Find linux kernel version of a router firmware from the filesystem

Question

I've downloaded the file DAP2690-firmware-v101-rc019.bin (link) which is a firmware update to some D-Link router.

I've extracted it using binwalk -e DAP2690-firmware-v101-rc019.bin (Binwalk v1.2b) and now I have the root filesystem in the folder squashfs-root.

I'd like to know the linux kernel version of this firmware only from the extracted files (preferably only from the folder squashfs-root).

How can I do this?

Answer 1

I would go and check the modules that were compiled on the filesystem. Every module has a vermagic number, which must be equal to the kernel vermagic in order for insmod to load the module.

Here is a link describing exactly how to extract it. It also shows how to use strings in order to look for the kernel version.