[EdLUG] Lubuntu 14.04 guest session login failure

Sun Jul 9 10:49:43 UTC 2017

I had this recently and was puzzled for 3 days. Eventually worked out that
.Xauthority was owned by root, so simply deleted the file!

Andrew Smith B.Sc(Hons), MBA

T:01383-411351
M: 0772-456-3636
E: asmith9983 at gmail.com

On 9 July 2017 at 04:15, Edinburgh Linux Users Group <
edlug at lists.edlug.org.uk> wrote:

> Hi, a volunteer with higher sys admin skills came by the low income
> shelter today and diagnosed a solution to the guest session login failure
> loop.  Here is what she wrote:
>
> In case anyone was curious as to what happened with this, I finally
> had some time to sit down on site this evening and do some debugging.
>
> Some background as to how the guest logins work in Lubuntu: A
> guest-XXXXX (random characters) user is created upon login, which is
> used throughout the session. It is then deleted when the user logs
> out.
>
> After some red herrings in the auth logs (mostly PAM errors around KDE
> and Gnome keyrings), I did some digging in the lightdm logs.
> Eventually I noticed the UID of the guest account trying to be created
> was the same every time a login attempt was made: 999. Odd. So I
> looked in /etc/passwd and noticed that there were hundreds of
> guest-XXXXX accounts. That's no good!
>
> Turns out, at some point the /etc/subgid.lock file got stuck in an
> existing state (wasn't deleted when the lock concluded), which meant
> the command to delete the user was not completing successfully upon
> logout. Users were piling up and never being deleted. Once the UIDs
> hit 999 it was failing to create new guest users, so the login would
> fail. A quick mv (rm didn't work) of the subgid.lock file and a script
> to delete all the guest accounts got us going again.
>
> I'm considering my options to get us out of this reoccurring issue in
> the future. I'm thinking of just a cron job on each machine that
> checks for a subgid.lock file sticking around for more than a couple
> days and moving it out of the way, but I'll sleep on it. More clever
> suggestions welcome ;)
>
> Thanks for everyone who tried to help.  Any suggestions are welcome!
>
> On Sat, Jul 8, 2017 at 5:03 PM, Edinburgh Linux Users Group <
> edlug at lists.edlug.org.uk> wrote:
>
>> Hi,
>>
>> I don't see how a guest could be causing this issue.  We are experiencing
>> this guest session login failure loop on several machines at several
>> difference low income shelters.  We are still stymied.  Someone suggested
>> that removing appamor would work, but it didn't.
>>
>> On Tue, Apr 4, 2017 at 1:33 AM, Edinburgh Linux Users Group <
>> edlug at lists.edlug.org.uk> wrote:
>>
>>> Hi Christian
>>>
>>> Are you saying that this problem occurs on one machine only? Could it be
>>> that a "guest" has tried to make changes to the guest login and has broken
>>> something?
>>>
>>> If these machines are all standard installs, would it be simpler to
>>> reinstall instead of trying to solve a mysterious problem? If reinstalling
>>> seems too much work (if there are a lot of customisations) I suggest making
>>> an image backup (from one of the working machines) and restore (may be
>>> handy to keep an image backup for this purpose anyway)
>>>
>>> Let us know how you get on.
>>>
>>> Regards
>>> Geetam
>>>
>>> ---
>>> I don't know
>>> ...
>>> I don't know what it is
>>> ...
>>> I don't know what it is that I don't know
>>>
>>> Isn't it beautiful
>>>
>>> On 4 April 2017 07:19:28 Edinburgh Linux Users Group <
>>> edlug at lists.edlug.org.uk> wrote:
>>>
>>>> Hi,
>>>>
>>>> I am experiencing a very strange thing for which there are no ready
>>>> answers by googling.  I am a volunteer for a non-profit which puts
>>>> GNU-Linux computers in low income shelters.  They are stand-alone machines
>>>> connected directly to the Internet via a hub on a dedicated ethernet cable.
>>>>
>>>> The shelters don't want the users to be able to store anything directly
>>>> to the machine's hard drive.  To give them that functionality, we ask them
>>>> to use the guest session, which wipes out all data by default when the
>>>> session ends.
>>>>
>>>> Right now, however, we are experiencing a failure of logging into the
>>>> guest session.  Normally, you just choose the guest session in the Lubuntu
>>>> login screen, and hit enter, and it boots up a full guest session.  No
>>>> password is required.
>>>>
>>>> Now, when I chose the guest session and hit enter, the system appears
>>>> to head toward a normal login, but then quickly fails and returns to the
>>>> login screen.
>>>>
>>>> The system's SU admin account is performing normally.  To get into the
>>>> admin account, I just choose it in the login screen, enter the password,
>>>> and the admin session boots up normally.
>>>>
>>>> This whole thing is very strange, and I have never seen anything like
>>>> it before.  We are using 14.04 on 13 machines with identical or similar
>>>> hardware and are not having any such problems.  This email is being written
>>>> on one of those such machines, and the guest session works just fine.
>>>>
>>>> I ran updates on the malfunctioning machines, rebooted, no joy.
>>>>
>>>> Thanks very much in advance.
>>>>
>>>> --
>>>> Christian Einfeldt
>>>> _______________________________________________
>>>> EdLUG mailing list
>>>> EdLUG at lists.edlug.org.uk
>>>> https://lists.edlug.org.uk/mailman/listinfo/edlug
>>>>
>>>
>>> _______________________________________________
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>>> EdLUG at lists.edlug.org.uk
>>> https://lists.edlug.org.uk/mailman/listinfo/edlug
>>>
>>>
>>
>>
>> --
>> Christian Einfeldt
>>
>> --
>> EdLUG mailing list
>> EdLUG at lists.edlug.org.uk
>> https://lists.edlug.org.uk/mailman/listinfo/edlug
>>
>
>
>
> --
> Christian Einfeldt
>
> --
> EdLUG mailing list
> EdLUG at lists.edlug.org.uk
> https://lists.edlug.org.uk/mailman/listinfo/edlug
>
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