In order to recover from catastrophic loss of service in case of a major hardware or software malfunction, it is absolutely essential to have a backup. The backup is supposed to let you restore the software (or rather the software's configuration) and other data that you need to reestablish your service. This includes the users' mails, the system's mail queue, and their authentication data among other things.
This chapter will guide you through the steps necessary to safeguard your system from failure and, if failure occurs, how to recover from it. After reading through this chapter you will know: