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#1 2019-08-22 05:45:05

TarsolyGer
Member
From: Korea
Registered: 2019-05-19
Posts: 56

session locks on Linux - how do they work?

Hi!

This is not a support thread, even though I have ran into technical difficulties, I belive that the problem is my lack of proper understanding of the underlying principles.
I of course read the Arch Wiki page on the topic, but unfortunately I didn't find what I was looking for, and google-ing (duckduckgo-ing) for the different combinations of the terms of "linux", "screen lock", "session lock", "screen saver", "systemd" only resulted in very specific forum threads such as "how to disable screensaver on Ubuntu" and the likes. I also watched hours of videos on systemd that were very informative, but had not cover what I was looking for. The only semi-technical thing I found was this short post that directed me to this and this blogpost.

These writings frankly mostly confuse me, don't clarify what I'm looking for, as they are mostly about the fact that X11 doesn't actually has screen locking functionality, meaning it's always implemented without actually being really secure. So session locking from a TTY is not affected by these problems, and is implemented totally differently than screen locking on X? How systemd (logind) come to the picture?

Sorry for the poor wording of these questions, but the more I'm looking for answers, the more confused I get. If someone could point me in the direction of some basic information where to start with this, that would be much appreciated.


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#2 2019-09-21 21:41:45

loqs
Member
Registered: 2014-03-06
Posts: 9,312

Re: session locks on Linux - how do they work?

loginctl locksession provided by systemd locks sessions that have a screen-locker registered with systemd for them.
vlock will lock a TTY.

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#3 2019-09-22 08:28:07

TarsolyGer
Member
From: Korea
Registered: 2019-05-19
Posts: 56

Re: session locks on Linux - how do they work?

loqs wrote:

loginctl locksession provided by systemd locks sessions that have a screen-locker registered with systemd for them.
vlock will lock a TTY.

I see. So if loginctl locks the session, even if the screen-locker crashes for some reason, the session still can not be accessed?


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#4 2019-09-22 12:28:09

loqs
Member
Registered: 2014-03-06
Posts: 9,312

Re: session locks on Linux - how do they work?

loginctl only sends a request to the registered screen-lock for that session.
The screen-lock is then responsible for ensuring the screen becomes locked.

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