Mounting qcow2 drive

The qcow2 (or QEMU copy-on-write) is a virtual disk image format primarly used by QEMU for guest systems. In many circustances, such as reseting passwords, editting or recovering files etc., mouting a qcow2 disk images without running a guest system is required. This can be acheived by Network Block Device module (or nbd) on host linux system. At first, we need to define maximum number of partitions expected for the qcow2 disk and then the disk can be mouted with following commands:

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modprobe nbd max_part=8   # maximum partition = 8
qemu-nbd --connect=/dev/nbd0 /var/lib/vz/images/100/vm-100-disk-1.qcow2
fdisk /dev/nbd0 -l  # For finding virtual machine partitions
mount /dev/nbd0p1 /mnt/somepoint/    #mount partition on /mnt/somepoint

The disk image can be unmounted with following commands:

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umount /mnt/somepoint/
qemu-nbd --disconnect /dev/nbd0
rmmod nbd

Depending upon system configuration, you may need to run either one or all commands as root user.