Lark: Gentoo in the Windows Subsystem for Linux


Microsoft’s recent introduction of the Subsystem for Linux (awkwardly called ‘Bash on Ubuntu on Windows’) had me intrigued from the day of its announcement. Though it’s a transparent attempt to keep developers from leaving their Windows environments behind in a world now focused on development for UNIX-like platforms, and though I’m not particularly interested in supporting such an agenda per-se, I find the notion of a new NT kernel subsystem capable of handling Linux syscalls exotic, and so I had to subject it to some stress testing.

Test 1: Gentoo Stage3

The first test was simply to see whether or not I could unpack a Gentoo stage3 tarball and replace the Ubuntu rootfs with it. This took the following form:

  1. Download the latest stage3-nomultilib tarball within the default Ubuntu environment. I used wget to do this, and I was in root’s home directory after a ‘sudo su -’ so that proper filesystem attributes and permissions would be applied to the extracted files when I performed the next step:
  2. Unpack it into a directory I named rootfs_gentoo
  3. Exit all open ‘Bash on Ubuntu on Windows’ shells
  4. Using Windows Explorer, cut the rootfs_gentoo folder (as mentioned in 1. this was in root’s home directory - in the Windows environment, this is located at \Users\\AppData\Local\lxss\root) and paste it in \Users\\AppData\Local\lxss\
  5. Rename the existing ‘rootfs’ containing the Ubuntu install downloaded by Microsoft
  6. Rename my new ‘rootfs_gentoo’ folder to ‘rootfs’

I also had to make sure the Linux subsystem opened a shell as root, as this new Gentoo environment had no users created just yet. This was accomplished with:

C:\ > lxrun /setdefaultuser root

In an elevated command prompt window. So far so good. I created a user for myself, added it to wheel, set a password, and ran the same command above to set the Linux environment to use this new user. I also needed to manually update /etc/resolv.conf in order to perform DNS lookups.

Test 2: Rebuild @world

I wanted to quickly strain WSL’s capabilities. I made sure /etc/portage/make.conf was configured so that ~amd64 packages would be installed, and then:

# emerge gcc -u 

# gcc-config x86\_64-pc-linux-gnu-6.3.0

# . /etc/profile

# emerge world -eav --keep-going

Impressively, around 200 packages were rebuilt from source using the latest GCC (elucidation for those unfamiliar with Gentoo) without an issue. Things are getting serious. In an upcoming post I’ll discuss how I built on this basis to launch Gentoo’s OpenRC init system, and use that to run services like SSHD.