SSH uses public-key cryptography to authenticate the remote computer and allow the remote computer to authenticate the user, if required. You can create ssh keys as follows on any Linux or UNIX-like operating systems including Mac OS X.[donotprint]
ssh-keygen command to Generate SSH Keys
The ssh-keygen command generates, manages and converts authentication keys for ssh client and server usage. Type the following command to generate ssh keys (open terminal and type the command):
Generate SSH keys looks as follows:
Generating public/private rsa key pair. Enter file in which to save the key (/home/vivek/.ssh/id_rsa): Created directory '/home/vivek/.ssh'. Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /home/vivek/.ssh/id_rsa. Your public key has been saved in /home/vivek/.ssh/id_rsa.pub. The key fingerprint is: 58:3a:80:a5:df:17:b0:af:4f:90:07:c5:3c:01:50:c2 vivek@debian The key's randomart image is: +--[ RSA 2048]----+ | .+o++o. | | +E. ++ | | o . o o. | | . o B . | | . B S | | * | | . . | | o | | . | +-----------------+
The above command creates ~/.ssh/ directory. So if your user name is vivek, than all files are stored in /home/vivek/.ssh/ or $HOME/.ssh/ directory as follows:
- $HOME/.ssh/id_rsa – Your private key. Do not share this file with anyone. Keep it private
- $HOME/.ssh/id_rsa.pub – Your public key.
Please note that the passphrase must be different from your current password and do not share keys or passphrase with anyone. Also, make sure you have correct and secure permissions on $HOME/.ssh/ directory:
ls -ld $HOME/.ssh/ chmod 0600 $HOME/.ssh/
SSH Keys Are Generated, What Next?
You need to copy $HOME/.ssh/id_rsa.pub file to remote server so that you can login using keys instead of the password. Use any one of the following command to copy key to remote server called vpn22.nixcraft.net.in for vivek user:
On some *nix system such as OS X ssh-copy-id command may not be installed, use the following commands (when prompted provide the password for remote user account called vivek) to install/append the public key on remote host:
ssh email@example.com "umask 077; mkdir .ssh"
cat $HOME/.ssh/id_rsa.pub | ssh firstname.lastname@example.org "cat >> .ssh/authorized_keys"
To login simply type:
The following command will help to remember passphrase
exec ssh-agent $SHELL
Optional ssh-keygen command syntax for advance users
The following syntax specifies the 4096 of bits in the RSA key to creation (default 2048):
ssh-keygen -t rsa -b 4096 -f ~/.ssh/aws.key -C "My AWs cloud key"
- -t rsa : Specifies the type of key to create. The possible values are “rsa1” for protocol version 1 and “dsa”, “ecdsa”, “ed25519”, or “rsa” for protocol version 2.
- -b 4096 : Specifies the number of bits in the key to create.
- -f ~/.ssh/aws.key : Specifies the filename of the key file.
- -C "My AWs cloud key" : Set a new comment.
Now install the ~/.ssh/aws.key, run:
ssh-copy-id -i ~/.ssh/aws.key user@aws-server-ip
Test it with the ssh command:
ssh -i ~/.ssh/aws.key ec2-user@aws-server-ip
See “How To Set up SSH Keys on a Linux / Unix System” for more info.
You learned how to create and generate ssh keys using the ssh-keygen command.
- Howto Linux / UNIX setup SSH with DSA public key authentication (password less login)
- sshpass: Login To SSH Server / Provide SSH Password Using A Shell Script
- keychain: Set Up Secure Passwordless SSH Access For Backup Scripts
- Openssh man pages here
- Man pages – ssh-keygen(1)
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