Partition Table (System Administration Guide, Volume 1)

System Administration Guide, Volume 1

Partition Table

An important part of the disk label is the partition table which identifies a disk's slices, the slice boundaries (in cylinders), and total size of the slices. A disk's partition table can be displayed using the format utility. The table below describes partition table terminology.

Table 28-7 Partition Table Terminology


Partition Term	Value	Description
Number	`0-7`	Partition or (slice number). Valid numbers are 0-7.
Tag	`0=UNASSIGNED 1=BOOT 2=ROOT 3=SWAP 4=USR 5=BACKUP 7=VAR 8=HOME`	A numeric value that usually describes the file system mounted on this partition.
Flags
	`wm`	The partition is writable and mountable.
	`wu rm`	The partition is writable and unmountable. This is the default state of partitions dedicated for swap areas. However, the `mount` command does not check the "not mountable" flag.
	`rm`	The partition is read only and mountable.

Partition flags and tags are assigned by convention and require no maintenance.

See "How to Display Disk Slice Information" or "How to Examine a Disk Label" for more information on displaying the partition table.

Examples--Partition Tables

The following partition table example is displayed from a 1.05-Gbyte disk using the format utility:

Total disk cylinders available: 2036 + 2 (reserved cylinders)

Part      Tag    Flag     Cylinders        Size            Blocks
  0       root    wm       0 -  300      148.15MB    (301/0/0)   303408
  1       swap    wu     301 -  524      110.25MB    (224/0/0)   225792
  2     backup    wm       0 - 2035     1002.09MB    (2036/0/0) 2052288
  3 unassigned    wm       0               0         (0/0/0)          0
  4 unassigned    wm       0               0         (0/0/0)          0
  5 unassigned    wm       0               0         (0/0/0)          0
  6        usr    wm     525 - 2035      743.70MB    (1511/0/0) 1523088
  7 unassigned    wm       0               0         (0/0/0)          0

The partition table contains the following information:

Column Name	Description
`Part`	Partition (or slice number). See Table 28-7 for a description of this column.
`Tag`	Partition tag. See Table 28-7 for a description of this column.
`Flags`	Partition flag. See Table 28-7 for a description of this column.
`Cylinders`	The starting and ending cylinder number for the slice.
`Size`	The slice size in Mbytes.
`Blocks`	The total number of cylinders and the total number of sectors per slice in the far right column.

The following example displays a disk label using the prtvtoc command.

# prtvtoc /dev/rdsk/c0t1d0s0
* /dev/rdsk/c0t1d0s0 partition map
*
* Dimensions:
*     512 bytes/sector
*      72 sectors/track
*      14 tracks/cylinder
*    1008 sectors/cylinder
*    2038 cylinders
*    2036 accessible cylinders
*
* Flags:
*   1: unmountable
*  10: read-only
*
*                          First     Sector    Last
* Partition  Tag  Flags    Sector     Count    Sector  Mount Directory
       0      2    00          0    303408    303407   /
       1      3    01     303408    225792    529199
       2      5    00          0   2052288   2052287
       6      4    00     529200   1523088   2052287   /usr

The disk label includes the following information:

Dimensions - This section describes the physical dimensions of the disk drive.

Flags - This section describes the flags listed in the partition table section. See Table 28-7 for a description of partition flags.

Partition (or Slice) Table - This section contains the following information:

Column Name	Description
`Partion`	Partition (or slice number). See Table 28-7 for a description of this column.
`Tag`	Partition tag. See Table 28-7 for a description of this column.
`Flags`	Partition flag. See Table 28-7 for a description of this column.
`First Sector`	The first sector of the slice.
`Sector Count`	The total number of sectors in the slice.
`Last Sector`	The last sector number in the slice.
`Mount Directory`	The last mount point directory for the file system.