I work in Hertfordshire schools, which use a proxy eg http://wf1.thegrid.org.uk on port 80 to allow graded access by all users, within the schools, to the Internet. I have Ubuntu 10.04LTS successfully running and I want to set up 12.04LTS to replace it.

Many other replies to this question have answered questions about stand-alone computers and not addressed the LTSP server and its clients. I have come to a complete stop over the problem of the proxy server settings not promulgating over the local network to Ubuntu 12.04 thin or fat clients.

When you input this setting (there are others for HTTPS and FTP) into the System Settings/Network Manager GUI on the server, then when a user logs into the server, both Firefox and Chrome can read the settings and will gain access to the Internet. HOWEVER, these settings are not promulgated to either thin or fat clients on the local network.

Their System Settings/Network Manager GUI remains stubbornly blank. I have rebuilt the image after inputting the proxy settings, but it appears they are not part of the image. /etc/environment (on the server) already has:

PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games"
http_proxy="http://wf1.thegrid.org.uk:80/"
https_proxy="https://wf1.thegrid.org.uk:80/"
ftp_proxy="ftp://proxy.intra.thegrid.org.uk:3128/"

I have also tried this

export http_proxy="http://wf1.thegrid.org.uk:80"
export https_proxy="http://wf1.thegrid.org.uk:80"
export ftp_proxy="http://proxy.intra.thegrid.org.uk:3128"
within /etc/environment, and that had no effect, either.
etc/apt/apt.conf also has:
Acquire::http::proxy "http://wf1.thegrid.org.uk:80/";
Acquire::https::proxy "https://wf1.thegrid.org.uk:80/";
Acquire::ftp::proxy "ftp://proxy.intra.thegrid.org.uk:3128/";

The clients still have no proxy settings in their Network Manager, and no client user can access the Internet from Firefox or Chrome. Three questions:

1. Why doesn't the “Apply system wide” button work? It does on 10.04, and every new user, and all existing users have access to the internet through the proxy without problem.

2. How can I set up proxy settings that work for all the 12.04 clients?

3. I noticed that if user West input the settings himself, they would follow him around the clients. However, this is not secure, because there are grades of settings which prevent visits to various sites, eg wf3 allows fewer sites than wf2 or wf1, so I can't allow users to input this setting themselves. Since the proxy setting followed the user around the clients, the setting must be somewhere in the user profile, since none of the other users have the proxy settings.

Do you know where, and how I could fix the setting for users, or better, groups? The setting must then be unchangeable by the user, with no access to the Network Manager. If either 2. or 3. can't be done, then the Ubuntu 12.04LTS server is simply no use to us...