SSH Passwordless Login to a Server

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A concise guide to passwordless SSH login on Unix-like systems: generate a key pair, upload the public key, fix permissions, and connect.

The following commands are only for Unix-like systems.
Windows does not need this solution. Many PuTTY-like tools on Windows can choose “remember password” to implement passwordless login.
I did not find a similar password-remembering solution on Mac, but using a key is actually a more secure method.

A private key remains safely inside a home lighthouse while its matching public pattern opens a distant server gate

Step 1: Generate an RSA Key Pair

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ssh-keygen -t rsa

Step 2: Upload the RSA Public Key to the Server

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cat id_rsa.pub | ssh -p 26757 root@138.128.193.150 'cat >> .ssh/authorized_keys'

Step 3: Change Permissions

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ssh -p 26757 root@138.128.193.150 "chmod 700 .ssh; chmod 640 .ssh/authorized_keys"

Step 4: Success!

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ssh -p 26757 root@138.128.193.150

reference:
ssh-passwordless-login-using-ssh-keygen-in-5-easy-steps