Yesterday I recommended for Facebook followers a couple of free parental control programs that can be used in Windows, today thanks to a hotfixed post I discover Gnome Nanny, an application of the same style for Linux.
It can be downloaded and installed from the Synaptic Package Manager or Ubuntu Software Center, searching for parental control or simply nanny. From the terminal: sudo apt-get install nanny
Once installed it will appear in the menu System / Administration / Parental control. As you can see in the following image, it is in Spanish and its options are quite intuitive:
Nanny's web filter (arrow)
Each user of the equipment can be configured individually, they can be set usage limits -by days and hours- for the PC in general, browsers, email clients and messenger programs. In addition, it includes a web filter which allows you to configure a blacklist of sites for block inappropriate content, this function is found in the Web browser tab:
Example of a blocked site
Nanny also allows loading blacklists already created to avoid having to add the sites one by one, these lists have a special .nbl format, from the project website it is possible to download one but I could not import it into Ubuntu (in other distros like Molinux already An included package comes and seems simpler). If anyone finds out how to add them in Ubuntu I'd appreciate the comment.
Beyond the pre-configured lists, the rest of the program seemed great to me. The solution is very similar to the parental controls that Windows has by default.
Lastly, mentioning an alternative, OpenDNS, can be useful to block sites on several computers at the same time, regardless of their operating system.