New user permissions
 

I know very little about linux / unix users and groups. Im going to be setting up 2 computers for my children under the age of 10 to use. They will mainly be used for school / internet.

Which groups should i put them in so that they cannot screw anything up but still use libreoffice and mozilla? I would also prefer them to not be able to view any other users home directory data.

Please remember that i am new to this and am still getting familiar with chmod and all the other commands. If you can and do not care to explain the whats and the whys.

I have been using slackware exclusively now for about a month and love it.

Thanks in advance

You do not state what tasks your children need to complete. Do they need access to printing, writing CD/DVD, scanning, etc? Without that information it's difficult to recommend which groups.

Internet games / school websites. I want them to be able to print. No writing CDs, scanners or usb.

Any ordinary user can use libreoffice and firefox. You don't need any special privileges to run applications.

To keep them out of each other's home directories, give each one a separate group. Most distros will do this by default when you create new users. So Sylvia will have user name sylvia and group sylvia. Brian will have user name and group brian. He will not be able to modify files that belong to sylvia. To ensure that he will not be able even to read them, you should set sylvia's home directory to have no world access. That can be done with the command:
carried out as the root user.

You will probably need to make your users members of other groups as well but this can be done when required. For example, if you want them to be able to use the printer, make them members of the lp group.

If you don't want them to be able to use usb sticks, keep them out of the plugdev group and don't put media drives into /etc/fstab.

Both being under 10 I wouldn't think that overly restricting access to anything is going to be necessary, at least if they're just typical kids (unless you've already exposed them to working in a terminal and taught them some CLI tricks). You can micro-manage each computer locking it down to the point whenever they want to do anything they have to get you to set it up for them, or just let them be creative and experiment.
Pay attention to set up a good, solid root password only for your access on each computer, and just set up a general user account and add that account to the commonly used groups. I'd recommend you read through the Slackware documentation page on setting up a new install and then tailor things accordingly:
http://docs.slackware.com/slackware:beginners_guide

I worked several years doing tech support in a Chicago elementary school. Kids in that age range don't focus on 'hacking' and getting past any impositions like content filtering or other restrictions. Their minds just aren't working like that (this in complete contrast to older, high school aged kids). Since you're providing each of them their own computer I'd just let them personalize things to their own liking. They won't have any root access running a general user account so while they might be able to inadvertently mess something up in their own account, it's not like they can do anything serious to the installed OS. It's also really vital you have a good, automatic backup solution in place -- if one of them accidentally deletes something like a homework folder, that's when you step in and restore it.

Thanks everyone. Great input.

Keep in mind that on Slackware all users are automatically added to the "users" group. You can specify a different group while creating a user with the "adduser" script. Just pay attention to how you are adding each user and you will be fine.