Enable SSH public key authentication (2024)

This article describes the procedure to set up a Secure Shell (SSH) public key authentication.

Log in to the server.
Verify that the user exists:
See Also
How to Handle CSV Files Over SFTP: Best Practices Set Up the SFTP Private Key SFTP Basics SFTP Authentication with SSH keys
```
`getent passwd <username>`
```
Look up the value assigned to the AuthorizedKeysFile parameter within
/etc/ssh/sshd_config to determine the file where the key is stored:
```
 `grep AuthorizedKeysFile /etc/ssh/sshd_config`
```
Note: The default location is ~/.ssh/authorized_keys within the
user's default home directory.
Switch to the user's home directory:
```
`cd /directory-path`
```
Note: Substitute directory-path with user's home directory path.
Check permission levels for the .ssh/ directory. It should have 0700
permissions and be owned by the user.
```
 `ls .ssh`
```
a. If the directory does not exist, create it and set the permissions to 0700:
```
 `mkdir -m 700 .ssh`
```
b. If the directory exists, you can set ownership separately:
See Also
How to Set Up SFTP Public Key Authentication with FileZilla Pro Enterprise Server - FileZilla Pro
```
 `chmod 700 .ssh/` `chown -R username:username /path/to/home/.ssh`
```
Switch to .ssh/ directory and authorized_keys file:
```
```cd .ssh/vim authorized_keysll```
```
Add the SSH Public Key to the end of the authorized_keys file:
```
`vim authorized_keys`
```

Change permissions to 600 and ensure proper ownership of the file:

`chmod 600 authorized_keys``chown -R username:username authorized_keys`

Disable password authentication

If you want all users to log in with public keys and not passwords, you can disable password authentication.

Important: Disabling password authentication locks users who used a password
to access the server if SSH authentication is not configured for their account.

Create a backup of the sshd_config file before making
any changes:

mkdir /home/username/backupcp /etc/ssh/sshd_config /home/username/backup/sshd_config.bak

Open the sshd_config file:
```
`vim /etc/ssh/sshd_config`
```
Find the PubkeyAuthentication parameter and set it to yes. If the line is commented, remove any
comment indicators (#).
Find fthe PasswordAuthentication parameter within the same file and set it to no.
Save the changes to the file and exit the file.
Check the syntax by using sshd -t. If there are no errors, reload sshd:
```
`service sshd reload`
```

Additional notes:

The private key file on your local workstation (client-side) should have permissions set to
600, and the .ssh directory should have the permissions set to 700. The
authorized_keys files also work with 644 permissions, but 600 is
more secure.

Updated 9 months ago