In this article I am going to de-mystify Linux file compression and archiving for you. By the end of the article you’ll be compressing and decompressing files in your sleep. And, as a bonus, you’ll know how to do this both via command line and GUI.

Compression versus archiving

The difference between compression and archiving is simple: Compression makes a file (or directory) smaller and Archiving takes many seperate files (such as a directory containing sub-directories and/or files) and turns it into a single file. You can have a compressed archive (such as .tar.gz or .tgz) and you can even have an archive of compressed files (such as a directory that contains a bunch of compressed files). But how do you know what are compressed files verses archived files? Here’s a list of file extensions and what they are.

.tar – This is an uncompressed Tar archive file. This type of archive is unpacked with the command tar xvf file.tar.

.tgz – This is a compressed Tar archive file. This type of archive is decompressed and unpacked with the command tar xvzf file.tgz.

.gz – This is a file compressed with the gzip program. This type of file is decompressed with the command gunzip file.gz.

.zip – This is a compressed file. This type of file is decompressed with the command unzip file.zip

.bz2 – This is a compressed file. This type of file is decompressed with the command bunzip2 file.bz2.

Which compression to use?

Of the three compression utilities (bzip2, zip, and gzip) the tool that will result in the most compression (the smallest file) is bzip2. The only disadvantage to bzip2 is that the algorithm uses more processor to complete than does the other utilities.

If you are sharing your compressed files with Windows users your best bet is to use zip for compression. Although there are tools (such as Stuffit Deluxe for Windows) that can handle bz2 files, the default supported is .zip.

Using the GUI

If you are a fan of the GUI (and who isn’t these days?) you will be glad to know that most all Linux file managers can handle compressed and archived files. In both Nautilus (GNOME) and Dolphin (KDE) you can simply right click a compressed, archived, or compressed archive file and select Extract. Both file managers also offer compression and archiving options when you right click a file or directory.

Final thoughts

Working with compression and archiving is very simple with the Linux operating system. You have plenty of options in both the command line and the GUI worlds.

Of course you can do the same thing, quickly, from the command line. But, for many, the choice between a user-friendly GUI tool and the command line is a no-brainer.

With File Roller you can both create archives and unpack archives. File Roller deals with the following types:

• .tar
• .tar.gz
• .tar.bz2
• .tar.lzma
• .jar
• .ar
• .cbz
• .zip

File Roller also does automatic archive typing, so when you are opening an archive you do not have to declare the type.

Running File Roller

File Roller Main Window

From the GNOME main menu you will find File Roller in the Accessories sub-menu of the Applications menu. When File Roller opens you will be presented with a fairly blank window.

From the main window you can either open an archive for unpacking or create a new archive. When you create a new archive what you are doing is first creating a folder that will contain all of the files, and then File Rollers packs everything up for you automatically.

Let’s create an archive for example’s sake.

Creating An Archive

The first thing to do is click the New Button. When you do this a File dialog will open where you will name your archive. This window can be deceiving because it looks like it wants you to select a file. That is not the case. What you want to do is enter the name of your new Archive in the Name text field. Once you have done that select the type of archive you want to create. After you have taken care of those two options, click the Create button.

At first glance you might think nothing happened. Look again at the title bar of the File Roller window and you will notice the file name of your new archive (see the image to the right).

TEST.tar.gz

Now it’s time to add files and/or folders to your archive. To add a file(s) click the Add Files button. To add multiple files at once click and hold the Ctrl key as you select files. Once you are satisfied with the files you have added click the Add button. What you will see now is the main File Roller window with your files included.

Your Archive Is Ready

You don’t have to save your archive. Once the files are added, the archive is ready. You can check your home directory and you will find it waiting for you.

Don’t think, however, the only thing you can now do is unpack your archive. With this archive open you can add more files or directories. simply go through the process again to add more.

Extracting an Archive

Extracting an archive is very simple. Open a new session of File Roller, click the Open button, select the archive you want to extract, and click the Open button. Once the archive is open you will see the entire contents of the archive. That doesn’t mean the archive is unpacked. In order to unpack the archive you have to hit the Extract button. Once you do that you will have to select a location to extract the contents to. This is a nice feature because, without this step, you could easily fill your ~/ directory with the contents of the archive.

Final Thoughts

I have always been a fan of the command line, because I was weened on Linux with the command line. But for those who do not have the time or inclination to learn the command line, tools like File Roller are ideal for accomplishing every day tasks like unpacking archives.

Naturally the first thing you will need to do is to download the Firefox source. Once the source is downloaded you have a choice to make. You can install Firefox for each user on the system (if there is only one user you don’t really have much to worry about) or you can install Firefox “system wide”. If you choose to install for just one user then place the source file in the users home directory. If you want to install it “system wide” move the file to the /opt directory (you will have to have root permissions or use sudo to do this.)

Now that the file is in place it is time to unpack the file. More than likely the source package will be in bunzip2 format. To unpack the file you will issue the command bunzip2 firefox-XXX.tar.bz2. (Where XXX this the release number you downloaded.) Once bunzip2 has done its thing you will be left with a tar file firefox-XXX.tar (Again where XXX is the release number.)

When you unpack the Firefox tar file a new directory will be created called simply firefox. This new directory contains everything Firefox needs to run. All you have to do now is issue the command ~/firefox/firefox to start up the browser.

Starting Firefox

Naturally you don’t want to have to start Firefox from command line every time you want to run the browser. What you will want to do is edit the preferences in either your menu entries or the Firefox application icons on either your Panel or your desktop. When you do edit the preferences you will want to change the command entry. The entry that came with the pre-installed Firefox will most likely be:

firefox %u

You will to change that to:

~/firefox/firefox %u

Installing Flash

Once you have Firefox up and running you can install plugins manually. For instance, installing the Macromedia Flash plugin involves downloading the Flash plugin, (download the source, not the binary) unpacking the file with the command: tar xvzf install_flash_player_10_linux.tar.gz, change into the newly created directory with the command cd install_flash_player_10, issue the command ./flashplayer-installer, and answer the necessary questions. When you are asked where the installation directory is you will enter ~/firefox.

You’re done. Now you can fire up Firefox and enter about:plugins to make sure the flash player plugin is installed (it will also tell you which flash version you are using.)

Final Thoughts

It may not be the easiest method of installation, but it’s the best when you want to have more control over your web browser. You will also find it much easier to keep up to date with both the browser itself as well as the plugins you install.

The script made use of the following tools: date, cat, tar, mv, and rm. That’s it. The script will create backups with the date in the file name and then move the backups to a central location. Without further adieu, let’s get to the script.

#! /bin/sh

TMP=”/tmp/”

#Format the date in YEAR-MO-DY format
TODAY=`date +%F`

# Check to see if there is a lastbackup file in /tmp, if not create it,
# if so then set LAST equal to $TODAY
if [ -f /tmp/lastbackup ]; then
LAST=`cat /tmp/lastbackup`
else
LAST=$TODAY
fi

# Set the web directory backup name to the following
WEB_FILENAME=”inc-”$TODAY”-web.tar.gz”

# Set database backup name to the following
DB_FILENAME=”inc-”$TODAY”-db.tar.gz”

# this tars up my web directory into web.tar.gz tarball.
/bin/tar -czf $TMP$WEB_FILENAME –after-date=$LAST /var/www/html

# Move the web back to the backup directory
/bin/mv $TMP$WEB_FILENAME /data

# Remove web backup file from temp director
rm $TMP$WEB_FILENAME

# this tars up my database directory into $TODAY-db.tar.gz tarball.
/bin/tar -czf $TMP$DB_FILENAME –after-date=$LAST /var/lib/mysql

# Move the backup database to the backup directory
/bin/mv $TMP$DB_FILENAME /data

# Remove web backup file from temp directory
rm $TMP$DB_FILENAME

What I wanted this to do is create daily backups and move the backups to the /data directory on the drive housing the server. These backups will be saved for one month. After the month is completed i have a second script that deletes the months backups prior to running the next backup (so there is always a backup to fall to). How I made use of this script is simple. I save the script (called backup.sh) in the root user directory and create a second script called rm_backups.sh that looks like this:

#! /bin/sh

rm /data/*gz

With these two files in place I create two cron entries. The first cron entry is for running the backup.sh script and looks like:

0 23 * * *     ~/backup.sh

The second cron entry is for running the rm_backups.sh script and looks like:

0 20 1 * *     ~/rm_backups.sh

Both of the above cron jobs are created as the root user.

Final Thoughts

Naturally this solution could be easily modified (using such tools rsync) to set up an offsite backup solution. What should be obvious is that creating a simple, flexible server backup system on Linux is easy. With the help of a little ingenuity, you can create your own automated backup service.