ssh

• https://en.wikibooks.org/wiki/OpenSSH
  

  Host [vps]
      HostName [host]
      user [user]
      IdentityFile ~/.ssh/[file]
      ProxyCommand nc -X 5 -x 127.0.0.1:9050 %h %p # use TOR
      Compression yes
      ConnectTimeout 300

• Then
  
• ssh-copy-id -i .ssh/[file] [vps]
  

• ssh -L 54321:127.0.0.1:5432 -N <ip_externa>
  
• https://unix.stackexchange.com/questions/46235/how-does-reverse-ssh-tunneling-work/118650#118650
  

Cool, now we are on the server. First thing to do is to disable password
login via SSH.

/etc/ssh/sshd_config find #PasswordAuthentication yes and change it
for PasswordAuthentication no

Then, let’s create a new user (in case you are loging in as root).

  useradd -G sudo -s /bin/bash -m [user]
  passwd [user]

In order to be able to log in directly with this user via ssh, we should
copy our public key to its own ~/.ssh/authorized_keys file. We can
copy the one from the root user and change its permissions.

  mkdir /home/[user]/.ssh
  cp /root/.ssh/authorized_keys /home/[user]/.ssh/
  chown -R [user]: /home/[user]/.ssh # [user]: will make [user] the owner and : will make [user]'s default group the folder's owner group user:user in stead of user:root (group not changed)

Now you should try loging in with this user (modify local
~/.ssh/config if necessary). If all goes right, you can now disable
SSH root login.

/etc/ssh/sshd_config find PermitRootLogin yes and change it to
PermitRootLogin no

For now on, you shold connect via ssh with a regular user using keypairs
in stead of plain text passwords, and then login as root with
sudo su -. This adds a layer of protection against 0-days, bots,
script kiddies… ;-)

Bonus: you should definetly take a look at
fwknop.

Bonus 2: /etc/passwd -> /usr/sbin/nologin

https://superuser.com/questions/988185/how-to-avoid-being-asked-enter-passphrase-for-key-when-im-doing-ssh-operatio
Start ssh-agent if not started:

eval `ssh-agent -s`

Add your private key using ssh-add

ssh-add ~/.ssh/id_rsa_key Enter passphrase for /home/user/.ssh/id_rsa_key: Identity added: /home/user/.ssh/id_rsa_key (/home/user/.ssh/id_rsa_key)

Check if the key is added (parameter is a lowercase L):

ssh-add -l 2048 55:96:1a:b1:31:f6:f0:6f:d8:a7:49:1a:e5:4c:94:6f /home/user/.ssh/id_rsa_key (RSA)

Try to connect to your Git server:

ssh git.example.com

mosh the mosh

Útil si tienes más usuarios que usan sudo y no usan vim

sudo sh -c "export EDITOR=vim && crontab -e"

“Proxyjump, the SSH option you probably never heard of” por Khris Tolbert https://medium.com/maverislabs/proxyjump-the-ssh-option-you-probably-never-heard-of-2d7e41d43464

• ssh connection takes forever to initiate, stuck at “pledge: network” - Server Fault
  

• A comprehensive guide to fixing slow SSH logins – JRS Systems: the blog
  En la RPi4 era comentar esto en /etc/pam.d/common-session:
  

    #session optional pam_systemd.so