Linux uses SSH public key for password-free login to Linux

SSH login with no password to use the public and private keys. Linux can be used to generate a public/private key pair with Ssh-keygen, below I take CentOS as an example.

There is machine A (192.168.1.155), B (192.168.1.181). Now want to a through SSH password-free login to B.
First, take the root account login as an example.

1. Generate a public/private key pair under the a machine.

[[email protected] ~]# ssh-keygen-t rsa-p '

-P for the password,-p ' means the empty password, you can not use the-p parameter, so that three cars to enter, with-P on a return.
The command will generate a pair of keys Id_rsa and id_rsa.pub under the/root/.ssh directory.

The RSA key for SSH is generally used:
Id_rsa private Key
Id_rsa.pub Public Key
The following command produces different types of keys
Ssh-keygen-t DSA
SSH-KEYGEN-T RSA
Ssh-keygen-t RSA1

2. Copy the/root/.ssh/id_rsa.pub under the a machine into the/root/.ssh/authorized_keys file of the B machine, first create a good/root/.ssh directory on the B machine and copy it with SCP.

[Email protected] ~]# scp/root/.ssh/id_rsa.pub[email protected]:/root/.ssh/authorized_keys
[email protected] ' s password:
Id_rsa.pub 100% 223 0.2kb/s 00:00

Since there is no password-free login, enter the root password of machine B once.

If the Authorized_keys file is already on the B machine and there is content in it, copy the id_rsa.pub you just generated to the B machine and then use cat id_rsa.pub >>/root/.ssh/authorized_ The keys is appended to the end of the file.

In addition, you can use the following method to directly copy the newly generated id_rsa.pub to the corresponding user.

Ssh-copy-id [email protected]

You can do it. will automatically pass the public key to the owner of the server. [email protected] to log in with Root.
If the server is not port 22, specify the port:

Ssh-copy-id "-p port [email protected]"

3.Authorized_keys's authority if!!!

[Email protected] ~]# chmod 600/root/.ssh/authorized_keys

4.A Machine login B machine.

[Email protected] ~]# ssh-l root 192.168.1.181
The authenticity of host ' 192.168.1.181 (192.168.1.181) ' can ' t be established.
RSA key fingerprint is 00:a6:a8:87:eb:c7:40:10:39:cc:a0:eb:50:d9:6a:5b.
Is you sure want to continue connecting (yes/no)? Yes
warning:permanently added ' 192.168.1.181 ' (RSA) to the list of known hosts.
Last Login:thu Jul 3 09:53:18 from root
[Email protected] ~]#

The first time you log in is when you want to enter Yes.

Now a machine can be no password login B machine.

Summary: Log on the machine can have a private key, the machine to be logged on to have the public key of the machine. This public/private key pair is typically generated on the private key host. Above is the RSA algorithm's public/private key pair, of course, you can also use DSA (the corresponding file is id_dsa,id_dsa.pub)

Want to let A, B machine without password mutual login, that machine is configured in the same manner as above.

The use of Ssh-keygen

Suppose A is a customer machine and B is the target machine;

To achieve the purpose:
A machine SSH login B machine does not need to enter a password;
Encryption mode RSA|DSA can be selected, the default DSA

Practice:
1. Log In a machine
2, Ssh-keygen-t [RSA|DSA], will generate a key file and a private key file id_rsa,id_rsa.pub or id_dsa,id_dsa.pub
3. Copy the. pub file to the. SSH directory of the B machine, and cat id_dsa.pub >> ~/.ssh/authorized_keys
4, finished, from a machine login B machine's target account, no longer need password;

Ssh-keygen do password verification to enable SSH to the other machine, the SCP does not use the password.
Here's how:
SSH-KEYGEN-T RSA
Then all returns, with default values.

This generates a pair of keys that are stored under the ~/.ssh of the user directory.
Test the public key into the user directory of the other machine and copy it into the ~/.ssh/authorized_keys.

Be sure that both SSH and Authorized_keys have write permissions for the user. Otherwise, validation is not valid. (Today is the problem, looking for a long time the problem), in fact, think carefully, this is done so as not to appear system vulnerabilities.

Linux uses SSH public key for password-free login to Linux