How
it works
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 or her
home directory on the remote machine. It also asks for a passphrase. The
passphrase may be empty to indicate no passphrase (host keys must have an empty
passphrase), or it may be a string of arbitrary length. Instead of RSA, DSA can
also be used. The steps to create authorization keys by using the ssh-keygen
tool are as follows:
Some of the
important options of ssh-keygen command are as follows:
|
ssh-keygen command options
|
description
|
|
-b bits
|
Specifies the number
of bits in the key to create. The minimum bit length is 768 bits and the
default length is 2048 bits.
|
|
-C comment
|
Provides new comment.
|
|
-p
|
Requests changing the
passphrase of a private key file instead of creating a new private key.
|
|
-t
|
Specifies the type of
key to create.
|
|
-q
|
quiets ssh-keygen. It
is used by the /etc/rc file while creating a new key.
|
|
-N
|
Provides a new
Passphrase.
|
|
-F
|
For ssh-keygen2, dumps
the key's fingerprint in Bubble Babble format
|
Enter
following command to generate public/private rsa key pair.
ssh-keygen
-t rsa
Generating
public/private rsa key pair.
Enter the
path to store the keys.
By default keys
will be stored at “/home/user/.ssh/” folder.
Enter
file in which to save the key (/home/user/.ssh/id_rsa):
Created
directory '/home/user/.ssh'.
Enter the
passphrase to encrypt the private key.
The passphrase
you will enter will be used for encrypting your private key. A good passphrase
should be alphanumeric having 10-30 character length. Press enter if you don’t
want to enter passphrase.
Enter
passphrase (empty for no passphrase):
Re-enter
the passphrase to confirm
Enter
same passphrase again:
Your
identification has been saved in /home/user/.ssh/id_rsa.
Your
public key has been saved in /home/user/.ssh/id_rsa.pub.
The
key fingerprint is:
7e:64:77:08:42:ab:bb:6b:c6:82:cb:fc:9b:3e:95:f6
user@localhost
The private key
was saved in .ssh/id_rsa file which is a read-only file.
The public key is
saved in .ssh/id_rsa.pub file.
Copy the Public Key onto remote systems' ~/.ssh/authorized_keys
file:
Now, you have to
copy the public key onto a remote systems' ~/.ssh/authorized_keys file. Create
/home/user1/.ssh folder at remote machine if it does not exist.
scp
/home/user/.ssh/id_rsa.pub
215.72.60.264:/home/user1/.ssh/authorized_keys
ssh user1@215.72.60.264
Last login: Mon Aug 12 15:31:52 2013 from user.
[user1@localhost ~]$
Done.
