Rapid Recovery 6.1.3 - User Guide

Using Bourne shell and Bash scripting with Rapid Recovery

Bourne shell (sh) is a shell language or command-line interpreter for Unix-based operating systems. Bourne shell is used in Rapid Recovery with Linux to customize environments and specify certain operations to occur in a predetermined sequence. The .sh is the file extension and naming convention for Bourne shell files.

Bourne Again Shell (Bash) is a similar shell language that implements the same grammar, parameter, and variable expansion, redirection and quoting. Bash also uses the same .sh file extension. The information here applies equally to Bash.

Using pre and post transfer, pre and post snapshot, and post export script hooks, you can perform system operations before and after a transfer or snapshot, or after virtual export. For example, you may want to disable a certain cronjob while a transfer is occurring and enable it once the transfer has finished. As another example, you may need to run commands to flush application-specific data to disk. The contents are written to a temporary file and run using exec. The script then runs using the interpreter defined in the first line of the script, for example, (#!/usr/bin/env bash). If the specified interpreter is not available, the script uses the default shell defined in the $SHELL environment variable.

You can substitute and use any interpreter. For example, on the #! line of the script, you can replace “bash” with “zsh” (Z shell), “tcsh” (tee shell), and so on, based on your preference.

You can add available objects from the TransferPrescript parameter or add your own commands to the PreTransferScript.sh and PostTransfer.sh scripts to customize them.

Only PreTransferScript and PostTransferScript receive parameters. The snapshot and export scripts do not.

This section describes the scripts that administrators can use at designated occurrences in Rapid Recovery for Windows and Linux. It includes the following topics:

Prerequisites for shell scripting

Rapid Recovery provides the ability to run Bourne shell, Bash, and other shell scripts on a protected Linux machine before and after a transfer. The following scripts are supported for Linux machines protected with the Rapid Recovery Agent software.

NOTE: If a script is not executable, the transfer job fails. • PreTransferScript.sh • PostTransferScript.sh • PreSnapshotScript.sh • PostSnapshotScript.sh • PostExportScript.sh

To use these scripts, ensure that they reside in the /opt/apprecovery/scripts/ directory.

Execution timing for pre and post scripts

For context, the following diagram shows the difference in timing for running pre and post transfer and snapshot scripts.

Figure 8. When pre and post scripts execute

Supported transfer and post-transfer script parameters

The following parameters are supported on Linux for transfer scripts. For more information, see Sample shell scripts.

The following parameters are supported on Linux for post transfer scripts.

Testing shell scripting

You can test the scripts you want to run by using the editor for the script (.sh) files.

NOTE: If the pre or post script fails, the job also fails. Information about the job is available in the /var/log/apprecovery/apprecovery.log file. Successful scripts return the exit code 0.

Input parameters for shell scripting

The parameters for shell scripting in Rapid Recovery are described in the following tables.

TransferPrescriptParameters_VolumeNames

The following table presents the available objects for the TransferPrescript parameter.

TransferPostscriptParameter

The following table presents the available objects for the TransferPostscript parameter.

Sample shell scripts

This section describes the sample shell scripts available for administrative users to run on protected machines.

CAUTION: The sample scripts provided in this document function as they exist when run by qualified administrators. Take precautions when modifying functioning scripts to retain working versions. Any modifications to the script samples included here, or any scripts you create, are considered customization, which is not typically covered by Quest Support.

NOTE: Protected machines use the 'exec' shell command to launch the script. You can indicate which interpreter should run the script by defining that information in the first line of the script. If you do not specify the interpreter, the default shell interprets the script. If you choose something other than the default shell, you must ensure that the specified interpreter is available on all protected machines. All sample shell scripts in this document are tested and run successfully as Bourne shell or Bash scripts.

The sample scripts for protected machines include:

PreTransferScript.sh

The PreTransferScript is run on the protected Linux machine immediately before the backup snapshot transfer begins.

NOTE: For clarification on when pre and post scripts are run, see .Execution timing for pre and post scripts.

The following script stores the values from input parameters in PreTransferScriptResult.txt, which is stored in the root home directory.

Sample PreTransferScript