Quick guide on how to create a lightweight systemd container for Arch Linux, using systemd-nspawn and pacstrap, in under 1 minute!
pacman -S arch-install-scripts mkdir /srv/subarch pacstrap -c -d /srv/subarch base systemd-nspawn -bD /srv/subarch
You also need to add "audit=0" to the kernel parameters, as compatibility with the kernel auditing subsystem is currently broken. For more details, see the systemd-nspawn's man page.
And that's it! Log in as "root" with no password.
You can remove the kernel to save space within the container. DO NOT RUN THIS ON THE HOST!
pacman -Rsn linux
Once you're done with the container just shut it down with
systemctl stop machine-subarch.scope. (replace "subarch" with the name of yout container)