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

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