TLDR;

Step1: obtain an public SSH key (either one stored in your password manager or local machine, or generate a new one)

Step2: login normally with username/password for the first time: ssh -p 2222 admin@example.com.au

Step3: edit ~/.ssh/authorised_keys file on the server to add the public key obtained in step1

Step4: edit ~/.ssh/config on your local machine

  • (if you are using 1Password SSH Key Agent:

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    Host example.com.au
  HostName example.com.au
  Port 2222
  User example_user
  IdentityAgent "~/Library/Group Containers/XXXXXXXXXXX.com.1password/t/agent.sock"

  • (if you are using your locally stored ssh key:

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    Host example.com.au
    HostName example.com.au               # The real domain or IP of the remote server
    Port 2222                             # Custom SSH port
    User example_user                     # Remote username
    IdentityFile ~/.ssh/id_rsa_cpanel     # Path to your private key
    IdentitiesOnly yes                    # Ensures only this key is used for aut

Step5: attempt to login using SSH (without username/password) ssh example.com.au

(Optional) Generate SSH Key

If you do not have SSH (Public+Private) key pair, you can generate it via the following command:

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ssh-keygen -t rsa -f ~/.ssh/id_rsa_cpanel
# this will generate
# - private key located at: ~/.ssh/id_rsa_cpanel
# - public  key located at: ~/.ssh/id_rsa_cpanel.pub

Alternatively if you happen to already have a private key, but does not have a public key in hand, you can generate the public key based on the private key:

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ssh-keygen -f ~/.ssh_id_rsa_cpanel -y > ~/.ssh/id_rsa_cpanel.pub
# this will generate
# - public key located at: ~/.ssh/id_rsa_cpanel.pub

(If you happen to already have public/private key stored in 1Password, then you can download the private key via hovering the down chevron and click on “Download”, (naming doesn’t really matter):

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Install SSH Public Key to Server

Before you proceed with the next command, you will need to know username & password, if you happen to be using WHM/CPanel, this can be found in the “List Account” page, you can override/reset the password if you forgot the existing one:

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Then run the following ssh-copy-id command will install your nominated public SSH key onto the remote server, in our case it is a CPanel server:

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# Copy your SSH public key to the remote server so you can log in without a password
ssh-copy-id \
  -p 2222 \                         # Use port 2222 instead of the default port 22
  -i ~/.ssh/id_rsa_cpanel.pub \     # Specify the path to your public key
  example_user@example.com.au       # Remote username and host

> /usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
> Please Enter Password             # You will be prompted to enter your password
> example_password                  # enter your CPanel password

> Number of key(s) added: 1
> Now try logging into the machine, with:   "ssh -p 2222 'example_user@example.com.au'"
> and check to make sure that only the key(s) you wanted were added.

Connecting to SSH Session - Manual

After running the ssh-copy-id to install the public key to host, you will be able to login the host (CPanel server) via SSH Key without then need of typing a password. This is known as key-based ssh authentication:

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ssh \
	-p 2222 \                    # Use port 2222 instead of the default port 22
	-i /.ssh/id_rsa_cpanel \     # Specify the path to your private key
	example_user@example.com.au  # Remote username and host

example_user@bash-4.4$

Connecting to SSH Session - Automatic

If you do not want to enter the username, port-number, specify the private key every time, you can define a host alias and configure its setting in ~/.ssh/config file:

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# Shortcut configuration for opctest server
Host example.com.au
    HostName example.com.au               # The real domain or IP of the remote server
    Port 2222                             # Custom SSH port
    User example_user                     # Remote username
    IdentityFile ~/.ssh/id_rsa_cpanel     # Path to your private key
    IdentitiesOnly yes                    # Ensures only this key is used for aut

Then the connection command can be much simpler:

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ssh example.com.au
example_user@bash-4.4$

Connecting to SSH Session - via 1Password SSH Agent

For those user using 1Password to store the SSH public/private key, after proper configuration outlined at “1Password SSH agent”. The agent will be available to automatically fill-in the private key when you starts SSH session.

  1. Declare SSH Key in /.config/1Password/ssh/agent.toml file:
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[[ssh-keys]]
	item = "SSH Key - CPanel example.com.au"      # Item name  (OR USE item UUID if you want to have the freedom of changing name in the future)
	vault = "Personal"                            # Vault name (e.g. General, Private, Public, Company)
  1. Alter ~/.ssh/config file to use 1Password SSH Agent:
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Host example.com.au
  HostName example.com.au
  Port 2222
  User example_user
  IdentityAgent "~/Library/Group Containers/XXXXXXXXXXX.com.1password/t/agent.sock"

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# Host *
#  IdentityAgent "~/Library/Group Containers/2BUA8C4S2C.com.1password/t/agent.sock"
# ↑
# [(AND/OR) add this line if you want 1password ssh agent to take over all ssh connection]
  1. Retry connecting to the example.com.au server via ssh again: you will now be prompted to unlock your 1Password (either via password or bio-identity depending on setting) to use SSH key for the key-based authentication:

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Reference