A base system that boots using SharpInit into a shell and little else.
After initializing an auxiliary partition using initenv, populate vars.sh with information that pertains to your setup, and run generate-symlinks.sh (once) and push-to-aux.sh (whenever, to sync up the contents of target-root and $SHARPINIT_PATH with the auxiliary partition). The result should be a bootable system that drops you into a shell. The root account is root:root, and the user account is user:test.