Mar 252010


How to use multiple SSH keys for password less login

by Vivek Gite

I’ve already written about howto log in, on your local system, and make passwordless ssh connections using ssh-keygen command. However, you cannot just follow these instructions over and over again, as you will overwrite the previous keys.

It is also possible to upload multiple public keys to your remote server, allowing one or more users to log in without a password from different computers.

Step # 1: Generate first ssh key

Type the following command to generate your first public and private key on a local workstation. Next provide the required input or accept the defaults. Please do not change the filename and directory location.
workstation#1 $ ssh-keygen -t rsa

Finally, copy your public key to your remote server using scp
workstation#1 $ scp ~/.ssh/ [email protected]:.ssh/authorized_keys
Step # 2: Generate next/multiple ssh key

a) Login to 2nd workstation

b) Download original the authorized_keys file from remote server using scp:
workstation#2 $ scp [email protected]:.ssh/authorized_keys ~/.ssh

c) Now create the new pub/private key:
workstation#2 $ ssh-keygen -t rsa

d) Now you have new public key. APPEND this key to the downloaded authorized_keys file using cat command:
workstation#2 $ cat ~/.ssh/ >> ~/.ssh/authorized_keys

e) Finally upload authorized_keys to remote server again:
workstation#2 $ scp ~/.ssh/authorized_keys [email protected]:.ssh/

You can repeat step #2 for each user or workstations for remote server.
Step #3: Test your setup

Now try to login from Workstation #1, #2 and so on to remote server. You should not be asked for a password:
workstation#1 $ ssh [email protected]
workstation#2 $ ssh [email protected]

This worked like a dream. I’ve simplified this process down to a script to use;

# setup ssh keys multiple server instances
scp [email protected]:.ssh/authorized_keys ~/.ssh
ssh-keygen -t rsa
cat ~/.ssh/ >> ~/.ssh/authorized_keys
scp ~/.ssh/authorized_keys [email protected]:.ssh/

To use this script, simply
touch ~/
insert the above lines for the script, modifying them for the hosts ip address you want to login to, then save the file.
chmod +x
add pw for server
add pw for server
rm -f

 Posted by at 2:51 am