As you can see in Listing 3-2, fdisk presents you with a warning about the size of the disk. The warning relates to older systems and disks and is not especially relevant these days. Older operating systems used to talk to the disks in a system by directly querying its BIOS for a specific coordinate on the disk expressed in terms of a cylinder, head, and sector address. With space being at a premium in the old days, the amount of space allocated to actually store those coordinates was very low (10 bits). For those of you who haven't already done the binary math in your head, that equates to a total of 1,024 possible addresses on the disk, and this is the problem fdisk is telling us about. DOS is an OS that is therefore unable to handle these larger disks; even the Linux LILO boot loader had this limitation until a few years ago. It is unlikely that this limitation will affect you as most modern computer BIOSes have resolved these issues.
After starting the fdisk command and seeing any introductory messages, you are presented with its internal prompt, Command (m for help):. We issued the p command to print out the partition map. This produces the same output as the fdisk -l command, but only for the disk specified on the command line (/dev/sda).
The following example shows how to create an extended partition and logical partitions within it. Listing 3-3 shows a transcript of this fdisk session, with our sample responses highlighted in bold.
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