The tar command
Archiving and compressing files are useful when creating backups and transferring data across a network. One of the oldest and most common commands for creating and working with backup archives is the tar command. tar stands for “tape archive,” a utility that is used to bundle multiple files and directories together into a single archive file. With tar, users can gather large sets of files into a an archive. A tar archive is a structured sequence of file data mixed in with metadata about each file and an index so that individual files can be extracted. The archive can be compressed using gzip, bzip2, or xz compression. However, tar alone merely packages files together; it’s the compression algorithms like gzip,bzip2 , and xz that turn tar into a potent file compression tool. In this blog, we’ll explore the world of file compression using tar with these three methods and learn how to wield their power effectively.
tar command Options
The tar command expects one of the three following options:
-cor--createoption to create an archive.-t or--listoption to list the contents of an archive.-x or--extractoption to extract an archive.-
-f or--file=option with a file name as an argument of the archive to operate. -v or--verboseoption for verbosity;
File Compression Using tar with gzip, bzip2, and xz
The tar command supports three compression methods.
tar Compression Options
1. Gzip: Fast and Efficient Compression
The gzip compression is the fastest and oldest one and is most widely available across distributions and even across platforms. It is known for its speed and efficiency. It uses the DEFLATE compression algorithm to shrink file sizes while maintaining a good balance between compression speed and compression ratio.
Compress using Gzip
Here’s how you can use gzip with tar :
-z or --gzip  filename.tar.gz or filename.tgz
To create a gzip compressed archive named /root/etcback.tar.gz, with the contents from the /etc directory on a host:
# Compress using gzip
[root@rocky9 ~]# tar -czf /root/etcbackup.tar.gz /etc
tar: Removing leading /' from member names
</pre>
<h4>Extract Gzip Archive</h4>
To decompress the file that we compressed above(<i>/root/etcbackup.tar.gz</i>) with <em>gzip </em>in the <strong><em>/tmp/etc_backup</em></strong> directory, use the following command:
<pre class="EnlighterJSRAW" data-enlighter-language="generic">[root@rocky9 ~]# mkdir /tmp/etc_backup
[root@rocky9 ~]# cd /tmp/etc_backup
[root@rocky9 etc_backup]# tar -xzvf /root/etcbackup.tar.gz
etc/
etc/mtab
etc/fstab
etc/crypttab
etc/lvm/
etc/lvm/devices/
etc/lvm/devices/system.devices
etc/lvm/archive/
</pre>
<h3>2. Bzip2: High Compression Ratio</h3>
<p class="p1"><code class="EnlighterJSRAW" data-enlighter-language="generic">bzip2</code> , short for "<em>Burrows-Wheeler block-sorting file compressor</em>," is another compression utility that excels in providing high compression ratios. It achieves this by using the <em>Burrows-Wheeler transform</em> and <em>Run-Length Encoding</em>. While <em><strong>bzip2</strong></em> might be slower than <em>gzip</em>, its superior compression ratio often justifies the extra time.</p>
<h4>Compress using Bzip2</h4>
Here's how you can use <em>Bzip2</em> with <code class="EnlighterJSRAW" data-enlighter-language="generic">tar</code> :
<code class="EnlighterJSRAW" data-enlighter-language="generic">-j</code>Â or <code class="EnlighterJSRAW" data-enlighter-language="generic">--bzip2</code> <em>filename.tar.bz2</em>
Confirm Bzip2 is installed on your system. If not you can install it:
<pre class="EnlighterJSRAW" data-enlighter-language="generic">[root@rocky9 ~]# yum install bzip2
Rocky Linux 9 - AppStream 4.6 kB/s | 4.5 kB 00:00
Dependencies resolved.
======================================================================================================================================================================================================================
Package Architecture Version Repository Size
======================================================================================================================================================================================================================
Installing:
bzip2 x86_64 1.0.8-8.el9 baseos 52 k
Transaction Summary
======================================================================================================================================================================================================================
Install 1 Package
Total download size: 52 k
Installed size: 94 k
Is this ok [y/N]: y
Downloading Packages:
bzip2-1.0.8-8.el9.x86_64.rpm
1/1
Verifying : bzip2-1.0.8-8.el9.x86_64 1/1
Installed:
bzip2-1.0.8-8.el9.x86_64
Complete!
</pre>
Here's how to use <strong><em>Bzip2</em></strong> with <code class="EnlighterJSRAW" data-enlighter-language="generic">tar</code> to create a <em>bzip2</em> compressed archive named <strong><em>/root/varlogauditbackup.tar.bz2</em></strong>, with the contents from the <em>/var/log/audit</em> directory:
<pre class="EnlighterJSRAW" data-enlighter-language="generic">[root@rocky9 ~]# tar -cjf /root/varlogauditbackup.tar.bz2 /var/log/audit
tar: Removing leading /' from member names
Extract Bzip2 Archive
To extract the file that we compressed above(/root/varlogbackup.tar.bz2) with Bzip2 in the /tmp/logbackup directory, use the following commands:
[root@rocky9 ~]# mkdir /tmp/logauditbackup [root@rocky9 ~]# cd /tmp/logauditbackup [root@rocky9 logbackup]# tar -xjvf /root/varlogauditbackup.tar.bz2 var/log/audit/ var/log/audit/audit.log.4 var/log/audit/audit.log.3 var/log/audit/audit.log.2 var/log/audit/audit.log.1 var/log/audit/audit.log
3. Xz: Maximum Compression
xz is the heavyweight champion of compression when it comes to squeezing the last bit of space out of your files. It employs the LZMA2 compression algorithm, offering an excellent balance between high compression ratios and reasonable compression speeds.
Compress using Xz
Here’s how you can use Xz with tar :
-J or -xz filename.tar.xz
To create a xz compressed archive named, /root/sshconfig.tar.xz, with the contents from the /etc/ssh directory, this how to do it:
[root@rocky9 ~]# tar -cJf /root/sshconfig.tar.xz /etc/ssh tar: Removing leading `/' from member names
Lets verify the contents of the xz archive using the tf options of the tar command:
[root@rocky9 ~]# tar -tf /root/sshconfig.tar.xz etc/ssh/ etc/ssh/moduli etc/ssh/ssh_config etc/ssh/ssh_config.d/ etc/ssh/ssh_config.d/50-redhat.conf etc/ssh/sshd_config etc/ssh/sshd_config.d/ etc/ssh/sshd_config.d/50-redhat.conf etc/ssh/sshd_config.d/01-permitrootlogin.conf etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf etc/ssh/sshd_config.d/00-complianceascode-hardening.conf etc/ssh/ssh_host_ed25519_key etc/ssh/ssh_host_ed25519_key.pub etc/ssh/ssh_host_ecdsa_key etc/ssh/ssh_host_ecdsa_key.pub etc/ssh/ssh_host_rsa_key etc/ssh/ssh_host_rsa_key.pub
Extract XZ Archive
To extract the file that we compressed above(/root/sshconfig.tar.xz) with xz in the /tmp/sshbackup directory, use the following commands:
Decompress using xz
[root@rocky9 ~]# mkdir /tmp/sshbackup [root@rocky9 ~]# cd /tmp/sshbackup # Decompress using xz [root@rocky9 sshbackup]# tar -xJvf /root/sshconfig.tar.xz etc/ssh/ etc/ssh/moduli etc/ssh/ssh_config etc/ssh/ssh_config.d/ etc/ssh/ssh_config.d/50-redhat.conf etc/ssh/sshd_config etc/ssh/sshd_config.d/ etc/ssh/sshd_config.d/50-redhat.conf etc/ssh/sshd_config.d/01-permitrootlogin.conf etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf etc/ssh/sshd_config.d/00-complianceascode-hardening.conf etc/ssh/ssh_host_ed25519_key etc/ssh/ssh_host_ed25519_key.pub etc/ssh/ssh_host_ecdsa_key etc/ssh/ssh_host_ecdsa_key.pub etc/ssh/ssh_host_rsa_key etc/ssh/ssh_host_rsa_key.pub
Conclusion
In the world of file compression, the tar utility serves as the foundation upon which the power of gzip, bzip2, and xz is harnessed. Each compression method has its strengths and weaknesses, allowing you to tailor your approach based on your specific needs.
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