pacman -Syu openssh
systemctl enable sshd.service

ssh-keygen -t ed25519 -C "comment"
ssh-copy-id -i ~/.ssh/key.pub -p port usr@ip

EDIT /etc/ssh/sshd_config
    PermitRootLogin no
    PasswordAuthentication no
    PubkeyAuthentication yes

ssh -i /path/to/key -p port usr@ip
ssh hostname -t "tmux new -As ssh"  # -t open tty
## this will set env
ssh hostname -t "exec env LANG=en_US.utf8 tmux new -A"
## for tmux, -u can be used
ssh hostname -t "tmux -u new -A"

# connect SSH through port - localport and remoteport refer to machine behind router
# -L can be used multiple times to tunnel multiple ports at the same time
ssh -i /path/to/key -p port -L localport:localhost:remoteport usr@ip

# chmod to 600
# Other options see /etc/ssh/ssh_config
EDIT .ssh/config
    HOST hostname
        HostName 8.8.8.8
        User user
        Port 22001
        IdentityFile ~/.ssh/id_ed25519
        LocalForward 5901 localhost:5901
        Compression yes
        LogLevel INFO
        RemoteCommand tmux -u new -A
        RequestTTY  yes
ssh hostname
ssh -o "User=anotherUser" hostname
ssh -F /path/to/alt/config hostname
ssh -F /dev/null user@ssh-example.com # ignore config file

sftp -oPort=number usr@host
sftp -P port -i /path/to/key name@host
> help
> ls
> lls
> put filename