If you want to boot your operating system from the drive you are about to partition, you will need:
A primary partition
One or more swap partitions
Zero or more primary/logical partitions
Any other drive:
One or more primary/logical partitions
Zero or more swap partitions
Your boot partition ought to be a primary partition, not a
logical partition. This will ease recovery in case of disaster, but it
is not technically necessary. It must be of type 0x83 "Linux
native". If you are using a version of
21-3 (ie, from the 1990s),
your boot partition must be contained within the first 1024 cylinders of
the drive. (Typically, the boot partition need only contain the kernel
If you have more than one boot partition (from other OSs,
for example,) keep them all in the first 1024 cylinders (All
DOS partitions must be within the first 1024). If you are
using a modern version of lilo, or a
means other than lilo loading your kernel (for example, a boot disk or
the LOADLIN.EXE MS-DOS based Linux loader), the
partition can be anywhere.
See the Large-disk
HOWTO for details.
Unless you swap to files you will need a dedicated swap partition. It
must be of type 0x82 "Linux swap". It may be positioned anywhere on
the disk (but see notes on placement: Section 4.4.2).
Either a primary or logical partition can be used for swap.
More than one swap partition can exist on a drive. 8 total (across drives)
are permitted. See notes on swap size below Section 4.4.1.
A single primary partition must be used as a container (extended
partition) for the logical partitions. The extended partition can go
anywhere on the disk. The logical partitions must be contiguous, but
needn't fill the extended partition.
4.3. File Systems
4.3.1. Which file systems need their own partitions?
Everything in your linux file system can go in the same (single)
partition. However, there are circumstances when you may want to
restrict the growth of certain file systems. For example, if your mail
spool was in the same partition as your root fs and it filled the
remaining space in the partition, your computer would basically
This fs contains spool directories such as those for mail and
printing. In addition, it contains the error log
directory. If your machine is a server and develops a
chronic error, those msgs can fill the partition. Server
computers ought to have /var in a different partition than
This is where most executable binaries go. In addition, the
kernel source tree goes here, and much documentation.
Some programs write temporary data files here. Usually, they
are quite small. However, if you run computationally
intensive jobs, like science or engineering applications,
hundreds of megabytes could be required for brief periods of
time. In this case, keep /tmp in a different partition than
This is where users home directories go. If you do not impose
quotas on your users, this ought to be in its own partition.
This is where your kernel images go. See discussion above
for placement on old systems.
4.3.2. File lifetimes and backup cycles as partitioning criteria
With ext2, partitioning decisions should be governed by backup
considerations and to avoid external fragmentation Section 7.3
from different file lifetimes.
Files have lifetimes. After a file has been created, it will
remain some time on the system and then be removed. File
lifetime varies greatly throughout the system and is partly
dependent on the pathname of the file. For example, files in
/bin, /sbin, /usr/sbin, /usr/bin and similar directories are
likely to have a very long lifetime: many months and above.
Files in /home are likely to have a medium lifetime: several
weeks or so. File in /var are usually short lived: Almost no
file in /var/spool/news will remain longer than a few days,
files in /var/spool/lpd measure their lifetime in minutes or
For backup it is useful if the amount of daily backup is
smaller than the capacity of a single backup medium. A daily
backup can be a complete backup or an incremental backup.
You can decide to keep your partition sizes small enough that
they fit completely onto one backup medium (choose daily full
backups). In any case a partition should be small enough that
its daily delta (all modified files) fits onto one backup
medium (choose incremental backup and expect to change backup
media for the weekly/monthly full dump - no unattended
Your backup strategy depends on that decision.
When planning and buying disk space, remember to set aside a
sufficient amount of money for backup! Unbackuped data is
worthless! Data reproduction costs are much higher than backup
costs for virtually everyone!
For performance it is useful to keep files of different
lifetimes on different partitions. This way the short lived
files on the news partition may be fragmented very heavily.
This has no impact on the performance of the / or /home
4.4. Swap Partitions
4.4.1. How large should my swap space be?
A general rule of thumb is the same amount as your RAM, but there is no technical
reason for this. Other techical considerations are:
In Linux, RAM and swap space add up (This is not true for all
Unices). For example, if you have 256 MB of RAM and 256 MB swap
space, you have a total of about 512 MB virtual memory.
On older machines, you should have at least 16 MB
of total virtual memory. So for 4 MB of RAM consider at least
12 MB of swap, for 8 MB of RAM consider at least 8 MB of
swap. The rule of thumb for older machines with limited memory is to assign twice
as much space to swap as there is RAM.
Currently, the maximum size of a swap partition is
architecture-dependent. For i386 and PowerPC, it is approximately
2Gb. It is 128Gb on alpha, 1Gb on sparc, and 3Tb on sparc64. For linux
kernels 2.1 and earlier, the limit is 128Mb. The partition may be
larger than 128 MB, but excess space is never used. If you want more
than 128 MB of swap for a 2.1 and earlier kernel, you have to create
multiple swap partitions. See the man page for mkswap for details.
When sizing swap space, keep in mind that too much swap space
may not be useful at all.
A very old rule of thumb in the days of the PDP and the Vax was that
the size of the working set of a
program is about 25\% of its virtual size. Thus it is probably useless
to provide more swap than three times your RAM.
But keep in mind that this is just a rule of thumb. It is
easily possible to create scenarios where programs have
extremely large or extremely small working sets. For example,
a simulation program with a large data set that is accessed
in a very random fashion would have almost no noticeable
locality of reference in its data segment, so its working set
would be quite large.
On the other hand, an xv with many simultaneously opened
JPEGs, all but one iconified, would have a very large data
segment. But image transformations are all done on one single
image, most of the memory occupied by xv is never touched.
The same is true for an editor with many editor windows
where only one window is being modified at a time. These
programs have - if they are designed properly - a very high
locality of reference and large parts of them can be kept
swapped out without too severe performance impact.
One could suspect that the 25\% number from the age of the
command line is no longer true for modern GUI programs
editing multiple documents, but I know of no newer papers
that try to verify these numbers.
So for a configuration with 16 MB RAM, no swap is needed for a
minimal configuration and more than 48 MB of swap are probably
useless. The exact amount of memory needed depends on the
application mix on the machine (what did you expect?).
4.4.2. Where should I put my swap space?
The short answer is anywhere is fine. However, if you are
interested in extracting as much speed as possible, there are
two basic strategies (other than buying more RAM.
Split the swap space across multiple drives, or at least on the
drive you write to least.
Put each swap partition on the outer tracks.
Here are the considerations:
If you have a disk with many heads and one with less heads and both are
identical in other parameters, the disk with many heads will be faster.
Reading data from different heads is fast, since it is purely
electronic. Reading data from different tracks is slow, since it
involves physically moving the head.
It follows then that writing swap on a separate drive will be
faster than moving the head back and forth on a single drive.
Older disks have the same number of sectors on all tracks.
With these disks it will be fastest to put your swap in the
middle of the disks, assuming that your disk head will move
from a random track towards the swap area.
Newer disks use ZBR (zone bit recording). They have more
sectors on the outer tracks. With a constant number of rpms,
this yields a far greater performance on the outer tracks
than on the inner ones. Put your swap on the fast tracks.
Usage: Of course your disk head
will not move randomly. If you have swap space in the middle of a disk
between a constantly busy home partition and an almost unused archive
partition, you would be better of if your swap were in the middle of the
home partition for even shorter head movements. You would be even better
off, if you had your swap on another otherwise unused disk, though.
Summary: Put your swap on a fast disk with
many heads that is not busy doing other things. If you have multiple
disks: Split swap and scatter it over all your disks or even different