The matters are complicated thus the party with the highest interests + power will always win, no matter how risky it can be. The best example is the proposal which took place few years ago to give Internet porn sites an extension of their own (I think it was ".xxx").
This was great news for parents especially because all we have to do to keep your kid using these types of websites was to install a simple firewall and tell it to block any site with the ".xxx" extension and all of those sites will be blocked using a single command. But the sad truth is that, it didn't happen!. To this day I have no idea of their reasons, yet this is the nature of the that world we live in.
To make things more worse, in MS Windows platform, there are actually several excellent parent control applications that once configured... well they are quite powerful. But in GNU/Linux, they're still somewhat, rare to find.
So, if you have installed Ubuntu (you can use it on other GNU/Linux distributions as well) and exhausted after trying to find a "decent" utility for that purpose, then there is such an app that has a simple GUI (GTK+written) and lets you do things such as ...
*. Control the time that your young ones spend their time using the PC.
*. Block the Web browser completely or add sites of your own that has to be blocked, etc.
|The best "Nanny" ever!... ;-)|
*. Control instant messaging client using times or completely disabling it.
These are the options that you're given. Although when comparing with other apps, this may not sound like much, but I think when it comes to protecting your child from his/her Computer and internet that has GNU/Linux installed ... this application called "Nanny!" is pretty useful.
If you use Ubuntu 11.04 Natty Narwhal (should work in 10.04 and 10.10), you can install Nanny by entering the below command in your Terminal.
sudo apt-get install nanny
For instance, lets say under the "PC use time" tab, I entered 1 hour. Then this is a total value, meaning that the little ones can take breaks in between, only the total time they spent using the computer will be counted (as long as they're logged in to their accounts).
But lets say that, you wanted block them using the computer from 9 am to 10 am Monday. Then you can click on those "Green" buttons (on the appropriate application - web browser, pc usage, e-mail, etc) which will turn them into Red, meaning that, at that time period, no matter how much time they've "left" to use the computer, still within that time-scale, it's completely forbidden!. You can cancel it by again clicking on the Red buttons as well.
|The "1" hour I put does not "count" from 9am to 10am in Mondays...|
If you want to block certain website access, then, as you can see from the below screenshot, after clicking on the "Web browser" tab, add the time period and then click on the "Configure" button which will let you add/block certain types of web sites.
The Nanny parent control system for GNU/Linux comes with an excellent help file which you can access by clicking on the "Help" button on the lower left end which explains pretty much everything. Good luck.