SSH: Client Configuration

Resources:

Some terminals (e.g. Alacritty) might be fucky to use (e.g. backspace generates weird characters, making it difficult to use at all) in conjunction with ssh. Quick fix:


TERM=xterm-256color ssh ...

The "proper" fix is to execute toe -a on the remote machine to get the list of supported terminals. Either install the terminfo of your terminal onto the remote machine, or set the environment variable TERM to a supported one before connecting.

Use public key authentifcation when possible, it's generally more secure and more convenient than passwords. Use ssh-keygen to generate key pairs:

Public keys can be shared with anyone. E.g. git over ssh might require to upload your public key onto the git instance.
Private keys should never be shared with anyone else.
The private key can be given an optional password (which cannot be recovered if lost).

To manage different configurations a variety of hosts, create ~/.ssh/config, where you can add an entry for each host. Here's an example configuration with a few neat options:


Host shorthand
	# General options
	HostName 127.0.0.1   # Either a remote IP or a domain, e.g. example.com
	User root            # The user to login as
	Port 3029            # Default Port is 22
	
	# To be able to use your public keys on the remote machine
	ForwardAgent yes
	
	# Force the usage of a specific "identity" / private key:
	IdentitiesOnly yes
	IdentityFile ~/.ssh/private_key_file
	
	# Environment variables. If the server is extra fucky, 
	# specify special terminal info here:
	SetEnv TERM=xterm

	# To get a non-default shell (which is installed on the remote system):
	RequestTTY force
	RemoteCommand fish  # Runs the "fish" shell

Then you can connect to the machine:


> ssh shorthand
# is now equivalent to:
> TERM=xterm ssh                \
	root@127.0.0.1              \
	-p 3029                     \
	                            \
	-A                          \
	                            \
	-i ~/.ssh/private_key_file  \
	                            \
	-t                          \
	fish

For key forwarding with ForwardAgent, the ssh-agent needs to be running before connecting:


# Run the agent for the duration of the given command, 
# here we'll create a shell session (using "fish" shell)
> ssh-agent fish

# Add keys to agent
# Omit the argument to add all keys to the agent
> ssh-add ~/.ssh/public_key_file  

# Connect, agent forwarding should work now
> ssh shorthand

If agent forwarding does not work, a workaround is to generate a new password encrypted key-pair on the remote machine. Alternatively, generate the encrypted key-pair locally and upload it using scp:


# Use -r to downloading / uploading a whole folder

# Upload from local machine to remote host
> scp ./localFile shorthand:/path/to/outputFolder

# Download from remote machine to local host
# (using the local machine)
> scp shorthand:/path/to/file ./

# If the host is not in the ssh config, use
# [user@]host[:port][/path]