What is Role?

A role is a way to define certain patterns and processes that exist across nodes in an organization as belonging to a single job function. Each role consists of zero (or more) attributes and a run-list. Each node can have zero (or more) roles assigned to it. When a role is run against a node, the configuration details of that node are compared against the attributes of the role, and then the contents of that role’s run-list are applied to the node’s configuration details. When a chef-client runs, it merges its own attributes and run-lists with those contained within each assigned role.

How to use Roles in Chef?

1. Create a Role and add the cookbooks into it.
2. Assign the role into each node or bootstrap new nodes using roles
3. The the run list

How to create Role?

Method 1: In Chef Server directly

> knife role create client1

&

Add the run list e.g. “recipe[nginx]” under “run_list”

Save & exit

The role will be created in Chef Server.

Example

{ "name": "client1", "description": "", "json_class": "Chef::Role", "default_attributes": { }, "override_attributes": { }, "chef_type": "role", "run_list": [ "recipe[nginx]", "recipe[phpapp::web]" ], "env_run_lists": { } } 

Let’s download the role from the Chef server so we have it locally in a Chef repository.

> knife role show client1 -d -Fjson > roles/client1.json

Now, Lets bootstrap the node using knife with roles

> knife bootstrap --run-list "role[client1]" --sudo hostname

How to edit the roles in chef Server?

> knife role edit client1

Method 2: In local repo under chef-repo folder

> vi webserver.rb

example –

name "web_server" description "Role for web servers" run_list(   "role[base]",   "recipe{web_server]" ) 

& Then upload to chef server using following commands.

> knife role from file path/to/role/file

How Assigning Roles to Nodes?

> knife node list

> knife node edit node_name

This will bring up the node’s definition file, which will allow us to add a role to its run_list:

{ "name": "client1", "chef_environment": "_default", "normal": { "tags": [  ] 	}, "run_list": [ 	"recipe[nginx]" ] } 

For instance, we can replace our recipe with our role in this file:

{ "name": "client1", "chef_environment": "_default", "normal": { "tags": [ ] }, "run_list": [ "role[web_server]" ] } 

How to bootstrap node using role?

> knife bootstrap {{address}} --ssh-user {{user}} --ssh-password '{{password}}' --sudo --use-sudo-password --node-name node1 --run-list 'role[production]'

> knife bootstrap --run-list "role[phpapp-web]" --sudo hostname

How to run roles against nodes?

You can run chef-client on multiple nodes via knife ssh command like, To query for all nodes that have the webserver role and then use SSH to run the command sudo chef-client, enter:

> knife ssh "role:webserver" "sudo chef-client"

To find the uptime of all of web servers running Ubuntu on the Amazon EC2 platform, enter:

> knife ssh "role:web" "uptime" -x ubuntu -a ec2.public_hostname

Reference

http://docs.chef.io/roles.html

https://docs.chef.io/knife_ssh.html

https://docs.chef.io/knife_role.html

The post How to Implement Chef roles using Chef server ? appeared first on scmGalaxy.

Problems Area –

Our infrastructure has many cookbooks that aim to be reusable, primarily through encapsulating behaviour in LWRPs. This led to an explosion of LWRPs and sometimes the documentation didn’t keep up or did just not exist.

Solution 1: Follow Best Practices 

This command will create a README.rdoc by default, and I prefer Markdown, so I specify the -r md option.

> knife cookbook create smartmontools -r md

Solution 2: Automate using plugins

README.md which should be generated automatcially must contain information about the recipes, attributes, platform compatibility and cookbook requirements (i.e. depends, recommends, suggests etc).

Mathias Lafeldt wrote a knife plugin that generates an initial README.md from the metadata.rb file in a a cookbook.

Link –

• https://github.com/mlafeldt/knife-cookbook-readme
• http://mlafeldt.github.io/knife-cookbook-readme/

Extension of Mathias Lafeldt was done here with regenerate README.md from the cookbook source code

• https://github.com/realityforge/knife-cookbook-doc

Please refer these useful blogs as well which is referenced in order to write this article…

• http://realityforge.org/code/2013/04/01/documenting-cookbooks.html

The post Chef – Documenting Cookbooks automatically appeared first on scmGalaxy.