Big data introduction: introduction to SSH

What is ssh?

To put it simply, SSH is a network protocol that is used for encrypted login between computers.

If a user logs in to another remote computer from the local computer using the SSH protocol, we can assume that the login is secure and that the password will not be disclosed even if intercepted halfway.

In the earliest days, Internet communications were all plaintext communications, and once intercepted, the content was undoubtedly exposed. In 1995, Finnish scholar Tatu Ylonen designed SSH protocol, which encrypts all login information, which has become a basic solution of Internet security. It has been rapidly promoted all over the world, and has become the standard configuration of Linux system.

It should be pointed out that SSH is just a protocol, and there are multiple implementations, both commercial and open source. The implementation of this paper is OpenSSH, which is free software and has a wide range of applications.

Ssh principle

Check to see if centos automatically installs these software

Command: yum list installed | grep ssh

Configure SSH

1) check if ssh-related software packages (openssh-server + openssh-clients + openssh) are installed

$yum list installed | grep ssh

2) check whether the sshd process is started

$> ps-Af | grep sshd

3) generate public and private key pairs on the client side.

$> ssh-keygen-t rsa-P''- f ~ / .ssh/id_rsa

4) generate ~ / .ssh folder with id_rsa (private key) + id_rsa.pub (public key)

5) append the public key to the ~ / .ssh/authorized_keys file (file name and location are fixed)

$> cd ~ / .ssh

$> cat id_rsa.pub > > authorized_keys

6) the permission to modify authorized_keys is 64. 4.

$> chmod 644 authorized_keys

Others can't have w, which doesn't have permission.

7) Test

$> ssh localhost

Rwx