Solaris 8 System Administrator Collection >> System Administration Guide, Volume 1 >> 28. Disk Management (Overview) >> About Disk Labels
 Previous: The format Utility |
A special area of every disk is set aside for storing information about the disk's controller, geometry, and slices. That information is called the disk's label. Another term used to described the disk label is the VTOC (Volume Table of Contents). To label a disk means to write slice information onto the disk. You usually label a disk after changing its slices.
If you fail to label a disk after creating slices, the slices will be unavailable because the operating system has no way of "knowing" about the slices.
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 TerminologyPartition 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.
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. |
 Next: Dividing a Disk Into Slices |
