System backup

Once your system is in use, your next consideration should be to back up the file systems, directories, and files. If you back up your file systems, you can restore files or file systems in the event of a hard disk crash. There are different methods for backing up information.

Backing up file systems, directories, and files represents a significant investment of time and effort. At the same time, all computer files are potentially easy to change or erase, either intentionally or by accident.

Attention: When a hard disk crashes, the information contained on that disk is destroyed. The only way to recover the destroyed data is to retrieve the information from your backup copy.

If you use a careful and methodical approach to backing up your file systems, you should always be able to restore recent versions of files or file systems with little difficulty.

Several methods exist for backing up information. One of the most frequently used methods is called backup by name, file name archive, or regular backup. This is a copy of a file system, directory, or file that is kept for file transfer or in case the original data is unintentionally changed or destroyed. This method of backup is done when the i flag is specified and is used to make a backup copy of individual files and directories. It is a method commonly used by individual users to back up their accounts.

Another frequently used method is called backup by i-node, file system archive, or archive backup. This method of backup is done when the i flag is not specified. This is used for future reference, historical purposes, or for recovery if the original data is damaged or lost. It is used to make a backup copy of an entire file system and is the method commonly used by system administrators to back up large groups of files, such as all of the user accounts in /home. A file system backup allows incremental backups to be performed easily. An incremental backup backs up all files that have been modified since a specified previous backup.

The compress and pack commands enable you to compress files for storage, and the uncompress and unpack commands unpack the files once they have been restored. The process of packing and unpacking files takes time, but once packed, the data uses less space on the backup medium. For more information about these commands, see compress, pack, uncompress, and unpack.

Several commands create backups and archives. Because of this, data that has been backed up needs to be labeled as to which command was used to initiate the backup, and how the backup was made (by name or by file system).

Item Description
backup Backs up files by name or by file system. For more information, see backup.
mksysb Creates an installable image of the rootvg. For more information, see mksysb.
cpio Copies files into and out of archive storage. For more information, see cpio.
dd Converts and copies a file. Commonly used to convert and copy data to and from systems running other operating systems, for example, mainframes. dd does not group multiple files into one archive; it is used to manipulate and move data. For more information, see dd.
tar Creates or manipulates tar format archives. For more information, see tar.
rdump Backs up files by file system onto a remote machine's device. For more information, see rdump.
pax (POSIX-conformant archive utility) Reads and writes tar and cpio archives. For more information, see pax.