Updates

The most important promise first: an update never deletes the fleet database and never recreates it. All existing data is fully preserved.

How an update works

   Development             Server                    Workstations
   -----------             ------                    -----------
   Release package   --->  Updates\1.1.0\      --->  Notice at startup
                           Updates\latest.json       Run the update
                                                     Restart the program

In the update folder on the server sits the file latest.json. It states which version is current. Every workstation reads it at startup and reports when a newer version is available.

Structure of the update folder

D:\Fleet\Updates\
    latest.json                  describes the current version
    1.1.0\
        Vehistra-Update.exe      the update package itself
        release-notes.txt        what has changed
        checksums.sha256         checksums of all files
        Dokumentation\           the guides for this version
    Archive\
        1.0.0\                   the previous version

The previous version stays in the Archive folder. That is your way back.

Publishing a new version

1. Extract the release package into a new version folder.
2. Compare the checksums.
3. Point latest.json at the new version.

From the next program start the workstations report the update themselves.

What happens during the update

• Before the start the checksum of the update package is verified. The expected value comes from latest.json; if it is missing, the checksum file next to the package applies. If it does not match, or if neither exists, the update does not start. The check sits in the update service, not in the interface.

• Under “Updates” the result is shown in plain words before you click install.

• Before every database change a backup is created and verified. If the backup fails, the update stops.

• If several workstations start at the same time, a lock in the database prevents the migration from running twice.

• Migrations build on each other; nothing is deleted and nothing is recreated.

Going back to the previous version

The way back is always: install the previous program version from Archive and restore the backup from before the update – see Backup and restore.

That is why the backup before the update is not optional.

What the checksum does – and what it does not

It detects a package that was copied incompletely or altered afterwards. It does not protect against someone who may write to the update share: whoever swaps the package can change the checksum in latest.json along with it.

Two things help against that:

• an update folder that only administrators may write to,
• a code signature on the packages.