Archive, compress, unpack, and uncompress files using tar, gzip, and bzip2

1. Understand and Use Essential Tools

📘Red Hat Certified System Administrator (RHCSA – EX200)

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1. Introduction: Why We Archive and Compress

In Linux, you often need to:

• Combine multiple files into a single file for easier management. This is called archiving.
• Reduce file size to save disk space or make transferring files faster. This is called compression.

The main tools for these tasks are:

• tar – used to create or extract archives (combines files into one).
• gzip – compresses files using the .gz format.
• bzip2 – compresses files using the .bz2 format.

Often, you combine tar + gzip or tar + bzip2 to archive and compress at the same time.

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2. The tar Command – Archiving Tool

tar stands for tape archive. It’s used to pack multiple files/directories into one archive file.

Basic Syntax:

tar [options] archive_name files_or_directories

Key Options for RHCSA:

Option	Meaning
-c	Create a new archive
-x	Extract files from an archive
-t	List contents of an archive
-v	Verbose – show progress/details
-f	Specify the filename of the archive
-C	Change directory before operation (useful when extracting)

Examples:

1. Create an archive of /etc directory:

tar -cvf etc-backup.tar /etc

• -c → create
• -v → show files being added
• -f → specify filename

2. List contents of an archive:

tar -tvf etc-backup.tar

3. Extract an archive:

tar -xvf etc-backup.tar

4. Extract to a specific directory:

tar -xvf etc-backup.tar -C /tmp

Tip: On the exam, they may ask you to extract files somewhere specific, so remember -C.

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3. Compression with gzip and gunzip

gzip compresses files, creating .gz files. Unlike tar, it compresses individual files, not directories.

Basic Usage:

1. Compress a file:

gzip filename

• Original file filename is replaced by filename.gz.

2. Uncompress a file:

gunzip filename.gz

• Restores the original file.

3. Keep the original file while compressing:

gzip -c filename > filename.gz

• -c writes output to a new file and keeps the original.

Important: On the exam, you may be asked to compress multiple files with gzip using tar.

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4. Compression with bzip2 and bunzip2

bzip2 is another compression tool. It generally compresses better than gzip (smaller file size), but is slightly slower.

Basic Usage:

1. Compress a file:

bzip2 filename

• Creates filename.bz2 and deletes the original file.

2. Uncompress:

bunzip2 filename.bz2

3. Keep the original file:

bzip2 -k filename

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5. Combining tar with gzip or bzip2

Most often in IT environments, we archive directories AND compress at the same time:

1. Using gzip (.tar.gz or .tgz):

tar -czvf backup.tar.gz /var/log

• -c → create
• -z → compress with gzip
• -v → verbose
• -f → file name

Extract .tar.gz:

tar -xzvf backup.tar.gz

• -x → extract
• -z → gzip
• -v → verbose
• -f → filename

2. Using bzip2 (.tar.bz2):

tar -cjvf backup.tar.bz2 /var/log

• -j → compress with bzip2

Extract .tar.bz2:

tar -xjvf backup.tar.bz2

Exam Tip: -z → gzip, -j → bzip2. They test if you know the difference.

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6. Listing Contents Without Extracting

Sometimes you need to see what’s inside an archive before extracting:

• .tar → tar -tvf archive.tar
• .tar.gz → tar -tzvf archive.tar.gz
• .tar.bz2 → tar -tjvf archive.tar.bz2

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7. Practical IT Use Examples (Exam Style)

• Back up /etc configuration files before upgrading a server:

tar -czvf etc-backup-$(date +%F).tar.gz /etc

• Extract a compressed log archive to /tmp to check logs:

tar -xzvf logs.tar.gz -C /tmp

• Compress a single database dump to save space:

gzip /backup/db.sql

Tip for RHCSA: They may give you a directory and ask you to create a compressed archive in a certain format. You must know: .tar, .tar.gz, .tar.bz2 commands.

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8. Summary Table – Commands at a Glance

Task	Command Example
Create tar archive	tar -cvf archive.tar /path/to/files
Extract tar archive	tar -xvf archive.tar
List tar archive	tar -tvf archive.tar
Create gzip compressed tar	tar -czvf archive.tar.gz /path
Extract gzip compressed tar	tar -xzvf archive.tar.gz
Create bzip2 compressed tar	tar -cjvf archive.tar.bz2 /path
Extract bzip2 compressed tar	tar -xjvf archive.tar.bz2
Compress single file (gzip)	gzip file
Uncompress single file (gzip)	gunzip file.gz
Compress single file (bzip2)	bzip2 file
Uncompress single file (bzip2)	bunzip2 file.bz2

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✅ Exam Key Points to Remember

1. tar = archive multiple files/directories.
2. gzip = compress individual files (fast, moderate compression).
3. bzip2 = compress individual files (slower, better compression).
4. tar + gzip = .tar.gz
5. tar + bzip2 = .tar.bz2
6. -c → create, -x → extract, -t → list
7. -z → gzip, -j → bzip2
8. -v → verbose, -f → filename
9. -C → extract to a specific directory