1. Show the List of Installed Packages on Ubuntu :
The command we need to use is dpkg –get-selections, which will give us a list of all the currently installed packages.
$ dpkg --get-selections adduser install alsa-base install alsa-utils install apache2 install apache2-mpm-prefork install apache2-utils install apache2.2-common install apt install apt-utils install
You can filter through grep to get results for the exact package you need. For instance, I wanted to see which php packages I had already installed through apt-get:
dpkg --get-selections | grep php libapache2-mod-php5 install php-db install php-pear install php-sqlite3 install php5 install php5-cli install php5-common install php5-gd install php5-memcache install php5-mysql install php5-sqlite install php5-sqlite3 install php5-xsl install
2. How do I get a list of installed files from a package
To see all the files the package put onto your system, do this:
dpkg-query -L <package_name>
dpkg -L php5-gd /. /usr /usr/lib /usr/lib/php5 /usr/lib/php5/20060613 /usr/lib/php5/20060613/gd.so /usr/share /usr/share/doc /etc /etc/php5 /etc/php5/conf.d /etc/php5/conf.d/gd.ini /usr/share/doc/php5-gd
3. Get a list of installed Python modules
in a Python shell/prompt.
4. Find all packages installed with easy_install/pip
will output a list of installed packages and their versions. It also allows you to write those packages to a file that can later be used to set up a new environment.