Passwordless SSH access

It is possible to configure your Pi to allow your computer to access it without providing a password each time you try to connect. To do this you need to generate an SSH key:

Check for existing SSH keys

First, check whether there are already keys on the computer you are using to connect to the Raspberry Pi:

ls ~/.ssh

If you see files named id_rsa.pub or id_dsa.pub you have keys set up already, so you can skip the generating keys step (or delete these files with rm id* and make new keys).

Generate new SSH keys

To generate new SSH keys enter the following command:

ssh-keygen

Upon entering this command, you'll be asked where to save the key. We suggest you save it in the default location (/home/pi/.ssh/id_rsa) by just hitting Enter.

You'll also be asked to enter a passphrase. This is extra security which will make the key unusable without your passphrase, so if someone else copied your key, they could not impersonate you to gain access. If you choose to use a passphrase, type it here and press Enter, then type it again when prompted. Leave the field empty for no passphrase.

Now look inside your .ssh directory:

ls ~/.ssh

and you should see the files id_rsa and id_rsa.pub:

authorized_keys  id_rsa  id_rsa.pub  known_hosts

The id_rsa file is your private key. Keep this on your computer.

The id_rsa.pub file is your public key. This is what you share with machines you want to connect to. When the machine you try to connect to matches up your public and private key, it will allow you to connect.

Take a look at your public key to see what it looks like:

cat ~/.ssh/id_rsa.pub

It should be in the form:

ssh-rsa <REALLY LONG STRING OF RANDOM CHARACTERS> [email protected]

Copy your public key to your Raspberry Pi

To copy your public key to your Raspberry Pi, use the following command to append the public key to your authorized_keys file on the Pi, sending it over SSH:

ssh-copy-id <USERNAME>@<IP-ADDRESS>

Note that this time you will have to authenticate with your password.

Alternatively, if the ssh-copy-id is not available on your system, you can copy the file manually over SSH:

cat ~/.ssh/id_rsa.pub | ssh <USERNAME>@<IP-ADDRESS> 'mkdir -p ~/.ssh && cat >> ~/.ssh/authorized_keys'

If you see the message ssh: connect to host <IP-ADDRESS> port 22: Connection refused and you know the IP-ADDRESS is correct, then you probably haven't enabled SSH on you Pi. Run sudo raspi-config in the Pi's terminal window, enable SSH, and then try to copy the files again.

Now try ssh <USER>@<IP-ADDRESS> and you should connect without a password prompt.

If you see a message "Agent admitted failure to sign using the key" then add your RSA or DSA identities to the authentication agent ssh-agent then execute the following command:

ssh-add

If this did not work, delete your keys with rm ~/.ssh/id* and follow the instructions again.

You can also send files over SSH using the scp command (secure copy). See the SCP guide for more information.