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You could do as minitech suggested and use the same SSH public key on both servers. To do so, open the file /.ssh/idrsa.pub in your text editor, copy the contents of the file exactly without adding any new spaces or newlines, and add this to the server you want to connect to. If your user name on the server is 'user' at IP address 123.45.56.78, use the command 'ssh-copy-id [email protected]. Apr 02, 2019 Home Linux Basics: How To Create and Install SSH Keys on the Shell. Users would be able to copy the public key into the authorizedkeys file of the new machine using the ssh-copy-id command. Given below is the prescribed format (strictly an example) for keying in the username and IP address, and must be replaced with actual system values.
Jan 13, 2015 Bash, Shell, Terminal, Command Line ssh. This command will copy your ssh public key from your local machine to your server. This is an alternative for when you don’t have the ssh-copy-id command (for example, on Windows). Replace user@host with your own username and host. Ssh-copy-id inserted into the same file as my cut and paste so the file environment is identical. I'm mostly curious if there's any other action that ssh-copy-id does to 'activate' the key on the remote server. If not, I need to figure out how my cut and paste is altering the public key. – DanHeidel Mar 28 '14 at 1:01.
Introduction
Establishing an SSH (Secure Shell) connection is essential to log in and effectively manage a remote server. Encrypted keys are a set of access credentials used to establish a secure connection.
This guide will walk you how to generate SSH keys on Ubuntu 18.04. We will also cover setting up SSH key-based authentication to connect to a remote server without requiring a password.
- A server running Ubuntu 18.04
- A user account with sudo privileges
- Access to a terminal window / command line (Ctrl-Alt-T)
If you are already running an Ubuntu 18.04 server, you can skip this step. If you are configuring your server for the first time, you may not have SSH installed.
1. Start by installing the tasksel package:
The system will first ask for confirmation before proceeding:
2. Next, use tasksel to install the ssh-server:
3. Load the SSH server service, and set it to launch at boot:
On your client system – the one you’re using to connect to the server – you need to create a pair of key codes.
To generate a pair of SSH key codes, enter the commands:
This will create a hidden directory to store your SSH keys, and modify the permissions for that directory. The ssh-keygen command creates a 2048-bit RSA key pair.
For extra security, use RSA4096:
If you’ve already generated a key pair, this will prompt to overwrite them, and those old keys will not work anymore.
The system will ask you to create a passphrase as an added layer of security. Input a memorable passphrase, and press Enter.
This process creates two keys. One is a public key, which you can hand out to anyone – in this case, you’ll save it to the server. The other one is a private key, which you will need to keep secure. The secure private key ensures that you are the only person who can encrypt the data that is decrypted by the public key.
Step 2- Copy Public Key to the Ubuntu Server
First, get the IP address of the Ubuntu server you want to connect to.
In a terminal window, enter:
The system’s IP address is listed in the second entry:
On the client system, use the ssh-copy-id command to copy the identity information to the Ubuntu server:
Replace server_IP with the actual IP address of your server.
If this is the first time you’re connecting to the server, you may see a message that the authenticity of the host cannot be established:
Type yes and press Enter.
The system will check your client system for the id_rsa.pub key that was previously generated. Then it will prompt you to enter the password for the server user account. Type it in (the system won’t display the password), and press Enter.
The system will copy the contents of the ~/.ssh/id_rsa.pub from the client system into the ~/.ssh/authorized_keys directory of the server system.
The system should display:
If your system does not have the ssh-copy-id command, you can copy the key manually over the SSH.
Use the following command:
To log in to a remote server, input the command:
The system should not ask for a password as it is negotiating a secure connection using the SSH keys. If you used a security passphrase, you would be prompted to enter it. After you do so, you are logged in.
If this is the first time you’ve logged into the server, you may see a message similar to the one in part two. It will ask if you are sure you want to connect – type yes and press Enter.
Step 4- Disable Password Authentication
This step creates an added layer of security. If you’re the only person logging into the server, you can disable the password. The server will only accept a login with your private key to match the stored public key.
Edit the sshd_config file:
Search the file and find the PasswordAuthentication option.
Edit the file and change the value to no:
Save the file and exit, then restart the SSH service:
Verify that SSH is still working, before ending the session:
If everything works, you can close out and resume work normally.
By following the instructions in this tutorial, you have setup SSH-key-based authentication on an Ubuntu 18.04 server.
The connection is now highly secure as it uses a set of unique, encrypted SSH keys.
Ssh Generate Key Unix
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You can login to a remote Linux server without entering password in 3 simple steps using ssky-keygen and ssh-copy-id as explained in this article.
ssh-keygen creates the public and private keys. ssh-copy-id copies the local-host’s public key to the remote-host’s authorized_keys file. ssh-copy-id also assigns proper permission to the remote-host’s home, ~/.ssh, and ~/.ssh/authorized_keys.
This article also explains 3 minor annoyances of using ssh-copy-id and how to use ssh-copy-id along with ssh-agent.
ssh-keygen creates the public and private keys. ssh-copy-id copies the local-host’s public key to the remote-host’s authorized_keys file. ssh-copy-id also assigns proper permission to the remote-host’s home, ~/.ssh, and ~/.ssh/authorized_keys.
This article also explains 3 minor annoyances of using ssh-copy-id and how to use ssh-copy-id along with ssh-agent.
Step 1: Create public and private keys using ssh-key-gen on local-host
Step 2: Copy the public key to remote-host using ssh-copy-id
Note: ssh-copy-id appends the keys to the remote-host’s .ssh/authorized_key.
![Ssh Generate Key Ssh-copy-id Ssh Generate Key Ssh-copy-id](/uploads/1/2/6/1/126141566/937414831.png)
Step 3: Login to remote-host without entering the password
The above 3 simple steps should get the job done in most cases.
We also discussed earlier in detail about performing SSH and SCP from openSSH to openSSH without entering password.
If you are using SSH2, we discussed earlier about performing SSH and SCP without password from SSH2 to SSH2 , from OpenSSH to SSH2 and from SSH2 to OpenSSH.
Ssh Keys Download
Using ssh-copy-id along with the ssh-add/ssh-agent
When no value is passed for the option -i and If ~/.ssh/identity.pub is not available, ssh-copy-id will display the following error message.
If you have loaded keys to the ssh-agent using the ssh-add, then ssh-copy-id will get the keys from the ssh-agent to copy to the remote-host. i.e, it copies the keys provided by ssh-add -L command to the remote-host, when you don’t pass option -i to the ssh-copy-id.
Three Minor Annoyances of ssh-copy-id
Following are few minor annoyances of the ssh-copy-id.
- Default public key: ssh-copy-id uses ~/.ssh/identity.pub as the default public key file (i.e when no value is passed to option -i). Instead, I wish it uses id_dsa.pub, or id_rsa.pub, or identity.pub as default keys. i.e If any one of them exist, it should copy that to the remote-host. If two or three of them exist, it should copy identity.pub as default.
- The agent has no identities: When the ssh-agent is running and the ssh-add -L returns “The agent has no identities” (i.e no keys are added to the ssh-agent), the ssh-copy-id will still copy the message “The agent has no identities” to the remote-host’s authorized_keys entry.
- Duplicate entry in authorized_keys: I wish ssh-copy-id validates duplicate entry on the remote-host’s authorized_keys. If you execute ssh-copy-id multiple times on the local-host, it will keep appending the same key on the remote-host’s authorized_keys file without checking for duplicates. Even with duplicate entries everything works as expected. But, I would like to have my authorized_keys file clutter free.
Ssh-keygen Ssh-copy-id
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