Downgrade to Firefox 3.6 on Ubuntu 11.04 Natty

We have a requirement in the office to downgrade to Firefox 3.6 on some test machines running Ubuntu Natty (11.04). To do this you can pin the firefox and firefox-branding packages to older packages from the Ubuntu Maverick (10.10) release.

Step 1: Edit your software sources to add Maverick

1. Open your sources.list file:
   

   sudo gedit /etc/apt/sources.list

   
   
2. Add the folowing three lines:
   

   # Maverick, used for firefox and firefox-branding 
   deb http://ftp.iinet.net.au/pub/ubuntu/ maverick main 
   deb http://ftp.iinet.net.au/pub/ubuntu/ maverick-updates main

   
   
3. Save and close the file

Step 2: Pin the packages firefox and firefox-branding

1. Create the pin file for firefox:
   

   sudo gedit /etc/apt/preferences.d/firefox

   
   
2. Add the following:
   

   Package: firefox
   Pin: release n=natty
   Pin-Priority: -10
   
   Package: firefox
   Pin: release n=maverick
   Pin-Priority: 900

   
   
3. Save and close the file.
   
   
4. Create the pin file for firefox-branding:
   

   sudo gedit /etc/apt/preferences.d/firefox-branding

   
   
5. Add the following:
   

   Package: firefox-branding
   Pin: release n=natty
   Pin-Priority: -10
   
   Package: firefox-branding
   Pin: release n=maverick
   Pin-Priority: 900

   
   
6. Save and close the file.
   

Step 3: Check your apt policy to make sure it worked

1. Update your apt cache:
   

   sudo apt-get update

   
   
2. Show the apt policy for firefox:
   

   sudo apt-cache policy firefox

   
   Sample output:
   

   sudo apt-cache policy firefox
   firefox:
     Installed: 5.0+build1+nobinonly-0ubuntu0.11.04.2
     Candidate: 3.6.18+build2+nobinonly-0ubuntu0.10.10.1
     Package pin: 3.6.18+build2+nobinonly-0ubuntu0.10.10.1
     Version table:
    *** 5.0+build1+nobinonly-0ubuntu0.11.04.2 900
           500 http://ftp.iinet.net.au/pub/ubuntu/ natty-updates/main i386 Packages
           500 http://ftp.iinet.net.au/pub/ubuntu/ natty-security/main i386 Packages
           100 /var/lib/dpkg/status
        4.0+nobinonly-0ubuntu3 900
           500 http://ftp.iinet.net.au/pub/ubuntu/ natty/main i386 Packages
        3.6.18+build2+nobinonly-0ubuntu0.10.10.1 900
           500 http://ftp.iinet.net.au/pub/ubuntu/ maverick-updates/main i386 Packages
        3.6.10+build1+nobinonly-0ubuntu3 900
           500 http://ftp.iinet.net.au/pub/ubuntu/ maverick/main i386 Packages

   
   The line you are most interested in is "Candidate".
   This indicates the package that apt ranks as the installation candidate.
   
   
3. Repeat this check for firefox-branding
   

   sudo apt-cache policy firefox-branding

Step 4: Install firefox 3.6

1. Remove firefox 5.x:
   

   sudo apt-get remove firefox

   
   
2. Install firefox 3.6:
   

   sudo apt-get install firefox

And you're done. Enjoy your outdated version of Firefox!

---

Update - July 24th 2011:

How to reverse the process:

1. Remove these three (3) lines you added to /etc/apt/sources.list
   

   # Maverick, used for firefox and firefox-branding 
   deb http://ftp.iinet.net.au/pub/ubuntu/ maverick main 
   deb http://ftp.iinet.net.au/pub/ubuntu/ maverick-updates main
   

2. Unpin the firefox and firefox-branding packages:
   

   sudo rm /etc/apt/preferences.d/firefox
   sudo rm /etc/apt/preferences.d/firefox-branding
   

3. Update your apt cache
   

   sudo apt-get update
   

4. Install the latest Firefox:
   

   sudo apt-get upgrade
   

5. Close ALL your Firefox windows and re-open Firefox.
   

---

Update - December 6th 2011:

From the comments people have posted below I can see that this process works to downgrade Firefox on Ubuntu 11.10 as well as Ubuntu 10.04.

Downgrading packages to the Ubuntu 10.10 release will only work on Ubuntu 11.04 or better. Do not use this procedure on Ubuntu releases older than 11.04. If you try to do this you will be upgrading packages not downgrading.

Proxy environment variables and sudo in Ubuntu

At work we use a proxy server to access the internet from our test network. We also have an internal Ubuntu mirror on the test network to install updates and packages, this server must be accessed by the test machines directly without the proxy.

Setting up the proxy and the exception for the mirror can be done in a terminal using the environment variables http_proxy, https_proxy, ftp_proxy, and no_proxy.

In Ubuntu these variables are all set in the /etc/environment file. On my test system this file contains the following:

trastle@trastle-test:~$ cat /etc/environment
...
http_proxy="http://webproxy:3128/"
ftp_proxy="ftp://webproxy:3128/"
https_proxy="https://webproxy:3128/"
no_proxy="office-mirror"

Testing that these settings have been applied to the current terminal can be done by calling printenv:

trastle@trastle-test:~$ printenv | grep proxy
http_proxy=http://webproxy:3128/
ftp_proxy=ftp://webproxy:3128/
https_proxy=https://webproxy:3128/
no_proxy=office-mirror

This output shows that all of the required environment variables are set. However when I try to perform an update from the office mirror it fails! The http_proxy is being used to access hosts clearly specified in the no_proxy variable.

trastle@trastle-test:~$ sudo apt-get update
Ign http://office-mirror jaunty Release.gpg
...
Err http://office-mirror jaunty/main Packages
503 Service Unavailable
...
W: Failed to fetch http://office-mirror/ubuntu/dists/jaunty/main/binary-i386/Packages
503 Service Unavailable
...
E: Some index files failed to download, they have been ignored, or old ones used instead.

This all makes more sense when you check the environment variables that sudo is running with:

trastle@trastle-test:~$ sudo printenv | grep proxy
http_proxy=http://webproxy:3128/

For safety sudo runs with an minimal environment. This default list is hard coded into sudo (initial_keepenv_table in env.c if you want to go read the source). Ubuntu patches this list to include http_proxy but not no_proxy. This breaks the ability to get updates from the local mirror. Sudo can be queried to determine which environment variables it preserves by default:

trastle@trastle-test:~$ sudo sudo -V
Sudo version 1.6.9p17
...
Sudoers path: /etc/sudoers
...
Environment variables to preserve:
http_proxy
XAUTHORIZATION
XAUTHORITY
TZ
PS2
PS1
PATH
MAIL
LS_COLORS
KRB5CCNAME
HOSTNAME
HOME
DISPLAY
COLORS
...

The solution to this problem is to modify the list of environment variables that sudo will preserve by editing the /etc/sudoers file and providing an explicit list of which environment variables to be preserved, overwriting the default list. The configuration that must be added to /etc/sudoers is as follows:

Defaults env_keep="no_proxy http_proxy https_proxy ftp_proxy XAUTHORIZATION \
XAUTHORITY TZ PS2 PS1 PATH MAIL LS_COLORS KRB5CCNAME HOSTNAME HOME DISPLAY COLORS"

This will preserve all of the default environment variables as well as no_proxy, https_proxy and ftp_proxy. You can test this setting to prove that sudo is now preserving these extra environment variables by running:

trastle@trastle-test:~$
sudo printenv | grep proxy
http_proxy=http://webproxy:3128/
ftp_proxy=ftp://webproxy:3128/
https_proxy=https://webproxy:3128/
no_proxy=office-mirror

With these additional environment variables preserved updates and installs from the command line using your local mirror and ignoring your proxy server will work like a charm.