Volume Headers

Volume Headers

A partition called the volume header is stored on the partition that begins at disk block 0. (For proper system operation, the volume header must begin at disk block 0). It contains a minimal filesystem with a few files that contain information about the device parameters, the partition layout, the version number of the most recently used version of fx, and logical volume information. It also may contain some standalone programs.

The files and standalone programs that may be in a volume header are:

sgilabel

This file contains fx version number information. It is important not to delete this file from the volume header.

symmon

symmon is a standalone program used to debug the kernel. See the symmon(1M) reference page for more information.

xlvlab*, lvlab*

Logical volume information is stored in files called logical volume labels in the volume header. lv logical volume information is stored in files whose names begin with lvlab and XLV logical volume information is stored in files whose names begin with xlvlab. This information is used by the system to assemble logical volumes when the system is booted. Logical volume labels are created automatically when logical volumes are created.

ide

ide (integrated diagnostics environment) is a diagnostics program for low-end systems only. ide is executed when you choose the third item, "Run Diagnostics," on the System Maintenance Menu. Newer systems execute ide from the /stand directory if it isn't in the volume header.

fx

fx is the standalone version of the IRIX fx command. It is a disk utility used primarily for repartitioning disks. Older systems sometimes included a copy of the command fx in the volume header. There is no longer any need for fx in the volume header.

sash

On system disks, a copy of the standalone program sash (the standalone shell) must be in the volume header; it is required to boot a system. sash is a processor-specific program. Therefore, if you ever need to copy it from the /stand directory of another system or from the /stand directory of a software distribution CD, you must copy the correct version. If you copy from another system, both systems must have the same processor type. If you copy it from a software distribution CD, use the hinv command to identify the processor type of your system and Table 1-3 to identify the version of sash needed for that system.

Processor Types and sash Versions
Processor Type sash Version
IP17 sashIP17
IP19, IP20, IP22 sashARCS
IP21, IP26 sash64

Processor Types and *sash* Versions
Processor Type	sash Version
IP17	sashIP17
IP19, IP20, IP22	sashARCS
IP21, IP26	sash64

The fx command can be used to display and modify the device parameters and the partition layout. See the fx(1M) reference page and the section "Repartitioning a Disk With fx" in Chapter 2. Using fx has the side effect of creating the file sgilabel in the volume header.

The command prtvtoc is also used to display partition layout information. See the section "Displaying a Disk's Partitions With prtvtoc" in Chapter 2 for instructions.

The dvhtool command can be used to add and delete standalone programs from the volume header. dvhtool can also be used to delete logical volume labels from the volume header. See the sections "Adding Files to the Volume Header With dvhtool," and "Removing Files in the Volume Header With dvhtool" in Chapter 2 for more information.

The volume header is consulted (and therefore any mistakes made creating or modifying the volume header become apparent) only at these times:

during the boot up process
when creating or growing filesystems
when creating or growing logical volumes
when adding swap areas