≡ Menu


Download Of The Day: OpenSSH 5.1

OpenSSH server and client version 5.1 has just been released and available for download. New features in OpenSSH 5.1:
=> Introduce experimental SSH Fingerprint ASCII Visualisation to ssh(1) and ssh-keygen(1).

=> sshd now support CIDR address/masklen matching.

=> Added an extended test mode (-T) to sshd(8) to request that it write its effective configuration to stdout and exit.

=> ssh(1) now prints the number of bytes transferred and the overall connection throughput for SSH protocol 2 sessions when in verbose mode.

=> Added a MaxSessions option to sshd_config(5) to allow control of the number of multiplexed sessions supported over a single TCP connection.

Download OpenSSH 5.1

=> Visit offical site to grab latest OpenSSH 5.1

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/id_rsa.pub user@remote.server.com:.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 user@remote.server.com:.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/id_rsa.pub >> ~/.ssh/authorized_keys

e) Finally upload authorized_keys to remote server again:
workstation#2 $ scp ~/.ssh/authorized_keys user@remote.server.com:.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 user@remote.server.com
workstation#2 $ ssh user@remote.server.com

Updated for accuracy.

The SSH protocol is recommended for remote login and remote file transfer which provides confidentiality and security for data exchanged between two computer systems, through the use of public key cryptography. The OpenSSH server provides this kind of setup under Linux. It is installed by default. This how-to covers generating and using ssh keys for automated usage such as:

  1. Automated Login using the shell scripts.
  2. Making backups.
  3. Run commands from the shell prompt etc.

[click to continue…]