I downloaded an raw SD card image that has two partitions.
It caused some file system errors when I tried to dd it directly into an SD card. I am not sure if the card is defective or the image.
Is there a way to examine this image without writing it to a physical card? Like trying to mount the partitions separately or checking the tables?
You can use kpartx or partx to create loop devices for the partitions on the image, and then mount them. So either:
$ sudo kpartx -v -a file.iso
add map loop0p1 (253:17): 0 8382464 linear 7:1 2048
$ mount /dev/mapper/loop0p1 ./mnt_point
... do something with the partition ...
$ umount ./mnt_point
$ kpartx -d -v file.iso
del devmap : loop0p1
loop deleted : /dev/loop0
or:
$ sudo partx -a -v file.iso
partition: none, disk: file.iso, lower: 0, upper: 0
Trying to use '/dev/loop0' for the loop device
/dev/loop0: partition table type 'dos' detected
range recount: max partno=1, lower=0, upper=0
/dev/loop0: partition #1 added
$ mount /dev/loop0p1 ./mnt_point
... do something with the partition ...
$ umount /dev/loop0p1 ./mnt_point
$ sudo partx -d -v /dev/loop0
partition: none, disk: /dev/loop0, lower: 0, upper: 0
/dev/loop0: partition #1 removed
See also How can I mount a disk image?
losetup -Pf in util-linux >= 2.21 (Ubuntu 16.04)
sudo losetup -Pf disk.img
sudo mkdir /mnt/loop0p1
sudo mount /dev/loop0p1 /mnt/loop0p1
See the losetup(8) man page and also https://askubuntu.com/questions/69363/mount-single-partition-from-image-of-entire-disk-device/673257#673257
losetup -P automation
Here are functions to automate if further. Usage:
$ los my.img
/dev/loop0
/mnt/loop0p1
/mnt/loop0p2
$ ls /mnt/loop0p1
/whatever
/files
/youhave
/there
$ sudo losetup -l
NAME SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE DIO
/dev/loop1 0 0 0 0 /full/path/to/my.img
$ # Cleanup.
$ losd 0
$ ls /mnt/loop0p1
$ ls /dev | grep loop0
loop0
Source:
los() (
img="$1"
dev="$(sudo losetup --show -f -P "$img")"
echo "$dev"
for part in "$dev"?*; do
if [ "$part" = "${dev}p*" ]; then
part="${dev}"
fi
dst="/mnt/$(basename "$part")"
echo "$dst"
sudo mkdir -p "$dst"
sudo mount "$part" "$dst"
done
)
losd() (
dev="/dev/loop$1"
for part in "$dev"?*; do
if [ "$part" = "${dev}p*" ]; then
part="${dev}"
fi
dst="/mnt/$(basename "$part")"
sudo umount "$dst"
done
sudo losetup -d "$dev"
)
The answer by @Catskul and @Cristian Ciupitu is perfectly fine, but it misses the loop unmount command. So if you have to do a second image, you will end up with using loop1, loop2 etc.
you can check which loop devices are connected to which images by calling losetup:
pk:~# partx -v -a /home/pkolmann/img/Test.img
partition: none, disk: /home/pkolmann/img/Test.img, lower: 0, upper: 0
Trying to use '/dev/loop1' for the loop device
/dev/loop1: partition table type 'dos' detected
range recount: max partno=2, lower=0, upper=0
/dev/loop1: partition #1 added
/dev/loop1: partition #2 added
pk:~# losetup
NAME SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE DIO LOG-SEC
/dev/loop1 0 0 0 0 /home/pkolmann/img/Test.img 0 512
/dev/loop0 0 0 0 0 /home/pkolmann/img/Test.img 0 512
after unmounting the partitions with
pk:~# partx -v -d /dev/loop0
partition: none, disk: /dev/loop0, lower: 0, upper: 0
/dev/loop0: partition #1 removed
/dev/loop0: partition #2 removed
pk:~# partx -v -d /dev/loop1
partition: none, disk: /dev/loop1, lower: 0, upper: 0
/dev/loop1: partition #1 removed
/dev/loop1: partition #2 removed
the loop devices are still used:
pk:~# losetup
NAME SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE DIO LOG-SEC
/dev/loop1 0 0 0 0 /home/pkolmann/img/Test.img 0 512
/dev/loop0 0 0 0 0 /home/pkolmann/img/Test.img 0 512
These need to be removed extra:
wspk:~# losetup -d /dev/loop0
wspk:~# losetup -d /dev/loop1
wspk:~# losetup
This answer on ServerFault suggests:
use losetup to get a /dev/loop? device, then use kpartx on it to create dev mappings for the partitions in the image file.
You could try:
mount -t type -o loop ./image /mnt
where "type" = fs type and "image" is the name of your downloaded file
