Awesome
Runlinux
cd into a Linux kernel source tree, run one command, and get a running QEMU VM with BusyBox.
This is better: https://github.com/cirosantilli/linux-kernel-module-cheat
Based on: https://github.com/ivandavidov/minimal Merge back declined at: https://github.com/ivandavidov/minimal/issues/20
Tested in Ubuntu 14.04 AMD64, QEMU 2.0.0.
Install
sudo apt-get install git qemu
sudo apt-get build-dep busybox linux-image-$(uname -r)
mkdir -p ~/bin
cd ~/bin
git clone --recursive https://github.com/cirosantilli/runlinux
echo 'PATH="$PATH:'$(pwd)'/runlinux"' >> ~/.bashrc
. ~/.bashrc
Examples
git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
cd linux
git checkout v4.2
runlinux
It takes a while the first time because things have to be built, but later runs will be faster.
Then hack the kernel source to your liking, and run:
runlinux
again to try it out.
Out-of-tree build with custom configuration:
export KBUILD_OUTPUT="$(pwd)/../build"
make menuconfig
runlinux
If an existing configuration is not found at KBUILD_OUTPUT
, make defconfig
is used. If found, it is used and left untouched.
Pass extra options to QEMU:
runlinux -- -bios ~/path/to/OVMF.fd
This for example uses the OVMF UEFI X64 r15214 instead of the default BIOS.
Run on real hardware
Generate a main.img
file in your build directory:
runlinux -i
Insert an USB and determine its device (/dev/sdX
):
sudo lsblk
sudo fdisk -l
Burn the image to the USB:
sudo dd if=main.img of=/dev/sdX
Then:
- insert the USB in a computer
- during boot, hit some special hardware dependant key, usually F12, Esc
- choose to boot from the USB
You can also ensure that the image works fine with:
qemu-system-x86_64 -enable-kvm -hda main.img
Tested on: ThinkPad T400.
Options
Custom initrd
n
If you just want to run your own root filesystem and ignore BusyBox completely, use:
runlinux -n /path/to/my/directory/
runlinux -n /path/to/my/init
If you pass it:
-
a directory, the directory will be packed into a filesystem.
The first thing that Linux runs is the
/init
executable of that directory. You usually want that to be an executable without dependencies that never exits. -
a file, it will be renamed to
init
and put at the root of the packed filesystem.
See this SO answer for more details on how to create your own simple initrd
.
g
TODO this is currently broken: https://sourceware.org/bugzilla/show_bug.cgi?id=13984 but I've since found the workaround and just need to stop being lazy and implement it: http://stackoverflow.com/questions/11408041/how-to-debug-the-linux-kernel-with-gdb-and-qemu/33203642#33203642
Debug the kernel on GDB:
../runlinux/runlinux -g
This will set the CONFIG_DEBUG_INFO
configuration and rebuild the kernel if necessary.
It runs QEMU on the background of the current shell, and opens GDB there.
You are now ready to debug, e.g.:
# Has to be hardware breakpoint. TODO why https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/901944/comments/12
hbreak start_kernel
list
continue