User-mode Linux

UML

Good lightweight virtualization.

TODO check Major downside: the root filesystem has to have user mode features?

Good tutorial: https://web.archive.org/web/20110311190407/http://kuparinen.org/martti/comp/ubuntu/en/uml.html

https://en.wikipedia.org/wiki/User-mode_Linux

Run Linux as a user process inside a Linux.

Before was a fork, later merged in 2.6 as a new architecture under arch/um.

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/virtual/uml/UserModeLinux-HOWTO.txt?id=refs/tags/v4.0 TODO: does it need the patch mentioned there or not?

http://askubuntu.com/questions/33958/how-to-correctly-start-a-ubuntu-user-mode-linux-from-the-command-line

Not very active apparently: https://askubuntu.com/questions/796512/user-mode-linux-on-xenial

Example

https://unix.stackexchange.com/questions/73203/how-to-create-rootfs-for-user-mode-linux-on-fedora-18 Almost works on a Buildroot image with UML on host, just needed to patch inittab with:

Quickstart tested on Kernel 4.0 source on a 3.13 host: TODO get working.

make mrproper
make defconfig ARCH=um
make ARCH=um
./kernel32-2.6.37.5 ubda=Ubuntu-MaverickMeerkat-i386-root_fs mem=256m root=/dev/ubda init=/bin/bash