Backing up a system involves copying data from the system's hard disks onto removable media that can be safeguarded in a secure area. Backing up system data is one of the most crucial system administration functions and should be performed regularly. Backups are used to restore data if files become corrupted or if a system failure or another disaster destroys data. Having a fault-tolerant disk array is not enough. Disk mirroring and RAID 5 protect data in case of a hardware failure, but they do not protect against file corruption, natural disaster, or accidental deletion of a file. In other words, disk mirroring does not protect against flood damage or fire. In addition, if a program corrupts a particular file, the file will be just as corrupt on the mirrored copy as in the original. Therefore, you need to have in place some type of offline backup of your data. Backing up system datathe most important task you perform as a system administratormust be done on a regular basis. Although even a comprehensive backup scheme can't guarantee that information will not be lost, you can use backups to make sure the loss will be minimal.
This chapter describes the methods available to perform backups, the types of backups, how to develop a solid backup strategy, and how to restore data if you encounter a loss. This chapter begins with a look at backup media and then an explanation of the tar, dd, cpio, and pax commands, which are used to copy data from disk to disk or from disk to tape. Then you'll learn about the ufsdump and ufsrestore utilities, the preferred methods of backing up data from a Solaris system to tape on a regular basis. This chapter also introduces a method of backing up live file systems, called fssnap. Finally, this chapter describes how to back up an entire Solaris operating environment by using the Solaris Flash Archive.
Many third-party backup applications are available for Solaris but are not covered on the exam. Therefore, this chapter describes only the methods that are available in the standard Solaris 10 distribution.