apt-get command

What is apt-get?

apt get list

APT, short for Advanced package Tool, is a package management system.
apt get allows you to quickly and easily install, update, and remove software from the command line. Aside from its simplicity, one of the best things about APT is the face that it automatically resolves dependency issues for you.

This means that if the package you are installing requires additional software, apt get will automatically locate and install the additional software.
This is a massive improvement over the old days of “ dependency hell” .

installing software with apt get is very straightforward.
For example, let us assume you want to install the classic network-mapping tool Cheops, Once you know the name of the package you want to install, from the command line you can run apt-get install followed by the name of the software you want to install.
It is always a good idea to run apt-get update before installing software.
This will insure that you are getting the latest version available.

install a Package: Installation of packages using the apt-get tool is quite simple. For example, to install the network scanner nmap, type the following:

 sudo apt-get install nmap

Remove a Package: Removal of a package (or packages) is also straightforward. To remove the package installed in the previous example, type the following:

sudo apt-get remove nmap

update the Package Index: The APT package index is essentially a database of available packages from the repositories defined in the /etc/apt/sources.list
To update the local package index type the following:

sudo apt-get update

Upgrade Packages: To upgrade your system, first update your package index as outlined above, and then type:

sudo apt-get upgrade

More with the apt-get

1) apt-get update
update is used to resynchronize the package index files from their sources
if you are using a non root user you should add sudo to the  beginning of the command and it will look like this  sudo apt get update

2) apt-get upgrade
upgrade is used to install the newest versions of all packages currently installed on the system from the sources enumerated in /etc/apt/sources.list.
 on a non root user you will always need to add sudo at the beginning of the command
sudo apt get upgrade

3) apt-get dselect-upgrade
dselect-upgrade is used in conjunction with the traditional Debian packaging front-end.

4) apt-get dist-upgrade
dist-upgrade in addition to performing the function of upgrade, also intelligently handles changing dependencies with new versions of packages; apt-get has a "smart" conflict resolution system, and it will attempt to upgrade the most important packages at the expense of less important ones if necessary.
So apt-get dist-upgrade command may remove some packages. The /etc/apt/sources.list file contains a list of locations from which to retrieve desired package files. See also apt_preferences(5) for a mechanism for overriding the general settings for individual packages.

apt get uninstall ? there is no command like that , but the right command is apt-get remove or sudo apt-get remove if you are on a non root user.

5) apt get --purge remove 

To uninstall a program, use the “ apt-get remove ” command, which is the general command for uninstalling programs on Linux.

For example, the following command uninstalls nmap and deletes all the configuration files, using the “--purge”  command.

sudo apt-get --purge remove nmap

and If you don’t want to remove the configuration files, simply leave out the “--purge” command,
example

sudo apt-get remove nmap

6) apt get reinstall 
You can reinstall a package with apt-get install --reinstall packagename.
This completely removes the package (but not the packages that depend on it) then reinstall's it.
for example if we want to reinstall nmap the command would be like that :

apt-get install --reinstall nmap

7) apt get autoremove
autoremove is used to remove packages that were automatically installed to satisfy dependencies for some package and no longer needed

apt-get autoremove

8) apt get clean
This command removes the aptitude cache in “/var/cache/apt/archives”,
every time  you install a program, the package file is downloaded and stored in that directory.
You don’t need to keep the files in that directory and that what apt-get clean will do removing that files

sudo apt-get clean

9) apt get search
To search for a particular package by name or description:
From the command-line, use:

apt-cache search keyword

where the search keyword can be all or part of a package name or any words used in its description.

For example, apt-cache search proxy includes both these packages:

tinyproxy - A lightweight, non-caching, optionally anonymizing HTTP proxy
tircd - ircd proxy to the twitter API
Note: the list may be long, so you can pipe the output to less to make it scrollable one line or one screen at a time, i.e. apt-cache search something | less.

--no-install-recommends
           Do not consider recommended packages as a dependency for
           installing. Configuration Item: APT::Install-Recommends.

       -d, --download-only
           Download only; package files are only retrieved, not unpacked or
           installed. Configuration Item: APT::Get::Download-Only.

       -f, --fix-broken
           Fix; attempt to correct a system with broken dependencies in place.
           This option, when used with install/remove, can omit any packages
           to permit APT to deduce a likely solution. If packages are
           specified, these have to completely correct the problem. The option
           is sometimes necessary when running APT for the first time; APT
           itself does not allow broken package dependencies to exist on a
           system. It is possible that a system's dependency structure can be
           so corrupt as to require manual intervention (which usually means
           using dselect(1) or dpkg --remove to eliminate some of the
           offending packages). Use of this option together with -m may
           produce an error in some situations. Configuration Item:
           APT::Get::Fix-Broken.

       -m, --ignore-missing, --fix-missing
           Ignore missing packages; If packages cannot be retrieved or fail
           the integrity check after retrieval (corrupted package files), hold
           back those packages and handle the result. Use of this option
           together with -f may produce an error in some situations. If a
           package is selected for installation (particularly if it is
           mentioned on the command line) and it could not be downloaded then
           it will be silently held back. Configuration Item:
           APT::Get::Fix-Missing.

       --no-download
           Disables downloading of packages. This is best used with
           --ignore-missing to force APT to use only the .debs it has already
           downloaded. Configuration Item: APT::Get::Download.

       -q, --quiet
           Quiet; produces output suitable for logging, omitting progress
           indicators. More q's will produce more quiet up to a maximum of 2.
           You can also use -q=# to set the quiet level, overriding the
           configuration file. Note that quiet level 2 implies -y, you should
           never use -qq without a no-action modifier such as -d, --print-uris
           or -s as APT may decided to do something you did not expect.
           Configuration Item: quiet.

       -s, --simulate, --just-print, --dry-run, --recon, --no-act
           No action; perform a simulation of events that would occur but do
           not actually change the system. Configuration Item:
           APT::Get::Simulate.

           Simulation run as user will deactivate locking (Debug::NoLocking)
           automatic. Also a notice will be displayed indicating that this is
           only a simulation, if the option
           APT::Get::Show-User-Simulation-Note is set (Default: true). Neither
           NoLocking nor the notice will be triggered if run as root (root
           should know what he is doing without further warnings by apt-get).

           Simulate prints out a series of lines each one representing a dpkg
           operation, Configure (Conf), Remove (Remv), Unpack (Inst). Square
           brackets indicate broken packages and empty set of square brackets
           meaning breaks that are of no consequence (rare).

       -y, --yes, --assume-yes
           Automatic yes to prompts; assume "yes" as answer to all prompts and
           run non-interactively. If an undesirable situation, such as
           changing a held package, trying to install a unauthenticated
           package or removing an essential package occurs then apt-get will
           abort. Configuration Item: APT::Get::Assume-Yes.

       -u, --show-upgraded
           Show upgraded packages; Print out a list of all packages that are
           to be upgraded. Configuration Item: APT::Get::Show-Upgraded.

       -V, --verbose-versions
           Show full versions for upgraded and installed packages.
           Configuration Item: APT::Get::Show-Versions.

       -b, --compile, --build
           Compile source packages after downloading them. Configuration Item:
           APT::Get::Compile.

       --install-recommends
           Also install recommended packages.

       --no-install-recommends
           Do not install recommended packages.

       --ignore-hold
           Ignore package Holds; This causes apt-get to ignore a hold placed
           on a package. This may be useful in conjunction with dist-upgrade
           to override a large number of undesired holds. Configuration Item:
           APT::Ignore-Hold.

       --no-upgrade
           Do not upgrade packages; When used in conjunction with install,
           no-upgrade will prevent packages on the command line from being
           upgraded if they are already installed. Configuration Item:
           APT::Get::Upgrade.

       --force-yes
           Force yes; This is a dangerous option that will cause apt to
           continue without prompting if it is doing something potentially
           harmful. It should not be used except in very special situations.
           Using force-yes can potentially destroy your system! Configuration
           Item: APT::Get::force-yes.

       --print-uris
           Instead of fetching the files to install their URIs are printed.
           Each URI will have the path, the destination file name, the size
           and the expected md5 hash. Note that the file name to write to will
           not always match the file name on the remote site! This also works
           with the source and update commands. When used with the update
           command the MD5 and size are not included, and it is up to the user
           to decompress any compressed files. Configuration Item:
           APT::Get::Print-URIs.

       --purge
           Use purge instead of remove for anything that would be removed. An
           asterisk ("*") will be displayed next to packages which are
           scheduled to be purged.  remove --purge is equivalent to the purge
           command. Configuration Item: APT::Get::Purge.

       --reinstall
           Re-Install packages that are already installed and at the newest
           version. Configuration Item: APT::Get::ReInstall.

       --list-cleanup
           This option defaults to on, use --no-list-cleanup to turn it off.
           When on apt-get will automatically manage the contents of
           /var/lib/apt/lists to ensure that obsolete files are erased. The
           only reason to turn it off is if you frequently change your source
           list. Configuration Item: APT::Get::List-Cleanup.

       -t, --target-release, --default-release
           This option controls the default input to the policy engine, it
           creates a default pin at priority 990 using the specified release
           string. This overrides the general settings in
           /etc/apt/preferences. Specifically pinned packages are not affected
           by the value of this option. In short, this option lets you have
           simple control over which distribution packages will be retrieved
           from. Some common examples might be -t '2.1*', -t unstable or -t
           sid. Configuration Item: APT::Default-Release; see also the
           apt_preferences(5) manual page.

       --trivial-only
           Only perform operations that are 'trivial'. Logically this can be
           considered related to --assume-yes, where --assume-yes will answer
           yes to any prompt, --trivial-only will answer no. Configuration
           Item: APT::Get::Trivial-Only.

       --no-remove
           If any packages are to be removed apt-get immediately aborts
           without prompting. Configuration Item: APT::Get::Remove.

       --auto-remove
           If the command is either install or remove, then this option acts
           like running autoremove command, removing the unused dependency
           packages. Configuration Item: APT::Get::AutomaticRemove.

       --only-source
           Only has meaning for the source and build-dep commands. Indicates
           that the given source names are not to be mapped through the binary
           table. This means that if this option is specified, these commands
           will only accept source package names as arguments, rather than
           accepting binary package names and looking up the corresponding
           source package. Configuration Item: APT::Get::Only-Source.

       --diff-only, --dsc-only, --tar-only
           Download only the diff, dsc, or tar file of a source archive.
           Configuration Item: APT::Get::Diff-Only, APT::Get::Dsc-Only, and
           APT::Get::Tar-Only.

       --arch-only
           Only process architecture-dependent build-dependencies.
           Configuration Item: APT::Get::Arch-Only.

       --allow-unauthenticated
           Ignore if packages can't be authenticated and don't prompt about
           it. This is useful for tools like pbuilder. Configuration Item:
           APT::Get::AllowUnauthenticated.

       -h, --help
           Show a short usage summary.

       -v, --version
           Show the program version.

       -c, --config-file
           Configuration File; Specify a configuration file to use. The
           program will read the default configuration file and then this
           configuration file. See apt.conf(5) for syntax information.

       -o, --option
           Set a Configuration Option; This will set an arbitrary
           configuration option. The syntax is -o Foo::Bar=bar.  -o and
           --option can be used multiple times to set different options.