Managing PC Operating Systems

with a Revision Control System

Ing.Mag. Gottfried Rudorfer

Gottfried.Rudorfer@gmx.at

Wirtschaftsuniversität Wien

October 25, 1997

Want a unique system configuration– Correct

preferences for• Windows-Profile• MS-Office • Firefox

System

AdministratorUsers

Tasks– Updates – New software– Configuration of

• operating system• applications

The problem

Large scale managementof PCs Problem: The

administrative effort increases proportional with the number of PCs.

Goal: Software for automatic administration of the software

PC specific problems

Users with physical access to the computer may be able to change the software configuration – The user installs another operating

system from USB device– The user may change files and/or

partitions especially when having admin-rights

ConsequencesThe installed software on the

clients has to be regarded as non safe.

A changed software configuration has to be expected.

A software distribution system has to consider this consequences!

Existing approaches

If the user reports problems with the installation, the PC is reinstalled from scratch.

Unattended system installation with– Network-boot with access to a

repository server– Setup of software packages with

default settings

Our approach

A system which– does not require a complete re-install

but rather performs a software check.– tries to repair the existing

configuration without a fresh install.– is much faster compared to

unattended full installations

Functionality for the userVerification of a client. Speed. Verification is fast because:

– Installation from scratch is only necessary when there was a serious change in system configuration.

– The content of files is not transmitted to the client when the attributes of the file are identical with the current master copy.

Benefits for the administratorPrograms for the generation of a

new master copy. A revision control system to store

different versions of the master copy at the same time.

Only one PC client has to be managed!

Relationship between clients, server and repository

Updating a client

Load the operating system for the installation.

Run the installation program.

Reboot the system.

Provides the master copy.

ServerClient

The operating system for the installation: Linux Generic boot loader

(LILO)– loads the kernel as ram

disk.

Initial RAM-Disk– the file system is mapped

into the main memory.– Finally /initrc is

executed.

The OS has unlimited access to the hard disk.

The installation programWritten in Perl5Functionality

– Check the partition table.– Check the file systems.– Mount the file systems.– Ask the server to update the client.– Dismount the file systems.– Write a new master boot record.– Do local customizations.

Replacing the current master copy

Boot LinuxLogin at the

server as pc7adm.

The server executes the command rdist at the client using rsh.

Management of different master copies with our fsrcs.

ServerClient

The master copy

Is a directory on the server which contains all files of a client.

Access with two accounts:– pc7inst: for reading the files– pc7adm: for writing files

Problem: A working master copy might be replaced by a non operational version.

Security on the serverThe clients shouldn’t have

unlimited root privileges.The upload program has to be run

with root privileges!Solution:

– .rhosts– No login shell for the upload and download

users. – All programs perform first a chroot to the

master copy.

The repository of fsrcs

PerformanceFresh installation of both operating

systems– 909 Mbytes of data– approx. 40,000 files– 42 minutes

Check with minor modifications of both operating systems– 8 minutes

Check with minor modifications of Windows 95– 202 Mbytes of data– approx. 3,500 files– 2 minutes

Future work

Management of different hardware configurations with one repository.

Merge rdist and fsrcs into a single application.

Managing PC Operating Systems

with a Revision Control System

Gottfried Rudorfer

Gottfried.Rudorfer@gmx.at