Hi, Thank for your answer.
I checked my partition, it is not full. I tried to place the grub-pc package after mysql-server in my package list class, and my installation is Ok. I don’t understand ?. For me, the grub-pc is installed by the DEFAULT class (PACKAGES aptitude GRUB_PC grub-pc grub-legacy- lilo-) which is before my class. Regards, Loïc