Bitter rivals Booba and Kaaris ended up behind bars last August after a running battle between their entourages shut down part of a Paris airport.
Kaaris, 39, posted a video of himself signing the contract for the fight while he nonchalantly ate some chicken and chips with the hashtag, “The rule is that there will be no rules.”
The fight at Orly airport was caught on camera.
Booba quickly took to social media to mock his rival.
“He's signed, he's signed,” he said. “I wanted (the fight) to happen earlier but the diva and actress wouldn't have it. The important thing is that it happens.”
The ultra-violent sport of MMA (mixed martial arts) is still banned in France, so the fight will take place in Geneva.
The winner will take home €1.5 million, while the loser will get a third of that, the promoters confirmed Monday.
While the Ivory Coast-born Kaaris has promised he will drink his rival's blood, Booba, aka Elie Yaffa, has replied in kind. “I will beat you to death, you son of a bitch,” he wrote.
The rappers' long-running dispute has sparked hilarity on social media.
A month in solitary confinement following the brawl at Orly airport, heavy fines and the threat of 18 months more behind bars have done nothing to cool their animosity.
Booba – whose Instagram account photo features his toned six-pack – spent the weekend posting videos of his training and dietary regime and promoting a gadget which he claims helps eliminate abominable fat.
“People tell me that it is going to be hard to keep up the training for eight months,” said the tattooed 42-year-old who calls himself the “Duke of Boulogne”.
“But what's hard is having to get up at six in the morning to fill the shelves of Monoprix (a French supermarket) for €1,000 a month,” he added.
The rumble in Geneva will be run by the Swiss MMA franchise, the Strength and Honor Championship.
Promoter Raid Salah said talks between the two men on setting up the fight had been “very difficult” with each throwing tantrums.
The airport scrap in August between the singers, who were both on their way to concerts in Barcelona, went viral after bystanders filmed the fight on their phones.
News of their cage fight set social media alight with mocking memes comparing the grudge match to the big money boxing match between legendary fighter Floyd Mayweather and Irish MMA star Conor McGregor in 2017, which the American won.