XS Blueprints:Datastore Simple Backup and Restore

Summary

At a school that has an XS in place, the Datastore Simple Backup (aka ds-backup) provides an automatic and invisible backup of the documents present in the Journal of each XO. This can be used for recovery of old documents if they have been deleted or overwritten and when the laptop is replaced or reflashed.

The storage of documents in the XS is also useful for other uses, such as a simple publishing mechanism.

A strong DS-Backup facility and good availability of the XS allows users to delete large documents to have space on their XOs, knowing that the XS will hold their docs.

Scenarios

• Jim has deleted or changed a TurteArt activity he did last month, and now he wants it back to use it as a starting point for a new activity.
• Jocinta's XO broke, and has been repaired and reflashed, so her documents are gone. She wants to retrieve them from the backup on the XS.

Test plans and user walkthrough

Joe - feel free to edit, expand and/or move this section to a different page as you see fit :-)

Testing the backup run

1. Start with an unregistered XO, register it with the XS - either over an Active Antenna mesh connection, or a regular AP wifi connection.
2. After registration, you need to restart the XO (this is part of the XO side of the registration process as of build 708 / joyride 2121, might not be needed in later builds).
3. Create some documents on the XO - or have them created before registration.
4. Wait until the backup run happens - it will be triggered once a day. How to recognize that it has happened?
   • On the XO, run `stat /home/sugar/.default/ds_backup-done` and look for the 'modified' time, which shows the last time it ran successfully. Check that the XO clock is set to GMT, and might be off-track. Try `TZ=America/New_York stat /home/sugar/.default/ds_backup-done` to see it in local time.
   • On the XS, a successful registration will have created a directory `/library/users/<Serial Number>` - and each successful backup run creates a new directory under `/library/users/<Serial Number>/datastore`. The directories have a datestamp, and when the backup run completes successfully, a symlink is updated to point to the latest one (called "datastore-latest").

Restore a single document with Moodle

Note: this describes a future feature.

TODOs and future work

• Automagic authentication & Moodle integration
• In order to be simple, the initial implementation does not cover a "complete restore" scenario, which requires more work
  • on the Sugar UI to trigger, display progress and manage (cancel/retry) a "complete restore"
  • on the user aliasing that needs to take place in the "replaced laptop" scenario
• We need to test, time and tune the traffic control & backoff settings.
• Must confine rsync-over-ssh with a chroot jail or a