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[Bug 1350357] Re: Support disabling of user switching per seat

 

** Description changed:

- Let me start by saying it's possible I'm missing some subtleties here,
- and if so, I'd be happy to get a more detailed explanation.
+ [Impact]
+ No method of disabling user switching for LightDM. Some system administrators require this. There are methods to disable this inside the session but it is preferrable for a single method of doing this.
  
- In LightDM 1.10.1 (Trusty), unity seats are forced to enable user
- switching (in seat-unity.c).  However, I think this is something that
- should be configurable in the display manager.  In a public computing
- environment, fast-user-switching is undesirable, as it interferes with
- serial re-usability and various cleanup tasks.  Most public computing
- labs want to maintain a 1-1 relationship between individuals and
- workstations, and a workstation should either be in use by one user, or
- not in use at all.  In the past, our site has accomplished this in
- various desktop environment configurations (such as the
- org.gnome.desktop.lockdown gsettings, etc).  Unfortunately, most of
- these settings are ignored in Unity (I have filed separate bugs about
- those).
+ [Test Case]
+ 1. Disable user switching in the LightDM configuration:
+  [SeatDefaults]
+  allow-user-switching=false
+ 2. Start LightDM
+ 3. Log in
+ 4. Attempt to switch user
+ Expected result:
+ User is unable to switch
+ Observed result:
+ Currently not supported - switching is allowed
  
- Obviously, there are workarounds, including stealing all the other VTs,
- or playing stupid D-Bus games, or wrapping X.  Currently, our preferred
- ("preferred") solution is to have our custom greeter check logind and
- refuse to do anything other than unlock the existing session if a user
- is already logged in on an X seat, but that's not ideal, because you
- still end up with a second greeter running, and in fact that becomes the
- primary greeter when the original user logs out.
- 
- That having been said, I believe it is the system administrator's
- prerogative to dictate that there shall be one and only one seat
- available on any given workstation, and instruct LightDM not to spawn
- any additional ones.  It would be great if this was added in future
- releases.   Alternatively, if that's not possible because of Unity
- design, it would be great if there was a way for a greeter to say to
- lightdm "I'm done, this seat is shutting down, switch back to an
- original session."  (And obviously, doing that if there is no other
- session to switch to would be an error).
+ [Regression Potential]
+ There is some risk of unrelated code being changed. This has been reduced by the use of regression tests, manual testing and providing this in the Ubuntu Desktop PPA.

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https://bugs.launchpad.net/bugs/1350357

Title:
  Support disabling of user switching per seat

Status in Light Display Manager:
  Fix Released
Status in Light Display Manager 1.10 series:
  Fix Released
Status in “lightdm” package in Ubuntu:
  Fix Released
Status in “lightdm” source package in Trusty:
  Confirmed
Status in “lightdm” source package in Utopic:
  Fix Released

Bug description:
  [Impact]
  No method of disabling user switching for LightDM. Some system administrators require this. There are methods to disable this inside the session but it is preferrable for a single method of doing this.

  [Test Case]
  1. Disable user switching in the LightDM configuration:
   [SeatDefaults]
   allow-user-switching=false
  2. Start LightDM
  3. Log in
  4. Attempt to switch user
  Expected result:
  User is unable to switch
  Observed result:
  Currently not supported - switching is allowed

  [Regression Potential]
  There is some risk of unrelated code being changed. This has been reduced by the use of regression tests, manual testing and providing this in the Ubuntu Desktop PPA.

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