How to set up ssh key linux

Linux-cliHow-ToBeginner · 3 min read

How to Set Up SSH Key on Linux: Simple Steps

To set up an ssh key on Linux, use ssh-keygen to create a key pair, then copy the public key to the remote server's ~/.ssh/authorized_keys file using ssh-copy-id. This enables secure, passwordless login via ssh.

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Syntax

The main commands to set up SSH keys are:

ssh-keygen -t rsa -b 4096 -C "your_email@example.com": Generates a new RSA key pair with 4096 bits and a comment.
ssh-copy-id user@remote_host: Copies your public key to the remote server for passwordless login.
ssh user@remote_host: Connects to the remote server using the SSH key.

Each part helps create, transfer, and use the SSH key securely.

bash

ssh-keygen -t rsa -b 4096 -C "your_email@example.com"
ssh-copy-id user@remote_host
ssh user@remote_host

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Example

This example shows how to generate an SSH key, copy it to a remote server, and connect without a password prompt.

bash

ssh-keygen -t rsa -b 4096 -C "alice@example.com"
# Press Enter to accept default file location and optionally set a passphrase
ssh-copy-id alice@192.168.1.10
ssh alice@192.168.1.10

Output

Generating public/private rsa key pair. Enter file in which to save the key (/home/alice/.ssh/id_rsa): Created directory '/home/alice/.ssh'. Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /home/alice/.ssh/id_rsa. Your public key has been saved in /home/alice/.ssh/id_rsa.pub. The key fingerprint is: SHA256:... alice@example.com Number of key(s) added: 1 Now try logging into the machine, with: "ssh 'alice@192.168.1.10'" and check to make sure that only the key(s) you wanted were added. Welcome to Ubuntu 20.04.4 LTS (GNU/Linux 5.4.0-104-generic x86_64) alice@remote:~$

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Common Pitfalls

Common mistakes when setting up SSH keys include:

Not setting correct permissions on ~/.ssh and authorized_keys (should be 700 for .ssh and 600 for authorized_keys).
Copying the private key instead of the public key to the server.
Using the wrong username or hostname when copying the key.
Not restarting the SSH service if configuration changes are made.

Fix permissions with chmod 700 ~/.ssh and chmod 600 ~/.ssh/authorized_keys.

bash

## Wrong: copying private key
scp ~/.ssh/id_rsa user@remote:~/.ssh/

## Right: copying public key
ssh-copy-id user@remote

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Quick Reference

Command	Description
ssh-keygen -t rsa -b 4096 -C "email@example.com"	Generate a new RSA SSH key pair with 4096 bits
ssh-copy-id user@host	Copy your public key to the remote server for passwordless login
ssh user@host	Connect to the remote server using SSH key authentication
chmod 700 ~/.ssh	Set correct permissions on .ssh directory
chmod 600 ~/.ssh/authorized_keys	Set correct permissions on authorized_keys file

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Key Takeaways

Use ssh-keygen to create a secure SSH key pair on your Linux machine.

Copy only the public key to the remote server using ssh-copy-id for easy setup.

Ensure correct permissions on ~/.ssh and authorized_keys to avoid access issues.

Test your SSH connection to confirm passwordless login works.

Avoid sharing your private key; keep it secure and private.