I have an old Pogoplug v4 series hacked to install Debian Linux based on this instruction long ago: http://blog.qnology.com/2014/07/hacking-pogoplug-v4-series-4-and-mobile.html
which boots on an SD card, which I used as a no-ip update client.

I realized some of the URLs to the package servers are broken. So here’s my notes to update it.

First apt-get doesn’t work anymore because the files has been moved to the archive package server. The solution is to replace all the contents (now obsolete) in /etc/apt/sources.list by this line:

deb http://archive.debian.org/debian wheezy main

Then you update the package manager (apt-get) with this command:

apt-get update && apt-get upgrade

Note that it’s still Debian 7 and it will not work with new software that requires later versions