S3 Make Ubuntu safe for children to use

ubuntu can be as kid-safe as any other operating system with a little work. Essentially, two things can be done. First you can create a new restricted user account for the child (or children) that stops them from doing anything that might break the system, or attempting to bypass any protective measures you enact. Secondly, you can install a web filtering system so that nothing that isn't entirely child-safe gets through when they're using Firefox.10

Creating a restricted user account

The first thing you should do is create a restricted user account for the child. This will give them their own login on the machine, so they

10. Note that no type of filtering software is perfect. There's an old saying: "Where there's a will, there's a way... " The instructions in the tip above are primarily for younger children who have no interest in by-passing web filters. The only way to be 100% sure of stopping children of any age seeing objectionable material is to prevent them using the computer in the first place.

won't have to share your administrator account. To create the account, click System ^ Administration ^ Users & Groups. Once the program starts, click the Unlock button. Then click the Add User button. Fill in the Username, Real name and password fields. In the Profile dropdown list, select Unprivileged. This stops the new user from administrating the system, thereby potentially getting around your lockdown measures by, say, installing or removing software. When done, click OK.

Installing web filtering software

Dansguardian is filtering software that filters by content. This means that anything requested by your web browser that includes objectionable words is blocked. This includes both outgoing and incoming requests, so if the child sends a request to Google that includes objectionable words, no results will be returned.

To install Dansguardian, follow these steps:

1. Use Synaptic to search for the dansguardian package. Whilst there, also install tinyproxy, which is a system component Dansguardian needs.

2. Once the two are installed, you'll need to tweak a couple of configuration files. Open the tinyproxy configuration file in Gedit, as follows:

$ gksu gedit /etc/tinyproxy/tinyproxy.conf

... then look for the lines that reads as follows:

# Port to listen on.

Port 8888

Change Port 8888 so that it reads Port 3128. When done, save and close the file.

3. Back at the terminal type the following to open the Dansguardian configuration file in Gedit:

$ gksu gedit /etc/dansguardian/dansguardian.conf

Look for the third line down that reads UNCONFIGURED - Please remove this line after configuration and type a hash symbol (#) at the beginning, so it reads #UNCONFIGURED - Please remove this line after configuration. Then save the file.

4. Following this, type the following to start Dansguardian (and also tinyproxy, a system service it relies upon):

$ sudo /etc/init.d/tinyproxy restart $ sudo /etc/init.d/dansguardian restart

You might see a warning message when Dansguardian restarts about an out of date virus database. This can be ignored. The antivirus component of Dansguardian updates itself automatically.

5. The user account now needs to be setup to let Dansguardian filter the incoming pages. To do this, you'll need to change the Web Proxy settings so that any application that attempts to access the web (such as Firefox, or any other browser you might install) will be routed through the Dansguardian software. To do this, log into the new account you made for the child and click System ^ Preferences ^ Network Proxy.

6. Select the Manual proxy configuration radio button and check Use the same proxy for all protocols. Then, in the HTTP proxy text field, type localhost. Leave the Port field as it is, and click the Close button.

The changes take effect straight away so, still in the child's user account, try using Firefox to browse to a website containing objectionable material (for example, http://www.playboy.com; see Figure 3.16, on the next page for an example of what you should see). You should see a page informing you that it has been blocked. I strongly advise you thoroughly test Dansguardian's filtering before allowing your children unrestricted access to the computer.

I'd also advise you visit http://dansguardian.org to learn more about how it works. There are two key things worth knowing. Firstly, if you find that Dansguardian blocks a site that you know to be fine, you can add it to the "exception" list (/etc/dansguardian/exceptionsitelist). Open the file in Gedit (gksu gedit /etc/dansguardian/exceptionsitelist) and add the address to the bottom, without the http:// or www components. For example, to add http://www.ubuntukungfu.org, you would add ubuntukungfu.org to the bottom of the file on a new line. Once done, save the file, close Gedit, and then restart the Dansguardian background service: $ sudo /etc/init.d/dansguardian restart

On the other hand, if there's a site that Dansguardian "lets through" that perhaps it shouldn't, then you can add it in exactly the same way to the file /etc/dansguardian/bannedurllist. You might choose to add various search engines to this list if you wish to stop children being able to seek-out objectionable material. For example, to stop Google being used, you could add google.com to the list. Bear in mind that you'll also need to

File Edit \^iew History Bookmarks Tools idelp tS |H http://Www.playboy.com/ ^Most Visitedl: Smart BookmarksGetting Started |~lLatest Headlines-'

File Edit \^iew History Bookmarks Tools idelp tS |H http://Www.playboy.com/ ^Most Visitedl: Smart BookmarksGetting Started |~lLatest Headlines-'

Figure 3.16: Dansguardian blocking an objectionable web site (see Tip 50, on page 113)

add the Google domain for the country you live in if you live outside the US (for example, you would need to add google.co.uk if you lived in the United Kingdom.) once you've added the site to the list, don't forget to restart Dansguardian, as mentioned above.

In child-proofing Ubuntu, you might also be interested in Tip 294, on page 341, which describes how to use the Ubuntu Tweak program to "lock down" program to disable certain features of the Ubuntu desktop.

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