question: What is the difference between primary and extended patitioning in Linux?
Answer: Primary and extended partitioning is only indirectly connected to Linux. All PCs are configured in BIOS to expect to find the Master Boot Record in a particular place on each hard drive. The Master Boot Record (MBR) aslo has a specific size which allows up to four partitions to be defined on the drive. There is also a flag to indicate what formatting is used for each partition. One of the values for the flag (0x05) indicates that the partition is an extended partition (Microsoft have also used 0x0f for extended partitions but that is non-standard). An extended partition contains its own partition table and is then further subdivided into as many logical partitions as you want (since this partition table can be as big as necessary).There is no need for more than one extended partition per drive and therefore this is all that the various operating systems support. Linux uses hda1 - hda4 (or sda1 - sda4) to reference the 4 primary partitions (or 3 primary and one extended) on your first drive and then hda5 (or sda5) onwards for the logical partitions within the extended partition. There is normally no need to reference the extended partition itself, usually you will want to reference the logical partitions it contains.
This article written by Stephen Chapman, Felgall Pty Ltd.