ostree-initrd: Make it an initramfs, not initrd

The reasoning here is to allow initramfs generated by this recipe
to be included in FIT.

To do so w/o changing openembedded-core (it allows only cpio format) -
init script should be able to execute from a rootfs (i.e. true initramfs),
not ramdisk (initrd).
See [1] for more information on these keywords.

The gist of this change is switch from `pivot_root` to `switch_root`.
This also allows to get rid of some clutter, since `switch_root` handles
transition to new sysroot all by itself.
Again, see [1] for details on these utility/syscall.

[1] https://www.kernel.org/doc/Documentation/filesystems/ramfs-rootfs-initramfs.txt

Signed-off-by: Yevgeny Popovych <yevgenyp@pointgrab.com>

2 files changed, 9 insertions, 23 deletions

diff --git a/recipes-sota/ostree-initrd/files/init.sh b/recipes-sota/ostree-initrd/files/init.sh
index d7e0429..4818a07 100644
--- a/recipes-sota/ostree-initrd/files/init.sh
+++ b/recipes-sota/ostree-initrd/files/init.sh
@@ -41,7 +41,6 @@ do_mount_fs sysfs /sys
 do_mount_fs devtmpfs /dev
 do_mount_fs devpts /dev/pts
 do_mount_fs tmpfs /dev/shm
-do_mount_fs tmpfs /tmp
 do_mount_fs tmpfs /run
 
 # check if smack is active (and if so, mount smackfs)
@@ -63,23 +62,10 @@ mount "$ostree_sysroot" /sysroot || {
         sleep 5
         mount "$ostree_sysroot" /sysroot || bail_out "Unable to mount $ostree_sysroot as physical sysroot"
 }
-ostree-prepare-root /sysroot
-
-# move mounted devices to new root
-cd /sysroot
-for x in dev proc run; do
-        log_info "Moving /$x to new rootfs"
-        mount -o move "/$x" "$x"
-done
-
-# switch to new rootfs
-log_info "Switching to new rootfs"
-mkdir -p run/initramfs
 
-pivot_root . run/initramfs || bail_out "pivot_root failed."
-
-log_info "Launching target init"
+ostree-prepare-root /sysroot
 
-exec chroot . sh -c 'umount /run/initramfs; exec /sbin/init' \
-          <dev/console >dev/console 2>&1
+log_info "Switching to rootfs"
+exec switch_root /sysroot /sbin/init
 
+bail_out "Failed to switch_root to $ostree_sysroot"
diff --git a/recipes-sota/ostree-initrd/ostree-initrd.bb b/recipes-sota/ostree-initrd/ostree-initrd.bb
index 6046c81..26525c8 100644
--- a/recipes-sota/ostree-initrd/ostree-initrd.bb
+++ b/recipes-sota/ostree-initrd/ostree-initrd.bb
@@ -1,20 +1,20 @@
-SUMMARY = "Extremely basic live image init script"
+SUMMARY = "Initramfs for booting into libostree managed system"
 LICENSE = "MIT"
 LIC_FILES_CHKSUM = "file://${COREBASE}/meta/COPYING.MIT;md5=3da9cfbcb788c80a0384361b4de20420"
+
 SRC_URI = "file://init.sh"
 
 S = "${WORKDIR}"
 
-PV = "3"
+PV = "4"
 
 do_install() {
         install -dm 0755 ${D}/etc
         touch ${D}/etc/initrd-release
         install -dm 0755 ${D}/dev
-        install -dm 0755 ${D}/sbin
-        install -m 0755 ${WORKDIR}/init.sh ${D}/sbin/init
+        install -m 0755 ${WORKDIR}/init.sh ${D}/init
 }
 
 inherit allarch
 
-FILES_${PN} += " /dev /etc/initrd-release /sbin/init "
+FILES_${PN} += " /dev /etc/initrd-release /init "