Backups are needed in case a file or a group of files is lost.
The reasons for losing files include
Hardware failure like disk breaking,
accidentally deleting wrong file and
computer being stolen.
Backups help in all the above situations. In addition, it may be
good to have access to older versions of files, for example a
configuration file worked a week ago, but since then it has been
changed and nobody remembers how, its just not working anymore.
There are other solutions, and they are good to have if you can
afford them. These include
redundant disks (RAID 1 or 5), so that one disk can break
without loss of data,
using an undelete system (or not making mistakes when deleting
locking up computers.
These help, but if there is anything you do not want to lose on
the computer, make sure there are backups and they can be
What to backup?
If there is room on the backup media, and time limits permit
running backups long enough, it probably is wisest to back up
everything. You may skip /tmp or other places where it is known
there are only temporary files that nobody wants to backup.
If space or time limits place restrictions, consider not backing
up the following
Files that come directly from a CD or other removable media. It
may even be faster to copy them again from CD than restoring
from backup media.
Files that can be regenerated easily. For example, object files
that can be made with make. Just make sure all the source files
and compilers are backed up.
If the Internet connection is fast, it may be easy enough to
download files again. Just keep a list of the files and where to
download them from.
Backup devices and media
You need some media to store the backups. It is preferable to
use removable media, to store the backups away from the computer
and to get "unlimited" storage for backups.
If the backups are on-line, they can be wiped out by mistake. If
the backups are on the same disk as the original data, they do
not help at all if the disk fails and is not readable anymore.
If the backup media is cheap, it is possible to take a backup
every day and store them indefinitely.
Floppy,Disk,Tapes,CD-R and CD-RW are the medias available for
Planning a Backup
Before doing a backup, plan it carefully. Consider:
Which files are irreplaceable without a back up. Irreplaceable
files probably include those in users' home directories
(including /root), and configuration files, such as those in the
Which files are on removable drives, such as cd s or floppies.
Since you probably do not need to back up removable drives, you
might unmount them before doing a complete system backup.
Which files can be easily replaced by installing a package or
doing a selective install or upgrade of the operating system.
You can save time and storage space by not including these files
in a backup.
Which files are unnecessary or dangerous to backup. For example,
files in /tmp are probably unnecessary, while restoring some
files that are in the /proc directory could crash the system.
Whether to compress files using gzip or bzip2 . Compressing
saves space, but adds another step to the backup. Also, while
compression is generally reliable, it creates another stage at
which the process can fail.
Whether users are responsible for backing up their own files.
Since only the root user has full permissions for all files on
the system, usually backups are best done by the root user.
However, if users back up their own files, you might omit
backing up the home directory, or at least not back it up
Choosing a Backup Tool
Linux has several tools for backing up and restoring files
dump / restore : Old tools that work with filesystems, rather
than files, and can back up unmounted devices. Although you can
easyly control what is backed up with dump by editing a single
column in the /etc/fstab file, for some reason these utilities
have fallen into disuse. Today, many distributions of Linux,
including Debian, do not even include them by default. If you
want to use dump and restore , you must install them yourself.
tar : A standard backup tool, and by far the easiest to use. It
is especially useful for backing up over multiple removable
devices using the -M option.
cpio : A very flexible command, but one that is hard to use
because of the unusual way in which the command must be entered.
Many commercial or free software back up tools are also