SSH adduser: Because friends don't let friends login or run stuff as root

Cheat Sheet

Many modern web programs (npm and postgres, for example) will not function correctly if run as root.

ssh-adduser will

  1. add the user app
  2. set a random, 32-character password (as a failsafe)
  3. copy the root user's ~/.ssh/authorized_keys (so the same users can still login)
  4. give the app user sudo (admin) privileges
  5. allow app to sudo without a password

How to create a new user named 'app':

# --disable-password prevents a password prompt
# --gecos "" skips the useless questions
adduser --disabled-password --gecos "" app

How to create a and set a random password:

# sets 'my_password' to 32 random hex characters (16 bytes)
my_password=$(openssl rand -hex 16)

# uses 'my_password' for to reset and confirm 'app's password
printf "$my_password"'\n'"$my_password" | passwd app

How to make the user 'app' a "sudo"er (an admin):

adduser app sudo

How to allow 'app' to run sudo commands without a password:

echo "app ALL=(ALL:ALL) NOPASSWD: ALL" | sudo tee /etc/sudoers.d/app

How to copy allowed keys from root to the new user:

mkdir -p /home/app/.ssh/
chmod 0700 /home/app/.ssh/

cat "$HOME/.ssh/authorized_keys" >> /home/app/.ssh/authorized_keys
chmod 0600 /home/app/.ssh/authorized_keys

chown -R app:app /home/app/.ssh/


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