Using kpartx to Manage Partition Mappings (with examples)

Add partition mappings:

kpartx -a whole_disk.img

Motivation: Adding partition mappings allows us to access individual partitions within a disk image file without the need for manual calculations or mounting the entire disk image.

Explanation: The -a option instructs kpartx to add partition mappings for the specified disk image file. In this case, whole_disk.img is the disk image file for which we want to create partition mappings.

Example Output: Suppose we have a whole_disk.img file that contains partitions /dev/loop0p1, /dev/loop0p2, and /dev/loop0p3. After running the kpartx -a whole_disk.img command, kpartx will create device mappings for each partition, making them accessible as /dev/mapper/loop0p1, /dev/mapper/loop0p2, and /dev/mapper/loop0p3.

Delete partition mappings:

kpartx -d whole_disk.img

Motivation: Deleting partition mappings is useful when we no longer need to access individual partitions within a disk image file. This allows us to clean up and avoid potential conflicts with other disk operations.

Explanation: The -d option tells kpartx to delete partition mappings associated with the specified disk image file. In this example, we are deleting partition mappings for whole_disk.img.

Example Output: If we have previously added partition mappings for whole_disk.img using the kpartx -a command, running kpartx -d whole_disk.img will remove the device mappings associated with the partitions. The output will not contain any information if the command is successful.

List partition mappings:

kpartx -l whole_disk.img

Motivation: Listing partition mappings helps us to identify and confirm which partitions are associated with a particular disk image file. This is especially useful when working with complex disk setups or troubleshooting partition-related issues.

Explanation: The -l option tells kpartx to list partition mappings for the specified disk image file. Here, whole_disk.img is the disk image file for which we want to display the partition mappings.

Example Output: Suppose we have previously added partition mappings for whole_disk.img. Running kpartx -l whole_disk.img will display a table of partition mappings associated with the disk image file. The output may look something like the following:

loop0p1 : 0 123456 /dev/loop0 2048
loop0p2 : 0 123456 /dev/loop0 123450368
loop0p3 : 0 123456 /dev/loop0 246900736

The output will show the partition name (loop0p1, loop0p2, etc.), the starting sector, the sector count, the device path (/dev/loop0 in this case), and the offset in sectors.