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Specifying the geometry

Disk geometry parameters are specified in the options section of the configuration file. Each disk parameter sub-section begins with disk= disk_device, similar to the way how boot images are specified. It is suggested to group disk parameter sections together, preferably at the beginning or the end of the options section.

For each disk, the following variables can be specified:

bios= bios_device_code
Is the number the BIOS uses to refer to that device. Normally, it's 0x80 for the first hard disk and 0x81 for the second hard disk. Note that hexadecimal numbers have to begin with ``0x''. If bios is omitted, LILO tries to ``guess'' that number.
sectors= sectors
and
heads= heads
specify the number of sectors per track and the number of heads, i.e. the number of tracks per cylinder. Both parameters have to be either specified together or they have to be entirely omitted. If omitted, LILO tries to obtain that geometry information from the kernel.
cylinders= cylinders
Specifies the number of cylinders. This value is only used for sanity checks. If cylinders is omitted, LILO uses the information obtained from the kernel if geometry information had to be requested in order to determine some other parameter. Otherwise,gif it just assumes the number of cylinders to be 1024, which is the cylinder limit imposed by the BIOS.

Additionally, partition sub-sub-sections can be added with partition= partition_device. Each partition section can contain only one variable:

start= partition_offset
Specifies the zero-based number of the start sector of that partition. The whole disk always has a partition offset of zero. The partition offset is only necessary when using devices for which the kernel does not provide that information, e.g. CD-ROMs.

Example:

disk = /dev/sda
  bios = 0x80
  sectors = 32
  heads = 64
  cylinders = 632
  partition = /dev/sda1
    start = 2048
  partition = /dev/sda2
    start = 204800
  partition = /dev/sda3
    start = 500000
  partition = /dev/sda4
    start = 900000

Because many SCSI controllers don't support more than 1 GB when using the BIOS interface, LILO can't access files that are located beyond the 1 GB limit of large SCSI disks on such controllers and reports errors in these cases.



next up previous contents
Next: Disk parameter table Up: Disk geometry Previous: Obtaining the geometry



Ross Biro
Sat May 20 13:51:22 PDT 1995