How to archive and extract files/directories using "tar" in Linux

The tar Command

Archiving and compressing ﬁles are useful when creating backups and transferring data across a network. One of the oldest and most common commands for creating and working with backup archives is the tar command.

With tar, users can gather large sets of ﬁles into a single ﬁle (archive). A tar archive is a structured sequence of ﬁle data mixed in with metadata about each ﬁle and an index so that individual ﬁles can be extracted. The archive can be compressed using gzip, bzip2, or xz compression. The tar command can list the contents of archives or extract their ﬁles to the current system.

Selected tar options

tar command options are divided into operations (the action you want to take): general options and compression options. The table below shows common options, long version of options, and their description:

Overview of tar Operations

OPTION	DESCRIPTION
-c, –create	Create a new archive.
-x, –extract	Extract from an existing archive.
-t, –list	List the table of contents of an archive.

Selected tar General Options

OPTION	DESCRIPTION
-v, –verbose	Verbose. Shows which files get archived or extracted.
-f, –file=	File name. This option must be followed by the file name of the archive to use or create.
-p, –preserve-permissions	Preserve the permissions of files and directories when extracting an archive, without subtracting the umask.

Overview of tar Compression Options

OPTION	DESCRIPTION
-z, –gzip	Use gzip compression (.tar.gz).
-j, –bzip2	Use bzip2 compression (.tar.bz2). bzip2 typically achieves a better compression ratio than gzip.
-J, –xz	Use xz compression (.tar.xz). The xz compression typically achieves a better compression ratio than bzip2.

Listing Options of tar Command

The tar command expects one of the three following options:

Use the -c or –create option to create an archive.
Use the -t or –list option to list the contents of an archive.
Use the -x or –extract option to extract an archive.

Other commonly used options are:

Use the -f or –file= option with a ﬁle name as an argument of the archive to operate.
Use the -v or –verbose option for verbosity; useful to see which ﬁles get added to or extracted from the archive.

Note: The tar command actually supports a third, old option style that uses the standard single-letter options with no leading -. It is still commonly encountered, and you might run into this syntax when working with other people’s instructions or commands. The info tar ‘old options’ command discusses how this differs from normal short options in some detail. You can ignore old options for now and focus on the standard short and long options syntax.

Archiving file and directories

The ﬁrst option to use when creating a new archive is the c option, followed by the f option, then a single space, then the ﬁle name of the archive to be created, and ﬁnally the list of ﬁles and directories that should get added to the archive. The archive is created in the current directory unless speciﬁed otherwise.

Note: Before creating a tar archive, verify that there is no other archive in the directory with the same name as the new archive to be created. The tar command overwrites an existing archive without warning.

The following command creates an archive named archive.tar with the contents of file1, file2, and file3 in the user’s home directory.

[user@host ~]$ tar -cf archive.tar file1 file2 file3

[user@host ~]$ ls archive.tar
archive.tar

The above tar command can also be executed using the long version options.

[user@host ~]$ tar --file=archive.tar --create file1 file2 file3

Note: When archiving ﬁles by absolute path names, the leading / of the path is removed from the ﬁle name by default. Removing the leading / of the path help users to avoid overwriting important ﬁles when extracting the archive. The tar command extracts ﬁles relative to the current working directory.

For tar to be able to archive the selected ﬁles, it is mandatory that the user executing the tar command can read the ﬁles. For example, creating a new archive of the /etc folder and all of its content requires root privileges, because only the root user is allowed to read all of the ﬁles present in the /etc directory. An unprivileged user can create an archive of the /etc directory, but the archive omits ﬁles which do not include read permission for the user, and it omits directories which do not include both read and execute permission for the user.

To create the tar archive named, /root/etc.tar, with the /etc directory as content as user root:

[root@host ~]# tar -cf /root/etc.tar /etc
tar: Removing leading `/' from member names
[root@host ~]#

Note: Some advanced permissions that we have not covered in this course, such as ACLs and SELinux contexts, are not automatically stored in a tar archive. Use the -xattrs option when creating an archive to store those extended attributes in the tar archive.

Listing of an Archive

The t option directs tar to list the contents (table of contents, hence t) of the archive. Use the f option with the name of the archive to be queried. For example:

[root@host ~]# tar -tf /root/etc.tar
etc/
etc/fstab
etc/crypttab
etc/mtab
...output omitted...

Extracting files from an archive

A tar archive should usually be extracted in an empty directory to ensure it does not overwrite any existing ﬁles. When root extracts an archive, the tar command preserves the original user and group ownership of the ﬁles. If a regular user extracts ﬁles using tar, the ﬁle ownership belongs to the user extracting the ﬁles from the archive.

To restore ﬁles from the /root/etc.tar archive to the /root/etcbackup directory, run:

[root@host ~]# mkdir /root/etcbackup
[root@host ~]# cd /root/etcbackup
[root@host etcbackup]# tar -tf /root/etc.tar
etc/
etc/fstab
etc/crypttab
etc/mtab
...output omitted...
[root@host etcbackup]# tar -xf /root/etc.tar

By default, when ﬁles get extracted from an archive, the umask is subtracted from the permissions of archive content. To preserve the permissions of an archived ﬁle, the p option when extracting an archive. In this example, an archive named, /root/myscripts.tar, is extracted in the /root/scripts directory while preserving the permissions of the extracted ﬁles:

[root@host ~]# mkdir /root/scripts
[root@host ~]# cd /root/scripts
[root@host scripts]# tar -xpf /root/myscripts.tar

Creating a Compressed Archive

The tar command supports three compression methods. There are three different compression methods supported by the tar command. The gzip compression is the fastest and oldest one and is most widely available across distributions and even across platforms. bzip2 compression creates smaller archive ﬁles compared to gzip but is less widely available than gzip, while the xz compression method is relatively new, but usually offers the best compression ratio of the methods available.

Note: The effectiveness of any compression algorithm depends on the type of data that is compressed. Data ﬁles that are already compressed, such as compressed picture formats or RPM ﬁles, usually lead to a low compression ratio.

It is good practice to use a single top-level directory, which can contain other directories and ﬁles, to simplify the extraction of the ﬁles in an organized way. Use one of the following options to create a compressed tar archive:

-z or –gzip for gzip compression (filename.tar.gz or filename.tgz)
-j or –bzip2 for bzip2 compression (filename.tar.bz2)
-J or -xz for xz compression (filename.tar.xz)

To create a gzip compressed archive named /root/etcbackup.tar.gz, with the contents from the /etc directory on host:

[root@host ~]# tar -czf /root/etcbackup.tar.gz /etc
tar: Removing leading `/' from member names

To create a bzip2 compressed archive named /root/logbackup.tar.bz2, with the contents from the /var/log directory on host:

[root@host ~]$ tar -cjf /root/logbackup.tar.bz2 /var/log
tar: Removing leading `/' from member names

To create a xz compressed archive named, /root/sshconfig.tar.xz, with the contents from the /etc/ssh directory on host:

[root@host ~]$ tar -cJf /root/sshconfig.tar.xz /etc/ssh
tar: Removing leading `/' from member names

After creating an archive, verify the content of an archive using the tf options. It is not mandatory to use the option for compression agent when listing the content of a compressed archive ﬁle. For example, to list the content archived in the /root/etcbackup.tar.gz ﬁle, which uses the gzip compression, use the following command:

[root@host ~]# tar -tf /root/etcbackup.tar.gz /etc
etc/
etc/fstab
etc/crypttab
etc/mtab
...output omitted...

Extracting a Compressed Archive

The ﬁrst step when extracting a compressed tar archive is to determine where the archived ﬁles should be extracted to, then create and change to the target directory. The tar command determines which compression was used and it is usually not necessary to use the same compression option used when creating the archive. It is valid to add the decompression method to the tar command. If one chooses to do so, the correct decompression type option must be used; otherwise tar yields an error about the decompression type speciﬁed in the options not matching the ﬁle’s decompression type.

To extract the contents of a gzip compressed archive named /root/etcbackup.tar.gz in the /tmp/etcbackup directory:

[root@host ~]# mkdir /tmp/etcbackup
[root@host ~]# cd /tmp/etcbackup
[root@host etcbackup]# tar -tf /root/etcbackup.tar.gz
etc/
etc/fstab
etc/crypttab
etc/mtab
...output omitted...
[root@host etcbackup]# tar -xzf /root/etcbackup.tar.gz

To extract the contents of a bzip2 compressed archive named /root/logbackup.tar.bz2 in the /tmp/logbackup directory:

[root@host ~]# mkdir /tmp/logbackup
[root@host ~]# cd /tmp/logbackup
[root@host logbackup]# tar -tf /root/logbackup.tar.bz2
var/log/
var/log/lastlog
var/log/README
var/log/private/
var/log/wtmp
var/log/btmp
...output omitted...
[root@host logbackup]# tar -xjf /root/logbackup.tar.bz2

To extract the contents of a xz compressed archive named /root/sshbackup.tar.xz in the /tmp/sshbackup directory:

[root@host ~]$ mkdir /tmp/sshbackup
[root@host ~]# cd /tmp/sshbackup
[root@host logbackup]# tar -tf /root/sshbackup.tar.xz
etc/ssh/
etc/ssh/moduli
etc/ssh/ssh_config
etc/ssh/ssh_config.d/
etc/ssh/ssh_config.d/05-redhat.conf
etc/ssh/sshd_config
...output omitted...
[root@host sshbackup]# tar -xJf /root/sshbackup.tar.xz

Listing a compressed tar archive works in the same way as listing an uncompressed tar archive.

Note: Additionally, gzip, bzip2, and xz can be used independently to compress single ﬁles. For example, the gzip etc.tar command results in the etc.tar.gz compressed ﬁle, while the bzip2 abc.tar command results in the abc.tar.bz2 compressed ﬁle, and the xz myarchive.tar command results in the myarchive.tar.xz compressed ﬁle. The corresponding commands to decompress are gunzip, bunzip2, and unxz. For example, the gunzip /tmp/etc.tar.gz command results in the etc.tar uncompressed tar ﬁle, while the bunzip2 abc.tar.bz2 command results in the abc.tar uncompressed tar ﬁle, and the unxz myarchive.tar.xz command results in the myarchive.tar uncompressed tar ﬁle.