Can someone explain this command for me?
from Epzillon@lemmy.ml to linux@lemmy.ml on 04 Sep 2024 08:27
https://lemmy.ml/post/19918651
from Epzillon@lemmy.ml to linux@lemmy.ml on 04 Sep 2024 08:27
https://lemmy.ml/post/19918651
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.
threaded - newest
I hate ycombinator but here:
news.ycombinator.com/item?id=36873927
Instead of just linking to the information, which may be removed in the future, you could have also pasted a snippet of a relevant section. Like:
As per systemctl(1) manual:
Ah, the --no-preserve-root flag equivalent for a reboot đ
Good old --no-preserve-root đ
Sounds like the equivalent of Alt+SysRq+B.
Iâd never use it on a production server due to the implications of data loss associated with such a command.
You could say this is the same as sysreq trigger b where everything is ignored and just reboot with ignorance.
.
You can force the kernel to terminate all processes and amount all filesystems
This is very valid but in our case we dont really store any important data on the computer. We make digital timetable signs for bus stops and train stations, the computers we build and put inside are just a base image we flash onto the disk and set hostname and IP on. Then they all connect and set themselves up via our servers and pull any displayed data from our actual main servers.
In this case its sad that it didnt actually restart, that means our client has to drive out and deassemble the entire sign. But it seems to be a failing disk so it had to be replaced either way.
As long as itâs not writing to disks, youâre probably safe. This is a good method to avoid getting a remote device stuck too.
Obligatory âsystemd was a mistake, they played us for absolute fools, yadda yadda yaddaâ
So hexbear now hates systemd. Good to know
I always try to consult the man pages for these kind of questions (you can search by typing â/â in the man page). Hereâs what the systemctl manual has to say in the specifications for the
âforceoption: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.In other words, RTFM
Weird choice tbh. Iâd make --force --force a separate option if possible.
You just really force it.
Itâs like with
-vin various applications.-vmeans âverboseâ, and-vvmeans âreally verboseâ, and-vvvmeans âan ungodly amount of data printed to the terminal, so much that it might crashâ.But thatâs all part of the same argument. If it was
-for-ffthatâd make sense. Duplicate parameters are usually ignored in like all other programs I can think of.The
-vvvI know is the same as-v -v -v. Canât check right now, but is the short parameter-f? So maybe give-ffa try âŚItâs a dangerous command - Iâd rather not run it by accidentally hitting the
fkey a second time.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
âforcewithout any way to know if itâs already been added elsewhere, this could lead to undesirable behavior.Even
âforceforcewould be better.Yeah, duplicate flags should just be ignored.
swear, but it is funny
âforce-and-I-really-mean-it-this-time
I would use the man pages but my working laptop uses Windows and since the system died i dont have any way to check them until I get home.
Thank you a lot for the answer though, that does explain a lot!
honestly glad you made the thread still cause I just love questions like this to see if I can answer them and if I canât I learn something
Manpages.org
It sounds like it should be a hookup app, but it actually is the online Linux man pages.
Or, for a less dubious sounding site, man7.org
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 âman systemctlâ
as far as the inability to reboot goes, if a regular
sudo rebootcanât bring the machine back up either then this is probably a hardware issue outside the sphere of the operating systemâs influence. canât 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 couldnât reliably get through the boot process with the thing present. Maybe thereâs a similar variable to your setup.What about if you use âsudo rebootâ command?
We did try that, it just have us Permission Denied
How about âsudo reboot -fâ?