Mass Unattended Linux Installation

Aaron Crane

aaron.crane@gbdirect.co.uk

UKUUG Linux 2003 Conference • August 2003

http://www.ukuug.org/events/linux2003/

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1 Installing Linux

Installing an operating system is usually fairly straightforward
- Certainly for modern Linux distributions
General procedure:
- Boot the system from the install media
- ‘Handhold’ the installation program, answering questions as appropriate
Most distributions reduce the handholding phase as much as possible

2 Zero Interaction

Handholding an installation is not always appropriate
Many situations require a large set of identical or near-identical hosts:
- Server farm (web serving, rendering, etc.)
- Classroom laboratory in a university or school
- Nodes in a Beowulf cluster
Automating installation has many benefits:
- Minimise effort
- Reduce cost of adding or replacing equivalent hosts
- Avoid mistakes and consequent loss of reliability

3 Obstacles

Variety of obstacles to unattended installation
- Not all apply in all situations
Repeatable package selection
Network configuration
Hardware detection
User accounts

4 Characteristics of a Solution

Not an auto-installer per se, but an auto-install builder
- Different situations require slightly different solutions
Might need several distinct automated installs
Often need support from the operating system vendor
- Especially for hardware detection/configuration and package selection
Many generic system-administration tools are helpful:
- DHCP to control network configuration
- Centralised site-wide user account management

5 Auto-Installation Tools

Most operating systems have auto-installation tools
KickStart for Red Hat
ALICE for SuSE
Three for Debian: FAI, Progeny auto-installer, Replicator
SystemImager works with a variety of Linux distributions
Non-Linux systems as well:
- JumpStart for Solaris
- RoboInst for Irix
- Ignite-UX for HP-UX
Relatively few differences between their approaches

6 Installation Method

Two basic techniques
‘Golden image’:
- Keep a disk image from a perfect installation
- Some systems insist that you keep an untouched, unused ‘golden host’
- Usually offers extremely fast installation
Automated full install:
- The installer performs the same steps as full installation
- Better suited to situations with varying hardware

7 Boot and Install Media

Variety of boot and install media used
PXE a good choice for booting in many environments
- Modern systems support PXE network booting out of the box
CD/DVD or floppy if network booting isn’t appropriate
Where does the installed software come from?
- CD/DVD, NFS, HTTP/FTP, rsync, …

8 Configuration Differences

Two relevant cases:
- Distinct use patterns for different groups of auto-installed machines
- Different hardware within one group
Two main ways to select a usage pattern:
- Make the admin specify when starting the install
- Tie configuration data to the machine’s MAC address
Handling hardware differences:
- Choosing by usage pattern might work
- Hardware detection (like a manual installation)

9 Case Study: GBdirect

GBdirect Ltd: consultancy, bespoke software development, technical training
Enormous rise in volume of training
Cost of delivery increasingly an issue
Existing procedures somewhat ad hoc and unreliable
Decision to create a mobile training suite:
- Custom-built flight case
- Set of laptops with all software needed for any course
- Students change things — reinstall after every course

10 Unusual Requirements

Change installed software comparatively frequently
Reinstall in remote locations, without internet access
- Use CD/DVD for both boot and software
No server to support installed systems
- Can’t use DHCP or centralised user accounts
Provide user environment suitable for customers with no Linux experience
Laptop hardware can cause problems
- No built-in Ethernet cards on some machines
- PCMCIA poorly supported by many auto-install tools

11 Approach to a Solution

Considerable in-house Debian expertise
- Building packages an option, unlike for other distributions
- Non-Debian choice sensible for us only if Debian can’t do the job
Progeny auto-install supports single-CD operation
- Also permits network operation where available
Some configuration (host names, etc.) tied to MAC address
- Choose matching inventory numbers for laptops and PCMCIA Ethernet cards — simplifies administration

12 Problems Encountered

Installation based on Debian 3.0 ‘Woody’
- Incomplete support for unattended installation
- Needed to rebuild a few critical packages to avoid interaction
- Forthcoming ‘Sarge’ release almost certainly won’t need this step
Progeny auto-install didn’t seem to handle PCMCIA well
- Use a 2.4-series kernel, with large build
- Mysterious problems with modules, so everything compiled in
- No direct support for 2.8Mb-floppy boot image
No ext3 support — convert after install

13 Current State

Reasonably fast
- Install a laptop in 30 to 45 minutes (depending on hardware)
- Install a whole suite in less than an hour if need be
Security updates fairly straightforward
Simple, powerful method for post-install actions
Successfully coped with changing requirements:
- USB floppy drive for floppy-free laptops
- Wireless Ethernet to let students share data
Reliable production use for over a year

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