I Know this post is old, but I have just encountered this problem, and I didn't find a good answer elsewhere, so here is my answer, hoping that this helps someone in the future.
In my case, when I was at the stage
ERROR: Root device mounted successfully, but /sbin/init does not exist.
Bailing out, you are on your own now. Good luck.
sh: can't access tty: job control turned off
[rootfs /]# _
There actually was a
/sbin/init, which was nothing but a symbolic link to
Here is what happened.
In Archlinux, the directory
/sbin is a symbolic link to /usr/sbin. And, as say other people,
/usr/sbin/init symlinks to
/lib/systemd/systemd. But, in my case, I found out that the
/usr directory was not mounted.
You basically need to mount the partition
/usr as explained on this ArchWiki page. You may also want to verify
/etc/fstab, especially if you use one generated by