Re: Not a request for help, but an explanation?

On 2024-05-11, The Natural Philosopher <tnp@invalid.invalid> wrote:

On 11/05/2024 05:55, Borax Man wrote:

On Thu, 9 May 2024 12:59:57 +0100
The Natural Philosopher <tnp@invalid.invalid> wrote:
 

On 09/05/2024 11:40, Borax Man wrote:

On 2024-05-08, The Natural Philosopher <tnp@invalid.invalid> wrote:

Yesterday, I installed the latest kernel in my mint MATE 20.3 desktop
here. It advised me to reboot, so I selected the reboot option after
closing all programs, and away we went. It rebooted fine and I got a
login prompt, that looked oddly different. I think it had my full name
instead of nothing above the login prompt.
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And no matter what I typed in as password, it wouldn't accept it.
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Thinking I might have to repair something from a live installation disk,
I decided that at least a hard reboot might be worth trying, and with a
proper power off it rebooted as normal.
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Anyone have a clue as to what that might have been?
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I am the only user on the system. It's mine, all mine, and one else ever
uses it.
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We should first establish whether the problem is authentication, or
something else.
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Are we talking about a graphical login prompt, or the console, text
mode login prompt?  Do you get an error message?  What does it say?
How does it fail?
  

It was  a normal GUI login screen except that instead of a normal input
box, it had my full name over it, possibly as if I was not the default user.
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But I am the ONLY user!
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I think Mint uses Light DM, which is the one I use.  I see that
behaviour myself, where it displays the username.  If you press up and
down, you can choose between the users.  I'm not sure how that would
act if there is only the one user, but maybe try the up and down
cursor keys to see if it selects or unselects something.
 

Try switching to a text based virtual console, pressing CTRL-ALT-F2
should do it.  Then try logging in with your username then password.
If that logs in, then at least your credentials still work.  Type
'logout' then enter to logout of the text prompt and press CTRL-ALT-F7
to go back to the graphical prompt.
  

Cant reproduce it. As I said it only happened when I rebooted rather
than shut down the system
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At the graphical prompt, is it asking specifically for your password,
or for a username?  Is there a way to change the username, or type it
in?
  

As I said, it only prompted for the password.  And failed to accept it.
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This is a mint login screen:
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https://fostips.com/login-background-linux-mint-21/
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As you can see normally it has the default login name above the password
entry on the left.
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In the odd case it had my FULL name ABOVE the whole box on the RIGHT.
I am wondering if it had defaulted to an unknown user on soft restart
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Let us know how you go.

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As I said, hard reset restored normal behaviour. It was only a curiosity
as to why a soft restart might have been different....
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I'm guessing by what you mean by "can't reproduce it", is that the
text based login worked.
 

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No. Powering the machine off, worked
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That is the curiousity.
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What information was retained across a soft reboot that was not retained
in a power off situation
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I have on many occasions had a machine hang after a soft reboot, and yet
behave perfectly normally once powered down and restarted. Fine, the
hardware would always be in a different state on soft restart, but this
is more like some software values neing preserved across a restart.
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I think the difference is minor.  A hard reboot runs through POST again
but a soft reboot doesn't.  Soft reboots call a BIOS interrupt, hard
reboots cut power and restore it.

I've been using PC's quite a while, but I think I may have at least once
experienced something which required a hard reboot instead of a soft
reboot.  I may be wrong, but I know I haven't experienced Linux
oddities.

There could be something in RAM, in the config which was retained, but I
can't say what.

My initial thought was some temporary file, which saved state, but
that should have been cleared on reboot, regardless of whether soft or
hard.
 

That's one I hadn't thought of. Mmm.
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LightDM keeps logs, these can be helpful.  They should be located at
/var/log/lightdm
 
lightdm.log will list the results of authentication, and whether it
was successfull or not.  During failure, check this log (log in at
text console if necessary) and see what it says about the
authentication failure.
 

I might try that if I have time.
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TBH I am only vaguely interested in what *might* have caused it, rather
than pinning it down exactly. Life is too short
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Yeah, it could be hardware.  I'd look at the logs, they may make it
obvious WHAT failed, but why may not be quite as easy to determine.