then use the lvdisplay command to list all the logical volumes.

lucanuscervus@omv:~$ sudo lvdisplay 
  --- Logical volume ---
  LV Path                /dev/vg-root/lv-root
  LV Name                lv-root
  VG Name                vg-root
  LV UUID                0vFCoR-dsbr-yJra-TBZy-dAan-FLGN-eY0Wyg
  LV Write Access        read/write
  LV Creation host, time ubuntudrone, 2016-04-09 09:23:21 +0100
  LV Status              NOT available
  LV Size                19.41 GiB
  Current LE             4968
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto

  --- Logical volume ---
  LV Path                /dev/vg-root/lv-swap
  LV Name                lv-swap
  VG Name                vg-root
  LV UUID                XMop7w-MR24-EjER-EWWd-cbE0-MEXx-EIlyaT
  LV Write Access        read/write
  LV Creation host, time ubuntudrone, 2016-04-09 09:23:46 +0100
  LV Status              NOT available
  LV Size                976.00 MiB
  Current LE             244
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto

  --- Logical volume ---
  LV Path                /dev/vg-root/lv-home
  LV Name                lv-home
  VG Name                vg-root
  LV UUID                DlguIf-pMPL-HY9l-SS1l-2gcD-9FYT-Z6U2kU
  LV Write Access        read/write
  LV Creation host, time ubuntudrone, 2016-04-09 09:23:56 +0100
  LV Status              NOT available
  LV Size                4.64 GiB
  Current LE             1187
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto

Once, I know where the root filesystem is, I made the volume group active and then I mounted root it in /mnt

lucanuscervus@omv:~$ sudo vgchange -ay vg-root
  3 logical volume(s) in volume group "vg-root" now active
lucanuscervus@omv:~$ sudo mount /dev/vg-root/lv-root /mnt

When I finish editing the file, I unmount, make the vg inactive, deactivate kpartx and stop qemu-nbd

sudo umount /mnt

#Make VG inactive. Output like  0 logical volume(s) in volume group "vg-root" now active
sudo vgchange -a n vg-root

#Deactivate kpartx
sudo kpartx -d /dev/nbd0

# Disconnect 
sudo qemu-nbd -d /dev/nbd0

Sources