the basics of secure shell (ssh)

0:00 what is secure shell protocol
1:15 openssh and how to use the ssh command
2:37 ssh keys
5:20 what are ports?
6:57 scp and file copying
7:17 run a local ssh server (ssh daemon setup)
8:24 opening your ssh server to the WAN
9:44 /etc/ssh/sshd_config
10:29 port forwarding
11:49 firewalls

After changing sshd configuration, restart sshd via systemctl. (https://wiki.archlinux.org/title/OpenSSH)
After changing ufw settings, reload ufw. (https://wiki.archlinux.org/title/Uncomplicated_Firewall)

*To allow only one ssh keyholder* ensure you have the user's public key at /home/username/.ssh/authorized_keys (with correct perms and owned by the user), then:
PasswordAuthentication no
PermitRootLogin no
ChallengeResponseAuthentication no
UsePAM no
AllowUsers username

*To allow only one IP in through ufw:*
sudo ufw allow from 192.168.1.0/24 to any port 22
sudo ufw deny 22

ssh keys: https://wiki.archlinux.org/title/SSH_keys

*More info about port forwarding, and security:*
https://wiki.archlinux.org/title/OpenSSH#Port_forwarding
The site the archwiki suggests to learn more about port forwarding: https://portforward.com/
https://wiki.archlinux.org/title/OpenSSH#protection

Painting is by Ivan Shishkin (1889) - "Morning in a Pine Forest".