Today I just learned that systemctl --force --force reboot is a command. We had a computer we remotely connected to which got permission errors and bus errors when we tried to reboot it normally. For some reason the mentioned command did actually manage to shutdown the computer bit did not manage to reboot it correctly.
I wonder what the double --force flag actually accomplishes and what possibly could hinder a regular reboot in this scenario.
I always try to consult the man pages for these kind of questions (you can search by typing '/' in the man page). Here's what the systemctl manual has to say in the specifications for the --force option:
Note that when --force is specified twice the selected operation is executed by systemctl itself, and the system manager is not contacted. This means the command should succeed even when the system manager has crashed.
man7 and such are better. This runs google analytics, and cannot work when fetch requests are disabled (also suitable for sending back anything), let alone disabling scripts
oftentimes (and this is more of a general statement) throwing into google exactly what you would otherwise type into your shell of choice should get you on the right track, ie searching for "man systemctl"
as far as the inability to reboot goes, if a regular sudo reboot can't bring the machine back up either then this is probably a hardware issue outside the sphere of the operating system's influence. can't say I experienced something like that myself. I guess the closest I witnessed would be a computer that when rebooted with an old USB-Keyboard plugged in just refused to get past the POST screen. The keyboard worked fine if plugged in later, but the computer couldn't reliably get through the boot process with the thing present. Maybe there's a similar variable to your setup.
It's like with -v in various applications. -v means "verbose", and -vv means "really verbose", and -vvv means "an ungodly amount of data printed to the terminal, so much that it might crash".
But that's all part of the same argument. If it was -f or -ff that'd make sense. Duplicate parameters are usually ignored in like all other programs I can think of.
I agree. Specifying the same param twice like this feels like it should be idempotent. Sometimes a final cmdline string is built by multiple tools concatenating their outputs together; if each one adds --force without any way to know if it's already been added elsewhere, this could lead to undesirable behavior.