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<sect2 arch="i386"><title>Partitioning for &arch-title;</title>
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If you have an existing other operating system such as DOS or Windows and
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you want to preseve that operating system while installing Debian, you may
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need to resize its partition to free up space for the Debian installation.
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The installer supports resizing of both FAT and NTFS filesystems; when you
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get to the installer's partitioning step, select the option to partition
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manually and then simply select an existing partition and change its size.
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The PC BIOS generally adds additional constraints for disk
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partitioning. There is a limit to how many <quote>primary</quote> and
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<quote>logical</quote> partitions a drive can contain. Additionally, with pre
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1994–98 BIOSes, there are limits to where on the drive the BIOS can boot
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from. More information can be found in the
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<ulink url="&url-partition-howto;">Linux Partition HOWTO</ulink> and the
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<ulink url="&url-phoenix-bios-faq-large-disk;">Phoenix BIOS FAQ</ulink>, but
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this section will include a brief overview to help you plan most situations.
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<quote>Primary</quote> partitions are the original partitioning scheme for PC
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disks. However, there can only be four of them. To get past this
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limitation, <quote>extended</quote> and <quote>logical</quote> partitions were invented. By
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setting one of your primary partitions as an extended partition, you
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can subdivide all the space allocated to that partition into logical
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partitions. You can create up to 60 logical partitions per extended
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partition; however, you can only have one extended partition per
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Linux limits the partitions per drive to 15 partitions for SCSI disks
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(3 usable primary partitions, 12 logical partitions), and 63
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partitions on an IDE drive (3 usable primary partitions, 60 logical
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partitions). However the normal &debian; system provides
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only 20 devices for partitions, so you may not install on partitions
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higher than 20 unless you first manually create devices for those
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If you have a large IDE disk, and are using neither LBA addressing,
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nor overlay drivers (sometimes provided by hard disk manufacturers),
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then the boot partition (the partition containing your kernel image)
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must be placed within the first 1024 cylinders of your hard drive
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(usually around 524 megabytes, without BIOS translation).
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This restriction doesn't apply if you have a BIOS newer than around
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1995–98 (depending on the manufacturer) that supports the <quote>Enhanced
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Disk Drive Support Specification</quote>. Both Lilo, the Linux loader, and
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Debian's alternative <command>mbr</command> must use the BIOS to read the
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kernel from the disk into RAM. If the BIOS int 0x13 large disk access
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extensions are found to be present, they will be utilized. Otherwise,
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the legacy disk access interface is used as a fall-back, and it cannot
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be used to address any location on the disk higher than the 1023rd
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cylinder. Once Linux is booted, no matter what BIOS your computer
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has, these restrictions no longer apply, since Linux does not use the
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If you have a large disk, you might have to use cylinder translation
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techniques, which you can set from your BIOS setup program, such as
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LBA (Logical Block Addressing) or CHS translation mode (<quote>Large</quote>).
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More information about issues with large disks can be found in the
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<ulink url="&url-large-disk-howto;">Large Disk HOWTO</ulink>. If you
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are using a cylinder translation scheme, and the BIOS does not support
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the large disk access extensions, then your boot partition has to fit
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within the <emphasis>translated</emphasis> representation of the
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The recommended way of accomplishing this is to create a small (5–10MB
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should suffice) partition at the beginning of the disk to be used as
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the boot partition, and then create whatever other partitions you wish
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to have, in the remaining area. This boot partition
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<emphasis>must</emphasis> be mounted on <filename>/boot</filename>,
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since that is the directory where the Linux kernel(s) will be stored.
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This configuration will work on any system, regardless of whether LBA
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or large disk CHS translation is used, and regardless of whether your
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BIOS supports the large disk access extensions.