sdighost(ADM)

sdighost -- lists and/or removes device nodes associated with Ghost Names

Synopsis

/sbin/sdighost [-lr]

Description

In a multipath I/O environment (see sdipath(ADM)) there can be multiple paths to any single disk. The name for the disk is determined by the first path discovered to the disk. Ghost Names are provided so that a disk can still be accessed when that disk is no longer accessible at the original device node address, but is still accessible through another path.

For example, when you move a disk from one controller to another, the disk obtains a new address. The old address is retained as a Ghost Name, and a mapping is created between the old address and the new address. The original device node names do not change.

In this case, the Ghost Name is used for making the device nodes so that:

the filesystems residing on the disk are mounted automatically without making any changes to filesystem tables
the disk remains accessible to applications that use the original device nodes

Note that, once a disk is moved from one controller to another, it occupies two addresses. A new disk cannot be added at the old address until the name mapping is removed. sdighost is used to remove the associated Ghost Name, and so clear the mapping.

sdighost reads the device table and lists all the disks together with any associated Ghost Names. The -r option removes all the Ghost Name entries and recreates the device nodes based on the old addresses of the devices. The system must be rebooted after any use of the -r option.

A record of Ghost Names from invocation to invocation is kept in /etc/device.tab. Initially, when a new disk is found, no Ghost Name is assigned, and the device nodes are created based on its real address.

If the device returns to its original address then the associated Ghost Name is removed.

Options

sdighost takes the following options:

-l: Lists all the disks and any Ghost Names.
-r: Removes the Ghost Names in use and recreates the device nodes based on the real addresses. A system reboot is required after use of -r.

Files

/etc/device.tab

Return values

On success, sdighost returns zero. If an error is detected, it returns a negative value.

References

sdimkdev(ADM), sdimkdtab(ADM), sdipath(ADM)