Because? People are stupid, we’re stupid sometimes…
If you’re like me, you probably SSH into a server occasionally and forget that it isn’t the local machine’s console when tabbing back to it after some time. This can really shoot you in the foot! Here are some ways to mitigate against accidental shutdowns which you can use on any server which is always-on. TLDR: Method #1 is probably the BEST.
NOTE: The systemd mask method would interrupt safe shutdown from say, your UPS telling the machine the battery is about to die. This is bad, so don’t create that situation. Unsafe shutdowns can lead to data loss!
Method #1 — Via the sudoers file. Never log into a server as root to monkey around. If you need root, it is best to su in, and exit out as soon as your task is done. This in and of itself is why sudo and doas are better options.
Here is how I can ensure that while logged in as “ben”, I won’t accidently fall victim to my sudo poweroff or sudo reboot stupidity.
This is on debian. Use whereis (command-name) to find the actual paths on your specific system. That won’t protect me if I’m logged in as root, but it will if I am logged in as ben. That is good enough for me, 99% of the time.
Method #2 — .bashrc of the user you normally use. This is not really effective, because if you prepend sudo to the command, it is going to run anyway!! This will however atleast remind you that you tried to do something dumb, and turn off the wrong machine. And yes, $SSH_CONNECTION is an environment variable you can use.
Method #3 — This is the only method that will truly stop the machine from shutting it down. If you’re using systemd, you can mask the commands and the system will not run them untill you re-enable them.
Probably not the best idea, because if say the power goes out now your machine won’t let the UPS trigger a safe shutdown. For now, I’ll move forward with the first two methods used together.
Moral of the story? Don’t do normal casual userspace work on the server! Just spin up a VM. Old habbits die hard, but this is definitely one I need to kill.