CODEWITHSUNDEEP
linux-kernelembedded-linux
waffleman
waffleman

Reputation: 4339

Getting uname information from a compressed kernel image

Is there a good way to extract the same information that uname does from a compressed kernel image? I want this to be able to check the dog tags of kernel sitting in dormant mtd's on an Embedded Linux system and compare it to the currently running kernel.

Upvotes: 9

Views: 7834

Answers (3)

Hridesh MG
Hridesh MG

Reputation: 21

You can actually do this very easily using the file command

file /boot/vmlinuz-linux

Output:

/boot/vmlinuz-linux: Linux kernel x86 boot executable bzImage, version 6.10.3-arch1-2 (linux@archlinux) #1 SMP PREEMPT_DYNAMIC Tue, 06 Aug 2024 07:21:19 +0000, RO-rootFS, swap_dev 0XC, Normal VGA

If you'd like to get just the kernel version, use cut:

file /boot/vmlinuz-hridesh | cut -f 9 -d ' '

Upvotes: 0

Z.T.
Z.T.

Reputation: 949

For Linux image compressed with gzip, use this:

dd if=arch/arm/boot/zImage bs=1 skip=$(LC_ALL=C grep -a -b -o $'\x1f\x8b\x08\x00\x00\x00\x00\x00' arch/arm/boot/zImage | head -n 1 | cut -d ':' -f 1) | zcat | grep -a 'Linux version'

For Linux image compressed with xz, use this:

dd if=arch/arm/boot/zImage bs=1 skip=$(LC_ALL=C grep -a -b -o $'\xFD\x37\x7A\x58\x5A\x00' arch/arm/boot/zImage | head -n 1 | cut -d ':' -f 1) | xzcat | grep -a 'Linux version'

Because the image file contains data after the end of the compressed stream, you'll get an error you can ignore.

The string constant appears to be part of the frozen userspace visible kernel API:

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=init/version.c;hb=HEAD#l40

Upvotes: 15

Raúl Salinas-Monteagudo
Raúl Salinas-Monteagudo

Reputation: 3660

$ mkimage -l uImage

Image Name:   Linux-2.6.39
Created:      Wed Jun  6 13:49:58 2012
Image Type:   ARM Linux Kernel Image (uncompressed)
Data Size:    3091036 Bytes = 3018.59 kB = 2.95 MB
Load Address: 80008000
Entry Point:  80008000

Upvotes: 4

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