Backing up your files

Let's face it, computers aren't perfect. Linux is an "almost perfect" operating system, but things do happen and data is sometimes lost. The best way to avoid problems is to backup your files. Linux provides two key programs to do this: 'tar' and 'gzip'

First we'll start with 'tar'. This program assembles various files into one package, commonly called a "tarball". Let's say you have some files - notes that you've taken during this course. You have:

* notes_1.txt
* notes_2.txt
* notes_3.txt
* notes_4.txt
* notes_5.txt

and you've placed them in a directory called /linux_course. You want to back them up and keep them on a floppy, let's say. You would type the following command to package them in a tarball.

tar -cvf linux_notes.tar notes*.txt

First, you have tar, the name of the program. Then you have the options, c (--create) v (--verbose-show what files they are) (f--file -make a file - should always be the last option) Then you have the name of the file you want to create ( linux_notes.tar) and the files you want to backup (notes*.txt).

This presupposes that you may have other files in the directory that you don't want to include. If you want to include ALL files in a directory, just substitute notes*.txt for *.*.

If you've got good data storage capabilities (Jaz or Zip drives, a CD writer or a tape backup drive), you might want to back up whole directories along with their corresponding subdirectories. Then you would enter in the directory, let's say /home/bob/ and issue the command:

tar -cvf bob_backup.tar *

With one asterisk, you will include directories and files without extensions (my_file as opposed to my_file.txt). Be prepared to get a fairly voluminous tarball.

This is the first step in the backup process. Now let's look at the second step; the compression of these files.
Using 'gzip'

As we mentioned, 'tar' just assembles the files together into only one file. There is no reduction in the size of these files (the tarball might even be bigger!) Now we would have to do one more thing in order to reduce this file into a more manageable size: use 'gzip'.

gzip is the preferred compression tool for Linux. To reduce the size of your tar file, you would issue the following command:

gzip your_tar_file.tar

and the tar file would be compressed. You can also compress a regular file using the same command, but gzip is used primarily with tarballs.

The result would be a file like this: your_tar_file.tar.gz

The two file extensions show us that the file is a tarball and it is compressed with the 'gzip' format. You can now proceed to store this as you see fit.
Putting it all together
'tar' has an option built into it to use 'gzip' to zip the file at the same time you make the tarball. If you add z to the options, and change the name of the file to create to a .gz extension, you have the whole shebang in one step. Our previous example would be modified to this:

tar -czvf bob_backup.tar.gz *

Remember f should always be the last option.