Backup and Recovery

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Things do not always go smoothly, and this is especially true for system administration. Experience shows that the data in the directory will soon become very important throughout the whole enterprise. Applications increasingly begin to use the directory for authentication or information management, and sooner or later this data becomes of vital importance for the everyday life of the whole company.

There are several possible types of failures of directory services:

• Hardware failure: A hardware component fails. This could be a hard disk, a network card, the motherboard, or any other hardware component compromising the functionality of the directory server.

• Operating-system failure: The operating system, like any other program, is not error proof. It can crash and destroy data.

• Software errors in application programs: Because there will be applications updating the directory, there is a possibility that an error in one of these programs could alter the data in the directory.

• Operator errors: Human error in the administration and maintenance of the directory could result in accidental erasure of files or directories.

This mean that we, as system administrators, face two different categories of failure:

1. System failures: Resources at the file-system level become unavailable or corrupt

2. Application failures: Resources at the application level become unavailable or corrupt.

The first category is the responsibility of the system administrator, who provides tools to save the data at regular intervals on tape or other media and reinstalls it as needed. The system administrator also provides a maintenance contract to replace defective hardware or reinstall system software.

The second category falls under the job of the administrator of the directory server. To recover from this type of failure, the administrator needs a copy of the directory in a consistent state. It is a good idea to define a policy of regularly exporting and backing up data from the directory server.

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