mbrfs

A FUSE-filesystem provides the partitions from a disk device or image.

Motivation

When creating images that hold a filesystem, I always needed to use root to create a loopback device. From the loopback device I could access the different partitions of that image. I did this in an automated build process and didn't like that it needed root. FUSE allows users to mount filesystems and with mbrfs you can get the functionality of dividing devices into partitions, like loopback devices have.

Compiling

$ make

Usage

mbrfs DEVICE MOUNTPOINT [FUSE OPTIONS...]

• DEVICE is the block device or image that has a MBR partition table with multiple partitions
• MOUNTPOINT is a directory where the partitions will be located.

To unmount mbrfs use fusermount -u MOUNTPOINT.

Example

Say you want to create an image with two FAT partitions. We can do the following:

First create a file of 100MB:

$ fallocate --length 100M test.img

Now create a partition table on the image using cfdisk. This will allow you to interactively create the 2 partitions:

$ cfdisk test.img

Next, we use mbrfs to be able to access those partitions:

$ mkdir test
$ mbrfs test.img test

mbrfs will have created the following files:

test/1
test/2

We can format those partitions using mkfs:

$ mkfs.vfat test/1
$ mkfs.vfat test/2

Lastly we unmount mbrfs:

$ fusermount -u test

If you now write test.img to an USB drive it'll show up as two FAT partitions.