Cleaning up with apt-get

Running apt-get commands on a Debian-based system is routine. Packages are updated fairly frequently and commands like apt-get update and apt-get upgrade make the process quite easy. On the other hand, how often do you use apt-get clean, apt-get autoclean or apt-get autoremove?

These commands clean up after apt-get’s installation operations and remove files that are still on your system but are no longer needed – often because the application that required them is no longer installed.

apt-get clean

The apt-get clean command clears the local repository of retrieved package files that are left in /var/cache. The directories it cleans out are /var/cache/apt/archives/ and /var/cache/apt/archives/partial/. The only files it leaves in /var/cache/apt/archives are the lock file and the partial subdirectory.

You might have a number of files in the directory prior to running the clean operation:

/var/cache/apt/archives/db5.3-util_5.3.28+dfsg1-0.6ubuntu1_amd64.deb
/var/cache/apt/archives/db-util_1%3a5.3.21~exp1ubuntu2_all.deb
/var/cache/apt/archives/lock
/var/cache/apt/archives/postfix_3.4.5-1ubuntu1_amd64.deb
/var/cache/apt/archives/sasl2-bin_2.1.27+dfsg-1build3_amd64.deb

You should only have these afterwards:

$ sudo ls -lR /var/cache/apt/archives
/var/cache/apt/archives:
total 4
-rw-r----- 1 root root    0 Jan  5  2018 lock
drwx------ 2 _apt root 4096 Nov 12 07:24 partial

/var/cache/apt/archives/partial:
total 0			
The apt-get clean command is generally used to clear disk space as needed, generally as part of regularly scheduled maintenance.
apt-get autoclean
The apt-get autoclean option, like apt-get clean, clears the local repository of retrieved package files, but it only removes files that can no longer be downloaded and are virtually useless. It helps to keep your cache from growing too large.
apt-get autoremove
The autoremove option removes packages that were automatically installed because some other package required them but, with those other packages removed, they are no longer needed. Sometimes, an upgrade will suggest that you run this command.
The following packages were automatically installed and are no longer required:
  g++-8 gir1.2-mutter-4 libapache2-mod-php7.2 libcrystalhd3
  libdouble-conversion1 libgnome-desktop-3-17 libigdgmm5 libisl19 libllvm8
  liblouisutdml8 libmutter-4-0 libmysqlclient20 libpoppler85 libstdc++-8-dev
  libtagc0 libvpx5 libx265-165 php7.2 php7.2-cli php7.2-common php7.2-json
  php7.2-opcache php7.2-readline
Use 'sudo apt autoremove' to remove them.			
The packages to be removed are often called "unused dependencies". In fact, a good practice to follow is to use autoremove after uninstalling a package to be sure that no unneeded files are left behind.