When running command **sudo apt update** and using a proxy configured on the Linux machine, you receive a timeout error \\
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Create a new empty file to configure apt
<cli>$ sudo vi /etc/apt/apt.conf</cli>
In this new file insert the following: 
<cli>Acquire::http::Proxy "http://user:password@proxyhost:port";</cli>
If you do not have any authentication on the proxy type following:
<cli>Acquire::http::Proxy "http://proxyhost:port";</cli>