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# Linux: Mounting a disk image using the loop device

This section was contributed by Volker Ruppert. It describes how to access a floppy or hard disk image within Linux using the loop device. Why would you want to do this? Let's say you have made a small Linux disk image for Bochs, and you want to install some more software on it. You have already downloaded the software onto your real system, so now you want to transfer it to the Bochs disk image. A fast way to transfer the files is to mount the disk image using the loop device.

Here is what Volker writes:

    Today I have made some tests with the loop device, because I want to exchange
    files with the bochs disk images.  This is what I found out:

    1.  Using Floppy images is easy, because there is no partition table:

        losetup /dev/loop0 /usr/local/bochs/dlxlinux/floppya.img

        Now you can use the image like a real floppy:

        - format           : mkfs.minix /dev/loop0
        - filesystem check : fsck.minix /dev/loop0
        - mount            : mount /dev/loop0 -o loop /mnt/floppy

        Before you want to restart bochs you must do this:

        losetup -d /dev/loop0

        Don't forget to umount before.

    2.  If you want access to a hard disk image, you have to calculate the size of
        the first cylinder. This value is the offset argument for losetup.

        offset = bytes per sector * sectors per cylinder

        The command for dlxlinux image looks like this:

        losetup /dev/loop0 /usr/local/bochs/dlxlinux/hd10meg.img -o 8704

        For images created by bximage you must use the value 32256.

    3.  The hard disk image access doesn't work if the image contains more than
        one partition.

    4.  I have made this tests with linux and I don't know how
        this could be done with other operating systems.

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