Let's test dracut's --mount command line option.
+++ /dev/null
-/dev/disk/by-id/scsi-0QEMU_QEMU_HARDDISK_root /usr btrfs subvol=usr,ro 0 0
# Create what will eventually be our root filesystem onto an overlay
"$DRACUT" -N --keep --tmpdir "$TESTDIR" \
--add-confdir test-root \
- -i ./fstab /etc/fstab \
+ --mount "/dev/disk/by-id/scsi-0QEMU_QEMU_HARDDISK_root /usr btrfs subvol=usr,ro" \
-f "$TESTDIR"/initramfs.root
mkdir -p "$TESTDIR"/overlay/source && mv "$TESTDIR"/dracut.*/initramfs/* "$TESTDIR"/overlay/source && rm -rf "$TESTDIR"/dracut.*