Linux File Compression and Backup

📦 UNIX File Compression & Backup Guide

UNIX systems provide several utilities for archiving and compressing files. This guide covers:

• tar – Tape Archiver
• cpio – Copy In/Out Archiver
• compress & gzip – File Compression Tools
• Modern Alternatives – bzip2, xz, zip, and rsync

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1. tar – Tape Archiver

tar is used to bundle multiple files and directories into a single archive file. It preserves file metadata (permissions, ownership, timestamps) but does not compress by default.

Basic Syntax

tar [options] [archive-file] [files...]

Common Options

Option	Meaning
-c	Create a new archive
-x	Extract files from an archive
-t	List archive contents
-v	Verbose output (show processed files)
-f	Specify archive file name
-z	Compress with gzip
-j	Compress with bzip2
-J	Compress with xz
--exclude=PATTERN	Exclude files matching pattern

Examples

• Create an archive:

tar -cvf backup.tar /home/user/documents

• Create and compress with gzip:

tar -czvf backup.tar.gz /home/user/documents

• List contents:

tar -tvf backup.tar

• Extract archive:

tar -xvf backup.tar

• Extract to a specific directory:

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

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2. cpio – Copy In/Out Archiver

cpio reads and writes archives from standard input/output. It’s often used with find for flexible file selection.

Basic Syntax

cpio [options] < archive
cpio [options] > archive

Common Options

Option	Meaning
-o	Create archive (copy-out mode)
-i	Extract archive (copy-in mode)
-t	List archive contents
-v	Verbose output
-d	Create directories as needed
-u	Overwrite existing files
-H	Specify archive format (tar, crc, odc, etc.)

Examples

• Create a tar-format archive from current directory:

find . -depth -print | cpio -ov -Htar > backup.tar

• List contents:

cpio -tv < backup.tar

• Extract files:

cpio -idv < backup.tar

• Extract and overwrite existing files:

cpio -iduv < backup.tar

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3. compress & gzip – File Compression

These tools compress individual files.

compress

• Produces .Z files.
• Compress:

compress file.txt

• Decompress:

compress -d file.txt.Z

gzip

• Produces .gz files.
• Compress:

gzip file.txt

• Decompress:

gzip -d file.txt.gz

• View compressed file without decompressing:

zcat file.txt.gz

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4. Modern Alternatives & Improvements

While tar, cpio, compress, and gzip are still widely used, modern tools offer better compression ratios and faster performance.

Tool	Extension	Pros	Example
bzip2	.bz2	Better compression than gzip	tar -cjvf backup.tar.bz2 dir/
xz	.xz	Very high compression ratio	tar -cJvf backup.tar.xz dir/
zip	.zip	Cross-platform compatibility	zip -r backup.zip dir/
rsync	N/A	Incremental backups over network	rsync -avz /source user@host:/backup

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5. Best Practices

• Always test restores to ensure backups are valid.
• Use compression for storage efficiency, but note that it increases CPU usage.
• For large datasets, consider rsync or borgbackup for incremental backups.
• Store backups offsite or in cloud storage for disaster recovery.