create_disk: Explicitly unmount partitions and fsck /boot

[cgwalters]

For reasons I don't fully understand, trying to use
tune2fs -U random /dev/disk/by-label/boot fails without
this explicit fsck step, even though the filesystem appears
cleanly unmounted.

This is for coreos/fedora-coreos-config#354
to regenerate the UUID of /boot on firstboot.

Anyways, explicitly unmounting things seems better than relying
on umount -R to sort it, and having a fsck on /boot is
cheap.

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[cgwalters]

It relates to this bit

		if (!ext2fs_has_feature_csum_seed(fs->super) &&
		    (ext2fs_has_feature_metadata_csum(fs->super) ||
		     ext2fs_has_feature_ea_inode(fs->super))) {
			check_fsck_needed(fs,
				_("Setting the UUID on this "
				  "filesystem could take some time."));
			rewrite_checksums = REWRITE_ALL;
		}

Calling into here.

which hmm...I guess the UUID is somehow entangled into the metadata checksums? That kind of rains on the parade if so...

[cgwalters]

Ah OK we probably really want

walters@toolbox ~/s/g/c/coreos-assembler> git diff
diff --git a/src/create_disk.sh b/src/create_disk.sh
index 6a2f0110..fa514094 100755
--- a/src/create_disk.sh
+++ b/src/create_disk.sh
@@ -205,9 +205,12 @@ bootargs=
 if [ "${boot_verity}" = 1 ]; then
     # Need blocks to match host page size; TODO
     # really mkfs.ext4 should know this.
-    bootargs="-b $(getconf PAGE_SIZE) -O verity"
+    bootargs="-b $(getconf PAGE_SIZE)"
+    bootopts="verity,"
+else
+    bootopts=""
 fi
-mkfs.ext4 ${bootargs} "${disk}${BOOTPN}" -L boot -U "${bootfs_uuid}"
+mkfs.ext4 ${bootargs} -O "${bootopts}"metadata_csum_seed "${disk}${BOOTPN}" -L boot -U "${bootfs_uuid}"
 if [ ${EFIPN:+x} ]; then
        mkfs.fat "${disk}${EFIPN}" -n EFI-SYSTEM
        # partition $BIOPN has no FS, its for bios grub
walters@toolbox ~/s/g/c/coreos-assembler> 

except it looks like grub2 needs patching to know about that feature flag 😢

grub2-install: error: ../grub-core/kern/fs.c:120:unknown filesystem.

[cgwalters]

OK I changed coreos/fedora-coreos-config#354 to just explicitly fsck first for now, though at some point we should patch grub.

[dustymabe]

except it looks like grub2 needs patching to know about that feature flag

related issues:

• https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1844012
• https://savannah.gnu.org/bugs/index.php?56897