Chef- Roles

Chef – Roles

So far, we’ve been just adding recipes directly to a single node. But that’s not how your infrastructure works.

Roles are there in Chef to group nodes with similar configuration. Typical cases are to have roles for web servers, database servers, and so on.

Roles make it easy to configure many nodes identically without repeating yourself each time

In your organization, if your infrastructure grows to be multiple, redundant servers that all perform the same basic tasks. For instance, these might be web servers that a load balancer passes requests to. They would all have the same basic configuration and could be said to each satisfy the same -role”.

You can set custom run lists for all the nodes in your roles and override attribute values from within your roles.

Creating Roles

For creating any role we need to follow below steps

Create a role
Upload the role on the Chef server
Update Run list
Assign the role to the nodes
Run the Chef client

we can create Role in two ways

Using Knife [JSON]- Create Role in Chef Server directly
Using Ruby - In local repo under chef-repo folder

1.Using Knife [JSON]- Create Role in Chef Server directly

1.Create a role

knife role create <ROLE_NAME>

2.Update Run list

{
   "name":"client1",
   "description":"",
   "json_class":"Chef::Role",
   "default_attributes":{

   },
   "override_attributes":{

   },
   "chef_type":"role",
   "run_list":[
      "recipe[nginx]",
      "recipe[phpapp::web]"
   ],
   "env_run_lists":{

   }
}

3.Upload the role on the Chef server
By closing Knife will auto save with Chef Server. To check

knife role show <ROLE_NAME> -d -Fjson

4.Assign the role to the nodes

knife node run_list set Node2 "role[<ROLE_NAME>]"

5.Run the Chef client

sudo chef-client

2.Using Ruby - In local repo under chef-repo folder

1.Create a role
Create a role folder inside chef-repo & create webserver.rb file with runlists.

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

2.Upload the role on the Chef server

knife role from file chef-repo/roles/webserver.rb

3.Update Runlist

Already Did at Step #1

4.Assign the role to the nodes
knife node edit <node_name>

5.Run the Chef client
sudo chef-client

Create Role for Webserver

we are creating a Role; it consists of following recipes. we download these from Supermarket.

knife supermarket download apt
knife supermarket download nginx
knife supermarket download ohai

#Exatract It
tar -zxxvf  -C cookbooks/

#upload Cookbooks
knife cookbook upload apt/nginx/ohai

Each role file can be written either in Ruby, or in JSON.

Create a roles directory in chef-repo:
$ mkdir roles

We’re going to create a .json file representing the role data. A basic role has a

name:
description: and
run_list:
a long list of recipes

Create a Role for Web Server: Ruby

vi web_server.rb

Start with Name of the Roles & Description: what this role for

name "web_server"
description "A role to configure our front-line web servers"

Next, we can specify the runlist, contain cookbooks (recipe[“"]), recipes (cookbook::recipe), and other roles. Remember, a run_list is always executed sequentially, so put the dependency items before the other items.

name "web_server"
description "A role to configure our front-line web servers"
run_list "recipe[apt]", "recipe[nginx]"

To Upload Role to Chef Server manually, using below command

knife role from file web_servers.rb

Create a Role Using JSON

To create a webserver role:
knife role create webserver

It should look something like this:

{
  "name": "test",
  "description": "",
  "json_class": "Chef::Role",
  "default_attributes": {
  },
  "override_attributes": {
  },
  "chef_type": "role",
  "run_list": [

  ],
  "env_run_lists": {
  }
}

When we save a JSON file created using the knife command, the role is created on the Chef server. But for Ruby.rb, we need to Upload Role to Chef Server manually

Change json file it as per Our Role

{
  "name": "webserver",
  "description": "A role to configure our front-line web servers",
  "json_class": "Chef::Role",
  "default_attributes": {
    "nginx": {
      "log_location": "/var/log/nginx.log"
    }
  },
  "override_attributes": {
    "nginx": {
      "gzip": "on"
    }
  },
  "chef_type": "role",
  "run_list": [
    "recipe[apt]",
    "recipe[nginx]"
  ]
}

After closing, it will automatically Saved in Chef Server. If we want to get our JSON file from the server.

knife role show webserver -Fjson

Add Role to a Node
Now we need to add our role to a node. For that first find list of nodes available

knife node list

Node1
Node2

And then we would give a command like:

knife node edit <node_name>
knife node edit Node1

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

{
  "name": "Node1",
  "chef_environment": "_default",
  "normal": {
    "tags": [

    ]
  },
  "run_list": [
    "recipe[nginx]"
  ]
}

Now, we need to replace our recipe with our role in this file:

{
  "name": "Node1",
  "chef_environment": "_default",
  "normal": {
    "tags": [

    ]
  },
  "policy_name": null,
  "policy_group": null,
  "run_list": [
  "role[webserver]"
]

}

On close, it will automatically update Node1 run list with newly assigned role.

We can also do this in single command

knife node run_list set Node2 "role[webserver]"

Run the Chef-Client

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