GNU tar: an archiver tool

FTP release, version 1.35, 22 August 2023

John Gilmore, Jay Fenlason et al.

This manual is for GNU tar (version 1.35, 22 August 2023), which creates and extracts files from archives.

Copyright © 1992, 1994–1997, 1999–2001, 2003–2017, 2021–2023 Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with the Invariant Sections being “GNU General Public License”, with the Front-Cover Texts being “A GNU Manual”, and with the Back-Cover Texts as in (a) below. A copy of the license is included in the section entitled “GNU Free Documentation License”.

(a) The FSF’s Back-Cover Text is: “You have the freedom to copy and modify this GNU manual.”

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GNU tar: an archiver tool

This manual is for GNU tar (version 1.35, 22 August 2023), which creates and extracts files from archives.

Copyright © 1992, 1994–1997, 1999–2001, 2003–2017, 2021–2023 Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with the Invariant Sections being “GNU General Public License”, with the Front-Cover Texts being “A GNU Manual”, and with the Back-Cover Texts as in (a) below. A copy of the license is included in the section entitled “GNU Free Documentation License”.

(a) The FSF’s Back-Cover Text is: “You have the freedom to copy and modify this GNU manual.”

The first part of this master menu lists the major nodes in this Info document. The rest of the menu lists all the lower level nodes.

1 Introduction  
2 Tutorial Introduction to tar  
3 Invoking GNU tar  
4 GNU tar Operations  
5 Performing Backups and Restoring Files  
6 Choosing Files and Names for tar  
7 Date input formats  
8 Controlling the Archive Format  
9 Tapes and Other Archive Media  
10 Reliability and Security   
Appendices
Appendix A Changes  
Appendix B Recipes   Frequently used tar recipes
Appendix C Configuring Help Summary  
Appendix D Fixing Snapshot Files  
Appendix E Tar Internals  
Appendix F Genfile  
Appendix G GNU Free Documentation License  
Appendix H Index of Command Line Options  
Appendix I Index   
 — The Detailed Node Listing —

Introduction
1.1 What this Book Contains  
1.2 Some Definitions  
1.3 What tar Does  
1.4 How tar Archives are Named  
1.5 GNU tar Authors  
1.6 Reporting bugs or suggestions  
Tutorial Introduction to tar
2.1 Assumptions this Tutorial Makes  
2.2 Stylistic Conventions  
2.3 Basic tar Operations and Options  
2.4 The Three Most Frequently Used Operations  
2.5 Two Frequently Used Options  
2.6 How to Create Archives  
2.7 How to List Archives  
2.8 How to Extract Members from an Archive  
2.9 Going Further Ahead in this Manual   
Two Frequently Used Options
The ‘--file’ Option  
The ‘--verbose’ Option  
Getting Help: Using the ‘--help’ Option   
How to Create Archives
2.6.1 Preparing a Practice Directory for Examples  
2.6.2 Creating the Archive  
2.6.3 Running ‘--create’ with ‘--verbose’  
2.6.4 Short Forms with ‘create’  
2.6.5 Archiving Directories   
How to List Archives
Listing the Contents of a Stored Directory   
How to Extract Members from an Archive
2.8.1 Extracting an Entire Archive  
2.8.2 Extracting Specific Files  
2.8.3 Extracting Files that are Directories  
2.8.4 Extracting Archives from Untrusted Sources  
2.8.5 Commands That Will Fail   
Invoking GNU tar
3.1 General Synopsis of tar  
3.2 Using tar Options  
3.3 The Three Option Styles  
3.4 All tar Options  
3.5 GNU tar documentation   Where to Get Help.
3.6 Obtaining GNU tar default values   What are the Default Values.
3.7 Checking tar progress  
3.8 Checkpoints  
3.9 Controlling Warning Messages  
3.10 Asking for Confirmation During Operations  
3.11 Running External Commands  
The Three Option Styles
3.3.1 Long Option Style  
3.3.2 Short Option Style  
3.3.3 Old Option Style  
3.3.4 Mixing Option Styles  
All tar Options
3.4.1 Operations  
3.4.2 tar Options  
3.4.3 Short Options Cross Reference  
3.4.4 Position-Sensitive Options   
Controlling Warning Messages
3.9.1 Keywords controlling tar operation   Keywords applicable for tar --create.
3.9.2 Keywords applicable for tar --create  
3.9.3 Keywords applicable for tar --extract  
3.9.4 Keywords controlling incremental extraction  
3.9.5 Warning Classes   Convenience keywords control multiple warnings.
3.9.6 Default Warning Settings   Default settings for warnings. 
GNU tar Operations
4.1 Basic GNU tar Operations  
4.2 Advanced GNU tar Operations  
4.3 Options Used by ‘--create’  
4.4 Options Used by ‘--extract’  
4.5 Backup options  
4.6 Looking Ahead: The Rest of this Manual   
Advanced GNU tar Operations
4.2.1 The Five Advanced tar Operations  
4.2.2 How to Add Files to Existing Archives: ‘--append’  
4.2.3 Updating an Archive  
4.2.4 Combining Archives with ‘--concatenate’  
4.2.5 Removing Archive Members Using ‘--delete’  
4.2.6 Comparing Archive Members with the File System   
How to Add Files to Existing Archives: ‘--append’
4.2.2.1 Appending Files to an Archive  
4.2.2.2 Multiple Members with the Same Name   
Updating an Archive
4.2.3.1 How to Update an Archive Using ‘--update’   
Options Used by ‘--create’
4.3.1 Overriding File Metadata  
4.3.2 Extended File Attributes  
4.3.3 Ignore Failed Read   
Options Used by ‘--extract’
4.4.1 Options to Help Read Archives  
4.4.2 Changing How tar Writes Files  
4.4.3 Coping with Scarce Resources  
Options to Help Read Archives
Reading Full Records  
Ignoring Blocks of Zeros   
Changing How tar Writes Files
Options Controlling the Overwriting of Existing Files  
Overwrite Old Files  
Keep Old Files  
Keep Newer Files  
Unlink First  
Recursive Unlink  
Setting Data Modification Times  
Setting Access Permissions  
Directory Modification Times and Permissions  
Writing to Standard Output  
Writing to an External Program  
Removing Files   
Coping with Scarce Resources
Starting File  
Same Order   
Performing Backups and Restoring Files
5.1 Using tar to Perform Full Dumps  
5.2 Using tar to Perform Incremental Dumps  
5.3 Levels of Backups  
5.4 Setting Parameters for Backups and Restoration  
5.5 Using the Backup Scripts  
5.6 Using the Restore Script  
Setting Parameters for Backups and Restoration
5.4.1 General-Purpose Variables  
5.4.2 Magnetic Tape Control  
5.4.3 User Hooks  
5.4.4 An Example Text of ‘Backup-specs’  
Choosing Files and Names for tar
6.1 Choosing and Naming Archive Files   Choosing the Archive’s Name
6.2 Selecting Archive Members  
6.3 Reading Names from a File  
6.4 Excluding Some Files  
6.5 Wildcards Patterns and Matching  
6.6 Quoting Member Names   Ways of Quoting Special Characters in Names
6.7 Modifying File and Member Names  
6.8 Operating Only on New Files  
6.9 Descending into Directories  
6.10 Crossing File System Boundaries  
Reading Names from a File
6.3.1 NUL-Terminated File Names   
Excluding Some Files
Problems with Using the exclude Options   
Wildcards Patterns and Matching
Controlling Pattern-Matching   
Crossing File System Boundaries
6.10.1 Changing the Working Directory   Changing Directory
6.10.2 Absolute File Names  
Date input formats
7.1 General date syntax   Common rules
7.2 Calendar date items   21 Jul 2020
7.3 Time of day items   9:20pm
7.4 Time zone items   UTC, -0700, +0900, …
7.5 Combined date and time of day items   2020-07-21T20:02:00,000000-0400
7.6 Day of week items   Monday and others
7.7 Relative items in date strings   next tuesday, 2 years ago
7.8 Pure numbers in date strings   20200721, 1440
7.9 Seconds since the Epoch   @1595289600
7.10 Specifying time zone rules   TZ="America/New_York", TZ="UTC0"
7.11 Authors of parse_datetime   Bellovin, Eggert, Salz, Berets, et al. 
Controlling the Archive Format
8.1 Using Less Space through Compression  
8.2 Handling File Attributes  
8.3 Making tar Archives More Portable  
8.4 Making tar Archives More Reproducible  
8.5 Comparison of tar and cpio  
Using Less Space through Compression
8.1.1 Creating and Reading Compressed Archives  
8.1.2 Archiving Sparse Files  
Creating and Reading Compressed Archives
8.1.1.1 Using lbzip2 with GNU tar.  
Making tar Archives More Portable
8.3.1 Portable Names  
8.3.2 Symbolic Links  
8.3.3 Hard Links  
8.3.4 Old V7 Archives  
8.3.5 Ustar Archive Format   Ustar Archives
8.3.6 GNU and old GNU tar format   GNU and old GNU format archives.
8.3.7 GNU tar and POSIX tar   POSIX archives
8.3.8 Checksumming Problems  
8.3.9 Large or Negative Values   Large files, negative time stamps, etc.
8.3.10 How to Extract GNU-Specific Data Using Other tar Implementations  
GNU tar and POSIX tar
8.3.7.1 Controlling Extended Header Keywords  
How to Extract GNU-Specific Data Using Other tar Implementations
8.3.10.1 Extracting Members Split Between Volumes   Members Split Between Volumes
8.3.10.2 Extracting Sparse Members   Sparse Members 
Tapes and Other Archive Media
9.1 Device Selection and Switching   Device selection and switching
9.2 Remote Tape Server  
9.3 Some Common Problems and their Solutions  
9.4 Blocking  
9.5 Many Archives on One Tape   Many archives on one tape
9.6 Using Multiple Tapes  
9.7 Including a Label in the Archive  
9.8 Verifying Data as It is Stored  
9.9 Write Protection   
Blocking
9.4.1 Format Variations  
9.4.2 The Blocking Factor of an Archive  
Many Archives on One Tape
9.5.1 Tape Positions and Tape Marks  
9.5.2 The mt Utility  
Using Multiple Tapes
9.6.1 Archives Longer than One Tape or Disk  
9.6.2 Tape Files  
9.6.3 Concatenate Volumes into a Single Archive  

Reliability and Security
10.1 Reliability  
10.2 Security   
Reliability
10.1.1 Permissions Problems  
10.1.2 Data Corruption and Repair  
10.1.3 Race conditions   
Security
10.2.1 Privacy  
10.2.2 Integrity  
10.2.3 Dealing with Live Untrusted Data  
10.2.4 Security Rules of Thumb   
Recipes
B.1 Copying directory hierarchies  
B.2 Restoring Intermediate Directories   
Tar Internals
Basic Tar Format  
GNU Extensions to the Archive Format  
Storing Sparse Files  
Format of the Incremental Snapshot Files  
Dumpdir   
Storing Sparse Files
E.0.1 Old GNU Format  
E.0.2 PAX Format, Versions 0.0 and 0.1  
E.0.3 PAX Format, Version 1.0  
Genfile
F.1 Generate Mode   File Generation Mode.
F.2 Status Mode   File Status Mode.
F.4 Exec Mode   Synchronous Execution mode. 
Copying This Manual
Appendix G GNU Free Documentation License   License for copying this manual. 







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