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tar command

Overview

tar is a tool for processing archive files on GNU/Linux and other UNIX operating systems. It stands for "tape archive."

Storing files conveniently on magnetic tape was the initial use of tar archives. The name "tar" comes from this use. Despite the utility's name, tar can direct its output to available devices, files, or other programs (using pipes) and access remote devices or files (as archives).

The tar currently used on modern GNU/Linux initially came from the GNU Project. You can browse and download all versions of tar on GNU's website.

Note

The tar in different distributions may have different default options. Please be careful when you use them.

# RockyLinux 8 and Fedora 41
Shell > tar --show-defaults
--format=gnu -f- -b20 --quoting-style=escape --rmt-command=/etc/rmt --rsh-command=/usr/bin/ssh

Use tar

When using tar, note that it has two saving modes:

  • Relative mode (default): Remove the leading character '/' from the file. Even if you have added the file with an absolute path, tar will remove the leading character "/" in this mode.
  • Absolute mode: Keep the leading character '/' and include it in the file name. You need to use the -P option to enable this save mode. In this mode, you must represent all files as absolute paths. For security reasons, you should not use this save mode in most cases unless there are special scenario requirements.

When you use tar, you will encounter suffixes such as .tar.gz, .tar.xz, and .tar.bz2, which indicate that you create an archive first (categorizing related files as a single file) and then compress the file with the relevant compression type or algorithm.

The compression type or algorithm can be gzip, bzip2, xz, zstd, or another.

tar allows the extraction of a single file or a directory from a backup, viewing its contents, or validating its integrity.

The usage of creating an archive and using compression is:

  • tar [option] [PATH] [DIR1] ... [FILE1] .... For example tar -czvf /tmp/Fullbackup-20241201.tar.gz /etc/ /var/log/

The usage to extract a file from an archive is:

  • tar [option] [PATH] -C [dir]. For example tar -xzvf /tmp/Fullbackup-20241201.tar.gz -C /tmp/D1

antic

When you extract files from archived files, tar automatically selects the compression type based on the manually added suffix. For example, for .tar.gz files, you can directly use tar -vxf without using tar -zvxf. You must select the compression type for creating archive compressed files.

Note

In GNU/Linux, most files do not require an extension except for the desktop environment (GUI). The reason for artificially adding suffixes is to facilitate human users' recognition. If the systems administrator sees a .tar.gz or .tgz file extension, for instance, then he knows how to deal with the file.

Operating parameters or types

typesdescription
-AAppends all files in one archive to the end of another archive. Only applicable to archive non-compressed files of the .tar type
-cCreates archive. Very commonly used
-dCompares the differences between archived and corresponding unarchived files
-rAppends the files or directories to the end of the archive. Only applicable to archive non-compressed files of the .tar type
-tLists the contents of the archive
-uOnly appends newer files to the archive. Only applicable to archive non-compressed files of the .tar type
-xExtract from archive. Very commonly used
--deleteDeletes files or directories from the ".tar" archive. Only applicable to archive non-compressed files of the .tar type

Tip

The author recommends keeping the prefix "-" to preserve user habits regarding operation types. Of course, it won't be required. The operational parameters here indicate your primary function with tar. In other words, you need to choose one of the above types.

Common auxiliary options

optiondescription
-zUse gzip as its compression type. Both creating archives and extracting from archives are applicable
-vDisplays detailed processing details
-fSpecifies the file name for archiving (including file suffix)
-jUse bzip2 as its compression type. Both creating archives and extracting from archives are applicable
-JUse xz as its compression type. Both creating archives and extracting from archives are applicable
-CSaves location after extracting files from the archive
-PSaves using the absolute mode

For other auxiliary options not mentioned, see man 1 tar

Version difference

In some older versions of tar, option(s) are referred to as "key(s)", which means that using options with a "-" prefix may cause the tar not to work as expected. At this point, you need to remove the "-" prefix to make it work properly.

About styles of options

tar provides three styles of options:

  1. Traditional style:

    • tar {A|c|d|r|t|u|x}[GnSkUWOmpsMBiajJzZhPlRvwo] [ARG...].

  2. The usage of the short-option style is:

    • tar -A [OPTIONS] ARCHIVE ARCHIVE
    • tar -c [-f ARCHIVE] [OPTIONS] [FILE...]
    • tar -d [-f ARCHIVE] [OPTIONS] [FILE...]
    • tar -t [-f ARCHIVE] [OPTIONS] [MEMBER...]
    • tar -r [-f ARCHIVE] [OPTIONS] [FILE...]
    • tar -u [-f ARCHIVE] [OPTIONS] [FILE...]
    • tar -x [-f ARCHIVE] [OPTIONS] [MEMBER...]

  3. The usage of the long-option style is:

    • tar {--catenate|--concatenate} [OPTIONS] ARCHIVE ARCHIVE
    • tar --create [--file ARCHIVE] [OPTIONS] [FILE...]
    • tar {--diff|--compare} [--file ARCHIVE] [OPTIONS] [FILE...]
    • tar --delete [--file ARCHIVE] [OPTIONS] [MEMBER...]
    • tar --append [-f ARCHIVE] [OPTIONS] [FILE...]
    • tar --list [-f ARCHIVE] [OPTIONS] [MEMBER...]
    • tar --test-label [--file ARCHIVE] [OPTIONS] [LABEL...]
    • tar --update [--file ARCHIVE] [OPTIONS] [FILE...]
    • tar --update [-f ARCHIVE] [OPTIONS] [FILE...]
    • tar {--extract|--get} [-f ARCHIVE] [OPTIONS] [MEMBER...]

The second method is more commonly used and is in line with the habits of most GNU/Linux users.

Compression efficiency and frequency of use

tar does not have compression capabilities, so it must be used with other compression tools. Compression and decompression will impact resource consumption.

Here is a ranking of the compression of a set of text files from least to most efficient:

  • compress (.tar.Z) - Less popular
  • gzip (.tar.gz or .tgz) - Popular
  • bzip2 (.tar.bz2 or .tb2 or .tbz) - Popular
  • lzip (.tar.lz) - Less popular
  • xz (.tar.xz) - Popular

Naming convention for a tar

Here are examples of naming conventions for tar archives:

Main function and auxiliary optionsFilesSuffixFunctionality
-cvfhomehome.tar/home in relative mode, uncompressed form
-cvfP/etcetc.A.tar/etc in absolute mode, no compression
-cvfzusrusr.tar.gz/usr in relative mode, gzip compression
-cvfjusrusr.tar.bz2/usr in relative mode, bzip2 compression
-cvfPz/homehome.A.tar.gz/home in absolute mode, gzip compression
-cvfPj/homehome.A.tar.bz2/home in absolute mode, bzip2 compression

You may also add the date to the filename.

Example of use

-c type

  1. Archive and compress /etc/ in relative mode, with a suffix of .tar.gz:

    Shell > tar -czvf /tmp/etc-20241207.tar.gz /etc/

    Due to tar working in relative mode by default, the first line of the command output will display the following:

    tar: Removing leading '/' from member names

  2. Archive /var/log/ and select xz type for compression:

    Shell > tar -cJvf /tmp/log-20241207.tar.xz /var/log/

Shell > du -sh /var/log/ ; ls -lh /tmp/log-20241207.tar.xz
18M     /var/log/
-rw-r--r-- 1 root root 744K Dec  7 14:40 /tmp/log-20241207.tar.xz

  3. Estimate file size without generating an archive:

    Shell > tar -cJf - /etc | wc -c
tar: Removing leading `/' from member names
3721884

    The output unit of the wc -c command is bytes.

  4. Cut large .tar.gz files:

    Shell > cd /tmp/ ; tar -czf - /etc/  | split -d -b 2M - etc-backup20241207.tar.gz.

Shell > ls -lh /tmp/
-rw-r--r-- 1 root root 2.0M Dec  7 20:46 etc-backup20241207.tar.gz.00
-rw-r--r-- 1 root root 2.0M Dec  7 20:46 etc-backup20241207.tar.gz.01
-rw-r--r-- 1 root root 2.0M Dec  7 20:46 etc-backup20241207.tar.gz.02
-rw-r--r-- 1 root root  70K Dec  7 20:46 etc-backup20241207.tar.gz.03

    The first "-" represents the input parameters of tar while the second "-" tells tar to redirect the output to stdout.

    To extract these cut small files, you can point to the following operation:

    Shell > cd /tmp/ ; cat etc-backup20241207.tar.gz.* >> /tmp/etc-backup-20241207.tar.gz

Shell > cd /tmp/ ; tar -xvf etc-backup-20241207.tar.gz -C /tmp/dir1/

-x type

  1. Download the Redis source code and extract it to the /usr/local/src/ directory：

    Shell > wget -c https://github.com/redis/redis/archive/refs/tags/7.4.1.tar.gz

Shell > tar -xvf 7.4.1.tar.gz -C /usr/local/src/

  2. Extract only one file from the archive zip file

    Shell > tar -xvf /tmp/etc-20241207.tar.gz etc/chrony.conf

-A or -r type

  1. Append one .tar file to another .tar file:

    Shell > tar -cvf /tmp/etc.tar /etc/

Shell > tar -cvf /tmp/log.tar /var/log/

Shell > tar -Avf /tmp/etc.tar /tmp/log.tar

    This means that all files in "log.tar" will be appended to the end of "etc.tar".

  2. Append files or directories to a .tar file:

    Shell > tar -rvf /tmp/log.tar /etc/chrony.conf
tar: Removing leading `/' from member names
/etc/chrony.conf
tar: Removing leading `/' from hard link targets

Shell > tar -rvf /tmp/log.tar /tmp/dir1

Warning

Whether you use the -A or -r option, consider the saving mode of the relevant archive files.

Warning

-A and -r are not applicable for archived compressed files.

-t type

  1. Review the contents of the archive:

    Shell > tar -tvf /tmp/log.tar

Shell > tar -tvf /tmp/etc-20241207.tar.gz | less

-d type

  1. Compare file differences:

    Shell > cd / ; tar -dvf /tmp/etc.tar etc/chrony.conf
etc/chrony.conf

Shell > cd / ; tar -dvf /tmp/etc-20241207.tar.gz etc/

    For storage methods that use relative mode, when using the -d type, switch the file path to '/'.

-u type

  1. If there are multiple versions of the same file, you can use the -u type:

    Shell > touch /tmp/tmpfile1

Shell > tar -rvf /tmp/log.tar /tmp/tmpfile1

Shell > echo "File Name" >> /tmp/tmpfile1

Shell > tar -uvf /tmp/log.tar /tmp/tmpfile1

Shell > tar -tvf /tmp/log.tar
...
-rw-r--r-- root/root         0 2024-12-07 18:53 tmp/tmpfile1
-rw-r--r-- root/root        10 2024-12-07 18:54 tmp/tmpfile1

--delete type

  1. You can also use --delete to delete files inside a .tar file.

    Shell > tar --delete -vf /tmp/log.tar tmp/tmpfile1

Shell > tar --delete -vf /tmp/etc.tar etc/motd.d/

    When deleting, you will delete all files with the same name from the archive.

Common terminology

Some websites mention two terms:

  • tarfile - Refers to uncompressed archive files, such as .tar files
  • tarball - Refers to compressed archive files, such as .tar.gz and .tar.xz

Author: tianci li

Contributors: Ganna Zhyrnova