RCM Script Overview

Dynamic reconfiguration of system resources enables you to reconfigure system components while the system is still running. This feature has been available with the cfgadm command since the Solaris 8 release. The Reconfiguration Coordination Manager is the framework that manages the dynamic removal of system components. By using RCM, you can register and release system resources in an orderly manner.

In the Solaris 8 4/01 release, you can use the new RCM script feature to write your own scripts to shut down your applications, or to cleanly release the devices from your applications during dynamic reconfiguration. The RCM framework launches a script automatically in response to a reconfiguration request, if the request impacts the resources that are registered by the script.

Previously, you had to release resources from applications manually before you could dynamically remove the resource. Or, you could use the cfgadm command with the -f option to force a reconfiguration operation, but this option might leave your applications in an unknown state. Also, the manual release of resources from applications commonly causes errors.

The RCM script feature simplifies and better controls the dynamic reconfiguration process. By creating an RCM script, you can:

• Automatically release a device when you dynamically remove a device. This process also closes the device if the device is opened by an application.

• Run site-specific tasks when you dynamically remove a device from the system.

What Is an RCM Script?

An RCM script is:

• An executable shell script (Perl, sh, csh, or ksh) or binary program that the RCM daemon runs. Perl is the recommended language.

• A script that runs in its own address space by using the user ID of the script file owner.

• A script that is run by the RCM daemon when you use the cfgadm command to dynamically reconfigure a system resource.

What Can an RCM Script Do?

You can use an RCM script to release a device from an application when you dynamically remove a device. If the device is currently open, the RCM script also closes the device.

For example, an RCM script for a tape backup application can inform the tape backup application to close the tape drive or shut down the tape backup application.

How Does the RCM Script Process Work?

You can invoke a script as follows:

$ script-name command [args ...]

A script performs the following basic steps:

1. Takes the RCM command from command-line arguments.

2. Executes the command.

3. Writes the results to stdout as name-value pairs.

4. Exits with the appropriate exit status.

The RCM daemon runs one instance of a script at a time. For example, if a script is running, the RCM daemon does not run the same script until the first script exits.

RCM Script Commands

You must include the following RCM commands in an RCM script:

• scriptinfo – Gathers script information

• register – Registers interest in resources

• resourceinfo – Gathers resource information

You might include some or all of the following RCM commands:

• queryremove – Queries whether the resource can be released

• preremove – Releases the resource

• postremove – Provides post-resource removal notification

• undoremove – Undoes the actions done in preremove

See the rcmscript(4) man page for a complete description of these RCM commands.

RCM Script Processing Environment

When you dynamically remove a device, the RCM daemon runs:

• The script's register command to gather the list of resources (device names) that are identified in the script.

• The script's queryremove/preremove commands prior to removing the resource if the script's registered resources are affected by the dynamic remove operation.

• The script's postremove command if the remove operation succeeds. However, if the remove operation fails, the RCM daemon runs the script's undoremove command.