Re: C8 Question

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Il 24/01/20 23:00, Orion Poplawski ha scritto:
On 1/24/20 4:38 AM, Alessandro Baggi wrote:
Hi list,

I installed on my workstation C8.1 (1911) and performed a minimal install and
then installed XFCE from EPEL.

I noticed a strange behaviour (don't know if this is the wanted default). If I
try ,from normal user shell, to run command like "reboot" or "shutdown -h now"
system will reboot/shutdown. This happens on tty console, on xfce terminal and
ssh session.

My user is not in wheel and during install I have not enabled checkbox to give
that user administration permission. I tried to create a new user with adduser
but got the same problem.

To solve this I modified polkit login1 policy on
/usr/share/polkit-1/actions/org.freedesktop.login1.policy setting
<allow_active>no</allow_active> for statement that concern reboot and
shutdown/poweroff.

Why on CentOS a normal user can shutdown the system without root privileges? I
think that on any server normal user should not be able to shutdown the system
without privileges.

This is a bug or a wanted default?
So, as you figured out from the polkit setting - "active" user's (i.e. with a
"seat") have access to shut a machine down.  Now to figure out who has a seat
- and you use "loginctl" to see that.  For e.g. from my non-privileged user
logged into my CentOS 8.1 VM via ssh:

$ loginctl
SESSION   UID USER  SEAT TTY
       1 ##### user

it shows that I don't have a "seat" and so:

$ shutdown -h now
Failed to set wall message, ignoring: Connection timed out
Failed to power off system via logind: Interactive authentication required.
Failed to open initctl fifo: Permission denied
Failed to talk to init daemon.

as expected.  Perhaps you can start tracking down with loginctl who has a seat
and why.

Hi, thank you very much for your suggestion, loginctl did help me to understand this "problem". I tried to run loginctl on my VM logging in with ssh and I get this:

[testuser@localhost ~]$ loginctl
SESSION   UID USER       SEAT   TTY
           3  1000 testuser

1 sessions listed.

and try to run reboot give me the expected behaviour.
If I try from tty console I have a seat for testuser and can reboot the system.

I don't know what I done in the other test...

Thank you very much, I'm happy this is my mistake and not a centos bug.

Thank you to all user that helped me.


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