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I want to create an image of some directory tree that is writable directly to a USB drive, just like the images of many Linux distributions. For example, with openSUSE you can download an ISO image that is writable directly the USB using dd.

root@computer# dd if=openSUSE.iso of=/dev/sdb

I tried to create images using mkisofs, but when I ran the dd command above with that image didn't get a partition table, which made windows not recognize the format of the drive and Linux didn't present /dev/sdb1. I also tried to create an empty file, and then create a filesystem in that file using mkfs.vfat.

There seem to be a lot of tutorials on the web on how to write images to USB drives as well as dumping a USB drive to file, but I haven't found anything on creating an image with a partition table.

The problem I'm trying to solve with this is to distribute a pre-formatted USB stick, so there is no need for the stick to be bootable; I would also like to make this process scriptable.

6

You can use kpartx for this. Here is a way to create a complete disk image.

# create empty image
dd if=/dev/zero of=myvm.img bs=1G count=0 seek=100

# partition the image file with fdisk/gdisk or any other tool
gdisk myvm.img

# make the partitions in the image file available as individual devices
kpartx -a myvm.img

# work with the partitions
./someprogram /dev/mapper/loop0p1

# close the partitions
kpartx -d myvm.img

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