I am running Debian 8 as the only operating system on my Toshiba Satellite laptop, though I previously had other operating systems installed.Running the command sudo fdisk -l produces the following output:Disk /dev/sda: 698.7 GiB, 750156374016 bytes, 1465149168 sectorsUnits: sectors of 1 * 512 = 512 bytesSector size (logical/physical): 512 bytes / 4096 bytesI/O size (minimum/optimal): 4096 bytes / 4096 bytesDisklabel type: dosDisk identifier: 0x33d70f34Device     Boot      Start        End    Sectors   Size Id Type/dev/sda1  *          2048 1432047615 1432045568 682.9G 83 Linux/dev/sda2       1432049662 1465147391   33097730  15.8G  5 Extended/dev/sda5       1432049664 1465147391   33097728  15.8G 82 Linux swap / SolarisPartition 3 does not start on physical sector boundary.1) Why are sda2 and sda5 treated as different partitions when they almost exactly overlap?2) What happened to sda3 and 4?3) Why doesn't sda1 start at 0?
Odd output from fdisk -l: overlapping and missing partitions?
partition;fdisk
all information about partitions should be saved in some place. this place is a reserved portion of HDD at his beginning also called MBR (Master Boot Record).Depending on type of partition table chosen there can be used different partition layouts and in you case it's Disklabel type: dosdos partition table. Using this type of partition table you can create only four partitions, but what happen if you need five partitions? If you need more that 4 partition you need to create a special partition called extended partition which can then be organized in logical partitions. In this way, using this DOS partition table you can create 3 primary partitions and one extended ... the last one can be subdivided in logical partitions. In this way you can create more that 4 partitions on your HDD.Extended partition can be seen as a closure for logical drivers where all logical partition will reside. In you situation you have only one logical partition (sda5) which will take all space inside extended partition... so they seems to overlapping but the truth is that sda2 includes sda5why there aren't sda3 and sda4 ? ... it may depends on actions done at partition creation time or it make sens to reserve sda1, sda2, sda3 and sda4 for primary partitions and sda5 and so forth for logical drivers (partitions)