[solved] /etc/shutdown.allow

kajzer · l33t Joined: 27 Nov 2014 Posts: 897

The goal is to reboot as user, I know I can change the permissions of 'halt' or 'shutdown' but I'm looking into other approaches.

I've made /etc/shutdown.allow and the only line inside is the username
So, this command from that user should reboot the system

Anon-E-moose · Posted: Sat Nov 21, 2020 2:57 pm Post subject:

Why not sudo? It's designed to handle situations like that.

GDH-gentoo · Posted: Sat Nov 21, 2020 3:39 pm Post subject:

/etc/shutdown.allow is only used to decide whether shutdown should proceed or not, based on who's logged in. It doesn't grant privileges for running the shutdown program.

kajzer · l33t Joined: 27 Nov 2014 Posts: 897

kajzer · l33t Joined: 27 Nov 2014 Posts: 897

Actually I found another way, funny enough it uses /etc/shutdown.allow
With ctrlaltdel key combination it does reboot indeed , although I have to switch first to console, since X server captures that combination, which btw I would be happy to learn how to overcome.

Since I Use dwm all I have to do is quit from it, that actually exists from X, one more keypress is needed but that's fine.

Hu · Moderator Joined: 06 Mar 2007 Posts: 16506

You could allow sudo shutdown and no other sudo commands. Personally, I just use an xterm running under X to run /bin/su, and from there run reboot/shutdown as needed.

If you prefer that ctrl-alt-delete halt the system, you can make that change via /etc/inittab.

kajzer · l33t Joined: 27 Nov 2014 Posts: 897

Hu · Moderator Joined: 06 Mar 2007 Posts: 16506

According to man shutdown, -r requests a reboot. If you want the system to halt and power down, you should use -h instead. The default is -r. You could also install an ACPI listener and react to the power button as a request to halt. That should work even under X, but would require using the power button instead of the keyboard.

Anon-E-moose · Posted: Sat Nov 21, 2020 9:03 pm Post subject:

I never use halt/reboot, I've always done shutdown -h now to halt and shutdown -r now to reboot.
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kajzer · l33t Joined: 27 Nov 2014 Posts: 897

I found a way to get back control of the keyboard from X, by using key combination SysRq+r, after that ctrl-alt-del works fine.

Again it's pressing two key combinations, but I guess I could simulate those combinations with xdotool and put everything in bash script, which would then execute reboot.
And then configure keybinding to launch that script.

Hu · Moderator Joined: 06 Mar 2007 Posts: 16506

That will not work. SysRq+r is a kernel key sequence, even when you are in X. You cannot emulate it using xdotool. You can emulate it by writing to /proc/sysrq-trigger - which only root can open for writing. If you have root permission to do that, you could more easily run the appropriate shutdown command.

Why are you trying so hard to avoid using root permissions to reboot the system? This thread has described several ways you could do so without the need to present root's password.

kajzer · l33t Joined: 27 Nov 2014 Posts: 897

I have a very long and complicated root password

Well I guess that's why I'm using Linux, there's always a way to do something different.
I like to tinker and patch things.
But you're right, I can easily press reset button on a case and be done with it, why even bother ...

Hu · Moderator Joined: 06 Mar 2007 Posts: 16506

Not the reset button, the power button. On any even vaguely modern system, a single press of the power button, followed by a quick release, will generate an ACPI event. An ACPI listener on the system can receive this event and take any action, as root. That includes doing a controlled shutdown or an orderly reboot. The reset button would immediately reset the hardware without doing a controlled reset. I did not recommend that, and you should not do it.

Personally, my systems react to ACPI power button as hibernate, not shutdown. I find that to be convenient for when I want to quickly suspend the system without the need to log in. Some laptops are even more convenient here, in that the vendor incorrectly used ACPI events for what should have been keyboard events, so you have even more ACPI inputs to pick from. I once had a laptop where I could get separate ACPI events for lid closure, power button tapped, and a Fn+F? key sequence. That let me have all of suspend, shutdown, and hibernate, all through hardware interaction. I did not need sudo, nor to be logged in.

Tinkering is fine, but we have given you several solutions that are, in my opinion, both easier to use and better/safer than what you are inventing on your own.

kajzer · l33t Joined: 27 Nov 2014 Posts: 897

I don't know why are you triggered so much about this, I don't think I offended you or something.
You specifically gave me absolutely nothing actually, the other two posters did provide something.
My question and the post was very clear, the goal is to reboot as user, you keep talking how you do that in xterm with 'su' and then issue 'reboot'
That's an amazing find buddy but has nothing to do with my post, you only have to read carefully, nothing more than that.
Seems like that's too much for you, I marked this as solved yesterday but you just have to keep going and going, educating me how I should do things, what's easy for you and how you don't understand why that's not easy for me too.

You didn't help at all or give any constructive information, you are just spamming, would expect more from a moderator.
pfft whatever

Tony0945 · Posted: Sun Nov 22, 2020 7:35 pm Post subject:

Here's yet one more way, without sudo. It won't work if you use startX and may need modificaion if a display manager other than xdm is used:

Add the following at the end of the standard shell script /usr/lib64/X11/xdm/Xsetup

kajzer · l33t Joined: 27 Nov 2014 Posts: 897

I use startx
It's not a hard on about sudo, I just don't think I need it, when I need to do stuff as root I use su and when I'm done I exit from it.
Sudo/sudoers is nice to use when you want to do root stuff but without entering password, thus making things like reboot/shutdown done easily, however I don't want to install it just because of that.
I was doing reboots for a long time with modified permissions on a shutdown file, that was working nice, but few days ago I found out about /etc/shutdown.allow, not much information about it, I thought it was doing something else but like I learned from GDH-gentoo it's made for something else, I still found use for it and now I'm actually using that method to reboot, first I quit from X then i press ctrl-alt-del.

Hu · Moderator Joined: 06 Mar 2007 Posts: 16506

kajzer · l33t Joined: 27 Nov 2014 Posts: 897

Yeah I meant to say troll instead of spam, but doesn't matter, I don't want to argue with you.
Point is that after I said that I don't use sudo you were offering that as a solution, why I don't use it doesn't really matter.
As for shutdown binary you were giving useless information, saying what switches I should use, again ignoring the fact that I want to do that as user and keep going on with a root line.
What I didn't know is that -a switch only works from /etc/inittab and only with ctrl-alt-del key combination, which is taken by X
Reset button was a joke, clearly I want to reboot cleanly, otherwise I would code reboot myself in C++, again you are assuming how I don't use sudo because I want it to be difficult, you were saying something similar before, so I used reset button as something very easy, again you're giving lectures how that button is doing different things and it's a wrong solution, completely unnecessary.

btw since I've started using suckless software couple of years ago, dwm as my WM, st as terminal, dmenu etc. I started to dig that minimal approach, it's not just sudo, I don't want to install anything I don't actually need.
It might look confusing to some, I get that, but people are different, I don't get for example people using Gnome, full blown, running X as root, systemd etc. but I'm not going to try to reason with them explaining them why I think that's bad in my opinion, how they should use this and that instead.

Question was about /etc/shutdown.allow , my fault was not explaining in detail that I don't use sudo, login managers, systemd logind etc.
I know about other methods, I didn't know about this one, now I know, end of story.

Friendly advice, if you want to help next time look at GDH-gentoo and how he does it, concrete, on point, not giving lectures and get into reasons why someone does something.