DevOps Classroom Series – 30/Jan/2021

Chef Server

For Chef Server Installation Refer Here
Ensure you have a valid chef repo and bootstrap multiple nodes (4)
Now bootstrap nodes by executing knife node bootstrap
If you dont want to bootstrap manually you can bootstrap by chef unattended bootstrap Refer Here
Scenario lets create nodes which have the following purpose
On Appservers we need to install
- java
- tomcat
On WebServer we need to install
- lamp
On db server we need to install mysql
Lets bootstrap all the nodes
Now lets write a cookbook to install tomcat server and java on app servers
Refer Here for the changeset
Lets create one more cookbook which installs utilities
Refer Here for the changeset
Now we would like to run java installation and utilities installation on app servers. We need to create a run_list for every node
In chef to manage run_lists on nodes we have reusable concept called as roles. Refer Here
Now lets create a role called as appserver and in the role lets try to add these two recipes ltutils[utils],lttomcat[installation]
We can create role from ui and also from chef-repo. IN the chef-repo\roles create an .rb file with your role name
For creating a role file Refer Here
Now lets upload role to the chef server using knife role from file
Now consider this scenario, IN the appserver on production environment we need to execute java 8, and in qa environment we need to install java 11
For both the cookbooks we have new versions
In chef we have concept called as environment where we can put restrictions on which version of cookbook should be uploaded, By default on chef servers we have _default environment.
Now lets create two environments Refer Here for knife command line and Refer Here for environments documentation
In QA environment
Now lets upload new version to chef server
Now lets run the chef-client in prod

Attributes in Chef

In Chef attributes can be defined in
- recipes node.default['qttomcatserver']['version']='1.0.0'
- attribute files
- environment files
- roles files
Every attribute in chef has types. the types are
- default
- force_default
- normal
- override
- force_override
- automatic (Can be applied only by chef internally not by us)
Since attribute has types and multiple places where it can be defined, which attribute will be applied if it is defined at more than one place
For this chef has a priority table. Refer Here
During chef convergance if there is an attribute defined at multiple locations then chef will find the weight by looking into
Whatever has the higher weight will be applied on the node.
All the attributes collected by ohai will be of type automatic
By default the chef convergance value is 30 mins. How can we change it
- Refer Here
- Refer Here for the changeset
If you automatically want to converge like cron job use the custom resource chef_client_cron
Handling sensitive data as plain text is not secure
To handle sensitive data chef has a concept called as data bags Refer Here
Create a databag
Lets upload data bag item
Lets view contents of databag on chef server
Now we can encrypt the databag contents using secret text or secret file.
In this case i will be using secret text
In the chef server the data bag item is encrypted but in local file it is still un encrypted
Refer Here