enable installation of Cockpit on Raspberry

1

sudo nano /etc/apt/sources.list.d/backports.list

Add these lines:
# For Cockpit-Project
deb http://deb.debian.org/debian stretch-backports main

2

sudo apt-get install dirmngr
gpg --keyserver hkp://pool.sks-keyservers.net:80 --recv-key 8B48AD6246925553
gpg -a --export 8B48AD6246925553 | sudo apt-key add -
gpg --keyserver hkp://pool.sks-keyservers.net:80 --recv-key 7638D0442B90D010
gpg -a --export 7638D0442B90D010 | sudo apt-key add -
sudo apt-get update

sudo apt-get install cockpit
sudo systemctl enable --now cockpit.socket