Comment 25 for bug 1890803

@xnox 's patch does not actually fix the issue; it just prevents overlayroot from raising an error; the system is still left with a read-only rootfs and nothing to tell the rootfs' init to remount / as rw.

> Somehow overlayroot has to convey to systemd that / needs to be mounted
read-write.

overlayroot current communicates this via writing fstab with updated mounts; at minimum, the rootfs; possibly more depending on what's in the rootfs's /etc/fstab.

Then systemd-fstab-generator(8) runs and is what creates the .mount units which then mount/remount filesystems per fstab. It will read from an /etc/fstab (or kernel parameters) and it does not understand overlayroot kernel parameters, so without an fstab entry to indicate which path/device is root and that it should be mounted rw, it stays in read-only.