Athena Layering Requirements
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Athena Layering Requirements
This document is presented as the requirements for the Layered Athena
project. This introduction explains a bit more about what the project
is, since the Opportunity Evaluation was insufficiently clear. The
idea of layering Athena on vendor operating systems is not new, but
until now we have not really addressed it. Now is the time to do this
as an independent project. If we don't take this opportunity, we will
be forced into it by the small decisions that we make as we port the
environment to new platforms.
What is Layered Athena? By any account, Layered Athena is a clean
separation between the vendor operating system and Athena's value
The Layered Athena project has three motivations:
These varying viewpoints, which are described more fully below, make it
difficult to get the idea across and make sure we are all thinking of
the same thing. While these motivations are not mutually exclusive,
they do suggest different approaches to the problem.
- To make it easier for private workstation owners to use Athena,
- To make it easier for us to port Athena to new platforms and release
new and updated software.
- To do good computer science.
The two primary motivations of Layered Athena suggest different
tradeoffs and focus to this project. We realize that at this point
both of these approaches are strategically important to Athena. For
now we will assume that simplifying our release engineering process is
the primary goal, with making Athena more accessible to private
workstations secondary. Hopefully we will be able to do both, but
that focus gives us a better chance of completing the first phase of
this project and positioning DCNS for further work.
1. Cleanly layering Athena on the vendor operating system will give
the private workstation owner more flexibility. Making it easier for
private workstation owners to use Athena will in turn make Athena more
available in laboratories and departmental computing centers.
Layering will allow us to add Athena functionality to an existing
workstation and have everything continue to work, even if we have not
previously tested that exact hardware configuration. We should also
be able to remove the layered Athena product and return the
workstation to a working configuration. Layering enables us to keep up
with new hardware as fast as the vendor supports it. If the
workstation owner needs software support from the vendor, he can
temporarily remove Athena to show whether the problem is in our or
2. A clean layering can also make it easier to maintain the Athena
environment. By not releasing the vendor OS and Athena software in
one huge combined package, it is likely that ports of the environment
will be easier and faster. Currently, when porting the Athena
environment to a new platform, actually getting the bulk of the code
to compile and run is a small part of the effort. A larger part of
the effort is integrating everything with the vendor OS and properly
configuring it. Two pieces are particularly difficult to port: login
and the installation process. Layered Athena can help simplify a lot
of the integration/configuration work. By partitioning the
environment into packages, it becomes possible to release a port
before the difficult parts like login are done. Layering
would simplify regular releases on existing platforms as well.
3. Finally, layering is just plain good computer science. This was
the original motivation for the developers suggesting it several years
ago. Making a clear boundary between a standard (the vendor operation
system) and a local modification (the Athena changes) is a good idea
that makes an aesthetically better system. It also makes it easier to
support and maintain that system. Changing the architecture solely for
aesthetics is insufficient justification for the work required.
However combined with the benefits of easier porting, easier
maintenance, easier use by private workstation owners, aesthetics
provide compelling justification.
Are the goals exclusive or can they work together? This project
can have such diverse goals because it is a basic reorganization of
past work which can have a lot of impact on the system. A number of
other major features of Layered Athena fall out from the above goals.
One is actually identifying what Athena is, what software does this
apply to and what must be present on a workstation to consider it to
be running Athena. Another is partitioning Athena into pieces that
can be loaded on a workstation or ported to a new platform separately
from the rest of the suite. An important variation on the basic goal
of being able to layer Athena on the vendor OS is for the end user to
be able to use Athena services on a workstation that the system
manager has not already setup for this. Finally, a long-term goal for
this whole project is for public workstations to be a special case of
Layered Athena, rather than built with a different scheme.
Deliverables. The primary deliverable from this project will be
a framework for packaging the Unix Athena release. Specifically, we
will produce a sample port for one platform with a well-known vendor
OS, such as Ultrix 4.3 on the DECstation, along with the necessary
tools to install, update, and remove that software.
Due to the past difficulty in gathering requirements and communicating
with customers for similar projects, we are taking a different
approach with these requirements. This document was produced
internally without further data gathering. We are now seeking
comments on it from the potential customers of the layered Athena:
both our own operations groups and users in the wider MIT community.
The requirements presented here attempt to cover both the technical
and support sides of the project.
- Divisibility: the Athena release will be divided up into
smaller pieces, herein referred to as subsets. See example list of
subsets at the end of this document.
- Subsets are logical units which may be a single program or may
include many directories of fonts, libraries, utility programs, and
other support files.
- Use of some subsets may require the inclusion of others. These
dependencies must be made explicit, and form a hierarchy of subsets.
- For convenience, some popular groupings of common subsets may
- The number of different layers and subsets must be small
enough that it can be easily comprehended by a user whose primary
interest is not computers. We expect about ten subsets to be defined.
- It is not necessary that all subsets be available on all
platforms. While it is desirable to have them the same, this makes it
possible to begin using a port which is not yet complete.
- Placement: the workstation owner should have the choice of
placement of the system software.
Note that some subsets, such as those affecting basic networking on
the workstation, may only make sense copied to the local disk. We
also may want to limit some of these choices to make Layered Athena easier to
- Not having a given subset available at all.
- Being able to use a subset that resides on the fileserver. This
may require placing symbolic links or configuration files on the local
disk, while leaving as much as possible behind on the file server.
The fileserver being depended upon may be a centrally managed
Athena server or a local departmental server.
- Copying all parts of the subset to the local machine.
- Updates: as with the AUTOUPDATE variable in the current
workstation scheme, the workstation owner must have the option of:
It should be possible to back out of an update or even remove all of
the layered athena products from a workstation. We may want to limit
these options to make it easier to support this software and encourage
users to stay up to date.
- His workstation is updated automatically whenever a newer
version of a subset is available.
- He is notified that new software is available, but must take
- Conflicts with Vendor operating system. Whenever possible, we
should avoid conflicting with similar systems provided by the vendor.
- Use of Layered Athena on a workstation must not preclude the
loading of any third party software on that workstation.
- If we provide an enhanced version of a program the vendor also
provides, we must not remove the vendor version from the system,
merely rename it or put ours earlier in the users' search path.
- If our enhanced version lacks some feature that third-party
software may rely on, then we cannot move the vendor version at all.
- Wherever possible, locally developed programs, as well as enhanced
versions of vendor programs, should not depend on availability of vendor
- Tracking: we need to know what people are using so that we
can provide better service and know when it is safe to decommission
- Optional real time monitoring such as SNMP should be able to
tell us what subsets are loaded. While enabling this is optional, it
must be done in such a way that most people opt to do it.
- The install and update tools should record what is on a
workstation so that recreating that workstation or cloning a
configuration on many workstation is easier.
- A method must exist to locally determine how a workstation is
- We should encourage, but not require, the registration with I/S
of those workstations using Layered Athena.
- Scale: if someone manages a number of similar machines, it
should be possible to configure one, then duplicate that configuration
on the others. If a central database is used to store configurations,
it must easily handle tens of thousands of workstations.
Similarly, any automatic update mechanism must be able to handle tens
of thousands of workstations updating at the same time.
- Since someone with root privileges can do whatever they want to a
workstation, security really only applies to the stable storage of
- An unprivileged user may be allowed to temporarily use some
Athena software. While the system manager may not want to Athenize a
workstation, the users may still be able to use some parts of the
Athena environment without any privileged or permanent changes. Such
a change must be simple and quick to install and deinstall.
- Licensed Software: Important parts of the Athena software suite
are licensed third party software. It is important that making
layered Athena available not easily allow people to copy licensed
software off campus or otherwise violate licensing terms. We also
charge for access to this software. We must make sure that people pay
when they ``Athenize'' a workstation.
For now we will move forward with the Layered Athena project without
concern for technical solutions to enforce software licensing. A team
will be formed to examine the policy issues, and determine if it is
purely policy or if technical support is necessary. In any case, such
a technical solution would be outside the scope of Layered Athena, as
it would apply to regular Athena installations as well.
- Customization: The workstation owner may want a particular
subset with a simple local customization. There must be provision for
running a local customization script at install and update time to
- User Interface: a user interface must be supplied so that the
average workstation owner can customize their workstation without
calling for help from I/S. This interface must not make any
assumptions about what is already on the workstation (i.e. X Windows)
so that it can run on the raw vendor's software. The interface should
attempt to verify that the person running it is the owner of the
workstation and they are authorized to put ``Athena'' on this
workstation, then let them configure it however they want.
- Support: we have to be prepared to support these. To be able to
provide reasonable support, we need:
- Explicit written policy. With layered Athena it will become
much more fuzzy what is and isn't an Athena workstation. We need
Service Level Agreements with private workstation owners so that they
know what they can expect from us, and what we require of them to
provide service. This must be clearly communicated with the
workstation owners. We also must consider how the Athena Rules of Use
apply to Layered Athena.
- A way to load software. If layered Athena requires the vendor
OS to already be installed, then we need to be able to help
workstation owners install the vendor OS as well.
- Problem resolution. How do we deal with finger pointing between
vendor customer support and our software, especially when billable
calls are involved?
- Training for support personnel. Because this makes it easier
and faster to port and change the Athena environment, the developers
have to be especially sensitive to keeping the support organizations
informed and trained in a timely manner.
- Identifying the configuration. A simple method must exist for
support personnel (e.g. OLC consultants) to know the machine
configuration when they attempt to help a user.
- Documentation. We need to prepare documentation how to install
and update systems for the end user, a description of each of the
subsets, and an administrator's guide for Athena Operations personnel
and others who want a lot of detail.
- Training. No end-user training courses will be necessary for
installing and updating Layered Athena, although this may increase
interest in how to use Athena.
As is probably clear from reading the requirements, the solution is
both technical and procedural. In addition to programming the pieces
necessary to pull this together, we will have to document it and
identify how we deal with special cases, how we support customers
using this, and many other things.
This is a proposed list of subsets to support.
- Support to run kerberos clients. This includes a
couple of configuration files and a small set of utility programs.
- Transarc's AFS file service. This one will be tricky, as
it consists of kernel extensions, daemons, modifications to the system
startup scripts, several configuration directories, and allocation of
a large amount of disk space. It requires the kerberos subset to
- Basic Athena Services
- These are the core services that the
rest of Athena depends upon: hesiod, zephyr, moira, attach, and email.
This requires several configuration files, a couple of daemons, and a
number of utility programs. Email here means the ability to send
outgoing mail, and possibly POP support in some simple mail readers.
It requires the kerberos subset to function. Note that at this point,
people can attach lockers and run most third party applications.
- This is the locally built clients, and on some platforms,
server as well.
- This is the usual Athena login program, which will allow
anyone with an Athena account to use the workstation. It requires the
Basic Athena Services, and X if the workstation does not already have
an acceptable X implementation.
- Online documentation and consulting. This includes olc,
olh, the man pages, and whatever other help facilities we have
available. This requires the Basic Athena Services.
- This includes the TeX and LaTeX formatters, support
programs, fonts and macro libraries. It does not depend on anything else.
- This is the editor EZ and the other programs in that
suite. It includes a number of config files, fonts and utilities as
well. It also does not depend on anything else.
- Athena Applications
- These are the rest of the Athena
applications. Notably, it includes emacs, discuss, delete, the Athena
csh, mh, and many more. No other subsets are required, although some
applications will require Basic Athena Services.
- This includes the remaining configuration files and
pieces necessary to turn a workstation into a public Athena
workstation. It requires all of the other subsets.
Next: About this document
Bruce R. Lewis
Tue May 16 12:52:27 EDT 1995