"Linux" SSH password-free login

First, SSH free-secret configuration

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.

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.
It generates the. SSH directory under/HOME/CHENLB, with Id_rsa and id_rsa.pub under SSH.

2. Copy the id_rsa.pub under the A machine to B machine, in the. ssh/authorized_keys file of B machine, I use SCP to copy.

[Email protected] ~]$ SCP. ssh/id_rsa.pub [Email protected]:/home/chenlb/id_rsa.pub
[email protected] ' s password:
Id_rsa.pub 100% 223 0.2kb/s 00:00

Since there is no password-free login, enter the password.

The 3.B machine adds the id_rsa.pub copied from a machine to the. ssh/authorzied_keys file.

[email protected] ~]$ cat id_rsa.pub >>. Ssh/authorized_keys
[Email protected] ~]$ chmod Ssh/authorized_keys

The following is a list of permissions for the. SSH directory and sub-files:

drwx------  2 Hadoop hadoop 4096 2014-06-02 15:32.  DRWXR-xr-x hadoop 4096 2014-06-02 15:06.. -rw-r--r--  1 Hadoop hadoop 2252 2014-06-02 15:32 authorized_keys-rw-------  1 hadoop hadoop  668 2014-06-02 15:11 id_dsa-rw-r--r--  1 hadoop hadoop  615 2014-06-02 15:11 ID_DSA.  Pub-rw-------  1 hadoop hadoop 1675 2014-06-02 15:32 id_rsa-rw-r--r--  1 Hadoop hadoop  407 2014-06-02 15:32 Id_rsa. pub-rw-r--r--  1 hadoop hadoop  442 2014-06-02 15:08 known_hosts

4.A Machine login B machine.

[[email protected] ~]$ ssh 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 CHENLB
[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.

Reference: Ssh-keygen usage http://blog.163.com/[email protected]/blog/static/158584272007101862513886/

Second, SSH password-free login failed to find the wrong method

1. View SSH running status

Ps-e | grep ssh

If sshd and ssh-agent are found to indicate that the SSH service is basically functioning properly

2. Generate public and private keys

Ssh-keygen-t rsa-p ""

3. Append the public key to the file

Cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys

4. Test

SSH localhost

If you find that you can log in without entering your password, the SSH password-free mechanism is successful.

5. One of the reasons for the failure:. Permissions issues for SSH and its subordinate sub-files:

The preferred. SSH directory permissions are 700, two DSA and RSA private key permissions are 600, and the remaining file permissions are 644.

The following is a list of permissions for the. SSH directory and sub-files:

DRWX------  2 Hadoop hadoop 4096 2014-06-02 15:32.  DRWXR-xr-x hadoop 4096 2014-06-02 15:06.. -rw-r--r--  1 Hadoop hadoop 2252 2014-06-02 15:32 authorized_keys-rw-------  1 hadoop hadoop  668 2014-06-02 15:11 id_dsa-rw-r--r--  1 hadoop hadoop  615 2014-06-02 15:11 ID_DSA.  Pub-rw-------  1 hadoop hadoop 1675 2014-06-02 15:32 id_rsa-rw-r--r--  1 Hadoop hadoop  407 2014-06-02 15:32 Id_rsa. pub-rw-r--r--  1 hadoop hadoop  442 2014-06-02 15:08 known_hosts

6. Permissions issues for the parent directory of SSH (my question is here):

The parent directory file permission for SSH should be 755, which is the user file of the owning user (a user file from/home).

"Linux" SSH password-free login