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System Administration Guide: Devices and File Systems
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format.dat File

The format.dat file that is shipped with the Solaris OS supports many standard disks. If your disk drive is not listed in the format.dat file, you can do the following:

  • Add an entry to the format.dat file for the disk.

  • Add entries with the format utility by selecting the type command and choosing the other option.

Adding an entry to the format.dat file can save time if the disk drive will be used throughout your site. To use the format.dat file on other systems, copy the file to each system that will use the specific disk drive that you added to the format.dat file.

You might need to modify the /etc/format.dat file for your system if you have one of the following:

  • A disk that is not supported by the Solaris OS

  • A disk with a partition table that is different from the Solaris OS's default configuration


Note - Do not alter default entries in the /etc/format.dat file. If you want to alter the default entries, copy the entry, give the entry a different name, and make the appropriate changes to avoid confusion.


The /etc/format.dat is not applicable for disks with EFI labels.

Contents of the format.dat File

The format.dat contains disk drive information that is used by the format utility. Three items are defined in the format.dat file:

  • Search paths

  • Disk types

  • Slice tables

Syntax of the format.dat File

The following syntax rules apply to the /etc/format.dat file:

  • The pound sign (#) is the comment character. Any text on a line after a pound sign is not interpreted by the format utility.

  • Each definition in the format.dat file appears on a single logical line. If the definition is longer than one line long, all lines but the last line of the definition must end with a backslash (\).

  • A definition consists of a series of assignments that have an identifier on the left side and one or more values on the right side. The assignment operator is the equal sign (=). The assignments within a definition must be separated by a colon (:).

  • White space is ignored by the format utility. If you want an assigned value to contain white space, enclose the entire value in double quotation marks ("). This syntax causes the white space within the quotes to be preserved as part of the assignment value.

  • Some assignments can have multiple values on the right side. Separate values by a comma.

Keywords in the format.dat File

The format.dat file contains disk definitions that are read by the format utility when it is started. Each definition starts with one of the following keywords: disk_type or partition. These keywords are described in the following table.

Table 16-6 Keyword Descriptions for the format.dat File

Keyword

Description

disk_type

Defines the controller and disk model. Each disk_type definition contains information that concerns the physical geometry of the disk. The default data file contains definitions for the controllers and disks that the Solaris OS supports.

You need to add a new disk_type definition only if you have an unsupported disk. You can add as many disk_type definitions to the data file as you want.

partition

Defines a partition table for a specific disk type. The partition table contains the partition information, plus a name that lets you refer to it in the format utility. The default format.dat file contains default partition definitions for several kinds of disk drives. Add a partition definition if you recreated partitions on any of the disks on your system. Add as many partition definitions to the data file as you need.

Disk Type (format.dat)

The disk_type keyword in the format.dat file defines the controller and disk model. Each disk_type definition contains information about the physical geometry of the disk. The default format.dat file contains definitions for the controllers and disks that the Solaris OS supports. You need to add a new disk_type only if you have an unsupported disk. You can add as many disk_type definitions to the data file as you want.

The keyword itself is assigned the name of the disk type. This name appears in the disk's label, and is used to identify the disk type whenever the format utility is run. Enclose the name in double quotation marks to preserve any white space in the name. The following table describes the identifiers that must also be assigned values in all disk_type definitions.

Table 16-7 Required disk_type Identifiers (format.dat)

Identifier

Description

ctlr

Identifies the controller type for the disk type. Currently, the supported values are SCSI and ATA.

ncyl

Specifies the number of data cylinders in the disk type. This determines how many logical disk cylinders the system will be allowed to access.

acyl

Specifies the number of alternate cylinders in the disk type. These cylinders are used by the format utility to store information such as the defect list for the drive. You should always reserve at least two cylinders for alternates.

pcyl

Specifies the number of physical cylinders in the disk type. This number is used to calculate the boundaries of the disk media. This number is usually equal to ncyl plus acyl.

nhead

Specifies the number of heads in the disk type. This number is used to calculate the boundaries of the disk media.

nsect

Specifies the number of data sectors per track in the disk type. This number is used to calculate the boundaries of the disk media. Note that this number includes only the data sectors. Any spares are not reflected in the number of data sections per track.

rpm

Specifies the rotations per minute of the disk type. This information is put in the label and later used by the file system to calculate the optimal placement of file data.

Other identifiers might be necessary, depending on the controller. The following table describes the identifiers that are required for SCSI controllers.

Table 16-8 Required disk_type Identifiers for SCSI Controllers format.dat

Identifier

Description

fmt_time

Specifies a number that indicates how long it takes to format a given drive. See the controller manual for more information.

cache

Specifies a number that controls the operation of the on-board cache while the format utility is operating. See the controller manual for more information.

trks_zone

Specifies a number that identifies how many tracks that exist per defect zone, to be used in alternate sector mapping. See the controller manual for more information.

asect

Specifies a number that identifies how many sectors are available for alternate mapping within a given defect zone. See the controller manual for more information.

Example 16-1 Required disk_type Identifiers for SCSI Controllers (format.dat)

The following are examples of disk_type definitions:

disk_type = "SUN1.3G" \
        : ctlr = SCSI : fmt_time = 4 \
        : trks_zone = 17 : asect = 6 : atrks = 17 \
        : ncyl = 1965 : acyl = 2 : pcyl = 3500 : nhead = 17 : nsect = 80 \
        : rpm = 5400 : bpt = 44823

disk_type = "SUN2.1G" \
        : ctlr = SCSI : fmt_time = 4 \
        : ncyl = 2733 : acyl = 2 : pcyl = 3500 : nhead = 19 : nsect = 80 \
        : rpm = 5400 : bpt = 44823

disk_type = "SUN2.9G" \
        : ctlr = SCSI : fmt_time = 4 \
        : ncyl = 2734 : acyl = 2 : pcyl = 3500 : nhead = 21 : nsect = 99 \
        : rpm = 5400

Partition Tables (format.dat)

A partition table in the format.dat file defines a slice table for a specific disk type.

The partition keyword in the format.dat file is assigned the name of the partition table. Enclose the name in double quotation marks to preserve any white space in the name. The following table describes the identifiers that must be assigned values in all partition tables.

Table 16-9 Required Identifiers for Partition Tables (format.dat)

Identifier

Description

disk

The name of the disk_type that this partition table is defined for. This name must appear exactly as it does in the disk_type definition.

ctlr

The disk controller type that this partition table can be attached to. Currently, the supported values are ATA for ATA controllers and SCSI for SCSI controllers. The controller type that is specified here must also be defined for the disk_type that you specified in the disk_type definition.

The other identifiers in a slice definition describe the actual partition information. The identifiers are the numbers 0 through 7. These identifiers are optional. Any partition that is not explicitly assigned is set to 0 length. The value of each of these identifiers is a pair of numbers separated by a comma. The first number is the starting cylinder for the partition. The second is the number of sectors in the slice.

Example 16-2 Required Identifiers for Partition Tables (format.dat)

The following are some examples of slice definitions:

partition = "SUN1.3G" \
        : disk = "SUN1.3G" : ctlr = SCSI \
        : 0 = 0, 34000 : 1 = 25, 133280 : 2 = 0, 2672400 : 6 = 123, 2505120

partition = "SUN2.1G" \
        : disk = "SUN2.1G" : ctlr = SCSI \
        : 0 = 0, 62320 : 1 = 41, 197600 : 2 = 0, 4154160 : 6 = 171, 3894240

partition = "SUN2.9G" \
        : disk = "SUN2.9G" : ctlr = SCSI \
        : 0 = 0, 195426 : 1 = 94, 390852 : 2 = 0, 5683986 : 6 = 282, 5097708

Specifying an Alternate Data File for the format Utility

The format utility determines the location of an alternate file by the following methods in this order:

  1. If a file name is given with the format -x option, that file is always used as the data file.

  2. If the -x option is not specified, then the format utility searches the current directory for a file named format.dat. If the file exists, it is used as the data file.

  3. If neither of these methods yields a data file, the format utility uses the /etc/format.dat file as the data file. This file is shipped with the Solaris OS and should always be present.

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