How to set up password-less SSH login for a Dropbear client

Dropbear is a replacement for OpenSSH for environments with low memory and processor resources. With OpenSSH, you can use the well-known ssh-keyen command to create a private/public keypair for the client. In Dropbear, it is a bit different. Here are the commands on the client:

mkdir ~/.ssh
chmod 700 ~/.ssh/
dropbearkey -t rsa -f ~/.ssh/id_dropbear

Both private and public keys will be in ~/.ssh/id_dropbear, however in a binary format.

To output the public key to stdout in the usual SSH-compatible format, use:

dropbearkey -y -f ~/.ssh/id_dropbear

How to install yubikey-manager on Debian

yubikey-manager is a Python application requiring some dependencies for it to be installed from the Python repositories, because it is not yet in the official Debian package repository. Here is how:

apt-get install swig libpcsclite-dev
pip3 install yubikey-manager --user

Here is the main commandline utility:

~/.local/bin/ykman