Hvis du bruger en ny harddisk (eller ønsker at rydde hele partitionstabellen for din disk), så skal en ny partitionstabel oprettes. Den “Guidede partitionering” gør dette automatisk, men under manuel partitionering, flyt markeringen på topniveau-elementet for disken og tryk på Enter. Det vil oprette en ny partitionstabel på den disk. I eksperttilstand, vil du blive spurgt om partitionstabellens type. Standarden for UEFI-baserede systemer er “gpt”, mens standardværdien i den ældre BIOS-verden er “msdos”. I en installation med standardprioritet vil disse standarder blive anvendt automatisk.

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	Når en partitionstabel med typen “gpt” blev valgt (standarden for UEFI-systemer), vil 1 MB ledig plads automatisk blive oprettet i begyndelsen af disken. Dette er med vilje og krævet for at indlejre GRUB2-opstartsindlæseren.

If you have an existing other operating system such as Windows and you want to preserve that operating system while installing Debian, you may need to resize its partition to free up space for the Debian installation. The installer supports resizing of both FAT and NTFS filesystems; when you get to the installer's partitioning step, select the option Manual and then simply select an existing partition and change its size.

While modern UEFI systems don't have such limitations as listed below, the old PC BIOS generally adds additional constraints for disk partitioning. There is a limit to how many “primary” and “logical” partitions a drive can contain.

On such old PC BIOS system, “primary” partitions are the original partitioning scheme for PC disks. However, there can only be four of them. To get past this limitation, “extended” and “logical” partitions were invented. By setting one of your primary partitions as an extended partition, you can subdivide all the space allocated to that partition into logical partitions. You can create up to 60 logical partitions per extended partition; however, you can only have one extended partition per drive.