How to Create Sudo User & Set Up SSH Key

Setting up a new sudo user and configuring SSH key authentication is crucial for secure and convenient access to remote servers. In this comprehensive guide, we’ll walk through each step of creating a sudo user and setting up SSH keys for seamless and passwordless login.

Step 1: Access Remote Server via SSH
Before we begin, ensure you have SSH access to your remote server. Use the following syntax to connect:

ssh -p PORT USERNAME@HOSTIP

For example:

ssh -p 22 root@216.32.44.12

Step 2: Create a New User
To create a new user, use the adduser command:

adduser User_Name

For example:

adduser raj

Step 3: Make New User a Sudo User
Grant sudo privileges to the new user with the usermod command:

usermod -aG sudo User_Name

For example:

usermod -aG sudo raj

Step 4: Verify Sudo User Status
Confirm that the user has been added to the sudo group:

groups User_Name

For example:

groups raj

Step 5: Exit from Remote Server
Once the user setup is complete, exit from the remote server:

exit

Step 6: Generate SSH Key on Local Machine
Open your command line terminal and generate an SSH key for the new user:

ssh-keygen -f ~/.ssh/key_name -t ed25519

For example:

ssh-keygen -f ~/.ssh/raj_ed25519 -t ed25519

Step 7: Copy SSH Public Key to Remote Server
For Linux/macOS:

ssh-copy-id -p PORT -i ~/.ssh/keyname.pub Remote_Server_Username@Remote_Server_Host_IP

For example:

ssh-copy-id -p 22 -i ~/.ssh/raj_ed25519.pub raj@216.32.44.12

Step 8: Copy Public Key to Remote Server (for Windows)
If you’re using Windows, follow these steps:

1. Ensure the remote server user has a .ssh folder in their home directory:

ssh -P PORT Remote_Server_Username@Remote_Server_Host_IP "mkdir /home/Remote_Server_Username/.ssh"

For example:

ssh -P 22 raj@216.32.44.12 "mkdir /home/raj/.ssh"

2. Copy the public key to the remote server’s .ssh/authorized_keys file:

scp -P PORT SSH_PUBLIC_KEY_PATH Remote_Server_Username@Remote_Server_Host_IP:/home/Remote_Server_Username/.ssh/authorized_keys

For example:

scp -P 22 C:\Users\R\.ssh\raj_ed25519.pub raj@216.32.44.12:/home/raj/.ssh/authorized_keys

By following these steps, you’ll successfully create a sudo user and set up SSH key authentication, enhancing security and accessibility for your remote server.