Note that a partition is not a drive. A physical hard-drive usually has only 1 partition on it but may well have more. Windows calls a partition a 'drive' inaccurately.
Think of a Music Cd. A music Cd can have just 1 piece of music on it or it could have several songs. Each song is not a Cd. Think of a movie on Dvd. Again there might only be 1 film but there may be bonus features such as a theatrical trailer, deleted scenes. Or it might be a Dvd of a television series or perhaps a few short films on one Dvd. A film is not a Dvd. A Dvd with 4 films or episodes on it is not 4 Dvds.
Types of Partitions
When Microsoft developed it's 'new' partition table type around the 1980s it restricted the number of partitions a hard-drive could have to only 4. These have become known as "Primary Partitions". It would be inaccurate to think of this as the main episodes on a Dvd because these could be shorter than the bonus features.
Some clever people managed to make one of these a new type of partition that could hold a large number of other sub-partitions. This new type of partition became known as an "Extended Partition" (it should have been "Extending" not "Extended" but nevermind). Perhaps think of this as the bonus features menu on a Dvd. When you select "bonus features" it doesn't play anything, it just gives you another menu.
The sub-partitions became known as "Logical Partitions". When people quote the number of partitions on a drive they usually exclude the Extended Partition. Perhaps think of these as the the bonus features on a Dvd. However, the bonus features could be a lot longer than the movie or the episodes.
Windows needs to be installed on one partition. It can only really cope with one and if it can see another one then it seems to think it is another drive. Often Windows users may think they have 2 hard-drives even if they see it is 1 physical device. If they had 2 physical hard-drives, perhaps with 2 (or more) partitions on each, then they get very confused.
Which neatly brings us to another confusion. A hard-drive can have only 1 partition, it can have more but it can't have less (assuming it is being used). Yes, the name "partition" is very badly chosen because it does imply that there is more than 1. Before Microsoft developed their operating systems it was assumed that every operating system would need to use more than 1 partition. So, since Windows is mostly restricted to 1 partition on 1 hard-drive it tries to reduce any confusion by calling that partition a drive, which is fine until we have 2 or more partitions on one physical drive.
To Edit, Create or Delete Partitions
The easiest way to do this is to use the program GPartEd on the LiveCd of Ubuntu. (LiveCd just means boot-up (reboot) the machine with the normal Ubuntu Cd in the Cd/Dvd-drive). From the top taskbar/panel click on
System - Administration - "Partition Editor"
In the Ubuntu 10.04's (Lucid Lynx) menus it went back to being called GPartEd for Ubuntu & Xubuntu and so Kubuntu uses QtPartEd (which is the Kde version and is almost identical). Many other distros, not just Ubuntu, use these programs so if you are having trouble with it in Ubuntu you might find it better in the smaller and lighter sliTaz
or in the very specialist distro "GParted Live CD"
Most drives have 1 Primary Partition with Windows installed. Often Laptops and some other machines have a tiny "Recovery Partition" in front of it. This is usually another Primary Partition but it is usually hidden to stop people from accidentally over-writing anything on it (and to avoid Windows getting confused).
Occasionally some machines have another partition for data. If this has been created with partition editors developed for Windows then it will probably be a "Logical Partition" (and therefore be inside an Extended Partition).
At a minimum Ubuntu will use 2 partitions
- one for the operating system itself
a "Swap" partition to help Ram
A 3rd partition for /home (for data) is a good idea and although you can make many more it is almost always better to keep things down to those 3. If you dual-boot or multi-boot with another linux distro then the swap and /home can be shared by them. It is even possible to share the /home with Windows if the /home's partition's "file-system" is NTFS or another Windows format.
Example Partitioning Scheme
On a system with a Recovery Partition but plenty of space and plenty of Ram, it makes sense to arrange the partitions something like this
- sda1 Recovery Partition, unchanged
- sda2 Windows partition, shrunk preferably from inside Windows, hopefully about 30Gb
- sda3 Extended Partition at least 25Gb
- sda5 Logical Partition, 10Gb, file-system = ext3, in the Partitioning Section of the installer change the "Mount Point" = /
- sda6 Logical Partition, at least 10Gb, file-system = ext4 or to share with Windows as Ntfs, in the installer change the "Mount Point" = /home
- sda7 Logical Partition, 10Gb, file-system = ext3, no Mount Point. This is an experimental area for trying other distros and installing a new release of Ubuntu before upgrading to it properly
sda8 Logical Partition, between ram & 2xRam, perhaps slightly over 2xRam, 'file-system' = "linux-swap".
Notice the numbers 1 to 4 are reserved for Primary Partitions whereas Logical Partitions are numbered from 5 onwards.
For smaller drives or with Ram less than 1Gb I would arrange things very differently but the real variety starts when you include a 2nd or 3rd physical hard-drive as the /home and the swap partitions on the other drive from the / could improve performance quite a lot. Anyway something else that might be worth considering is a logical partition for each specific use, such as for a groupware partition (like Kolab, for example). I make this about 20 Gb and format it as ext3, since most specific uses (like Kolab) will be comfortable with ext3. A problem sometimes arises if there is a lot of empty space on 1 partition but another is overcrowded so i would try to avoid having too many partitions. It might be worth making a separate /boot partition as it only needs to be about 100Mb and many people prefer having it separate if they keep (re)installing operating systems.