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File and Directory Compression Tools in Linux

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    Owais Abbasi
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File and Directory Compression Tools in Linux

This post would be about the file and directory compression tools in Linux through shell commands.

After learning the commands below, you will be able to understand the use of archiving and compression tools like tar, gzip, and bzip2. Finally, concepts like hard links and soft links will be brushed up.

Creating a File with touch

Before starting the compression tools, let me give you an understanding of creating a file through the command line. This is the topic that was left out in the last post. You can achieve this through the touch command.

[centos@localhost demo]$ touch test_file
[centos@localhost demo]$ ls
test_file

Archiving, Compression, and Extraction Tools

tar Command

Creating a Tar File

tar stands for tape archive. It is a tool to archive any number of files into a single file. This can be achieved through the following command:

[centos@localhost demo]$ ls -l
total 0
drwxr-xr-x. 2 centos centos 137 Jan 13 16:25 contents
[centos@localhost demo]$ tar -cvf contents.tar contents
contents/
contents/file1
contents/file2
contents/file3
contents/file4
contents/file5
contents/file6
contents/file7
contents/file8
contents/file9
contents/file10
[centos@localhost demo]$ ls -hl
total 12K
drwxr-xr-x. 2 centos centos 137 Jan 13 16:25 contents
-rw-r--r--. 1 centos centos 10K Jan 13 16:27 contents.tar
  • c - Create
  • v - Verbose (list files being processed)
  • f - Specify the name of the archive file

Extracting a Tar File

To extract files from a tar file, use the following command:

[centos@localhost demo]$ ls
contents.tar
[centos@localhost demo]$ tar -xvf contents.tar
contents/
contents/file1
contents/file2
contents/file3
contents/file4
contents/file5
contents/file6
contents/file7
contents/file8
contents/file9
contents/file10

[centos@localhost demo]$ tree
.
├── contents
│   ├── file1
│   ├── file10
│   ├── file2
│   ├── file3
│   ├── file4
│   ├── file5
│   ├── file6
│   ├── file7
│   ├── file8
│   └── file9
└── contents.tar

1 directory, 11 files
[centos@localhost demo]$ ls -hl
total 12K
drwxr-xr-x. 2 centos centos 137 Jan 13 16:25 contents
-rw-r--r--. 1 centos centos 10K Jan 13 16:27 contents.tar
  • x - Extract
  • v - Verbose
  • f - Specify the name of the tar file

gzip Command

Creating a Gzip File

This tool compresses the size of files while archiving them. You can use it with tar as follows:

[centos@localhost demo]$ ls
contents
[centos@localhost demo]$ tar -cvzf contents.tar.gz contents
contents/
contents/file1
contents/file2
contents/file3
[centos@localhost demo]$ ls
contents  contents.tar.gz
  • z - Compress using gzip

The extension .gz denotes the compressed tar file.

Extracting a Gzip File

To extract a gzip-compressed tar file:

[centos@localhost demo]$ ls
contents.tar.gz
[centos@localhost demo]$ tar -xvzf contents.tar.gz
contents/
contents/file1
contents/file2
contents/file3
[centos@localhost demo]$ ls -l
total 4
drwxr-xr-x. 2 centos centos  45 Jan 13 16:34 contents
-rw-r--r--. 1 centos centos 237 Jan 13 16:36 contents.tar.gz
  • Replace c with x to extract.

bzip2 Command

Creating a Bzip2 File

bzip2 compresses files more efficiently than gzip. Use it with tar as follows:

[centos@localhost demo]$ ls
contents
[centos@localhost demo]$ tar -cvjf contents.tar.bz2 contents
contents/
contents/file1
contents/file2
contents/file3
[centos@localhost demo]$ ls
contents  contents.tar.bz2
  • j - Compress using bzip2

The extension .bz2 denotes the compressed tar file.

Extracting a Bzip2 File

To extract a bzip2-compressed tar file:

[centos@localhost demo]$ ls
contents.tar.bz2
[centos@localhost demo]$ tar -xvjf contents.tar.bz2
contents/
contents/file1
contents/file2
contents/file3
[centos@localhost demo]$ ls
contents  contents.tar.bz2
  • Replace c with x to extract.

Difference Between gzip and bzip2

Compression Algorithm

  • gzip: Faster but less compression.
  • bzip2: Slower but better compression.

If you prioritize speed, choose gzip. For better compression, choose bzip2.

Understanding Links in Linux

Hard Link

A hard link is an actual copy of an original file that shares the same inode number. Changes in one file reflect in the hard link, and vice versa. Deleting one does not affect the other.

Note:

  • Cannot be made across different partitions.
[centos@localhost demo]$ ls -l
total 4
-rw-r--r--. 1 centos centos 31 Jan 13 16:45 file1.txt
[centos@localhost demo]$ ln file1.txt hardened.txt
[centos@localhost demo]$ ls -il
total 8
2597316 -rw-r--r--. 2 centos centos 31 Jan 13 16:45 file1.txt
2597316 -rw-r--r--. 2 centos centos 31 Jan 13 16:45 hardened.txt

Soft Link

A soft link is a shortcut to a file. It does not share the inode number with the original file.

Characteristics:

  • Can be made across partitions.
  • If the original file is deleted, the soft link becomes unusable.
[centos@localhost demo]$ ls -il
total 4
2597316 -rw-r--r--. 1 centos centos 31 Jan 13 16:45 file1.txt
[centos@localhost demo]$ ln -s file1.txt softened.txt
[centos@localhost demo]$ ls -il
total 4
2597316 -rw-r--r--. 1 centos centos 31 Jan 13 16:45 file1.txt
2597337 lrwxrwxrwx. 1 centos centos  9 Jan 13 16:47 softened.txt -> file1.txt

Thank you!

A Bit More About Me

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