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SSH Guide

Check for existing SSH keys​

MAC OS​

  • open terminal and type ```ls ~/.ssh
  • check if the directory has one of the following public SSH keys
id_rsa.pub
id_ecdsa.pub
id_ed25519.pub
  • if none of it exist, generation of a new SSH key would be required

Generate a new SSH key​

  • open terminal with the following command

    ssh-keygen -t ed25519 -C "your_email@example.com"

    • If you are using a legacy system that doesn't support the Ed25519 algorithm, use: ssh-keygen -t rsa -b 4096 -C "your_email@example.com"
  • you will get the following prompt message, just press enter to save at default file location
Generating public/private ed25519 key pair.
Enter file in which to save the key (/Users/yourusername/.ssh/id_ed25519):
  • you will get the next prompt, key is a password for easy access
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
  • when completed, you will get something like the following
Your identification has been saved in /Users/yourusername/.ssh/id_ed25519.
Your public key has been saved in /Users/yourusername/.ssh/id_ed25519.pub.
The key fingerprint is:
SHA256:kgkYKGY+hjkbfcHKBVBUYVYVWbhlbfVYK your_email@example.com
The key's randomart image is:
+--[ED25519 256]--+
|    o.+.= .      |
|   . - o + .     |
|    . . * .      |
|   . + @ +       |
|  . O - S .      |
| o.ooo   +       |
|  +Boo+   o      |
|  ==E0 + .       |
| .oo+.. .        |
+----[SHA256]-----+

Adding SSH key to the ssh-agent​

  • start the ssh-agent in the background

    eval "$(ssh-agent -s)"

  • you will get something like the following Agent pid 59566
  • modify the ~/.ssh/config file to automatically load keys into the ssh-agent and store passphrases in the keychain
    • create file if it does not exist
    • file contents should have something like the following
    Host *
      AddKeysToAgent yes
      UseKeychain yes
      IdentityFile ~/.ssh/id_ed25519
    • UseKeyChain can be omitted if passphrase was not used
    • if an error /Users/USER/.ssh/config: line 16: Bad configuration option: usekeychain occur
      • add an additional line in the config file under Host IgnoreUnknown UseKeychain
  • add SSH private key to the ssh-agent and store passphrase in the keychain, omit -K if not using passphrase

    ssh-add -K ~/.ssh/id_ed25519

    • you will be prompty with
    Enter passphrase for /Users/yourusername/.ssh/id_ed25519:
    Identity added: /Users/yourusername/.ssh/id_ed25519 (your_email@example.com)

Adding a new SSH key to your server that you want to SSH to​

  • copy the SSH public key

    pbcopy < ~/.ssh/id_ed25519.pub

  • add and paste this value into the SSH key field in your server

Add server identity to your pc's known host​

  • you will get a prompt similar to this
The authenticity of host 'someonlineserver.com (11.12.123.123)' can't be established.
RSA key fingerprint is SHA256:kjlnfe7o8GBLU7o42ulgob24ofbuy.
Are you sure you want to continue connecting (yes/no/[fingerprint])?
  • if type yes it would be added to your ~/.ssh/known_hosts file
Warning: Permanently added 'github.com,11.12.123.123' (RSA) to the list of known hosts.