Administrator's Guide

1 About Dynamic Root Disk
1.1 Conceptual overview
This document describes the Dynamic Root Disk (DRD) toolset, which you can use to perform
software maintenance and recovery on an HP-UX operating system with minimum system downtime.
DRD enables you to easily and safely clone a system image from a root disk to another disk on
the same system and modify the image without shutting down the system. DRD significantly reduces
system downtime and allows you to do software maintenance during normal business hours. This
document is primarily for HP-UX system administrators who apply software maintenance on HP-UX
systems, such as installing new software product revisions, as well as updating from an older HP-UX
operating environment (OE) to a newer one. Some understanding of HP-UX system administration
is assumed.
Hewlett-Packard developed DRD to minimize the usual maintenance window during which you
shut down the system to apply software maintenance. With DRD, the system keeps running while
you clone the system image and apply software maintenance to the cloned image. DRD tools can
manage the two system images simultaneously. DRD also provides a fail-safe mechanism for
returning the system to its original state, if necessary.
Using DRD commands, you can perform software maintenance or make other modifications on
the cloned system image without affecting the active system image. When ready, you can boot
the cloned image on either the original system or a different system. The only downtime required
for this process is while the system reboots.
Other uses of DRD include using the clone for quick software recovery or using the clone to boot
another system, which is referred to as rehosting. For details of rehosting, see Rehosting and
unrehosting systems.
1.2 Terminology
In this guide, “root group” refers to the LVM volume group or VxVM disk group that contains the
root (“/”) file system. The term “logical volume” refers to an LVM logical volume or a VxVM volume.
IMPORTANT: DRD supports the following LVM root volume group versions:
• DRD A.3.5.* and earlier:
— HP-UX 11i v2: LVM 1.0
— HP-UX 11i v3: LVM 1.0
• DRD A.3.6.* and later:
— HP-UX 11i v2: LVM 1.0
— HP-UX 11i v3: LVM 1.0 and LVM 2.2
1.3 Commands overview
The drd command provides a command line interface to DRD tools. The drd command has nine
major modes of operation:
• activate After using the DRD commands to create and optionally modify a clone, using drd
activate invokes setboot(1M) and sets the primary boot path to the clone. After the clone
is booted, using drd activate invokes setboot(1M) to set the primary boot path to the
original system image. The drd activate command always sets the primary boot path to
the inactive (not booted) system image.
• clone Clones a booted system to an inactive system image. The drd clone mode copies
the LVM volume group or VxVM disk group, containing the volume on which the root file
system (“/”) is mounted, to the target disk specified in the command.
1.1 Conceptual overview 7