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Debian on embedded devices

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Author Topic: Possible to set qemu kernel version?
stevester
Pro
Posts: 108
Post Possible to set qemu kernel version?
on: August 25, 2011, 03:19

Hey amain, been having some issues building DebWRT for the rt-n16 since the second stage install phase was moved to the development machine. Since then I have unable to ssh into the router using the current plugin whereas before I could.

One thing I did notice and could possibly be part of the problem: When in the chroot using qemu the kernel version is 2.6.38 which is a problem since the rt-n16 is using kernel version 3.0 now. Is it possible to change the kernel version for the chroot? Any tips appreciated!

amain
Administrator
Posts: 137
Post Re: Possible to set qemu kernel version?
on: August 25, 2011, 20:36

Hey Stevester. I'm not sure why it would fail. But of course there can be small differences between native second stage and doing it emulated.

It is good to be aware of one thing: qemu is able to run in to modes: system and user. If run in system mode, a kernel is required, which is booted with the appropriate rootfs. In user mode, which is the mode I use for the second stage install, is nothing like that. No kernel is booted. Using the binfmt_misc functionality, qemu-linux-user is started when executing an alien binary, much like /bin/bash would be automatically started when you would execute a script file. In user mode binary code is directly emulated and system calls are directly emulated/translated to the host kernel.

Running alien binaries becomes now truly transparent.

So, in user mode, when doing a uname -a, you will get the host's kernel version. :-)

What you can do is for now run make menuconfig and switch off second stage install with qemu. Everything will behave like it normally would. You can test if your problems are caused by the qemu or if it is something else. Second you could put the rc.firstboot back in place and boot and investigate from there.

Let me know if something is wrong with the qemu second stage.
stevester
Pro
Posts: 108
Post Re: Possible to set qemu kernel version?
on: September 5, 2011, 00:59

Hey amain, problem seems to have gone away now since I updated the plugin to a newer kernel. Potential cause may have been missing modules, upstream issues in openwrt/debian that have since been resolved or maybe even a typo of mine who knows :)

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