Linux Partitioning and Hard Drive Numbering

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Linux Hard drive Partitioning

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1. A partition table must have at least one primary partition.

2. A partition table permits:

   • A maximum of 4 primary partitions.

   • 3 primary partitions and 1 extended partition.
     An extended partition is a special kind of primary partition that contains two or more logical partitions.

3. One and only one of the 4 possible primary partitions can be an extended partition.

4. Multiple logical drives can be established in an extended partition.

5. There can only be one primary partition active at a time.

Primary partitions in Linux are designated hda1, hda2, hda3, hda4.

Logical partitions always begin with hda5, even if there are less than 4 primary partitions.
So if your hard drive had just one big extended partition, then you would have

• hda1-Extended
  
• hda5-First logical partition
  
• hda6-Second logical partition
  
• and so on.

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Example partition schemes

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1. Single hard drive with:

   1 primary partition
   1 extended partiton - with 4 logical partitions

      Primary Partition hda1
      _______________________
      Logical partition hda5   \
      -----------------------   \
      Logical partition hda6     \
      -----------------------     >  Extended partition hda2
      Logical partition hda7     /   (a primary partition that contains logical partitions)
      -----------------------   /
      Logical partition hda8   /
      _______________________ 
   

2. Single hard drive with:

   3 primary partition
   1 extended partiton - with 4 logical partitions

      Primary Partition hda1
      _______________________
      Primary Partition hda2
      _______________________
      Primary Partition hda3
      _______________________
      Logical partition hda5   \
      -----------------------   \
      Logical partition hda6     \
      -----------------------     >  Extended partition hda4
      Logical partition hda7     /   (a primary partition that contains logical partitions)
      -----------------------   /
      Logical partition hda8   /
      _______________________ 
   

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Linux Hard drive Numbering

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The Linux designations convention for hard disk partitions is as follows:

hdx1 - First  Primary partition
hdx2 - Second Primary partition
hdx3 - Third  Primary partition
hdx4 - Fourth Primary partition

hdx5 - First  Logical partition within the extended partition
hdx6 - Second Logical partition within the extended partition
hdx7 - Third  Logical partition within the extended partition
hdx8 - Fourth Logical partition within the extended partition
hdx9 - Fifth  Logical partition within the extended partition
etc

Where x identifies the hard disk.

The Linux designations convention for hard disks is as follows

hda - Master hard disk on ide:0; (ide:0-0)
hdb - Slave  hard disk on ide:0; (ide:0-1)
hdc - Master hard disk on ide:1; (ide:1-0)
hdd - Slave  hard disk on ide:1; (ide:1-1)

hde - Master hard disk on ide:2; (ide:2-0)
hdf - Slave  hard disk on ide:2; (ide:2-1)
hdg - Master hard disk on ide:3; (ide:3-0)
hdh - Slave  hard disk on ide:3; (ide:3-1)

hdi - Master hard disk on ide:4; (ide:4-0)
hdj - Slave  hard disk on ide:4; (ide:4-1)
hdk - Master hard disk on ide:5; (ide:5-0)
hdl - Slave  hard disk on ide:5; (ide:5-1)