<<< Rasberry Pi Guides >>>
Enable SSH access via an RSA token
I prefer to run my Rasberry Pi in headless mode and so I need another method for connecting to my environment.
My method of choice is Virtual Network Computing or VNC, however sometimes I need to be able to ssh onto my Rasberry Pi to perform some quick tasks. And to make the process of connecting much simpler I prefer to setyp passwordless SSH access through the use of an RSA token.
This section takes you through the process of setting this up
First enable ssh on your Rasberry Pi
pi@raspberrypi:~ $ sudo systemctl enable ssh
Synchronizing state of ssh.service with SysV service script with /lib/systemd/systemd-sysv-install.
Executing: /lib/systemd/systemd-sysv-install enable ssh
Created symlink /etc/systemd/system/sshd.service ? /lib/systemd/system/ssh.service.
Created symlink /etc/systemd/system/multi-user.target.wants/ssh.service ? /lib/systemd/system/ssh.service.
pi@raspberrypi:~ $ sudo systemctl start ssh
Now you are ready to create your RSA equivalence files
Note: These copmmands are executed on the computer you will be connecting from, not the Rasberry Pi and you will probably get something like this
First check to see if you have an existing RSA token
iMac:~ Mike$ ls -al $HOME/.ssh
ls: cannot access '.ssh': No such file or directory
iMac:~ Mike$ mkdir $HOME/.ssh
iMac:~ Mike$ chmod 700 $HOME/.ssh
If this command returned an error as shown below, then you will have to create the directory as well
Generate new SSH key
If the previous command return the id_rsa.pub file then you can skip this step
Note:If you do run this step your output should be somewhat different to that shown below as I have obfuscated the secure information
iMac:~ Mike$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/home/mike/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):▩▩▩▩▩▩▩▩▩▩▩▩
Enter same passphrase again:▩▩▩▩▩▩▩▩▩▩▩▩
Your identification has been saved in /home/mike/.ssh/id_rsa.
Your public key has been saved in /home/mike/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:▩▩▩▩▩▩▩▩▩▩▩▩▩▩▩▩▩▩▩▩▩▩▩▩▩▩▩▩▩▩▩▩ <username>@<ip-address>
The key's randomart image is:
+---[RSA 2048]----+
| ★☒☆☉☁☉☆☒★☑|
| ★☒☆☉☁☉☆☒★☑|
| ★☒☆☉☁☉☆☒★☑|
| ★☒☆☉☁☉☆☒★☑|
| ★☒☆☉☁☉☆☒★☑|
| ★☒☆☉☁☉☆☒★☑|
| ★☒☆☉☁☉☆☒★☑|
| ★☒☆☉☁☉☆☒★☑|
| ★☒☆☉☁☉☆☒★☑|
+----[SHA256]-----+
You should now have 2 files in your directory
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.
iMac:~ Mike$ ls -al $HOME/.ssh
drwx------ 2 mike mike 4096 Mar 1 16:18 .
drwxr-xr-x 18 mike mike 4096 Mar 1 18:05 ..
-rw------- 1 mike mike 1876 Mar 5 18:05 id_rsa
-rw------- 1 mike mike 396 Mar 5 18:05 id_rsa.pub
Copy the public RSA key to your Rasberry Pi
This is the easiest way to copy the file
Note: You will still have to enter the password the first time you do this.
iMac:~ Mike$ e$ ssh-copy-id pi@172.16.47.11
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/Users/Mike/.ssh/id_rsa.pub"
The authenticity of host '172.16.47.11 (172.16.47.11)' can't be established.
ECDSA key fingerprint is SHA256:nt/ZZJIZ1Cho/KQtD0aamBcltUUUmvcVOsQSBpmB/CI.
Are you sure you want to continue connecting (yes/no)? yes
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
pi@172.16.47.11's password: ▩▩▩▩▩▩▩▩▩▩▩▩
Number of key(s) added: 2
Now try logging into the machine, with: "ssh '<username>@<ip-address>'"
and check to make sure that only the key(s) you wanted were added.
webmail:~ Mike$
But if your environment does not contain this command you can always do it old school
iMac:~ Mike$ cat $HOME/.ssh/id_rsa.pub | ssh <username>@<ip-address> 'mkdir -p $HOME/.ssh && cat >> $HOME/.ssh/authorized_keys'
<username>@<ip-address>'s password: ▩▩▩▩▩▩▩▩▩▩▩▩
Now try logging into the environment and running a command to test it works, and check to make sure that only the key(s) you wanted were added.
iMac:~ Mike$ ssh <username>@<ip-address> hostname
raspberrypi
iMac:~ Mike$ ssh <username>@<ip-address> 'ls -al $HOME/.ssh'
total 12
drwx------ 2 mike mike 4096 Mar 6 07:32 .
drwxr-xr-x 19 mike mike 4096 Mar 6 07:32 ..
-rw------- 1 mike mike 1128 Mar 6 07:32 authorized_keys