After an apt-get dist-upgrade attempt all apt-get calls on a raspberry pi with official raspbian distro returned an unhealthy illegal instruction response.

A quick look at my /etc/apt/sources.list showed that I specified a non raspbian source there. So I had to get the apt files back from http://archive.raspbian.org/raspbian/pool/main/a/apt/ as deb packages and install them again.

The commands, make sure to check the given url for the proper releases.

wget http://archive.raspbian.org/raspbian/pool/main/a/apt/apt_0.9.7.8%2brpi1_armhf.deb
wget http://archive.raspbian.org/raspbian/pool/main/a/apt/libapt-pkg4.12_0.9.7.8%2brpi1_armhf.deb

sudo dpkg -i apt_0.9.7.8+rpi1_armhf.deb libapt-pkg4.12_0.9.7.8+rpi1_armhf.deb