4

I want to partition a raw disk image with the following commands:

#creating the blank image
$ dd if=/dev/zero of=example.img bs=1M count=50

#write the partition table
$ parted example.img mktable msdos

#creating partition but not the file system
#creating fat32 primary partition 1 to 15 MB
$ parted example.img mkpart p fat32 1 15
#creating ext3 primary partition 16 to end
$ parted example.img mkpart p ext3 16 -0

These commands don't create a file system. How could I do that? I am trying the mkfs command in parted but it is showing no command found. How could I create file system externally?

7

Use the command kpartx to create a loopback device that can then be formatted.

kpartx -a /path/to/imagefile.img  # Presents partitions from the image file
mkfs.vfat /dev/mapper/loop0p1   # Format partition 1
mkfs.ext3 /dev/mapper/loop0p2   # Format partition 2
kpartx -d /path/to/imagefile.img  # Unmaps the partitions from the image file

Related kpartx examples here

3

Recent versions of losetup gained -P option. Quote from man 8 losetup:

-P, --partscan
          Force the kernel to scan the partition table on a newly created loop device.

Doing losetup -f my_partitioned.img not only creates /dev/loop0, but also partition devices:

$ ls -l /dev/loop0*
brw-rw---- 1 root disk   7, 0 Oct  5 18:43 /dev/loop0
brw-rw---- 1 root disk 259, 0 Oct  5 18:43 /dev/loop0p1
brw-rw---- 1 root disk 259, 1 Oct  5 18:43 /dev/loop0p2
1

With the usual mkfs commands, such as mkfs.ext4. You will need to use losetup to associate a loopback device with the file though in order to have somewhere to point mkfs to. You also may need to use partprobe to recognize the partitions on the loop device.

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