Updating database of manual pages
By default you may not have any cache built and all your searches will give you the nothing appropriate result.
You can generate the cache or update it by running environment variable.
An update should always be performed before an upgrade or dist-upgrade.
Used to install the newest versions of all packages currently installed on the system from the sources enumerated in /etc/apt/sources.list(5).
In addition to performing the function of upgrade, this option 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.
All command-line options may be set using the configuration file, the descriptions indicate the configuration option to set.
For boolean options you can override the config file by using something like -f-, --no-f, -f=no or several other variations. Attempt to correct a system with broken dependencies in place.
These latter features may be used to override decisions made by apt-get's conflict resolution system.
following the package name with an equals (=) and the version of the package to select.