[Ltsp-discuss] Ubuntu 14.04 ltsp-pnp, lock screen

Discussion:

Antti Hynönen

2015-02-05 15:12:08 UTC

Hi all!

I am using Ubuntu 14.04 ltsp-pnp but lock screen doesn't work on the clients?

Thanks for any advice!

Best regards,
Antti Hynönen
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John Hupp

2015-02-28 00:11:54 UTC

Permalink

Running LTSP-PNP (with ltspfs 1.3-1) on Lubuntu 14.04.2 i386, I'm
looking for elegant handling of flash drives. (Also music/data CD and
DVD discs, but starting with this question.) So far I'm finding this:

With the relevant lts.conf settings at default, and in Lubuntu, giving
regular users permission to mount user-space filesystems (FUSE):

If I insert a USB flash drive into the server, client screens get:
Error: Device /dev/sdb1 is already mounted at
'/media/user1/2cc1-2221'.
They have to OK out of that. All right, not too bad.

If I insert a flash drive into a client, the drive auto-mounts for the
logged in user on that client but it does not prompt to show the drive
in the file manager (as it does on the server, which seems to be the
usual experience). But to come to the most flagrant part of the
problem, if the user tries to unmount the drive, it produces:
Error: umount: /media/user2/usbdisk-sbd1 is not in the fstab (and
you are not root).

Anyone recognize the problem and have a solution?

Vagrant Cascadian

2015-02-28 03:21:58 UTC

Permalink

Post by John Hupp
Running LTSP-PNP (with ltspfs 1.3-1) on Lubuntu 14.04.2 i386, I'm
looking for elegant handling of flash drives. (Also music/data CD and
With the relevant lts.conf settings at default, and in Lubuntu, giving
Error: Device /dev/sdb1 is already mounted at
'/media/user1/2cc1-2221'.
They have to OK out of that. All right, not too bad.

There should be a way to deny user's access to the server's
mounts... not sure what it is exactly. I tend to run headless servers,
so there rarely are any users logging in at the console directly and
plugging in USB sticks and such.

Post by John Hupp
If I insert a flash drive into a client, the drive auto-mounts for the
logged in user on that client but it does not prompt to show the drive
in the file manager (as it does on the server, which seems to be the
usual experience).

You can create hooks in /etc/ltspfs/mounter.d/ that execute on device
insertion and removal, such as:

/usr/share/doc/ltspfs/examples/notify

Post by John Hupp
But to come to the most flagrant part of the
Error: umount: /media/user2/usbdisk-sbd1 is not in the fstab (and
you are not root).

There's a bug reported regarding not being able to unmount:

https://bugs.launchpad.net/ltsp/+bug/1094899

It's essentially a fundamental design issue with the way ltspfs works.
The user's data is mostly kept safe by unmounting the actual drive from
the client side, while the virtual mount point still appears mounted, so
it is safe to remove the drive after a few seconds of inactivity.

But the user experience is unlike the typical workflow of mounting and
unmounting devices manually.

Post by John Hupp
Anyone recognize the problem and have a solution?

If you're running fat clients, I'd suggest trying LOCALDEV=False in
lts.conf and figuring out how to use the "normal" mounting
mechanisms. For thin clients, well...

This is all on the (very long) list of things to reconsider and redesign
for the next major rewrite of LTSP...

live well,
vagrant

John Hupp

2015-03-04 17:28:28 UTC

Permalink

Post by Vagrant Cascadian

You can create hooks in /etc/ltspfs/mounter.d/ that execute on device
/usr/share/doc/ltspfs/examples/notify

Post by John Hupp
But to come to the most flagrant part of the
Error: umount: /media/user2/usbdisk-sbd1 is not in the fstab (and
you are not root).

https://bugs.launchpad.net/ltsp/+bug/1094899
It's essentially a fundamental design issue with the way ltspfs works.
The user's data is mostly kept safe by unmounting the actual drive from
the client side, while the virtual mount point still appears mounted, so
it is safe to remove the drive after a few seconds of inactivity.
But the user experience is unlike the typical workflow of mounting and
unmounting devices manually.

Post by John Hupp
Anyone recognize the problem and have a solution?

If you're running fat clients, I'd suggest trying LOCALDEV=False in
lts.conf and figuring out how to use the "normal" mounting
mechanisms. For thin clients, well...
This is all on the (very long) list of things to reconsider and redesign
for the next major rewrite of LTSP...
live well,
vagrant

Thanks, Vagrant. Those clues were enough to allow me to put together a
pretty decent compromise for the handling of USB storage devices on the
server and on the thin clients for standard users. The solution also
covers data CD's.

But I have never seen the "auto-unmount after a few seconds" statement
in any official documentation. Do you confirm that ltspfs does this for
all devices that it supports?

I still have questions about audio CD's and video DVD's, but I'll treat
that separately.

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Vagrant Cascadian

2015-03-13 19:20:37 UTC

Permalink

Post by John Hupp

Post by Vagrant Cascadian

Post by John Hupp
But to come to the most flagrant part of the
Error: umount: /media/user2/usbdisk-sbd1 is not in the fstab (and
you are not root).

...

Post by John Hupp
But I have never seen the "auto-unmount after a few seconds" statement
in any official documentation. Do you confirm that ltspfs does this for
all devices that it supports?

I've never seen a device where it doesn't behave that way. If there's
something preventing the device from unmounting (e.g. an open file or
directory), it will of course fail to unmount.

Unmounting when idle is briefly mentioned in the ltspfs_umount manpage:

ltspfs_umount is called by ltspfsd(1) when an ltspfs filesystem is no
longer used or idle.

It would seem that ltsp-docs is really in need of updates, after looking
it over briefly...

live well,
vagrant

John Hupp

2015-03-13 20:00:15 UTC

Permalink

Post by Vagrant Cascadian

Post by John Hupp

Post by Vagrant Cascadian

Post by John Hupp
But to come to the most flagrant part of the
Error: umount: /media/user2/usbdisk-sbd1 is not in the fstab (and
you are not root).

...

Post by John Hupp
But I have never seen the "auto-unmount after a few seconds" statement
in any official documentation. Do you confirm that ltspfs does this for
all devices that it supports?

I've never seen a device where it doesn't behave that way. If there's
something preventing the device from unmounting (e.g. an open file or
directory), it will of course fail to unmount.
ltspfs_umount is called by ltspfsd(1) when an ltspfs filesystem is no
longer used or idle.
It would seem that ltsp-docs is really in need of updates, after looking
it over briefly...
live well,
vagrant

Thanks for the confirmation.

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Vagrant Cascadian

2015-02-28 01:58:47 UTC

Permalink

Post by Antti HynÃ¶nen
I am using Ubuntu 14.04 ltsp-pnp but lock screen doesn't work on the clients?

If you have a really recent version of LTSP/LDM, the LDM_HASHPASS=true
option may help with that. Not sure how to re-enable locking on ubuntu,
though.

live well,
vagrant

John Hupp

2015-03-04 21:46:31 UTC

Permalink

In someone's recent thread with subject " Audio CD issues - LTSP
Edubuntu 14.04.1 64-bit," Vagrant replied:

/Audio CDs don't implement a mountable filesystem...//
//
//You could work around this issue by running the Audio CD playing
application as an LTSP localapp.//
//
//Long ago there was a standalone kernel module, maybe called
"cdfs-src", but I don't think it's been maintained in recent years://
//
////http://linux.about.com/cs/linux101/g/cdfssrc.htm//
//
//Another more difficult option would be to write a fuse filesystem that
dynamically transforms audio CDs into .wav files, much like how
"cdfs-src" did it, but probably a little more maintainable.//
/
So for someone like me who can't write a filesystem, and doesn't want to
try an old, unmaintained kernel module (sounds like a recipe for
failure), that left trying:
$ ltsp-localapps audacious

Audacious loaded and was able to play a CD via Services: Play CD. Thanks
for the workaround, Vagrant!

------------------------------------

Concerning video DVD's, I found that on a high-spec thin client, the DVD
was detected but not auto-mounted. (And my newly homemade ltspfs
notifier system was silent, so ltspfs does not support UDF?) I manually
mounted it in the file manager (pcmanfm), then ran VLC and used Open
Disc to select the DVD volume. The DVD ran nicely, even in a full screen.

But on a low-spec client, the DVD was not even detected, much less
auto-mounted.

What is the expected support and behavior with video DVD's?

John Hupp

2015-03-09 20:57:53 UTC

Permalink

Post by Vagrant Cascadian

Post by Antti HynÃ¶nen
I am using Ubuntu 14.04 ltsp-pnp but lock screen doesn't work on the clients?

If you have a really recent version of LTSP/LDM, the LDM_HASHPASS=true
option may help with that. Not sure how to re-enable locking on ubuntu,
though.
live well,
vagrant

I find the same problem on Lubuntu 14.04 with ltsp-pnp.

Trying to investigate, I note that Lubuntu uses the lxlock command to
lock the screen, and this works OK on standalone Lubuntu or on the LTSP
server.

The command is just a simple script located at /usr/bin/lxlock. Contents:
==================================
#!/bin/sh
#
# Try to lock the screen with those applications (in this order) :
# light-locker-command, xscreensaver, gnome-screensaver, slock, xlock,
i3lock and xdg-screensaver

if pidof light-locker >/dev/null; then
light-locker-command -l >/dev/null 2>&1
elif pidof xscreensaver >/dev/null; then
xscreensaver-command -lock >/dev/null 2>&1
elif pidof gnome-screensaver >/dev/null; then
gnome-screensaver-command --lock
elif which slock >/dev/null; then
slock &
elif which xlock 2>/dev/null; then
xlock $*
elif which i3lock >/dev/null; then
i3lock -d
else
# In the end, try to fallback to xscreensaver

# assert: gnome-screensaver is not running
xscreensaver -nosplash >/dev/null 2>&1 &
xscreensaver-command -lock >/dev/null 2>&1
fi
exit 0
==================================

The script finds that light-locker is indeed running and therefore
issues "light-locker-command -l". The output of that when run directly
in the terminal:

(light-locker-command:3417): GLib-CRITICAL **:
g_variant_is_object_path: assertion 'string != NULL' failed

(light-locker-command:3417): GLib-GIO-CRITICAL **:
g_dbus_message_new_method_call: assertion 'g_variant_is_object_path
(path)' failed

** (light-locker-command:3417): WARNING **: Couldn't allocate the
dbus message

==================================

I don't know how to interpret the messages above, but I do also note
that the light-locker-command manpage has this:

DESCRIPTION

light-locker-command is a tool for controlling an already
running
instance of light-locker. This is done though LightDM which
doesn't
ensure light-locker is running.

I note the Description phrase "This is done through LightDM." And now I
see that the light-locker package description also notes that it relies
on LightDM.

So for Lubuntu the issue seems to be that the display manager in use on
the clients is LDM rather than LightDM. Ubuntu also uses LightDM so the
same would apply.

Workarounds??

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Short, Kermit

2015-03-10 22:06:38 UTC

Permalink

I ran into something similar with Xubuntu. The problem seems to be based on multiple daemons running that are responsible for locking the screen. Simply uninstalling light-locker fixed my problem, but we're running gdm as the display manager...this may not be an option for you if you're running light-dm.

--
Kermit Short
Los Alamos National Laboratory

________________________________________
From: John Hupp [***@prpcompany.com]
Sent: Monday, March 09, 2015 2:57 PM
To: ltsp-***@lists.sourceforge.net
Subject: Re: [Ltsp-discuss] Ubuntu 14.04 ltsp-pnp, lock screen

Post by Vagrant Cascadian

Post by Antti HynÃ¶nen
I am using Ubuntu 14.04 ltsp-pnp but lock screen doesn't work on the clients?

If you have a really recent version of LTSP/LDM, the LDM_HASHPASS=true
option may help with that. Not sure how to re-enable locking on ubuntu,
though.
live well,
vagrant

John Hupp

2015-03-14 23:55:39 UTC

Permalink

Post by John Hupp

Post by Vagrant Cascadian

Post by Antti HynÃ¶nen
I am using Ubuntu 14.04 ltsp-pnp but lock screen doesn't work on the clients?

If you have a really recent version of LTSP/LDM, the LDM_HASHPASS=true
option may help with that. Not sure how to re-enable locking on ubuntu,
though.
live well,
vagrant

I find the same problem on Lubuntu 14.04 with ltsp-pnp.
Trying to investigate, I note that Lubuntu uses the lxlock command to
lock the screen, and this works OK on standalone Lubuntu or on the
LTSP server.
==================================
#!/bin/sh
#
# light-locker-command, xscreensaver, gnome-screensaver, slock, xlock,
i3lock and xdg-screensaver
if pidof light-locker >/dev/null; then
light-locker-command -l >/dev/null 2>&1
elif pidof xscreensaver >/dev/null; then
xscreensaver-command -lock >/dev/null 2>&1
elif pidof gnome-screensaver >/dev/null; then
gnome-screensaver-command --lock
elif which slock >/dev/null; then
slock &
elif which xlock 2>/dev/null; then
xlock $*
elif which i3lock >/dev/null; then
i3lock -d
else
# In the end, try to fallback to xscreensaver
# assert: gnome-screensaver is not running
xscreensaver -nosplash >/dev/null 2>&1 &
xscreensaver-command -lock >/dev/null 2>&1
fi
exit 0
==================================
The script finds that light-locker is indeed running and therefore
issues "light-locker-command -l". The output of that when run
g_variant_is_object_path: assertion 'string != NULL' failed
g_dbus_message_new_method_call: assertion 'g_variant_is_object_path
(path)' failed
** (light-locker-command:3417): WARNING **: Couldn't allocate the
dbus message
==================================
I don't know how to interpret the messages above, but I do also note
DESCRIPTION
light-locker-command is a tool for controlling an already
running
instance of light-locker. This is done though LightDM which
doesn't
ensure light-locker is running.
I note the Description phrase "This is done through LightDM." And now
I see that the light-locker package description also notes that it
relies on LightDM.
So for Lubuntu the issue seems to be that the display manager in use
on the clients is LDM rather than LightDM. Ubuntu also uses LightDM
so the same would apply.
Workarounds??

Help me with this idea: I want to modify the lxlock script so that thin
clients will run i3lock (now installed along with light-locker) instead
of futilely trying to run light-locker-command, which won't work under LDM.

I need a new first test in the if chain of lxlock (preceding the
light-locker test) that can detect if this is an LTSP session, and I
tried [[ `ltsp-localapps hostname -s` = ltsp* ]] as a test, but that
failed because hostname is not set up to run as a localapp.

Why won't that work? Or is there another approach that is better?

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by Intel and developed in partnership with Slashdot Media, is your hub for all
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conversation now. http://goparallel.sourceforge.net/
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https://lists.sourceforge.net/lists/listinfo/ltsp-discuss
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