Can't boot in to arch linux - '/sbin/init: Bad Exec Format' followed by kernel panic

Question

I dual boot Windows 7 & Arch Linux. Arch was stable for a while, but then it stopped booting into Arch, saying '/sbin/init: bad exec format'. This is followed by a kernel panic.

I'm not really sure how to fix this. Can I copy the binary off the USB stick I have that I installed Arch from? Or is it compiled when the kernel updates?

Answer 1

Yes, it looks like your /sbin/init has become corrupted. Provided the usb version of Arch you have is the same architecture, then you should be able to copy init from the usb to the main installation.

Of course it might be that more than init has broken, as it is one of the first executables run after the kernel loads, so you may have more cleaning to do.

Answer 2

You should have a fallback-image that got made when you updated your kernel or init ramdisk. Try it by selecting it from the GRUB menu (press Esc during boot if GRUB doesn't show up)

An alternative is using your USB stick to rescue the kernel. Here is a good howto (use USB-stick where it says cd) from the Archlinux forums.