A tale of disaster recoveryCfengine everyday, practices and tools

Nicolas Charles <nch@normation.com>Jonathan Clarke <jcl@normation.com>

FOSDEM 2011 @Brussels, Belgium

  

About the speakers

Nicolas Charles

Cfengine contributor

Cfengine ”Community Champion” (C3)

Scala Developer

Jonathan Clarke

OpenLDAP commiter

Sysadmin

But we get on pretty well!(mostly...)

  

1) Configuration Management 101

2) Our choice of tool

3) A tale of disaster recovery

4) Introducing Cfengine 3

5) Why we love Cfengine 3

Agenda

  

A bit aboutConfiguration Management...

  

Configuration management What is it ?

Configuration Management is a field of management that focuses on establishing and maintaining consistency of a system (..) throughout its life

Software configuration management is the task of tracking and controlling changes in the software

Sources:http://en.wikipedia.org/wiki/Configuration_managementhttp://en.wikipedia.org/wiki/Software_configuration_management

  

Configuration management Why is it useful ?

Control changes Reproduce over time and nodes Audit and keep history data Repair automaticaly

  

What we chose, and why

Configuration ManagementTools

  

Our choice Back in mid 2009 Needed a configuration management tool Criteria:

Open source Multi-platform agent (including Windows) Resilient Non-disruptive

  

Our choice: candidates

Cfengine 3 Puppet Chef

  

Our choice: candidates

Cfengine 3

More on thischoice later...

  

An ill-fated talefrom the recent past

Disaster Recovery

(CASE STUDY)

  

Before the disaster... Our company's IT infrastructure

Small company: small requirements Web site, email Git repository, Redmine...

Small company: small budget All on one hosted server

  

Asking for trouble? Just one hosted server! Critical services!

No, a ”safe” configuration: Redundant hardware, 3 disk RAID-5 array All services automatically installed and setup

using Configuration Management Backups: daily (several off-site locations) Several VMs to separate services

  

A critical failure 2 hard drives fail simultaneously

→ RAID-5 array is down

→ Almost all services fail immediately

→ ”The end of the world as we know it”

→ Need to rebuild everything NOW

  

Recovering Step 1: Panic! Step 2: Get a new server Step 3: Reinstall base OS + virtualization Step 4: Restore VM configuration... whoops Step 4: Re-create the VMs manually Step 5: Reinstall each OS in each VM...

  

Recovering Step 6: Installation Configuration Management Step 7: Sit back and watch all the services

coming back online as if by magic! Step 8: Huh, where's my data? Step 9: Manually restore backups Step 10: Make a list of missing data...

  

Lessons learned

1) Hard disks fail reliably

2) Restoring virtualization setups:● Backing up the config files would have helped● Need CM tools to describe the desired state!

(Cfengine Nova does this)

3) Configuration Management should tie in to our backup system

4) Backups were lacking some files: always test!

  

Wishlist and discussion Integrating Configuration Management tools

and backup systems is a crucial step for CM to be efficient for disaster recovery

What do others do?

Provisioning VMs and their resources (disks, network) should be automated too

Cloud providers are one solution What about ”plain” virtualization?

  

A bit about Cfengine 3...

Sources: across the Internet

  

Cfengine: History

Source:http://verticalsysadmin.com/blog/uncategorized/relative-origins-of-cfengine-chef-and-puppet

  

Cfengine 3: Intro Configuration management software Written in C Two versions :

Community (GPL v3) Nova (closed source) : Community + extra

features

Backed by Cfengine AS – Norway based company founded in 2009

  

Cfengine 3: Features

According to Kuleven comparative study of configuration management systems:

Very mature Cross platform (*BSD, AIX, HP-UX, Linux, Mac

OS X, Solaris, Windows) Strongly distributed Based on state description and convergence Very high scalabily ( > 10000 nodes ) Very small footprint

Source: http://distrinet.cs.kuleuven.be/software/sysconfigtools/overview

  

Cfengine 3: Components Cf-agent

Runs on all managed hosts Applies configuration – this is the heart Can connect to cf-serverd to get policies / files

Cf-serverd Distributes policies and files Must be run on policy server(s) Usually run on all hosts to enable remote runs

Cf-monitord Collects statistics on all nodes

  

Cfengine 3: Promises Configuration rules are called promises

”Promise” to be in the desired state Cfengine agent handles the steps to get there:

convergence

Promise theory is based on research done in the University of Oslo

  

Cfengine 3: Usage examples Large companies (Facebook, AMD, …) Critical systems: Joint Australia Tsunami

Warning Centre Personal computers Mobile devices: Nokia N900 Underwater devices: army submarines Small and medium companies...

  

Why we love Cfengine 3...

Sources: our experience and opinions

  

Memory usage Daemon consumption on managed hosts

  

Multi-platform Define a configuration for all operating systems

Windows, Linux Make it ”transparent” (forget about the

complexity) Existing standard library handling the

differences between each OS and distribution

  

File editing Only change what you need to

You like your distribution's defaults? You have various different systems already

setup and just need to change something?

Search for lines and replace/delete/add them Only change one field in a file

/etc/passwd for example...

  

Complex tasks Powerful class system to trigger promises

Based on nodes itself Based on time Based on whatever you might imagine

Complex workflow can be created

  

FOSDEM 2011 Configuration Management room

Thank you !

And those brave enough to wake up early