how to make secondary slave as readable in MongoDB?

How do I make a secondary slave as readable in MongoDB?

We can do this via shell command

rs.slaveOk()

But how we can do it permanently for all session via config file?

For mongo shell sessions there is a concept of mongorc files which include JavaScript to execute when the mongo shell starts. You can use this feature to extend or customise the behaviour of the interactive shell.

If you want secondary reads to be allowed by default for all shell sessions you can either:

-
add the rs.slaveOk() command to the .mongorc.js in the current user's home directory:

$ echo "rs.slaveOk()" >> ~/.mongorc.js

-
add to the global /etc/mongorc.js which is executed before the user-specific '~/.mongorc.js` (Note: requires MongoDB 2.6+):

$ echo "rs.slaveOk()" | sudo tee -a /etc/mongorc.js

StackExchange Database Administrators Q#105153, answer score: 4