`tar.xz` - High Compression Archives

.tar.xz combines tar (archiving directories) with XZ (LZMA2) compression. Use it when you want smaller archives than tar.gz and you can afford slower compression and (often) slower restores.

Quick Summary

Create: tar -cJf out.tar.xz /path/to/dir
Extract: tar -xJf out.tar.xz -C /tmp/restore-test
List: tar -tJf out.tar.xz
Test: xz -t out.tar.xz

Restore checklist

Use this checklist before restoring a .tar.xz backup into a live WordPress docroot.

Verify integrity: xz -t backup.tar.xz
List contents: tar -tJf backup.tar.xz | head
Extract to staging: /tmp/restore-test/
Confirm key paths exist: wp-content/uploads/, wp-config.php
Only then copy/sync into place and restart services

restore-drill-tar-xz.sh
sudo rm -rf /tmp/restore-test
sudo mkdir -p /tmp/restore-test
tar -xJvf /home/wpbackup/wp_full.tar.xz -C /tmp/restore-test

Avoid absolute paths in tar archives

If you create an archive from an absolute path, tar can store leading directories that make restores confusing.

Preferred pattern:

create-tar-xz-with-relative-paths.sh
tar -C /var/www/html -cJvf /home/wpbackup/wp-files.tar.xz .

Advanced tuning (optional)

If your tar build does not expose every XZ knob you want, you can use XZ_OPT to pass options to the underlying xz process.

set-xz-opt-for-tar.sh
XZ_OPT='-T0 -9' tar -C /var/www/html -cJf /home/wpbackup/wp-files-max.tar.xz .

warning

Aggressive settings (-9, multi-threading, large sites) can spike CPU and I/O. Schedule this off-peak or lower the level.

Cheat sheet (extra)

Task	Command
Create (relative paths)	`tar -C /var/www/html -cJf out.tar.xz .`
Extract to staging	`tar -xJf out.tar.xz -C /tmp/restore-test`
List contents	`tar -tJf out.tar.xz`
Test archive	`xz -t out.tar.xz`
Show stats	`xz -l out.tar.xz`

When to use tar.xz

tar.xz is a "size-first" format:

Good fit: cold storage snapshots, moving large sites over slow links, long retention backups.
Avoid for: high-frequency operational backups where restore speed matters.

If you want a more operational default, consider tar.zst (often faster) or tar.gz (widest compatibility).

Prerequisites

install-xz-utils-and-tar.sh
sudo apt update
sudo apt install -y xz-utils tar

Ensure xz-utils is installed (provides xz compression engine).
Have enough disk space for uncompressed files.
Verify access to your WordPress directory (/var/www/html or /home/dev_wpstrategist/public_html).

Core syntax and common patterns

tar-xz-common-patterns.sh
# =====================================================================
# 3. Core Syntax Formula — .tar.xz (WordPress VPS Context)
# =====================================================================

# ──────────────────────────────
# 1. Create an uncompressed archive (.tar)
tar -cvf [DESTINATION_PATH]/[ARCHIVE_NAME].tar [SOURCE_PATHS...]

# Example:
tar -cvf /home/wpbackup/sitefiles.tar /home/dev_wpstrategist/public_html
# Input directory: /home/dev_wpstrategist/public_html
# Output file: /home/wpbackup/sitefiles.tar

# ──────────────────────────────
# 2. Create an XZ-compressed archive (.tar.xz)
tar -cJvf [DESTINATION_PATH]/[ARCHIVE_NAME].tar.xz [SOURCE_PATHS...]

# Example:
tar -cJvf /home/wpbackup/sitefiles.tar.xz /home/dev_wpstrategist/public_html
# Input directory: /home/dev_wpstrategist/public_html
# Output file: /home/wpbackup/sitefiles.tar.xz

# ──────────────────────────────
# 3. Create maximum compression archive (.tar.xz)
tar -cJvf [DEST_PATH]/[ARCHIVE_NAME].tar.xz --xz -9 [SOURCE_PATHS...]

# Example:
tar -cJvf /home/wpbackup/wp_full_max.tar.xz --xz -9 /home/dev_wpstrategist/public_html
# Compression level: 9 (max)

# ──────────────────────────────
# 4. Extract a .tar.xz archive
tar -xJvf [INPUT_FILE.tar.xz] -C [OUTPUT_DIRECTORY]

# Example:
tar -xJvf /home/wpbackup/sitefiles.tar.xz -C /home/restore
# Input file: /home/wpbackup/sitefiles.tar.xz
# Output directory: /home/restore

# ──────────────────────────────
# 5. List contents without extracting
tar -tJvf [INPUT_FILE.tar.xz]

# Example:
tar -tJvf /home/wpbackup/sitefiles.tar.xz
# Output: List of files printed to terminal

# ──────────────────────────────
# 6. Test archive integrity
xz -t [INPUT_FILE.tar.xz]

# Example:
xz -t /home/wpbackup/sitefiles.tar.xz
# Output: "OK" if valid archive

# ──────────────────────────────
# 7. Decompress XZ layer only (keeping .tar)
xz -d [INPUT_FILE.tar.xz]

# Example:
xz -d /home/wpbackup/sitefiles.tar.xz
# Output file: /home/wpbackup/sitefiles.tar

# ──────────────────────────────
# 8. Compress existing .tar to .tar.xz
xz -z [INPUT_FILE.tar]

# Example:
xz -z /home/wpbackup/sitefiles.tar
# Output file: /home/wpbackup/sitefiles.tar.xz

# ──────────────────────────────
# 9. Create archive with date stamp
tar -cJvf /home/wpbackup/site_$(date +%F).tar.xz /var/www/html
# Output file: site_2025-10-26.tar.xz

# ──────────────────────────────
# 10. Backup WordPress + Database
mysqldump -u root -p'DB_PASS' wp_db > /home/tmp/db.sql && \
tar -cJvf /home/wpbackup/wp_full_$(date +%F).tar.xz /var/www/html /home/tmp/db.sql
# Input: WP files + DB dump
# Output file: /home/wpbackup/wp_full_YYYY-MM-DD.tar.xz

# =====================================================================

Key options

Option	Description	Example	Effect
`-c`	Create archive	`tar -cvf file.tar folder`	Start new archive
`-x`	Extract archive	`tar -xvf file.tar`	Unpack files
`-t`	List archive	`tar -tvf file.tar`	Show contents
`-v`	Verbose mode	`tar -cvf file.tar folder`	Print file names
`-f`	File name follows	`tar -cvf archive.tar folder`	Required before filename
`-J`	Use XZ compression	`tar -cJvf file.tar.xz folder`	Compress with XZ
`--xz`	Explicitly enable XZ mode	`tar -c --xz -f file.tar.xz folder`	Alternative to `-J`
`-C`	Change directory	`tar -xJvf file.tar.xz -C /home/restore`	Extract to path
`--exclude`	Skip file/directory	`--exclude=cache`	Ignore selected folder

WordPress VPS use cases

Scenario	Command	Goal
Full-site backup	`tar -cJvf /home/wpbackup/wp_full.tar.xz /var/www/html`	Complete compressed backup
File + DB backup	`mysqldump -u root -pPASS wp_db > db.sql && tar -cJvf /home/wpbackup/full.tar.xz /var/www/html db.sql`	Combine both data sources
Exclude cache folders	`tar -cJvf backup.tar.xz --exclude=cache /var/www/html`	Smaller archive
Restore backup	`tar -xJvf backup.tar.xz -C /home/restore`	Extract files
Verify archive	`xz -t backup.tar.xz`	Confirm integrity
Automate daily	`tar -cJvf /home/wpbackup/wp_$(date +%F).tar.xz /var/www/html`	Rotation-based backup

Comparison

Format	Command	Speed	Compression	File Size	Supported By
`.tar`	`tar -cvf`	⭐⭐⭐⭐	❌ None	Large	All Linux
`.tar.gz`	`tar -czvf`	⭐⭐⭐	⭐⭐	Medium	All Linux
`.tar.xz`	`tar -cJvf`	⭐⭐	⭐⭐⭐⭐	Smallest	Modern Linux
`.tar.zst`	`tar --zstd -cvf`	⭐⭐⭐⭐	⭐⭐⭐	Medium	Ubuntu 22+/Debian 11+

Troubleshooting

Issue	Cause	Fix
`tar: Removing leading '/'`	Normal notice	Safe to ignore
“Cannot open: Permission denied”	Lacks permission	Use `sudo`
“Unexpected EOF”	Corrupted file	Redownload or re-upload
“No space left on device”	Disk full	Free space or mount new volume
“Command not found: xz”	`xz-utils` missing	Install using `apt install xz-utils`

Quick lab

Step	Command	Expected Output
1	`cd /var/www/html`	Enter WordPress directory
2	`tar -cJvf /home/wpbackup/wp_full.tar.xz .`	Creates compressed archive
3	`tar -tJvf /home/wpbackup/wp_full.tar.xz`	Lists archive content
4	`xz -t /home/wpbackup/wp_full.tar.xz`	Integrity test shows “OK”
5	`tar -xJvf /home/wpbackup/wp_full.tar.xz -C /home/restore`	Files extracted

Cheat sheet

Task	Syntax
Create `.tar.xz`	`tar -cJvf archive.tar.xz folder`
Extract `.tar.xz`	`tar -xJvf archive.tar.xz`
List contents	`tar -tJvf archive.tar.xz`
Test archive	`xz -t archive.tar.xz`
Exclude folder	`tar -cJvf backup.tar.xz --exclude=cache folder`
Compress existing tar	`xz -z archive.tar`
Decompress to tar	`xz -d archive.tar.xz`
Add date to filename	`tar -cJvf backup_$(date +%F).tar.xz folder`

Mini quiz

#	Question	Options	Answer
1	What does `-J` flag in `tar` do?	a) gzip b) xz c) zip	b)
2	How to list files inside a `.tar.xz`?	a) `tar -xJvf` b) `tar -tJvf`	b)
3	Which command tests `.tar.xz` integrity?	a) `tar -t` b) `xz -t`	b)
4	Which flag extracts to directory?	a) `-C` b) `-v`	a)
5	Best use case for `.tar.xz`?	a) Fastest backup b) Highest compression	b)

Compression levels

tar.xz uses XZ compression levels from 0 (fastest) to 9 (smallest, slowest). The default is usually level 6; choose higher levels only when space matters more than time.

Range overview

Level	Syntax	Speed	Compression Ratio	Use Case
`-0`	`tar -cJvf backup.tar.xz --xz -0 folder`	🔥 Fastest	😐 Lowest	For quick local archives
`-3`	`tar -cJvf backup.tar.xz --xz -3 folder`	⚡ Fast	🙂 Moderate	For daily backups
`-6` (default)	`tar -cJvf backup.tar.xz folder`	⚖️ Balanced	⚖️ Balanced	Default when level not set
`-9`	`tar -cJvf backup.tar.xz --xz -9 folder`	🐢 Slowest	🏋️‍♂️ Best	For maximum space savings

Default level: -6 (medium balance between speed and size)

Example commands

Fast compression (levels 1-3)

create-tar-xz-fast.sh
tar -cJvf /home/wpbackup/wp_fast.tar.xz --xz -3 /var/www/html

Faster archive creation
Moderate compression

Standard compression (level 6)

create-tar-xz-standard.sh
tar -cJvf /home/wpbackup/wp_standard.tar.xz --xz -6 /var/www/html

Default balance between CPU usage and compression ratio
Ideal for regular WordPress backups

Maximum compression (level 9)

create-tar-xz-max.sh
tar -cJvf /home/wpbackup/wp_max.tar.xz --xz -9 /var/www/html

Slow compression (CPU-intensive)
Best for cold storage or long-term archives

Verify compression ratio

After creating your archive, check compression ratio:

xz-list-archive-compression-stats.sh
xz -l /home/wpbackup/wp_max.tar.xz

Expected Output Example:

example-xz-l-output.txt
Strms  Blocks   Compressed Uncompressed  Ratio  Check   Filename
1      1        512.1 MiB  2.4 GiB       0.21   CRC64   wp_max.tar.xz

In this example, compression ratio = 0.21, meaning ~79% reduction.

Multi-threaded compression (optional)

By default, xz uses one CPU core.

For faster compression on multi-core VPS:

tar-to-xz-multithreaded.sh
tar -cf - /var/www/html | xz -9 -T0 -c > /home/wpbackup/wp_multi.tar.xz

Flag	Description
`-T0`	Use all available CPU cores
`-9`	Max compression
`-c`	Write to stdout

Quick reference

Purpose	Command	Notes
Fastest	`tar -cJvf backup.tar.xz --xz -1 folder`	~2× faster, larger size
Balanced	`tar -cJvf backup.tar.xz folder`	Default level 6
Maximum	`tar -cJvf backup.tar.xz --xz -9 folder`	Slow but smallest
Multi-core max	`tar -cf - folder	xz -9 -T0 -c > backup.tar.xz`

Verification commands

Run these right after creating an archive, before you upload it offsite.

verify-tar-xz-backup.sh
xz -t /home/wpbackup/sitefiles.tar.xz
tar -tJf /home/wpbackup/sitefiles.tar.xz | sed -n '1,25p'

If both commands succeed and the listing looks like the paths you expect, the archive is usually safe to store.

Restore checklist​

Avoid absolute paths in tar archives​

Advanced tuning (optional)​

When to use tar.xz​

Prerequisites​

Core syntax and common patterns​

Key options​

WordPress VPS use cases​

Comparison​

Troubleshooting​

Quick lab​

Cheat sheet​

Mini quiz​

Compression levels​

Range overview​

Example commands​

Fast compression (levels 1-3)​

Standard compression (level 6)​

Maximum compression (level 9)​

Verify compression ratio​

Multi-threaded compression (optional)​

Quick reference​

Verification commands​