There is an undocumented setting, Acquire::http::ProxyAutoDetect
. This setting should contains the full path to the binary and cannot have arguments. The command should output the proxy to be used (example: http://10.0.0.1:8000
).
Given the above information, a script could be created that tries a proxy before setting it. If no proxy is available, a direct connection should be used.
Below is such a proxy detection script which tries the http://10.0.0.1:8000/
and http://10.0.0.2:8000
proxies.
Put the code in /etc/apt/detect-http-proxy
:
#!/bin/bash
# detect-http-proxy - Returns a HTTP proxy which is available for use
# Author: Lekensteyn <lekensteyn@gmail.com>
# Supported since APT 0.7.25.3ubuntu1 (Lucid) and 0.7.26~exp1 (Debian Squeeze)
# Unsupported: Ubuntu Karmic and before, Debian Lenny and before
# Put this file in /etc/apt/detect-http-proxy and create and add the below
# configuration in /etc/apt/apt.conf.d/30detectproxy
# Acquire::http::ProxyAutoDetect "/etc/apt/detect-http-proxy";
# APT calls this script for each host that should be connected to. Therefore
# you may see the proxy messages multiple times (LP 814130). If you find this
# annoying and wish to disable these messages, set show_proxy_messages to 0
show_proxy_messages=1
# on or more proxies can be specified. Note that each will introduce a routing
# delay and therefore its recommended to put the proxy which is most likely to
# be available on the top. If no proxy is available, a direct connection will
# be used
try_proxies=(
10.0.0.1:8000
10.0.0.2:8000
)
print_msg() {
# \x0d clears the line so [Working] is hidden
[ "$show_proxy_messages" = 1 ] && printf '\x0d%s\n' "$1" >&2
}
for proxy in "${try_proxies[@]}"; do
# if the host machine / proxy is reachable...
if nc -z ${proxy/:/ }; then
proxy=http://$proxy
print_msg "Proxy that will be used: $proxy"
echo "$proxy"
exit
fi
done
print_msg "No proxy will be used"
# Workaround for Launchpad bug 654393 so it works with Debian Squeeze (<0.8.11)
echo DIRECT
Now, APT must be configured to use the above proxy detection script, so put the following code in /etc/apt/apt.conf.d/30detectproxy
:
# Fail immediately if a file could not be retrieved. Comment if you have a bad
# Internet connection
Acquire::Retries 0;
# undocumented feature which was found in the source. It should be an absolute
# path to the program, no arguments are allowed. stdout contains the proxy
# server, stderr is shown (in stderr) but ignored by APT
Acquire::http::ProxyAutoDetect "/etc/apt/detect-http-proxy";
I've also put the next code to the file to prevent some host from being proxified.
# Override the default proxy, DIRECT causes a direct connection to be used
Acquire::http::Proxy {
deb.opera.com DIRECT;
dl.google.com DIRECT;
};
By default, the script outputs whether a proxy is used or not. To disable that, edit /etc/apt/detect-http-proxy
and change show_proxy_messages=1
to show_proxy_messages=0
.
Best Answer
Something like this should work:
/etc/NetworkManager/dispatcher.d
Fix permissions
Notes: