How to create a multi partition SD disk image without root privileges?

Question

Is it possible to create a complete SD image in linux without having root privileges (that is, no loopback mount)? I\'m looking for a way to automate embedded system image creat

Answer 1

I'm trying to do the same thing. My first attempt used the loopback block device, but I have found work-arounds to both steps that require loopback.

Steps with loopback

Here's what I'm doing ( $1 is image file name, $2 is file size):

1. create zeroed disk image file with dd if=/dev/zero of=$1 bs=512 count=$(($2/512))
2. create partition table with parted -s $1 mklabel msdos
3. create partition with parted -s $1 "mkpart primary 0% 100%"
4. attach partition to loop sudo losetup --find $1 --offset $OFFSET_TO_PARTITION_BYTES
5. make file system with mkfs.ext4 with mkfs.ext4 -I 128 -L BOOT -b 2048 -O ^has_journal /dev/loop0 $SIZE_IN_2048_BLOCKS
6. mount /dev/loop0

The loopback is used because

• in step 4 & 5, mkfs doesn't have an offset option so losetup is used to solve that problem
• in step 6, mount allows the use of the operating systems ext4 driver

Looback workarounds

Shitty work-around for step 4 & 5:

• xmount --in dd --out vdi disk.img mnt/
• vdfuse -f mnt/disk.vdi -r ./mnt2
• ./mnt2 will now have two files: EntireDisk, and Partition1
• point mkfs.ext4 at ./mnt2/Partition1

Work-around solution to step 6:

• follow all steps for step 5 work around
• use fuseext2 to mount ./mnt2/Partition1

Caveat

Caveat: ext4 support is not advertised in their documentation, and attempts to mount come with a warning:

This is experimental code, opening rw a real file system could be
dangerous for your data. Please add "-o ro" if you want to open the file
system image in read-only mode, or "-o rw+" if you accept the risk to test
this module

Update

vdfuse should be able to mount a raw image without the help of xmount, but there is a bug which ignores the RAW option.

I tracked down and fixed the bug with a patch here:

https://bugs.launchpad.net/ubuntu/+source/virtualbox-ose/+bug/1019075