Setting and Removing http_proxy in linux

1. For setting http_proxy
                export http_proxy="http://proxy:port/"

2. For unsetting
                  unset http_proxy=""

Removing http_proxy [ 407 proxy authentication required ] when using synaptic package manager:

Do the following:
1. Remove proxy from Preferences -> Network proxy [ use direct connection ]
2. Remove proxy from synaptic package manager -> preferences -> Network
3. use unset http_proxy
4. export http_proxy=""
           check if proxy is set or not by using: echo $http_proxy
Repeat steps (3) and (4) for ftp proxy also.


5. immediately do apt-get update once or twice
6. If still you get error [407 proxy authentication required]

    goto ~/.bashrc check if http_proxy is set if so remove it.

Please also check if you have changed the file sources.list in /etc/apt folder. If so reverse it back to the old version.