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I want to shutdown computer with my phone using KDE Connect. That can be easily done by adding a shutdown command in the setting of the Runcommand plugin within the KDE Connect program in Linux.

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The idea is to close the applications gracefully without abruptly killing them and losing last configurations, for example.

I know about systemctl poweroff.

I read under this question that "shutdown -h now or shutdown -r now are graceful", and also that scripts involved may vary depending on the distribution. What is the situation in Ubuntu?

Are the commands above preferable to systemctl poweroff for my purpose?

  • Related (but perhaps outdated): What is the proper terminal-way to shutdown? – Melebius Jan 23 '19 at 12:53
  • @Melebius - the title is similar but that question is not mentioning the "graceful" or "friendly" aspect. Anyway, I will edit my title to make it KDE-Connect-specific (I don't want sudo etc). –  Jan 23 '19 at 13:07
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    I suppose (but don’t know) every single one of the different shutdown commands kills the processes equally gracefully by sending SIGTERM – that’s kill’s default signal and widely considered to be The Right Thing™ to do. Most importantly, every reasonable software saves its data and only then exits when receiving this signal. – dessert Jan 23 '19 at 13:26
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    Oh, run file $(which shutdown) to see what shutdown in fact is. ;) Well, I suppose there’s not really a difference… – dessert Jan 23 '19 at 13:37
  • qdbus org.kde.ksmserver /KSMServer logout 0 2 0 is what you want. This is from https://superuser.com/a/396091/. – jamadagni Feb 03 '19 at 03:27

1 Answers1

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A graceful shutdown means that the programs receive a hang up signal (HUP). If the program is developed properly, it will listen to this signal and act accordingly (prepare the program to get shut down, clearing used memory, deleting tmp files, etc.).

It does not really matter, if it is done on the GUI or on the terminal, the HUP signal will be send either way.

This also answers your question if Ubuntu behaves differently then other distros. It does not. The mechanism is the same. An odd behaviour can be expected from programs which don't act properly when they get a HUP signal, but this is because the program does not do it properly, it has nothing to do with the distro.

P.S.:

shutdown -h

will power off the system, while 

shutdown -r

will reboot the system (so this is unusable for you)

Just use shutdown or add -P or --poweroff (but this is the default anyway according to the man page).

s1mmel
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  • P.S.S.: this is totally different to reboot, which sends the KILL signal instead of HUP, hence the system just kills everything and reboots the system. Tr5y for yourself and do a time measurement of reboot and shutdown -r 0 – s1mmel Jan 23 '19 at 14:10
  • could you add a few info on why systemctl poweroff is also used/usable? is systemctl adding something to the procedure? –  Jan 23 '19 at 14:38
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    see systemctl as a "wrapper". systemctl is a command line tool from systemd and systemd is (not only but also) responsible for starting and stopping service. But in the end, systemd also sends a HUP signal. – s1mmel Jan 23 '19 at 15:49
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    According to man shutdown, shutdown -h is “[e]quivalent to --poweroff, unless --halt is specified”, while shutdown -H halts the machine! – dessert Jan 23 '19 at 16:46
  • @dessert - indeed. but is "halt the machine" (-H, --halt) action graceful? –  Jan 23 '19 at 17:24
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    @s1mmel - considering the man page: I see no -p argument, it's -P, --poweroff or -h. While "halt" is -H, not -h, as per dessert's comment. –  Jan 23 '19 at 17:36
  • @ciprius - shutdown is always graceful no matter if the machine is shutdown or halted. – s1mmel Jan 24 '19 at 11:13
  • BTW I changed -p to -P and HALT to power off. Thanks for the input. – s1mmel Jan 24 '19 at 11:15