I'm trying to create an ssh key for another user. I'm logged in as root. Other people may have the same question in a different situation. 'ssh keys should never be generated for another user': That is true in the simple case. (or rsa1 or rsa, depending on your security requirements) Generating public/private dsa key pair. Enter file in. Run it on your local computer to generate a 2048-bit RSA key pair, which is fine for most uses. Ssh-keygen The utility prompts you to select a location for the keys. By default, the keys are stored in the /.ssh directory with the filenames idrsa for the private key and idrsa.pub for the public key.
- Generate Ssh Key Pair Windows
- Generate Ssh Key Pair Aix Password
- Linux Ssh Keypair
- Generate Ssh Key Putty
SSH uses public-key cryptography to authenticate the remote computer and allow the remote computer to authenticate the user, if required. You can create ssh keys as follows on any Linux or UNIX-like operating systems including Mac OS X.[donotprint][/donotprint]
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ssh-keygen command to Generate SSH Keys
The ssh-keygen command generates, manages and converts authentication keys for ssh client and server usage. Type the following command to generate ssh keys (open terminal and type the command):
Generate SSH keys looks as follows:
$ ssh-keygen
Generate SSH keys looks as follows:
The above command creates ~/.ssh/ directory. So if your user name is vivek, than all files are stored in /home/vivek/.ssh/ or $HOME/.ssh/ directory as follows:
- $HOME/.ssh/id_rsa – Your private key. Do not share this file with anyone. Keep it private
- $HOME/.ssh/id_rsa.pub– Your public key.
Please note that the passphrase must be different from your current password and do not share keys or passphrase with anyone. Also, make sure you have correct and secure permissions on $HOME/.ssh/ directory:
SSH Keys Are Generated, What Next?
You need to copy $HOME/.ssh/id_rsa.pub file to remote server so that you can login using keys instead of the password. Use any one of the following command to copy key to remote server called vpn22.nixcraft.net.in for vivek user:
On some *nix system such as OS X ssh-copy-id command may not be installed, use the following commands (when prompted provide the password for remote user account called vivek) to install/append the public key on remote host:
To login simply type:
The following command will help to remember passphrase
ssh-copy-id [email protected]
On some *nix system such as OS X ssh-copy-id command may not be installed, use the following commands (when prompted provide the password for remote user account called vivek) to install/append the public key on remote host:
ssh [email protected] 'umask 077; mkdir .ssh'
cat $HOME/.ssh/id_rsa.pub | ssh [email protected] 'cat >> .ssh/authorized_keys'
To login simply type:
ssh [email protected]
The following command will help to remember passphrase
exec ssh-agent $SHELL
ssh-add
ssh [email protected]
Optional ssh-keygen command syntax for advance users
The following syntax specifies the 4096 of bits in the RSA key to creation (default 2048):
Where,
ssh-keygen -t rsa -b 4096 -f ~/.ssh/aws.key -C 'My AWs cloud key'
Where,
- -t rsa : Specifies the type of key to create. The possible values are “rsa1” for protocol version 1 and “dsa”, “ecdsa”, “ed25519”, or “rsa” for protocol version 2.
- -b 4096 : Specifies the number of bits in the key to create.
- -f ~/.ssh/aws.key : Specifies the filename of the key file.
- -C 'My AWs cloud key' : Set a new comment.
Now install the ~/.ssh/aws.key, run:
Test it with the ssh command:
See “How To Set up SSH Keys on a Linux / Unix System” for more info.
ssh-copy-id -i ~/.ssh/aws.key user@aws-server-ip
Test it with the ssh command:
ssh -i ~/.ssh/aws.key ec2-user@aws-server-ip
See “How To Set up SSH Keys on a Linux / Unix System” for more info.
Conclusion
You learned how to create and generate ssh keys using the ssh-keygen command.
- Howto Linux / UNIX setup SSH with DSA public key authentication (password less login)
- sshpass: Login To SSH Server / Provide SSH Password Using A Shell Script
- keychain: Set Up Secure Passwordless SSH Access For Backup Scripts
- Openssh man pages here
- Man pages – ssh-keygen(1)
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I recently read that SSH keys provide a secure way of logging into a Linux and Unix-based server. How do I set up SSH keys on a Linux or Unix based systems? In SSH for Linux/Unix, how do I set up public key authentication?This page explains a public key and shows you how to set up SSH keys on a Linux or Unix-like server. I am assuming that you are using Linux or Unix-like server and client with the following software:
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- OpenSSH SSHD server
- OpenSSH ssh client and friends on Linux (Ubuntu, Debian, {Free,Open,Net}BSD, RHEL, CentOS, MacOS/OSX, AIX, HP-UX and co).
What is a public key authentication?
OpenSSH server supports various authentication schema. The two most popular are as follows:
- Passwords based authentication
- Public key based authentication. It is an alternative security method to using passwords. This method is recommended on a VPS, cloud, dedicated or even home based server.
How to set up SSH keys
Steps to setup secure ssh keys:
- Create the ssh key pair using ssh-keygen command.
- Copy and install the public ssh key using ssh-copy-id command on a Linux or Unix server.
- Add yourself to sudo or wheel group admin account.
- Disable the password login for root account.
- Test your password less ssh keys login using ssh user@server-name command.
Let us see all steps in details.
How do I set up public key authentication?
You must generate both a public and a private key pair. For example:
Where,
Where,
- server1.cyberciti.biz – You store your public key on the remote hosts and you have an accounts on this Linux/Unix based server.
- client1.cyberciti.biz – Your private key stays on the desktop/laptop/ computer (or local server) you use to connect to server1.cyberciti.biz server. Do not share or give your private file to anyone.
In public key based method you can log into remote hosts and server, and transfer files to them, without using your account passwords. Feel free to replace server1.cyberciti.biz and client1.cyberciti.biz names with your actual setup. Enough talk, let’s set up public key authentication. Open the Terminal and type following commands if .ssh directory does not exists:
1: Create the key pair
On the computer (such as client1.cyberciti.biz), generate a key pair for the protocol.
Sample outputs:
You need to set the Key Pair location and name. I recommend you use the default location if you do not yet have another key there, for example: $HOME/.ssh/id_rsa. You will be prompted to supply a passphrase (password) for your private key. I suggest that you setup a passphrase when prompted. You should see two new files in $HOME/.ssh/ directory:
- $HOME/.ssh/id_rsa– contains your private key.
- $HOME/.ssh/id_rsa.pub – contain your public key.
Optional syntax for advance users
Generate Ssh Key Pair Windows
The following syntax specifies the 4096 of bits in the RSA key to creation (default 2048):
Where,
$ ssh-keygen -t rsa -b 4096 -f ~/.ssh/vps-cloud.web-server.key -C 'My web-server key'
Where,
- -t rsa : Specifies the type of key to create. The possible values are “rsa1” for protocol version 1 and “dsa”, “ecdsa”, “ed25519”, or “rsa” for protocol version 2.
- -b 4096 : Specifies the number of bits in the key to create
- -f ~/.ssh/vps-cloud.web-server.key : Specifies the filename of the key file.
- -C 'My web-server key' : Set a new comment.
2: Install the public key in remote server
Use scp or ssh-copy-id command to copy your public key file (e.g., $HOME/.ssh/id_rsa.pub) to your account on the remote server/host (e.g., [email protected]). To do so, enter the following command on your client1.cyberciti.biz:
OR just copy the public key in remote server as authorized_keys in ~/.ssh/ directory:
A note about appending the public key in remote server
On some system ssh-copy-id command may not be installed, so use the following commands (when prompted provide the password for remote user account called vivek) to install and append the public key:
Generate Ssh Key Pair Aix Password
3: Test it (type command on client1.cyberciti.biz)
The syntax is as follows for the ssh command:
Or copy a text file called foo.txt:
You will be prompted for a passphrase. To get rid of passphrase whenever you log in the remote host, try ssh-agent and ssh-add commands.
What are ssh-agent and ssh-add, and how do I use them?
To get rid of a passphrase for the current session, add a passphrase to ssh-agent and you will not be prompted for it when using ssh or scp/sftp/rsync to connect to hosts with your public key. The syntax is as follows:
Type the ssh-add command to prompt the user for a private key passphrase and adds it to the list maintained by ssh-agent command:
Enter your private key passphrase. Now try again to log into [email protected] and you will not be prompted for a password:
One can list public key parameters of all identities with the -L option:
Deleting all private keys from the ssh-agent can be done with the -D option as follows:
When you log out kill the ssh agent, run:
You can also add something like the below to your shell startup to kill ssh-agent at logout:
ssh-add -L
Deleting all private keys from the ssh-agent can be done with the -D option as follows:
ssh-add -D
When you log out kill the ssh agent, run:
kill $SSH_AGENT_PID
You can also add something like the below to your shell startup to kill ssh-agent at logout:
trap 'kill $SSH_AGENT_PID' 0
4: Disable the password based login on a server
Login to your server, type:
Edit /etc/ssh/sshd_config on server1.cyberciti.biz using a text editor such as nano or vim:
Warning: Make sure you add yourself to sudoers files. Otherwise you will not able to login as root later on. See “How To Add, Delete, and Grant Sudo Privileges to Users on a FreeBSD Server” for more info.
$ sudo vim /etc/ssh/sshd_config
OR directly jump to PermitRootLogin line using a vim text editor:
$ sudo vim +/PermitRootLogin /etc/ssh/sshd_config
Find PermitRootLogin and set it as follows:
Save and close the file. I am going to add a user named vivek to sudoers on Ubuntu Linux:
Finally, reload/restart the sshd server, type command as per your Linux/Unix version:
# adduser vivek
Finally, reload/restart the sshd server, type command as per your Linux/Unix version:
5: How to add or replace a passphrase for an existing private key?
To to change your passphrase type the following command:
ssh-keygen -p
6: How do I backup an existing private/public key?
Just copy files to your backup server or external USB pen/hard drive:
How do I protect my ssh keys?
Linux Ssh Keypair
- Always use a strong passphrase.
- Do not share your private keys anywhere online or store in insecure cloud storage.
- Restrict privileges of the account.
How do I create and setup an OpenSSH config file to create shortcuts for servers I frequently access?
See how to create and use an OpenSSH ssh_config file for more info.
Generate Ssh Key Putty
Conclusion
This page explained how to set up ssh keys for authentication purposes. For more info see the following resources:
- Man pages – ssh-keygen(1)
- OpenSSH project homepage here.
And, there you have it, ssh set up with public key based authentication for Linux or Unix-like systems.
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