2. What to do right now ?

If you read this by curiosity or just seeking information and you are on a running Linux system, do immediately the following :

• open a root terminal or xterm,
• key in " /sbin/fdisk -l" (that last character being l for Lima).

you will be gratified by a list of all current partitions on all disks presents on your computer.

• Write this back on paper (or do " /sbin/fdisk -l | lpr" to print it) and save it in a safe place for future use.

If you are not the system administrator, you should not be concerned by the problem and can stop reading this.