Diddy‘s just one of the boys behind bars … laughing and chatting with other inmates in the yard in new photos from Fort Dix.

We’ve obtained pics of the star hanging out with a few dudes in the prison yard Saturday — and, ya gotta check ’em out … ’cause Diddy’s got the biggest smile on his face.

Diddy’s bundled up in a thick dark blue coat, gray pants and gray beanie … shootin’ the you-know-what with the other guys.

At one point, Diddy seems to be shaking hand with someone … perhaps making a new friend. Regardless, all these guys seem interested just to chat with the guy — no tension in the air whatsoever.

This is the second set of pics we’ve seen that show Diddy … after we published a photo of the guy in prison yesterday where he appeared a bit more solemn in a bright orange beanie.

Diddy was assigned to Fort Dix earlier this week … a major win for the mogul who asked to go there. It’s a low-security prison in New Jersey where Diddy will serve his time after he was convicted on two counts of violating the Mann Act.

We hadn’t seen a pic of Diddy in more than a year — cameras weren’t allowed in the courtroom during his federal trial — and these photos gave us the first look at the rapper’s graying beard.

These times in the yard are a nice break for the mogul who’s already got a job in the joint … a little R&R after grinding on laundry duty.