configuration management 101 - a tale of disaster recovery using cfengine 3
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A tale of disaster recoveryCFEngine everyday, practices and tools
Nicolas Charles <nch@normation.com>Jonathan Clarke <jcl@normation.com>
RMLL 2011 @Strasbourg, France
About the speakers
Nicolas Charles
CFEngine contributor
CFEngine ”Community Champion” (C3)
Jonathan Clarke
CFEngine contributor
Contributor to various LDAP FLOSS projects
But we get on pretty well!(mostly...)
Scala Developer Sysadmin
1) Configuration Management 101
2) A tale of disaster recovery
3) Our choice of tool
4) About 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
A server crashed.
Install a new one, peoplecan't work without it!
OK, it'll be done inabout two days...
There's a new critical security patchwe must deploy on all our servers!
Get it out quickly!
Right, I'll put the wholeteam on it.
Why configuration management?
Why configuration management?
Automation
IndustrializationReproducibility
Why configuration management?
How do we setupservice X?
Ask Jim, he'sthe expert on that.
But he left the company...
Huh, this server has been loggingerrors for a few weeks.
Oh? I think Michael changedsomething on it recently...He'll tell you what it was.
Damn, he's on vacation!
Why configuration management?
Building-upknowledge
HistoryDocumentation
Why configuration management?
An intruder just stole our datausing a vulnerability in amodule we don't need...
I thought the project specificationensured that we disabled that?
Er, it did, but we enabled it tosolve a problem and forgot todisable it afterwards... sorry...
Why configuration management?
Vigilance
AlertsAutomatic repairs
Why configuration management?
I don't understand how thisserver is setup. It doesn't matchour best-practices.
Oh, that's a legacy server...
Well, it's a collection of littlethings, here and there...
Give me details on ourcurrent security policy.
Ah... Well, OK.Tell me: is it fully appliedon all our critical servers?
Er...
Why configuration management?
Rationalization
ControlNormalization
Configuration management
Rationalization
ControlNormalization
Vigilance
AlertsAutomatic repairs
Building-upknowledge
HistoryDocumentation
Automation
IndustrializationReproducibility
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 Step 4: Re-create the VMs manually Step 5: Reinstall each OS in each VM...
whoops
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?
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...
A bit about CFEngine 3...
Sources: across the Internet
CFEngine: History
Sou
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CFEngine 3: Intro Configuration management software Written in C Two versions :
Community (GPL v3) Nova (closed source)
Community + extra features Some features released in Community
Backed by CFEngine AS – Norway based company founded in 2009
CFEngine 3: Features
Large user base and community
Multi-agent technologyLightweight, non-intrusive
AutonomousFault-tolerant
Multi platform
Adapted toheterogeneousenvironments
Highly scalableProgressive
roll-out
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
Memory usage Daemon consumption on managed hosts
CFEngine 3: Usage examples Large companies Critical systems: Joint Australia Tsunami
Warning Centre Personal computers Mobile devices: Nokia N900 Underwater devices: army submarines Small and medium companies... Community
Feature: 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
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
Feature: 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
Feature: 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
Configuration example Install the LAMP stack
bundle agent caller { vars:
"pkg_list" slist => { "httpd", "php5", "mysql" };
packages: "${pkg_list}" package_method => generic, package_method => "addupdate";}
RMLL 2011
Thank you !
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
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