SSH

This is cheasheet/quicknote to connect and access remote servers through ssh.

1 Check your existing key

Enter this command in your temrinal:

ls -al ~/.ssh

This checks if you have any existing ssh key-pairs, with something like:

id_rsa.pub
id_ecdsa.pub
id_ed25519.pub

Note: If you receive an error that ~/.ssh doesn’t exist, you do not have an existing SSH key pair in the default location. You can create a new SSH key pair in the next step.

2 Add your key to other hosts

To authenticate with a remote-host using your public SSH key you will use the ssh-copy-id command. Use the -i flag to specify the public key to copy to the remote-host.

Enter this command in you terminal, replacing <username@host>:

ssh-copy-id -i ~/.ssh/id_rsa.pub <username@host>

This command copies your public key from your local laptop/PC to the remote servers you want. After successfully copied, you will be asked for the following:

$(username@host) Enter your password:

And you only need to enter this for the “last” time, after that you could just do ssh username@host without typing password anymore. Moreover, you could also, use the shorthand by replacing to a host alias in a config file under ~/.ssh (See below section) Note: 2 Factor-Authentication (2FA) is not avoidable.

3 Making alias for your known host servers

If you want to avoid typing out whole host and ip address of your servers, try the following:

create a file (if not extists yet) with touch ~.ssh/config
Use the template below to add the server you like to connect to:


# Indentation is required

# Host is the alias shorthand you want to be ugin later like:

# ssc <Host> , i.e. ssh foo
Host <the-alias-you-want-to-use>
    # The HostName is some domain like abc.cd.ef.gh, usually like a email link?
    HostName <this.should.be.domain>
    # User is the allocated user with permission alonsgside with the HostName
    User tliang19

# ideally like ssh User@HostName to ssh Host