File system type using dd and hexdump

[dk_zero-cool]

Hi.
I have been searching google for hours now, trying to find out how to check a partition for ext2(3,4) using dd and hexdump. Maybe I'm not using the correct search criteria, because I can't find anything. I have also been looking at the hexdump of all ext file systems, but I can't figure out which part describes the type of ext or that it is an ext file system in the first place.

I know you can use tools like file,blkid and such, but that is not an option for me, since these are not available where I need this.

[Krendoshazin]

Do you have access to the 'fsck' command? It's an essential tool that should come with any system, and it can tell you the filesystem type even if you don't have access to the device.

krendoshazin@null:~> cat /dev/root
cat: /dev/root: Permission denied
krendoshazin@null:~> /sbin/fsck -N /dev/root
fsck from util-linux 2.19
[/sbin/fsck.ext3 (1) -- /] fsck.ext3 /dev/xvda

-bash-4.0$ /sbin/fsck -N /dev/sdb1
fsck from util-linux-ng 2.16
[/sbin/fsck.jfs (1) -- /] fsck.jfs /dev/sdb1

[dk_zero-cool]

It's to be used on Android devices. fsck exists, but it shows fsck.auto an complains about /etc/fstab. I need something more independent that can do this check and exists on most devices by default and also can do this on unmounted partitions, hence dd and hexdump.

[drl]

Hi.

It's not clear (to me) that the Android has enough similarity to allow identification of filesystems:

Android's kernel is a fork of the Linux kernel and has further architecture changes by Google outside the typical Linux kernel development cycle.[64] Android does not have a native X Window System nor does it support the full set of standard GNU libraries, and this makes it difficult to port existing Linux applications or libraries to Android.[65]

-- Android (operating system) - Wikipedia, the free encyclopedia

However, if there is similarity, then the MBR will contain some information:
Master boot record - Wikipedia, the free encyclopedia
see offset 0x04, and then the partition types at reference [7], viz. Partition types: List of partition identifiers for PCs

Good luck ... cheers, drl

[dk_zero-cool]

Thx I will play with that.

For now I compiled a custom busybox with blkid file system support. Seams to work just fine identifying different ext and vfat file systems.