How to set up ssh password-free login to Linux server

Every time you log in to the test server, you always need to enter a password for ssh login. It's okay if there are few logins, but if there are too many logins, every extra line of command is redundant.

RSA authentication login method

Creating a key pair

Enter the following command in the client (local machine) terminal

ssh-keygen -t [rsa|dsa]

RSA and DSA represent different algorithms

For example:

ssh-keygen -t rsa

Just keep pressing Enter (no need to set a password)

The key file and private key file id_rsa, id_rsa.pub will be generated (if dsa is used, id_dsa, id_dsa.pub will be generated)

The generation location is in the /root/.ssh/ folder (I use the root user so under root, the generation process will prompt the file location)

.ssh is a hidden folder, use ls -a to view it

Put the public key in the server's specified location

Method 1: Direct copy

1. Copy the public key to the .ssh folder of the root user of the server (copy it to the .ssh folder of the user you log in as)

scp /root/.ssh/id_rsa.pub root@172.16.0.164:/root/.ssh/

2. Install the public key

Log in to the server cd /root/.ssh/

cat id_rsa.pub >> authorized_keys

Method 2: Use ssh-copy-id command to copy (recommended)

One command is OK

ssh-copy-id root@172.16.0.164

verify

If you do not enter a password, it will succeed, otherwise it will fail.

ssh root@172.16.0.164

Precautions

The above operation has been tested and there is no problem

There will be differences depending on the version of Linux and the user used.

If there is a problem, consider the following two points

1. File permission issues for id_rsa.pub and authorized_keys

chmod 600 authorized_keys
chmod 700 ~/.ssh

2. ssh configuration file

 vim /etc/ssh/sshd_config
 #Enable RSA authentication, the default is yes
 RSAAuthentication yes
 Enable public key authentication, default is yes
 PubkeyAuthentication yes
 #root user ssh loginPermitRootLogin yes

(I have not modified these configurations, mine is redhat7.2)

Customize a simple shell script

Create a file in the common folder

touch 164.sh

Editing a file

File content ssh root@172.16.0.164

 vim 164.sh
 #Add content ssh root@172.16.0.164
 Save and exit: wq

Increase the user's execution permissions

chmod u+x 164.sh

It's more fun to use it with the tab key

./164.sh

Expect command password-free login method

Maybe you think it is not good to operate the server system, of course you can just operate it locally.

Using the expect command only requires local operation, provided that you have the expect command locally

1. Create a file

touch expectssh.sh

Add the following content and change the user, ip, and password to your own

 #!/usr/bin/expect -f
 set username root 
 set hostname 172.16.0.164 
 set password 123456
 spawn ssh $username@$hostname
 set timeout 1
 expect { "yes/no" 
  {send "yes\r";exp_continue}
 }
 expect "$username@$hostname's password:"
 send "$password\r"
 interact

2. Add execution permissions to expectssh.sh

chmod u+x expectssh.sh

3. Execute commands

expect expectssh.sh

(1. Must be executed using the expect command 2. You can wrap it in another layer and use bash parsing to execute)

The above is the full content of this article. I hope it will be helpful for everyone’s study. I also hope that everyone will support 123WORDPRESS.COM.