How to access a Linux server through SSH and config key pairs?

To access a Linux server with SSH and configure key pairs, follow these steps:

Generate a new key pair on your local machine (if you don't already have one) using the ssh-keygen command. This will create two files:
- A private key (usually stored in ~/.ssh/id_rsa)
- A public key (stored in ~/.ssh/id_rsa.pub)
Copy the public key to the server using the ssh-copy-id command. This will add your public key to the authorized_keys file on the server, allowing you to authenticate using your private key:
```
ssh-copy-id user@server_address
```
If ssh-copy-id is not installed on your local machine, you can manually copy the contents of the public key file to the server using an editor or the following command:
```
cat ~/.ssh/id_rsa.pub | ssh user@server_address "mkdir -p ~/.ssh && cat >> ~/.ssh/authorized_keys"
```
Secure the private key on your local machine by setting the correct permissions:
```
chmod 600 ~/.ssh/id_rsa
```
Connect to the server using SSH, specifying the private key file with the -i option:
```
ssh -i ~/.ssh/id_rsa user@server_address
```

If your key file is named something other than id_rsa, replace id_rsa in the above command with the name of your key file.

That's it! You should now be able to access your Linux server using SSH with key pairs.

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