Working with disks, tapes, and CD-ROMs

Determining how many disks you need for a backup

You can back up a whole system onto floppy disks: to estimate how many floppy disks the backup requires, use the du(C) disk usage command, which returns the number of 512-byte blocks contained (recursively) within the current directory. Its -s option prints only a grand total:

   $ du -s
   24356	.

For example, if 24356 is displayed, this means that you require a total of 24356 x 512 bytes, or roughly 11.9MB. This would give a total of nine 1.4MB floppy disks to create a full backup. You can display the number of blocks for each individual file or directory by including the filename on the end of the du command, as in the following:

   $ du -s /dev
   46      /dev

Once you know how many floppy disks are required, you can use the tar(C) or cpio(C) commands to create the archive. See ``Creating a backup with tar'' and ``Creating a backup with cpio'' for details of how to use these commands.