These tools allow it to inspect and modify QEMU images within Linux. Internally they use qemu-nbd, the QEMU Disk Network Block Device Server. That takes a VM disk image, supported by QEMU, and exports it as a NBD device. This NBD device can be mounted and then used as any other disk. It needs no extra packages, just QEMU.
The qemu-mount scripts hide the use of NBD, they offer a similar interface as the normal mount tools. The scripts can be used as a normal user, the privileged commands are then started with sudo.
qemu-part shows the partition table of a qemu image, just use
qemu-mount has the following usage:
Usage: qemu-mount [OPTIONS] qemu_image mount_point Options: -p partition_number select, which partition to mount, default #1 -r mount read-only -t fstype set filesystem type -u set owner to current user
Without arguments it prints a list of mounted images.
The usage of qemu-umount is simple,
qemu-umount <qemu_image or mount_point>.