(1) Log into a Linux system (for CentOS, v5.8 or better) with your user account.

(2) Go to the directory ~/.ssh. If such directory is not present, create one and set the permissions to 755.

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mkdir ~/.ssh
chmod 755 ~/.ssh
cd ~/.ssh

(3) Generate your private and public keys

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[frak10-b13]$ ssh-keygen

When you get “Enter passphrase (empty for no passphrase):”, you can hit enter for a null passphrase for now. The passphrase can be changed later by using the -p option. Note that from the man page: “USING GOOD, UNGUESSABLE PASSPHRASES IS STRONGLY RECOMMENDED.”. If ssh-keygen returns with “You must specify a key type (-t).”, then add the flag “-t rsa”.

(4) The ssh-keygen tool stores the private key in $HOME/.ssh/id_rsa and the public key in $HOME/.ssh/id_rsa.pub in the user’s home directory. The user should then copy the contents of id_rsa.pub to the $HOME/.ssh/authorized_keys file in his home directory on the remote machine. Verify that you have and authorized_keys file in ~/.ssh. If not create one and set the permissions:

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cat id_rsa.pub >> authorized_keys
chmod 644 ~/.ssh/authorized_keys

Verify that you have a known_hosts file ~/.ssh/known_hosts. If not, you can begin to populate this file by doing an ssh session to the system you want to connect to and answer yes to this question:

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The authenticity of host 'reda64 (172.21.32.38)' can't be established.
RSA key fingerprint is 3f:39:60:a8:b6:c7:37:e6:a6:ff:f5:d2:0b:fc:86:83.
Are you sure you want to continue connecting (yes/no)?

Links

1. ssh-keygen