The difference between apt and apt-get in Ubuntu package management

History of apt and apt-get
Comparison of apt and apt-get commands
Examples of common commands
- Update repository index
- Upgrade installed packages
- list all available packages
- Keyword search installation package
- install software
- uninstall software
- View installation package information
- Clean up useless dependencies
- Clean up downloaded cache packages
- Clean up leftover configuration files
- View the dependencies of the installation package
refer to

Apt and apt-get development history

Debian uses a set of tools called Advanced Packaging Tool (APT) to manage software packages (not to be confused with the apt command, not the same thing), in Debian-based Linux distributions (such as Ubuntu), there are various tools that can be used with APT interacts to facilitate users to install, remove and manage software packages. apt-get and apt-cache are two of the most popular tools.

The usage of apt-get and apt-cache commands is very low-level. The commonly used software package management commands are scattered in different commands. You have to use apt-get for a while, and you have to use apt-cache for a while. The interface cannot be unified, which is very unfriendly.

To this end, Ubuntu 16.04 introduces the apt command set, which is optimized on the basis of apt-get and apt-cache, and is more structured and advanced. Apt ignores the needs of fetching and caching. With apt, you don’t have to switch back and forth between apt-get and apt-cache commands. With apt, you get all the necessary tools at once. Don’t get lost in the multitude of command options. Apt’s main goal is to provide a user-pleasing way to work efficiently with software packages. Its streamlined command options are easier to use and easier to remember.

Whether apt-get will be deprecated in the future is unknown, but many other Linux distributions are also following the steps of Ubuntu and starting to encourage users to use apt instead of apt-get. Unless you plan to do some specific operations, and these operations use more features of apt-get. Otherwise, use apt.

To sum up the difference between apt and apt-get is:

Apt is a new tool, used to replace apt-get and apt-cache, the purpose is a more friendly and easy-to-use package management tool;
apt-get has not been abandoned or outdated, and can still be used with confidence, but ordinary users are advised to switch to apt.

Comparison of apt and apt-get commands

Although apt does provide some options similar to apt-get, it is not backward compatible with apt-get. This means that if you just use apt instead of apt-get in the apt-get command, it won’t always work.

Let’s see which command options of apt-get and apt-cache are replaced by the apt command

apt command	replaced command	function of the command
apt update	apt-get update	update repository index
apt upgrade	apt-get upgrade	Upgrade all upgradeable packages
apt install	apt-get install	install package
apt remove	apt-get remove	remove package but keep config file
apt purge	apt-get purge	Remove the package and delete the configuration file
apt autoremove	apt-get autoremove	Automatically delete useless dependencies
apt full-upgrade	apt-get dist-upgrade	Automatically handle dependencies when upgrading packages
apt search	apt-cache search	Search applications
apt show	apt-cache show	Display the basic information of the specified installation package

apt also has some unique commands of its own:

New apt command	Command function
apt list	List packages containing conditions (installed, upgradable, etc.)
apt edit-sources	edit sources list

For their commonly used commands, see the help instructions of apt, apt-get and apt-cache:

$ apt -h
apt 2.0.9 (amd64)
Usage: apt [options] command

The command-line package manager apt provides functions such as package search, management and information query.
It provides the same functionality as other APT tools (like apt-get and apt-cache),
But by default it is set to be more interactive.

Common commands:
  list - list packages by name
  search - search package descriptions
  show - show package details
  install - Install a package
  reinstall - reinstall a package
  remove - remove a package
  autoremove - remove all automatically installed packages that are no longer in use
  update - update the list of available packages
  upgrade - update the system by installing/upgrading software
  full-upgrade - Update system by uninstall/install/upgrade
  edit-sources - Edit software source information files
  satisfy - Satisfy the system with dependency strings

$ apt-get -h
apt 2.0.9 (amd64)
Usage: apt-get [options] command
apt-get [options] install|remove package1 [package2...]
apt-get [options] source package1 [package2...]

apt-get can download packages and related information from certified software sources to install and upgrade packages,
Or for removing packages. During these processes, package dependencies are handled gracefully.

Common commands:
  update - Retrieve updated package list information
  upgrade - perform an upgrade
  install - install a new package (note: the package name should be something like libc6 not libc6.deb)
  reinstall - reinstalls the package (note: the package name should be something like libc6 not libc6.deb)
  remove - remove a package
  purge - Uninstall and purge a package's configuration
  autoremove - remove all automatically installed packages that are no longer in use
  dist-upgrade - distribution upgrade, see apt-get(8)
  dselect-upgrade - upgrade based on dselect selections
  build-dep - configures required build dependencies for source packages
  satisfy - Satisfy the system with dependency strings
  clean - delete all downloaded package files
  autoclean - remove old downloaded package files
  check - check to confirm the integrity of the system's dependencies
  source - Download the source package file
  download - download the specified binary package to the current directory
  changelog - Download the specified package and display its changelog (changelog)

$ apt-cache -h
apt 2.0.9 (amd64)
Usage: apt-cache [options] command
       apt-cache [options] show package1 [package2...]

apt-cache can query and display information about the availability of installed and installable packages.
It works exclusively on local data caches that can be accessed via, for example,
apt-get's 'update' command to update. If it's been too long since the last update,
Then the information it displays may be out of date. But in exchange, apt-cache does not rely on
Availability of the current software source (eg: offline status).

Common commands:
  showsrc - show the records of the source file
  search - search the list of packages based on a regular expression
  depends - displays the package's dependencies
  rdepends - show the names of all packages that depend on this package
  show - presents the package in a human-readable format
  pkgnames - list all package names
  policy - Displays the status of a package's installation settings

Example of common commands

For the following example, try to use the apt command.

Update repository index

Use the command apt update to resynchronize the file index from the source warehouse. This command must be executed when the source list is updated.

$ sudo apt update

Upgrade installed packages

Upgrade all installed packages:

apt-get upgrade

Only upgrade specific packages:

apt-get upgrade <package_name>

List all available packages

You can use this command to check whether the package you want to install is in the list of installable packages. This command will display all available installation packages and the installation status of each package, including information such as installed, upgradeable, and remaining configuration files.

apt list

Keyword search installation package

Before apt install, if you don’t know the exact package name, you can use apt search to search, which supports fuzzy search. The more detailed the keyword, the more accurate the search result. The keyword can be part of the package name or the package description part of the content.

apt search <search term>

Install software

install software:

apt install <package_name>

Install specific version software:

apt install <package_name>=<version_number>

Install multiple software at the same time:

apt install <package_1> <package_2> <package_3>

Uninstall the software

There are two ways to uninstall the software:

apt remove <package_name>
apt purge <package_name>

View installation package information

For example, check the basic information of the bash installation package

$ apt show bash
Package: bash
Version: 5.0-6ubuntu1.2
Priority: required
Essential: yes
Section: shells
Origin: Ubuntu
Maintainer: Ubuntu Developers <[email protected]>
Original-Maintainer: Matthias Klose <[email protected]>
Bugs: https://bugs.launchpad.net/ubuntu/ + filebug
Installed-Size: 1,700 kB
Pre-Depends: libc6 (>= 2.15), libtinfo6 (>= 6)
Depends: base-files (>= 2.1.12), debianutils (>= 2.15)
Recommends: bash-completion (>= 20060301-0)
Suggests: bash-doc
Conflicts: bash-completion (<< 20060301-0)
Replaces: bash-completion (<< 20060301-0), bash-doc (<= 2.05-1)
Homepage: http://tiswww.case.edu/php/chet/bash/bashtop.html

Clean up useless dependencies

When installing software on an Ubuntu system, the software’s dependencies are usually automatically installed as well. After we delete the software, its dependent packages may need to be manually deleted by using the following command:

apt autoremove

Clean up downloaded cache packages

When Ubuntu installs software through apt-get install, the downloaded packages are cached in the /var/cache/apt/archives/ directory. It is not immediately removed from the directory after the installation is complete. If you delete a package and then reinstall it, your system will look for the package in the cache and fetch it from there instead of re-downloading it.

Temporary directory for package management:
Store during download: /var/cache/apt/archives/partial
Store after downloading: /var/cache/apt/archives

If you want to clean up these downloaded cache packages, you can execute the command:

sudo apt-get clean
sudo apt-get autoclean

apt-get clean deletes all packages in /var/cache/apt/archives/ and /var/cache/apt/archives/partial/ directories (except locked packages).

apt-get autoclean only removes old (older than currently available) packages and useless packages (locked) in /var/cache/apt/archives/ and /var/cache/apt/archives/partial/ except software packages).

Clean up leftover configuration files

If you use apt remove to uninstall the software, the configuration files of the software will be kept, and there will be configuration files left in the system at this time. Residual configuration files can be viewed with the following command:

$ apt list | grep residual

WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

appmenu-qt5/now 0.3.0 + 16.04.20170216-0ubuntu1 amd64 [config file leftover]
apt-xapian-index/focal,focal 0.51ubuntu1 all [configuration file remains]
docutils-common/focal,focal,now 0.16 + dfsg-2 all [configuration leftover]
eclipse-platform/now 3.8.1-8 amd64 [configuration file remains]
fcitx-ui-qimpanel/focal 2.1.3-2build1 amd64 [config file leftover]

View the dependencies of the installation package

For example, check the bash installation package dependencies:

$ apt-cache depends bash
bash
  Pre-dependency: libc6
  Pre-dependency: libtinfo6
  Dependency: base-files
    base-files:i386
  Depends on: debianutils
    debianutils:i386
  Conflict: bash-completion
  Recommended: bash-completion
  Suggestion: bash-doc
  Replaces: bash-completion
  Replaces: bash-doc

Reference

https://blog.csdn.net/slampai/article/details/128072043
https://itsfoss.com/apt-vs-apt-get-difference/
https://itsfoss.com/apt-get-linux-guide/
https://linux.cn/article-4933-1.html

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