SSH

Generate a ssh key

ssh-keygen -t ed25519 -C "$USER@$(hostname)"

Change SSH server config

# make a save of the current config
cp /etc/ssh/sshd_config /etc/ssh/sshd_config.save

nano /etc/ssh/sshd_config
# change the config, for example
# Port 2233

# restart sshd deamon
systemctl restart sshd

# check if port is applied :
lsof -i -P -n | grep ssh

Generate a lot a ssh keys

#!/bin/bash
mkdir -p temp

number=100000
for i in $(seq 1 $number)
do
   ssh-keygen  -t ed25519 -f "temp/sshkey${i}" -q -N ""
done