Project Notebook:
Linux Athena Disconnected Operation

by Bill Cattey

Last Modified: $Date: 2005/01/25 22:06:41 $

Latest News

2 October 2003: Massive update to show we've delivered most of the project.

Overview

This notebook documents the ongoing efforts to make Linux Athena operate more gracefully when the host computer is sometimes disconnected from the network. Laptop computing creates a changing connectivity situation. The network connection may be hard-wired, wireless, or nonexistant. Because of old assumptions in the design of Linux and the Athena integration of OS, software, and services, extra work is needed to provide a user experience without pauses, crashes, or other unpleasant surprises.

Because operating systems, software, services, and user expectations are constantly evolving, it is expected that the developments and user experience around Disconnected Operation will also evolve over time. An attempt has been made to frame the Disconnected Operation into easily understood chunks, mini-projects, so that the scope of the effort is manageable. The purpose of this notebook is to describe the current user-visible state of Disconnected Operation, to preserve the historical record of what mini-projects have been completed, and to give status of current mini-project work. Possible future mini-projects along with some estimate of their costs and benefits are also described.

Although there may be other relevant Athena work on other platforms, such as Windows and Macintosh, this notebook is focused on work under the Athena Linux platform.

Success Criteria

For each of the use cases below, "Working" is defined as reasonably graceful operation without system hangups or crashes, ideally without complex or obscure methods of operation. The user interface should be as simple and graceful as possible.

Status	Use Case	Notes
Working	OS Installation and configuration for disconnectable operation	Future: Automatic detection of need to configure disconnectable. GUI for system administration.
Working	Adding a local account for operation without AFS home directory	Future: GUI for system admistration
Working	Getting logged into the system.	Working when local account is present
Caveat	Resuming operation after suspend and/or hibernate.	This is largely a matter of whether there is support in the currently shipping version of Red Hat Linux for this functionality on the particular laptop hardware in use. See also caveats below regarding detecting change of network state.
Caveat	Starting operation with no network.	TODO: Improve AFS timeout behavior causing slow off-network boots.
Working	Activating and Deactivating the network	Future: GUI to enable the user to activate and deactivate the network.
Pending	Switching between wired and wireless network	TODO: GUI to enable the user to switch between wired and wireless network is under development. (Existing solutions are too baroque.)
Working	Interoperating with AFS home directory	You create a local account, and use existing tools explicitly to copy files between local and AFS directories. `rsync` is one such tool.
Working	Interoperating with Zephyr	Caveat: if you use `zctl sub/unsub` for temporary subscriptions, those changes, normally lost at logout will be lost when you disconnect and then reconnect to the network. Future: Dealing better under the covers with how timeouts for zwgc affect operation of .startup.X.
Caveat	Interoperating with Athena software in AFS Lockers	If there are programs running with binaries in AFS and the system is disconnected from the net, the program dies without warning, and often not immediately. There is a framework for bringing locker software local. Future: More software using local locker framework. Supported installers to install important locker software locally.
Working	Performing Athena OS update	Caveat: In order for auto-update to work, the host must be left, for an extended period powered up, connected to the net, with nobody logged in. This is an extremely uncommon mode of use. So we recommend users perform updates explicitly. Future: Do better at announcing the availability of updates when the user will notice and choose to take proper action. GUI for system admistration

White Paper

An inventory of user expectations, the initial state of Athena Linux Disconnected Operation, the difference between the two, and a pragmatic, multi-phased approach to reconciling the differences is documented in a White Paper.

Current Efforts

The White paper provided an inventory of issues, and work areas. It recommended a set of initial features in each of the work areas. The implementation status of those features is in FEATURES.

Underlying the features is an architecture for managing events that occur as a system switches between various states such as connected and disconnected or enters the state of receiving a new IP address. That framework is documented in framework.txt.

A framework for bringing locker software local has been conceived and implemented. It is documented in lockers.txt.

Issues

Resolved: Running Xlogin inappropriately pauses while resolving some unknown host address.
Pending: Current Athena needs to be more careful to always set hwclock because it is used on resume. If system and hwclock are too far out of sync, mouse drag fails on a resume after a suspend.

Change Log

2 October 2003: Massive update to show we've delivered most of the project.

14 November 2002: Added some issues. Added critical success factors. Added rudimentary timeline.

6 November 2002: Added pointers to relevant documentation: FEATURES, framework.txt, lockers.txt.

5 November 2002: Initial creation of this Notebook.

Last updated: $Date: 2005/01/25 22:06:41 $ by $Author: ghudson $.
Comments to Athena Comments

Project Notebook:Linux Athena Disconnected Operation

by Bill Cattey

Project Notebook:
Linux Athena Disconnected Operation