How to generate ssh keys in linux?

petulia3478

To generate an RSA key pair:

$ /usr/bin/ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/testuser/.ssh/id_rsa):
Created directory '/home/testuser/.ssh'.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/testuser/.ssh/id_rsa.
Your public key has been saved in /home/testuser/.ssh/id_rsa.pub.
The key fingerprint is:
aa:bb:cc:dd:ee:ff:gg:hh:ii:jj:kk:ll:mm:nn:oo:pp testuser@server1

Assuming /home/testuser is testuser's home directory, the public key is written to /home/.ssh/id_rsa.pub and the private key is written to /home/.ssh/id_rsa.

Change the permissions of the .ssh directory:

# /bin/chmod 700 /home/testuser/.ssh

Copy the contents of id_rsa.pub into /home/testuser/.ssh/authorized_keys on the host you want to connect to i.e. on server2:

$ /bin/vi /home/testuser/.ssh/authorized_keys

Make sure the contents is on one line.

If the file /home/testuser/.ssh/authorized_keys already exists, append the contents of id_rsa.pub to the file.

Change the permissions of /home/testuser/.ssh/authorized_keys on server2:

# /bin/chmod 600 /home/testuser/.ssh/authorized_keys

When user testuser uses ssh from server1 to server2 (192.168.1.65), testuser will not be asked for his/her password:

$ /usr/bin/ssh 192.168.1.65
The authenticity of host '192.168.1.65 (192.168.1.65)' can't be established.
RSA key fingerprint is zz:yy:cc:dd:ee:ff:gg:hh:ii:jj:kk:ll:mm:nn:oo:pp.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.1.65' (RSA) to the list of known hosts.
Last login: Fri Jul 24 12:08:05 2009 from xxxxxx.home

To generate a DSA key pair:

$ /usr/bin/ssh-keygen -t dsa
Generating public/private dsa key pair.
Enter file in which to save the key (/home/testuser/.ssh/id_dsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/testuser/.ssh/id_dsa.
Your public key has been saved in /home/testuser/.ssh/id_dsa.pub.
The key fingerprint is:
aa:bb:cc:dd:ee:ff:gg:hh:ii:jj:kk:uu:mm:nn:oo:tt testuser@server1

Follow the instructions listed above for rsa but replace rsa with dsa.