Save and Restore

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Contents

Summary

A general architecture for saving and restoring stuff from application data areas to the USB drive.

Architecture

  • A binary C-based org.webosinternals.saverestore service provides the ability to run a set of pre-installed scripts
  • The service calls the scripts with a small set of known arguments (e.g. 'info', 'save', 'restore', etc)
  • The scripts are named according to the appId of the application that owns the data
  • The scripts are stored in a location that is only accessible by installing them as root (e.g. a signed app with a post-install script)
  • The service does not allow the execution of scripts outside of that location
  • Therefore, any script that is run by the service has been installed by a means that already had root access

Features of the service

  • A method to list the current set of available scripts with info about id, name, ...
  • A method to call an individual script, or the set of all scripts, with a command method
    • save
    • restore

Implementation Decisions

  • Where to store the data
    • Choose /media/internal/saverestore

Situations To Persist Across

  • Partial Erase
  • Profile Reset (/var and /media/cryptofs are wiped, but /media/internal is retained)

Locations of Application Data

  • /var/palm/data
  • /media/internal/.app-storage
  • /var/luna/data
  • additional files in the application directory
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