Even when running with the root filesystem read-only, running fsck (at least on ext4) updates the "Last Write Time" in the metadata of the filesystem. This results in the checksum not matching when attempting to do a binary-delta update.

For now, on Ubuntu specifically, I have worked around this by adding the following kernel command line parameters:

This doesn't seem like a good long-term solution though since it will skip the automatic fsck even on the writable partitions. Additionally, I can foresee other systems behaving differently but having similar issues.

Ideally we would find a way to account for this in the binary-delta code. The only difference seems to be exactly the "Last Write Time":

Suggested way to fix:

• Add a new variable READ_ONLY_ROOTFS to mender-convert, defaulting to 0, and if 1, trigger the check

• If check is triggered, check that -O ^64bit -O ^has_journal is passed to mkfs.ext4