There currently is one option to travel by night train from Paris (France) to Aurillac (France), taking approximately 12 hours: Namely the INTERCITES DE NUIT n° 3789 operated by SNCF.
The National Company of the French Railways (SNCF) operates a handful of lines throughout continental France.
SNCF night trains are equipped with standard seating carriages and couchette carriages offered in two comfort classes.
Couchette carriages generally have 4-person compartments in first class and 6-person compartments in second class. The berths are simply designed in both classes and are about 1.9 meters long.
Yes, it's possible to reserve an entire couchette compartment as a private compartment. This can also be done for a group.
First class berths are slightly wider than in second class and there are only four berths per compartment. Advantage of first class: In Paris and Toulouse, there are showers at the stations for first class passengers. In second class, six travelers share each compartment. For cyclists, it's possible to bring a bicycle in second class for an additional fee of 10 euros.
There is no dining car on board the Intercités de Nuit. It's recommended to bring your own food or eat in Paris before departure. It's possible to pre-order food and drinks. In first class, a small breakfast is offered. Each passenger receives a 'night kit' with a refreshing towelette, dental cleaning tablet, sleep mask, earplugs, and a small bottle of water.