Getting Started with Linux Fundamentals

Not all software is distributed in a repository. Sometimes, a software project distributes an application as a compressed archive. An archive is a single binary file that can contain multiple files and directories that are compressed within it. Several archive formats are available, such as the zip, 7z, and tar formats. The tar format is the most popular format on Linux systems. A tar archive is often referred to as a tarball. A tar archive can be compressed by using tools such as gzip or xz, but compression is optional.

Archives are a convenient way to send several files to someone, or to generate consolidated backups of important files. The GNOME Files application enables you to extract archives and to create archives from your files or directories.

You can create or extract an archive by right-clicking an item in the Files application. If the Files application identifies a compressed archive, then the Files application displays the option to extract its contents. If the Files application identifies a regular file or directory, then the Files application displays the option to compress the target.

Creating an Archive on the Desktop

To create an archive, right-click the directory that you intend to archive and select Compress from the context menu.

Figure 6.6: Creating an archive from the Files application

In the Create Archive dialog that displays, provide a name for the archive, and then choose a format from the drop-down list. By default, GNOME Files creates a .zip file, but the Files application can also produce a password-protected .zip file, a .tar.xz file, or a .7z file.

Figure 6.7: Selecting the name of the archive

After you create the archive, it appears in your current directory.

Create and extract archives on the command line with the tar and zip commands. Creating and extracting archives on the command line enables you to perform additional tasks, such as updating files in the archive with the latest changes, and using other compression tools.

[user@host Downloads]$ tar --create --gzip --file example.tar.gz example
[user@host Downloads]$ ls
example   example.tar.gz

[user@host Downloads]$ tar --list --file example.tar.gz
example/
example/file1.txt
example/file2.txt
example/file3.txt

[user@host Downloads]$ unzip example.zip
[user@host Downloads]$ ls
example   example.zip

[user@host Downloads]$ tar --extract --file --gzip example.tar.gz
[user@host Downloads]$ ls
example   example.tar.gz

Archives are sometimes used as backups for important files, and are also an alternative to distributing software through a Linux distribution's repository.

When installing software or restoring a backup, you extract an archived file tree and distribute the files throughout an existing file system. For example, an installable archive could contain the bin and etc subdirectories; the bin directory contains an executable file and the etc directory contains configuration files. If you extract the archive to the ~/.local directory, which contains the same subdirectories, then the executable and configuration files are distributed into the corresponding subdirectories.

To extract an archive into a specific directory, use the tar command with --directory option followed by a file path to the destination directory.

[user@host Downloads]$ tar --extract --file example.tar.gz \
--directory ~/.local

You can extract just one file from an archive by specifying the path of a file as it appears in the archive. For example, if you accidentally remove the file1.txt file, then you can recover it from your backup archive. Because the archive contains a directory called example, any file that is extracted from the archive into the current directory (.) is placed into the example directory.

[user@host Downloads]$ rm example/file1.txt
[user@host Downloads]$ ls example
file2.txt   file3.txt
[user@host Downloads]$ tar --extract --file example.tar.gz example/file1.txt
[user@host Downloads]$ ls example
file1.txt   file2.txt   file3.txt

If the directory does not already exist in the current directory, then it is created.

[user@host Downloads]$ rm -r example
[user@host Downloads]$ ls example
ls: cannot access 'example': No such file or directory
[user@host Downloads]$ tar --extract --file example.tar.gz example/file1.txt \
--directory .
[user@host Downloads]$ ls example
file1.txt