31.File_Compression_And_Extraction.md

Topic-19: Compression and Uncompression of Files (tar, gzip, gunzip, bzip2, bunzip2)

In system administration, it is often necessary to pack and compress a group of files. The main advantages are:

1. Improved memory utilization
2. Easier transportation
3. Reduced download times
4. And more...

The compression process generally involves the following two steps:

1. Creation of Archive File
2. Application of Compression Algorithms on the Archive File

1. Creation of Archive File

We can group multiple files and directories into a single archive file using the tar command.

tar stands for tape archive.

A Creating a tar File

To create a tar file containing specific files:

tar -cvf demo.tar file1.txt file2.txt file3.txt

To include all files in the current directory:

tar -cvf demo.tar *

B Displaying the Table of Contents of a tar File

To view the contents of a tar file:

tar -tvf demo.tar

C Extracting the Contents of a tar File

To extract the contents of a tar file:

tar -xvf demo.tar

2. Applying Compression Algorithms on the Archive File

There are multiple compression and decompression algorithms available:

1. gzip - Fast but with less compression power
2. bzip2 - Slower but provides higher compression power

Compression and Decompression Using gzip

1 To Compress a tar File

$ gzip demo.tar

This command creates a compressed file demo.tar.gz.

2 To Uncompress a gz File

$ gzip -d demo.tar.gz
# or
$ gunzip demo.tar.gz

This command restores the original demo.tar file.

Compression and Decompression Using bzip2

1 To Compress a tar File

$ bzip2 demo.tar

This creates a compressed file demo.tar.bz2.

2 To Uncompress a bz2 File

$ bunzip2 demo.tar.bz2

Creating and Compressing a tar File in a Single Command

1 Using gzip Compression

To create and compress a tar file in one command:

$ tar -cvzf demo.tar.gz *.txt

• The z option compresses the file.
• This creates demo.tar.gz, which is already compressed.

To uncompress and extract:

$ tar -xvzf demo.tar.gz

2 Using bzip2 Compression

Instead of z, use j for bzip2 compression:

$ tar -cvjf demo.tar.bz2 *.txt

• The j option compresses the file.
• This creates demo.tar.bz2, which is already compressed.

To uncompress and extract:

$ tar -xvjf demo.tar.bz2

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Use Case: Backup of User Home Directory

Example for creating a backup of the user home directory:

$ pwd
/home/durgasoft
$ tar -cvzf backup.tar *
$ mkdir newhome
$ mv backup.tar newhome
$ cd newhome
$ tar -xvzf backup.tar