update-alternatives

/etc/alternatives

Utility that manages which version of executables is going to be run through symlinks.

For example Ubuntu 14.04 comes with

which editor

as /usr/bin/editor, and:

readlink `which editor`

Gives:

/etc/alternatives/editor

And:

readlink /etc/alternatives/editor

Points to:

/usr/bin/vi

In this way, all preferences are stored under etc as specified by the LSB.

The update-alternatives utility can be used to manage that system.

For example, to configure the default browser use:

sudo update-alternatives --config x-www-browser

This will show the possibilities (TODO how does he know?) for you to choose from them.

Important alternatives include:

TODO: understand the following command:

sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.8 50

50: priority of the alternative. Metadata associated by update-alternatives. Alternative with greatest priority wins.

I used this to link gcc to gcc-4.8 instead of 4.6.