Generating public/private ssh keys

How to generate and use public / private ssh keys

This guide is tested on Centos 6
To generate RSA ssh key pair enter following command:

ssh-keygen -t rsa

To generate DSA ssh key pair enter following command:

ssh-keygen -t dsa

You will be prompted to specify a path to locate the keys

[root@localhost ~]# ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):

You can specify it or just press "enter" to accept default location.
Now you have the keys generated. The keys are id_rsa and id_rsa.pub.
Copy id_rsa.pub to remote host(s) in user directory, for example /home/alex/.ssh/ or ~/.ssh, and rename it to authorized_keys. Copying can be done with scp:

scp id_rsa.pub alex@1.2.3.4:/home/alex/.ssh/authorized_keys

If you have an issue like "command not found" install ssh clients on both sides entering:

yum install openssh-clients

Now open /etc/ssh/sshd_config on remote host and set following attributes:

RSAAuthentication yes
PubkeyAuthentication yes 
PasswordAuthentication no

Restart ssh service

/etc/init.d/sshd restart

To add one more public key to remote host simply append the key to existing authorized_key manually or using command:

cat ~/.ssh/another_one_id_rsa.pub >> ~/.ssh/authorized_keys

If you can't get why it doesn't work make sure you have selinux disabled

 

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