5. Partitioning with fdisk
This section shows you how to actually partition your hard drive with the fdisk utility. Linux allows only 4 primary partitions. You can have a much larger number of logical partitions by sub-dividing one of the primary partitions. Only one of the primary partitions can be sub-divided.
Examples:
Four primary partitions (see Section 5.2)
Mixed primary and logical partitions (see Section 5.3)
5.1. fdisk usage
fdisk is started by typing (as root) fdisk device at the command prompt. device might be something like /dev/hda or /dev/sda (see Section 2.1.1). The basic fdisk commands you need are:
p print the partition table
n create a new partition
d delete a partition
q quit without saving changes
w write the new partition table and exit
Changes you make to the partition table do not take effect until you issue the write (w) command. Here is a sample partition table:
Disk /dev/hdb: 64 heads, 63 sectors, 621 cylinders Units = cylinders of 4032 * 512 bytes Device Boot Start End Blocks Id System /dev/hdb1 * 1 184 370912+ 83 Linux /dev/hdb2 185 368 370944 83 Linux /dev/hdb3 369 552 370944 83 Linux /dev/hdb4 553 621 139104 82 Linux swap |
5.2. Four primary partitions
The overview:
Decide on the size of your swap space (see Section 4.4) and where it ought to go (see Section 4.4.3). Divide up the remaining space for the three other partitions.
Example:
I start fdisk from the shell prompt:
# fdisk /dev/hdb |
Command (m for help): p Disk /dev/hdb: 64 heads, 63 sectors, 621 cylinders Units = cylinders of 4032 * 512 bytes |
Command (m for help): n Command action e extended p primary partition (1-4) p Partition number (1-4): 1 First cylinder (1-621, default 1):<RETURN> Using default value 1 Last cylinder or +size or +sizeM or +sizeK (1-621, default 621): +384M |
Command (m for help): n Command action e extended p primary partition (1-4) p Partition number (1-4): 2 First cylinder (197-621, default 197):<RETURN> Using default value 197 Last cylinder or +size or +sizeM or +sizeK (197-621, default 621): +128M |
Device Boot Start End Blocks Id System /dev/hdb1 1 196 395104 83 Linux /dev/hdb2 197 262 133056 83 Linux |
Command (m for help): a Partition number (1-4): 1 |
Command (m for help): t Partition number (1-4): 2 Hex code (type L to list codes): 82 Changed system type of partition 2 to 82 (Linux swap) Command (m for help): p |
Disk /dev/hdb: 64 heads, 63 sectors, 621 cylinders Units = cylinders of 4032 * 512 bytes Device Boot Start End Blocks Id System /dev/hdb1 * 1 196 395104+ 83 Linux /dev/hdb2 197 262 133056 82 Linux swap /dev/hdb3 263 458 395136 83 Linux /dev/hdb4 459 621 328608 83 Linux |
Side topics:
5.3. Mixed primary and logical partitions
The overview: create one use one of the primary partitions to house all the extra partitions. Then create logical partitions within it. Create the other primary partitions before or after creating the logical partitions.
Example:
I start fdisk from the shell prompt:
# fdisk /dev/sda |
First I figure out how many partitions I want. I know my drive has a 183Gb capacity and I want 26Gb partitions (because I happen to have back-up tapes that are about that size).
183Gb / 26Gb = ~7
so I will need 7 partitions. Even though fdisk accepts partition sizes expressed in Mb and Kb, I decide to calculate the number of cylinders that will end up in each partition because fdisk reports start and stop points in cylinders. I see when I enter fdisk that I have 22800 cylinders.
> The number of cylinders for this disk is set to 22800. There is > nothing wrong with that, but this is larger than 1024, and could in > certain setups cause problems with: 1) software that runs at boot > time (e.g., LILO) 2) booting and partitioning software from other > OSs (e.g., DOS FDISK, OS/2 FDISK) |
Since I have 4 primary partitions, 3 of them can be 3258 long. The extended partition will have to be (4 * 3258), or 13032, cylinders long in order to contain the 4 logical partitions.
I enter the following commands to set up the first of the 3 primary partitions (stuff I type is bold ):
Command (m for help): n Command action e extended p primary partition (1-4) p Partition number (1-4): 1 First cylinder (1-22800, default 1): <RETURN> Using default value 1 Last cylinder or +size or +sizeM or +sizeK (1-22800, default 22800): 3258 |
Partition number (1-4): 4 First cylinder (9775-22800, default 9775): <RETURN> Using default value 9775 Last cylinder or +size or +sizeM or +sizeK (9775-22800, default 22800): <RETURN> Using default value 22800 |
/dev/sda1 1 3258 26169853+ 83 Linux /dev/sda2 3259 6516 26169885 83 Linux /dev/sda3 6517 9774 26169885 83 Linux /dev/sda4 9775 22800 104631345 5 Extended |
Command (m for help): n First cylinder (9775-22800, default 9775): <RETURN> Using default value 9775 Last cylinder or +size or +sizeM or +sizeK (9775-22800, default 22800): 13032 |
Device Boot Start End Blocks Id System /dev/sda1 1 3258 26169853+ 83 Linux /dev/sda2 3259 6516 26169885 83 Linux /dev/sda3 6517 9774 26169885 83 Linux /dev/sda4 9775 22800 104631345 5 Extended /dev/sda5 9775 13032 26169853+ 83 Linux /dev/sda6 13033 16290 26169853+ 83 Linux /dev/sda7 16291 19584 26459023+ 83 Linux /dev/sda8 19585 22800 25832488+ 83 Linux |
5.4. Submitted Examples
I'd like to submit my partition layout, because it works well with any distribution of Linux (even big RPM based ones). I have one hard drive that ... is 10 gigs, exactly. Windows can't see above 9.3 gigs of it, but Linux can see it all, and use it all. It also has much more than 1024 cylenders.
Table 7. Partition layout example
| Partition | Mount point | Size |
|---|---|---|
| /dev/hda1 | /boot | (15 megs) |
| /dev/hda2 | windows 98 partition | (2 gigs) |
| /dev/hda3 | extended | (N/A) |
| /dev/hda5 | swap space | (64 megs) |
| /dev/hda6 | /tmp | (50 megs) |
| /dev/hda7 | / | (150 megs) |
| /dev/hda8 | /usr | (1.5 gigs) |
| /dev/hda9 | /home | (rest of drive) |
I also noticed that you don't have any REAL examples of partition tables, and for newbies I HIGHLY suggest putting quite a few up. I'm freshly out of the newbie stage, and partitioning was what messed me up the most.