In the last two posts I went about how to get basic virutalization and why configuration management is necessary. In this part I will explain about setting up a Chef server and how to setup basic provisioning, In part 4 I will explain on how can we go about automated provisioning using OpenVZ and monitoring those instances.
Let's put the requirements upfront --
This is a typical chicken and egg problem -- if we do not have any configuration management tool, how do we configure the first hardware server? And if we do not have any containers, then how do we setup the first server? So the answer lies in one basic principle -- configure anything manually first and then we should not require to do it manually next time, we should automate it for next time - we kept this principle in mind.
I downloaded CentOS 6 OpenVZ template from here http://download.openvz.org/template/precreated/ and first thing was to install the Chef server, our aim was to create a self scaling private cloud based on OpenVZ - where we can add more hardware on demand, which provides HA and load balancing.
Since configuration management allows us to define configuration as source code, we should be able to redeploy that source code on any server thus recreating that server reliably when ever we have lost it or due to mis-configuration we have malfunction.
My team settled on following tool set --
Please read this post for chef basics. FrameOS have been doing awesome job in Linux + Ruby ecosystem, they have stable and latest ruby packages, we will be using FrameOS RBEL repo for setting up our chef server, although FrameOS blog mentions how to install chef easily, I will be kind of re-iterating same thing here but I will cover how do we continue setting up client, knife UI on your machine and verify chef client run. While you can use OpsCode client recipes - we will most probably will not use them because they are influenced hugely with Ubuntu Linux. Since we will be using RHEL/CentOS combo where ever possible - so we will end up modifying those scripts, so lets start with basic scripts on our own.
To Setup chef on your CentOS 6 box - you can refer to this post or use following shell script (trust me this is one of the few place we will be using shell script, mostly we will be using ruby to do our scripting as well, but since our bare bone container may or may not have ruby, we should use shell script to setup chef and then use ruby everywhere else), become root and execute these 4 statements
rpm -Uvh http://rbel.frameos.org/rbel6 yum install rubygem-chef-server service iptables stop setup-chef-server.sh
Once you are done with this setup, we are ready to hit chef server! so lets get going and setup our first chef client and a repo. Chef needs recipes which form a cookbook and in ideal scenario one of many cookbooks form a role which gets applied to a node*. Now login to http://your-chef-server:4040 user: admin password: chef321go
2. Admin Client
After loggin in as Admin, you will have to change default admin password - keep a note of it, after this, create user name for yourself. And create a client for yourself as well.
User name is required if you want to operate web-ui and client is required for knife to be able to help you manage roles, cookbooks, recipe and nodes on chef.
3. Repository Setup
Unlike puppet, Chef does not need a repository, what you do is to create repository for yourself and then upload cookbooks/recipes/nodes/roles from the repository to chef server. For basic stuff, you should have something like this
.. (up a dir) /Users/ajeygore/Documents/workspace/chef/ |+checksums/ |+cookbooks/ |+data_bags/ |+databags/ |+environments/ |+nodes/ |+roles/ `-scripts/
once you have setup repository, you might want to check it in Git or something similar. After this you will create a .chef directrory inside chef repo. Install chef client on your machine, and run knife configure. Once you have setup knife - enter knife node list as command and you should see empty node list.
That concludes our setup for Chef Client, In next post, I will conclude how can we start automating monitoring and basic setups with Chef, including provisioning. I hope by now you understand how chef works and how recipes work, its time to write a simple recipe which changes MOTD on linux machine to the motd of your choice.
*A node is a machine - whether its virtual, containers or physical box
Jan 12, 2012