Remotely manage Linux servers, start with SSH

Linux servers often require remote management during operation and maintenance. SSH is one of the most commonly used remote management tools. It allows administrators to log in to Linux servers remotely, execute commands and manipulate files. In this article, we will discuss how to use SSH to connect to a Linux server and share some practical tips for SSH.

As a system administrator, you plan to use OpenSSH on Linux to automate daily tasks, such as file transfers, backup database dump files to another server, etc. To achieve this, you need to be able to automatically log in to Host B from Host A. Automatic login means using ssh in a shell script without entering any password.

This article will tell you how to set up SSH password-free login on CentOS/RHEL. Once auto-login is configured, you can use it to move files using SSH (Secure Shell) and Secure Copy (SCP).

SSH is open source and the most reliable network protocol for remote login. System administrators use it to execute commands and transfer files to another computer over the network via the SCP protocol.

By configuring SSH password-free login, you can enjoy the following conveniences:

◆Use scripts to automate daily work.

◆Enhance the security of Linux servers. This is a recommended way to protect your Virtual Private Server (VPS) from brute force attacks, as SSH keys are nearly unbreakable by brute force alone.

What is Ssh-Keygen

ssh-keygen is a tool used to generate, create and manage public and private keys for SSH authentication. Through the ssh-keygen command, users can create keys that support both SSH1 and SSH2 protocols. ssh-keygen creates RSA keys for the SSH1 protocol, which can be RSA or DSA for SSH2.

What is Ssh-Copy-Id

ssh-copy-id is a script command used to copy the local public key to the remote authorized_keys file. It will also append the identity file to the ~/.ssh/authorized_keys file of the remote machine and send it to the remote host. appropriate permissions for the user's home directory.

SSH Key

SSH keys provide a better and secure mechanism for logging into Linux servers. After running ssh-keygen, a public and private key pair will be generated. You can place the public key on any server and use it to unlock when connecting to the server from a client holding the private key. When the two match, the system can be unlocked without a password.

Set up password-free login SSH on CentOS and RHEL

The following steps have been tested on CentOS 5/6/7, RHEL 5/6/7 and Oracle Linux 6/7.

Node 1: 192.168.0.9 Node 2: 192.168.0.10

Directory structure of this chapter

• step one :
• Step 2:
• Step 3:
• Step 4:

step one :

Test the connection and access from node 1 to node 2:

[root@node1 ~]# ssh root@192.168.0.10
The authenticity of host '192.168.0.10 (192.168.0.10)' can't be established.
RSA key fingerprint is 6d:8f:63:9b:3b:63:e1:72:b3:06:a4:e4:f4:37:21:42.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.0.10' (RSA) to the list of known hosts.
root@192.168.0.10's password:
Last login: Thu Dec 10 22:04:55 2015 from 192.168.0.1
[root@node2 ~]#

Step 2:

Use the ssh-key-gen command to generate the public key and private key. It should be noted here that the private key can be encrypted to enhance security.

[root@node1 ~]# ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.
The key fingerprint is:
b4:51:7e:1e:52:61:cd:fb:b2:98:4b:ad:a1:8b:31:6d root@node1.ehowstuff.local
The key's randomart image is:
+--[ RSA 2048]----+
| . ++ |
| o o o |
| o o o . |
| . o + .. |
| S . . |
| . .. .|
| o E oo.o |
| = ooo. |
| . o.o. |
+-----------------+

Step 3:

Use the ssh-copy-id command to copy or upload the public key to the remote host, and append the identity file to ~/.ssh/authorized_keys on node 2:

[root@node1 ~]# ssh-copy-id -i ~/.ssh/id_rsa.pub 192.168.0.10
root@192.168.0.10's password:
Now try logging into the machine, with "ssh '192.168.0.10'", and check in:
.ssh/authorized_keys
to make sure we haven't added extra keys that you weren't expecting.

Step 4:

Verify password-free SSH login to node 2:

[root@node1 ~]# ssh root@192.168.0.10
Last login: Sun Dec 13 14:03:20 2015 from www.ehowstuff.local

To summarize, SSH is a very important remote management tool in Linux systems. It can provide a safe and efficient remote access method. When using SSH, pay attention to strengthening security measures, such as using public key authentication, and setting reasonable configuration parameters. At the same time, we also shared some practical SSH tips, such as using proxies, forwarding ports, etc., which can help us better manage Linux servers. I believe these contents will be helpful to Linux operation and maintenance personnel.

The above is the detailed content of Remotely manage Linux servers, start with SSH. For more information, please follow other related articles on the PHP Chinese website!