[Ltsp-discuss] Only some users can log in?

Discussion:

Joseph Bishay

2017-05-15 03:24:40 UTC

Hello everyone,

I hope you are all doing very well today.

We have a new LTSP server for our school. It is a base OS of
Ubuntu-Mate that then has LTSP installed on top of it in 2-NIC
configuration. We've been running such a system for over a decade
with lots of success.

When we were copying over our users /home folders, we came across a
strange problem -- some users are able to log on from the fat clients,
but some users cannot. All users can log into the server directly if
they are standing at the server, but not all those same users can log
in from a fat client! I am unable to determine what is the difference
between those who are able to log in and those who cannot.

We have tried to update the SSH keys and the ltsp-image, but no
effect. Some users can log in, some cannot.

For those who cannot, what happens is they log in, put the correct
password, and they see the login screen go away as if it is loading
their desktop, the mouse turns into the loading cursor, and then it
just loads up the login screen again. It is definitely not the same
thing that happens if they were to put a wrong password.

Where should we look for clues? How could we fix this please?

Thank you!
Joseph

Alkis Georgopoulos

2017-05-15 06:09:19 UTC

Permalink

Check if those users have a ~/.dmrc file from which they select e.g. the
gnome-flashback session, which doesn't exist in mate.

If so, delete those files.

Post by Joseph Bishay
Hello everyone,
I hope you are all doing very well today.
We have a new LTSP server for our school. It is a base OS of
Ubuntu-Mate that then has LTSP installed on top of it in 2-NIC
configuration. We've been running such a system for over a decade
with lots of success.
When we were copying over our users /home folders, we came across a
strange problem -- some users are able to log on from the fat clients,
but some users cannot. All users can log into the server directly if
they are standing at the server, but not all those same users can log
in from a fat client! I am unable to determine what is the difference
between those who are able to log in and those who cannot.
We have tried to update the SSH keys and the ltsp-image, but no
effect. Some users can log in, some cannot.
For those who cannot, what happens is they log in, put the correct
password, and they see the login screen go away as if it is loading
their desktop, the mouse turns into the loading cursor, and then it
just loads up the login screen again. It is definitely not the same
thing that happens if they were to put a wrong password.
Where should we look for clues? How could we fix this please?
Thank you!
Joseph
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Joseph Bishay

2017-05-15 17:52:47 UTC

Permalink

Hello Alkis,

Thank you for your reply.

We wrote a little script to delete all the configuration files from
the users when we migrated their files. All the .something files and
folders were deleted before they logged in. All that is in their
directories are their documents. I double-checked and there is no
~/.dmrc file.

I tried to log in as a user and found after the failed log in attempt
there is a newly-created file called .xsession-errors. Inside that
file is the following:

Xsession: X session started for jbishay at Mon May 15 10:34:32 EST 2017
localuser:jbishay being added to access control list
openConnection: connect: No such file or directory
cannot connect to brltty at :0
/etc/X11/Xsession: 3: [: x: unexpected operator

Searching online for the openConnection shows me some postings about
Nvidia cards and driver errors, but we are using clients with ATI
cards. I also tried a different thin client and the same issue arose.

What else could it be? A permission's issue? A different UID or GID
between the old and new machines? To transfer the files over we used
rsync on /home from the old server to the new one. The new server
actually had an old backup of /home so rsync was a faster way of
updating everyone's files rather than trying to move over 600 GB of
users from scratch.

I appreciate the help!

Joseph

Post by Alkis Georgopoulos
Check if those users have a ~/.dmrc file from which they select e.g. the
gnome-flashback session, which doesn't exist in mate.
If so, delete those files.

------------------------------------------------------------------------------
Check out the vibrant tech community on one of the world's most
engaging tech sites, Slashdot.org! http://sdm.link/slashdot
_____________________________________________________________________
https://lists.sourceforge.net/lists/listinfo/ltsp-discuss
For additional LTSP help, try #ltsp channel on irc.freenode.net

Joseph Bishay

2017-05-18 20:31:17 UTC

Permalink

Hello Alkis,

I went to the school and followed your recommendation to test changing
the session to xterm fallback and then launching the desktop from
there so I can see the errors. I tried that but the xterm doesn't
launch. Exactly the same error occurs -- it appears to be loading
but then the screen blanks out and then reloads the login screen.

I also wondered if it was an issue with the users and how they were
rsynced. So I used Webmin to delete the users and all their files,
their group, home folders and files. I then imported into webmin a
clean list of users with the correct UID and hashed passwords. The
system correctly created their home directories with the right UID
permissions. I didn't move into it any of their old files. At the
server console I can log into the graphical interface as the user no
problem, but at a fat client I cannot - same issue that it appears to
load, then refreshes and brings up the login screen.

What do you think?

Thank you
Joseph

Post by Alkis Georgopoulos
Check if those users have a ~/.dmrc file from which they select e.g. the
gnome-flashback session, which doesn't exist in mate.
If so, delete those files.

Alkis Georgopoulos

2017-05-19 05:36:27 UTC

Permalink

Hi Joseph,

it sounds like a problem specific to your setup, caused by some
administrative actions. Its troubleshooting may require some time, so
it'd be best if you came to IRC some weekday morning (Greek timezone)
for remote support.

http://ltsp.org/irc

Cheers,
Alkis Georgopoulos

Post by Joseph Bishay
Hello Alkis,
I went to the school and followed your recommendation to test changing
the session to xterm fallback and then launching the desktop from
there so I can see the errors. I tried that but the xterm doesn't
launch. Exactly the same error occurs -- it appears to be loading
but then the screen blanks out and then reloads the login screen.
I also wondered if it was an issue with the users and how they were
rsynced. So I used Webmin to delete the users and all their files,
their group, home folders and files. I then imported into webmin a
clean list of users with the correct UID and hashed passwords. The
system correctly created their home directories with the right UID
permissions. I didn't move into it any of their old files. At the
server console I can log into the graphical interface as the user no
problem, but at a fat client I cannot - same issue that it appears to
load, then refreshes and brings up the login screen.
What do you think?
Thank you
Joseph

Joseph Bishay

2017-05-21 13:30:49 UTC

Permalink

Good day Alkis,

I hope you are doing very well today.

With regards to the situation where users can log into the main server
but cannot log into a thin client, I wanted to follow-up with what you
did.

After you had logged into the server and created the user LTSP using
the command line (instead of Webmin) I went to the school and tested
logging in as the user at a client. The user could not log in. The
same issue arises -- the system seems to be loading the desktop, then
it flashes back to the login screen.

I was also able to activate the VT-x in the BIOS and using Virtual
box, the same problem occurred.

I looked in the directory of the LTSP user that you had created and I
can see, after the failed login attempt the following new item:

Directories:
Desktop
Documents
Downloads
Music
Pictures
Public
Templates
Videos

Files:
.cache
.dbus
.Xauthority
.bash_history
.bash_logout
.bashrc
.profile
.xsession-errors

The only one that seemed relevant was .xsession-errors. The contents
of that file are:

Xsession: X session started for ltsp at Fri May 19 16:50:14 EST 2017
localuser:ltsp being added to access control list
openConnection: connect: No such file or directory
cannot connect to brltty at :0
/etc/X11/Xsession: 3: [: x: unexpected operator
Xsession: X session started for ltsp at Fri May 19 16:58:28 EST 2017
localuser:ltsp being added to access control list
openConnection: connect: No such file or directory
cannot connect to brltty at :0
/etc/X11/Xsession: 3: [: x: unexpected operator

Searching through the logs is throwing up a lot of things because the
username is LTSP! I can create a new user with a more unique name and
try to search the logs again. What else could I do?

Thank you!
Joseph

Post by Alkis Georgopoulos
Hi Joseph,
it sounds like a problem specific to your setup, caused by some
administrative actions. Its troubleshooting may require some time, so
it'd be best if you came to IRC some weekday morning (Greek timezone)
for remote support.
http://ltsp.org/irc
Cheers,
Alkis Georgopoulos