CHEF-tut

It is a congifuration management automations tool.

Chef is written in Ruby and Erlang.

Features of Chef

• Chef uses popular Ruby language to create a domain-specific language.
• Chef does not make assumptions on the current status of a node. It uses its mechanisms to get the current status of machine.
• Chef is ideal for deploying and managing the cloud server, storage, and software.

CHEF Architecture

Chef works on a three-tier client server model

1. Chef Workstation
2. Chef Server
3. Chef Nodes (contain ohai)

Cookbooks

• It is a directory where all cookbook are stored.
• Directory name should be cookbooks
• To create cookbook inside cookbooks don't create directly, use chef command to generate cookbook.

Command for generating cookbook

chef generate cookbook <cookbookname>

Recipe

Recipe is the file where all ruby code is written.Never create file manual or with touch or any other command. Use chef command to create recipe file.

create recipe being in cookbook directory

chef generate recipe <recipename>

we cann't wright code directly in recipe file. we have to right code being in cookbooks directory.

Ex- vi democookbook/recipes/demorecipe.rb

Command for syntax check

    chef exec ruby -c <democookbook/recipes/demorecipe.rb>

Convergence

We run chef-client to apply recipe to bring node into desired state.

convergence command

    chef-client -zr "recipe[<cookbookname>::<recipename>"

Runlist

TO run the recipes in a sequence order that use mention in a run list. With this process , we can run multiple recipes, but the condition is *** there must be only one Recipe from one cookbook ***.

runlist command

    chef-client -zr "recipe[<cookbook1>::<recipename>],recipe[<cookbook2>::<recipename>]"

To run multiply recipe of same cookbook: - we need to import all the necessary recipes inside default.rb recipe. - imported recipes should be of same cookbook.

include_recipe "::"

Chef-server (2-Architecture)

Firstly need to make account in manage chef io Then download chef starter kit and extract directory(chef repo). *** Alway work indise chef-repo ***

Bootstrap

Attaching a node to chef server is called bootstraping

To check whether workstation is connect to server - knife is use to talk with server and node

    knife ssl check

for uploading cookbook in chef server

    knife cookbook upload <cookbookName>

to check all the cookbook in the server

    knife cookbook list

connect server to node

    knife bootstrap <PrivateIpaddressOfNode> --ssh-user <user> --sudo -i <nodeKey> -N <NameOfNodeYouWantToCall>

To check all the node connectd to server

    knife node list 

define desire recipe for nodes

Here ,we set recipe for each node or more node depending upto needs.Only that recipe will be run in set node.If there is any changes/updates in setted recipe then node will take that changes and run recipe.But other than this recipe if any other recipes are updated/changed there will be no action performed by set node.

    knife node run_list set <NameOfNodeWeGaveNAmeToNode>  "recipe[<cookbookName>::<recipeNAme>]"

To check which node as set which recipe

    knife node show <NameOfNodeWeGaveNAmeToNode>

After completing all the step above ** chef Architecture is partially automated ** to run recipe in node.We need run command

chef-client

in node.

For automation we need to configure node

Go to node and configure /etc/crontab

    vi /etc/crontab

After running this CMD new console will open.Just write

* * * * * <userName> chef-client

Here, each star have it's own meaning.Inside crontab there is explaned meaning of each *

• defines the pulling period of chef-client

Now as we have configured node.Now there is no need to manual run chef-client in node.As we update/change in cookbook recipe node will pull that recipe and run in node.

*** Yet there is no Complete automation ***

we need to specify run_list for each recipe to each node that is tidious

If new recipe is created then again we need to run_list for recipe for each desired node. To solve this problem roles comes into the picture. Concept is attach role as run_list after any recipe you need to attach just put inside role,That's it.

Some important command

To delete cookbook from server

knife cookbook delete <cookbookName> -y

similary to delete node from server

knife node delete <nodeName> -y

similary to delete clients from chef-server

knife client delete <clientName> -y

To see list of roles

knife role list

To delete roles

knife role delete <roleName>

*** To upload role on server

knife role from file roles/<filename>.rb

Note : Whatever recipe we have included in role file upload that cookbook also in server.

attaching role run list to node

    knife node run_list set <NameOfNodeWeGaveNAmeToNode>  "role[filename]"

Now it is fully automated. *END