1. Cobbler for
Developers
Matthew Mosesohn
Mirantis IT

2. Developers? Uniformity?

3. Why Cobbler?
Simple system to automate installation and
preparation of systems.
Reduces the amount of time needed to begin
an installation.
Provides a flexible, intuitive means to manage
a large number of systems to meet your needs.

4. Why Cobbler?
● Simple web UI and command line
● Robust template interface via Cheetah
● Built to save time
● Open source
● Mature

5. Cobbler history
Developed by DevOps engineer Michael
DeHaan (former Red Hat employee)
Primary goal to simplify installation
Software environments require frequent
reinstallations

6. Manual network kickstart method
● Set up DHCP server to point to TFTP server
● Configure TFTP with pxelinux.0 and
installation tree
● Either handwrite MAC addresses for each
host or present a menu and manually
choose
● No scaleability
● No templating
● No reporting

7. When do you need Cobbler?
Scenarios:
● Complex software with many components
● Testing clustering software
● Testing software suites with no reset option
available
● Continuous integration (CI) testing
● Isolated network environment
● Rapidly changing hardware

8. When Cobbler is not appropriate
Scenarios:
● Simple application development
● Legacy system development
● Where automation is not possible
● Windows

9. Continuous Integration
Overview:
● High pace development style
● Automated deployment
● Integrate and test software
● Test every commit
● Similar to production environment

10. Continuous Integration
Advantages:
● Saves time and money
● Enables sophisticated QA
● Early warning of bugs
● Communication
● Develops metrics for analysis

11. Continuous Integration
Disadvantages:
● Setup time investment
● Full automation development

12. CI example: Jenkins
Jenkins is a fork from Hudson
Java based
Supports many SCM formats, including:
● git
● subversion
● mercurial
● cvs
Automate testing based on SCM changes or
regular schedule

13. Typical Uses
● DNS/DHCP management of a company
infrastructure
● Automation of installation of servers via PXE
● Power cycling of systems via ipmitool
● Local package repository mirror
● Simplified, standard installation process

14. What you should know already
● How to build virtual machines
● How to configure a DHCP server
○ hostnames
○ MAC addresses
○ gateway
● Where to find installation media for your
system (DVD and/or package repositories)

15. Considerations
Scale:
● How many sites
● Concurrent installations
● Number of systems
Complexity:
● Linux distros
● System builds
● Localization
● Post-installation scripts

16. Simple case: single node with virt
Internet:
● Create a private OS files
package
virtual network repositories
● Two VMs
● VM 1 is CentOS VM 1
Linux host
● VM 2 is Ubuntu Cobbler server
VM 2
System
OS files
configurati
packages
on

17. Common use case: Development lab
Internet:
OS files
package
repositories
Development Lab
System1 System2
Cobbler server System3 System4
System5 System6
OS files System
packages configuration

18. Unattended install script

19. Create kickstart file
● Set up install method
● Configure disks
● Configure language/keyboard/time
● Configure default package set
● Specify scripts in %post for automation

20. Example kickstart for installation
install
reboot
lang en_US
network --bootproto=dhcp
keyboard us
clearpart --all
part / --size 500 --grow
part swap --recommended
#set timezone
timezone --utc US/Eastern

21. Example kickstart for installation
#set root password
rootpw changeme
#rootpw --iscrypted $1$Rig3dbXb$OWcv00J/V2WsBGcgx0bmp1
%packages
@base
openssh-server
openssh-client
%post
#Your script here

22. Debian/Ubuntu preseed file
#Lang
d-i debian-installer/locale string en_GB.UTF-8
d-i console-setup/ask_detect boolean false
d-i keyboard-configuration/layoutcode string us
#Net
d-i netcfg/enable boolean true
d-i netcfg/get_hostname string system01
d-i netcfg/get_domain string example.com

23. Debian/Ubuntu preseed file
### Mirror settings
d-i mirror/country string russia
d-i mirror/http/hostname string archive.ubuntu.com
d-i mirror/http/directory string /ubuntu
d-i mirror/suite string precise
d-i clock-setup/utc boolean true
d-i time/zone string US/Eastern

24. Debian/Ubuntu preseed file
## Account setup
d-i passwd/root-password-crypted password [MD5 hash]
d-i passwd/user-fullname string Ubuntu User
d-i passwd/username string ubuntu
d-i passwd/user-password-crypted password [MD5 hash]
### Apt setup
d-i apt-setup/restricted boolean true
d-i apt-setup/universe boolean true
d-i apt-setup/backports boolean true
tasksel tasksel/first multiselect lamp-server, print-server

25. Debian/Ubuntu (cont'd)
d-i preseed/early_command string your_pre_installation_script
d-i preseed/late_command string your_post_installation_script

26. Preinstallation script
● Useful for a disclaimer, warning, or safety
message.
● Disk configuration manual steps

27. Postinstallation script
● Custom downloaded files/settings/scripts
● Enable configuration management
● Set up SSH keys
● Custom authentication if not possible
through preseed/kickstart

28. Cobbler kickstart extra features
● You can store snippets and call them in multiple
kickstarts
● You can use Cheetah template code directly in a
kickstart (just prepend with '#'). Syntax similar to Python
Examples:
%post
$SNIPPET('ntp_register')
%packages
#set $hostname = $getVar('$hostname', None)
#if test in $hostname or devel in $hostname
@development
#end if

29. Working with variables
cobbler system dumpvars --name=system
Built-in variables:
● $mac_address
● $ip_address
● $hostname
● $distro
● $profile
● $server

30. Flexibility with variables
● Set custom variables in ksmeta section.
● Profile variables override distro variables.
● System variables override profile variables.
● Use getVar('var-name','default-value') in
cases where an empty string would break
your installation
○ RH: rootpw $getVar('rootpw','changeme')
○ Deb: d-i passwd/root-password-crypted password $getVar
('rootmd5','$1$Rig3dbXb$OWcv00J/V2WsBGcgx0bmp1')

31. Adding systems to Cobbler

32. Add your distro
● Download base OS media
● mount -oloop /mnt/iso /path/to/os.iso
● cobbler import --path /mnt/iso --
name=distro_name

33. Adding profiles to Cobbler
● Log into Cobbler
Web
● Add new profile with
your distro and
kickstart

34. Remote install options
● Manual entry of systems
○ Requires MAC address
● PXE menu
○ Requires manual interaction on boot
● koan/virt-install
○ Create a virtual machine or reinstall existing system
and specify Cobbler server and profile to use

35. Koan examples
Reinstall a host:
● koan --server=cobbler.example.org --
replace-self --profile=name
Create a new virtual machine:
● koan --server=cobbler.example.org --virt --
system=name

36. Further automation
Puppet
Squid proxy
Jenkins
Continuous integration

37. Known limitations
Ubuntu installation works, but there are some
issues with virt-install for Ubuntu guests
Scaling and redundancy

38. Summary
● Cobbler allows you to automate installations
● Cobbler fits into CI testing
● Cobbler saves time
● Cobbler is extendable via Cheetah template
engine

39. Thank you!
Questions?

40. Additional reading
https://www.redhat.
com/about/news/archive/2008/4/provisioning-
our-new-middleware-architecture
https://github.com/cobbler