Red Hat ENTERPRISE LINUX 4 System Administration Manual page 219

Tip
A passphrase is a string of words and characters used to authenticate a user.
Passphrases differ from passwords in that you can use spaces or tabs in the
passphrase. Passphrases are generally longer than passwords because they are
usually phrases instead of a single word.
The public key is written to ~/.ssh/id_dsa.pub. The private key is written to ~/.ssh/id_dsa.
It is important never to give anyone the private key.
2. Change the permissions of the .ssh directory with the following command:
chmod 755 ~/.ssh
3. Copy the contents of ~/.ssh/id_dsa.pub into the file ~/.ssh/authorized_keys on the
machine to which you want to connect. If the file ~/.ssh/authorized_keys exist, append the
contents of the file ~/.ssh/id_dsa.pub to the file ~/.ssh/authorized_keys on the other
machine.
4. Change the permissions of the authorized_keys file using the following command:
chmod 644 ~/.ssh/authorized_keys
5. If you are running GNOME, skip to
you are not running the X Window System, skip to
20.3.4.3. Generating an RSA Key Pair for Version 1.3 and 1.5
Use the following steps to generate an RSA key pair, which is used by version 1 of the SSH Protocol.
If you are only connecting between systems that use DSA, you do not need an RSA version 1.3 or
RSA version 1.5 key pair.
1. To generate an RSA (for version 1.3 and 1.5 protocol) key pair, type the following command at a
shell prompt:
ssh-keygen -t rsa1
Accept the default file location (~/.ssh/identity). Enter a passphrase different from your
account password. Confirm the passphrase by entering it again.
The public key is written to ~/.ssh/identity.pub. The private key is written to ~/.ssh/
identity. Do not give anyone the private key.
2. Change the permissions of your .ssh directory and your key with the commands chmod 755
~/.ssh and chmod 644 ~/.ssh/identity.pub.
3. Copy the contents of ~/.ssh/identity.pub into the file ~/.ssh/authorized_keys on the
machine to which you wish to connect. If the file ~/.ssh/authorized_keys does not exist, you
can copy the file ~/.ssh/identity.pub to the file ~/.ssh/authorized_keys on the remote
machine.
Section 20.3.4.4, "Configuring ssh-agent with
Section 20.3.4.5, "Configuring
Generating Key Pairs
GNOME". If
ssh-agent".
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