Login screen showing Authentication Failure Switch to greeter...

[Andrew Neeson]

[Impact]

After locking, the login screen shows the message "Authentication Failure" and the user must click "Switch to greeter" to continue.

This SRU fixes the regression introduced in 44e6022, which causes the lock screen to start failing when session switching is involved. This can happen when you unlock the session from LightDM or from the CLI. We need to cancel the authentication in order to ensure that the next one does not fail.

[Test Case]

On a system with LightDM and more than one local user ("bob" and "alice"):
1. Login under bob.
2. Via upper-right menu switch to "alice".
3. On greeter screen select "alice", login under alice.
4. Logout, return to greeter screen.
5. Select bob (already logged in). Enter password.
6. Lock screen.

[Other Info]

This happens mostly after switching user sessions.
Syslog contains entries like:
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 compiz[1877]: WARN 2018-01-06 17:15:42 unity.lockscreen UserPromptView.cpp:500 Failed to start the authentication process. Retrying for 2 time.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Stéphane Charette (stephanecharette)]

Anyone know either the cause, or a solution?

If it helps, the two computers where I'm seeing this also happen to be the two host computers where I run Virtualbox.

[Andrew Neeson (andyrokit)]

My issues began shortly after upgrading from 16.10 -> 17.10. Most of my issues related to graphical components so perhaps it was related to the switch to Wayland?

...as for a fix - I ended up reformatting my machine with a fresh 17.10. Haven't seen any of the issues since.

See: https://bugs.launchpad.net/ubuntu/+source/gnome-control-center/+bug/1733318
for a list of other issues to happen at the same time.

[Eugene Romanenko (eros2)]

Same on 16.04.3 after updating Unity to latest proposed packages.
Also on 17.10 with installed unity-session.

For me, this issue appears after switching to another user.

Steps to reproduce (must be more than one local users on system, eg. "bob", "alice"):
1. Login under bob.
2. Via upper-right menu switch to "alice".
3. On greeter screen setect "alice", login under alice.
4. Logout, return to greeter screen.
5. Select bob (already logged in). Enter password.
6. Lock screen. Issue appeared.
Issue appeared on every screen lock.

Messages in syslog:

Jan 6 17:15:33 eugene-Lenovo-Flex-2-14 systemd[1411]: Stopped Backing Service for the Unity Panel in Lockscreen mode.
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 compiz[1877]: WARN 2018-01-06 17:15:42 unity.lockscreen UserPromptView.cpp:500 Failed to start the authentication process. Retrying for 1 time.
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 compiz[1877]: WARN 2018-01-06 17:15:42 unity.lockscreen UserPromptView.cpp:500 Failed to start the authentication process. Retrying for 2 time.
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 systemd[1411]: Starting Backing Service for the Unity Panel in Lockscreen mode...
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 compiz[1877]: WARN 2018-01-06 17:15:42 unity.glib.dbus.proxy GLibDBusProxy.cpp:487 Calling method "EmitEvent" on object path: "/com/ubuntu/Upstart" failed: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name com.canonical.Unity.Test.Upstart was not provided by any .service files
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 systemd-prestart-check[3804]: grep: /usr/share/gnome-session/sessions/ubuntu.session: Нет такого файла или каталога
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 systemd[1411]: Started Backing Service for the Unity Panel in Lockscreen mode.
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 systemd[1411]: Reached target A target that, when running, represents the screen being locked.
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 compiz[1877]: WARN 2018-01-06 17:15:42 unity.lockscreen UserPromptView.cpp:500 Failed to start the authentication process. Retrying for 3 time.
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 compiz[1877]: WARN 2018-01-06 17:15:42 unity.lockscreen UserPromptView.cpp:500 Failed to start the authentication process. Retrying for 4 time.
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 compiz[1877]: WARN 2018-01-06 17:15:42 unity.lockscreen UserPromptView.cpp:500 Failed to start the authentication process. Retrying for 5 time.

[hife (hife)]

Same as Eugene, the problem started popping up after upgrading Unity. When I lock my screen or wake from suspend, I get the described behaviour.

As a temporary fix, is there a way to just skip that screen and always go to the greeter when locking the screen or suspending?

[hife (hife)]

P.S.: To be precise, the message I get is not "Authentication failed", but "Authentication failure". This may be related to my system language being German.

[Luis Alberto Pabón (copong)]

I'm seeing this also upon 17.10 upgrade in unity / lightdm / unity greeter.

It doesn't happen 100% of the time, typically takes some time time to manifest (I only ever suspend my laptop from monday to friday), but once it starts happening, it always happens until I shut down.

[Eugene Romanenko (eros2)]

Appears on 16.04.3 after updating Unity to latest packages.
Also on 17.10 with installed unity-session.

For me, this issue appears after switching to another user.

Steps to reproduce (must be more than one local users on system, eg. "bob", "alice"):
1. Login under bob.
2. Via upper-right menu switch to "alice".
3. On greeter screen setect "alice", login under alice.
4. Logout, return to greeter screen.
5. Select bob (already logged in). Enter password.
6. Lock screen. Issue appeared.
Issue appeared on every screen lock.

Messages in syslog:

Jan 6 17:15:33 eugene-Lenovo-Flex-2-14 systemd[1411]: Stopped Backing Service for the Unity Panel in Lockscreen mode.
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 compiz[1877]: WARN 2018-01-06 17:15:42 unity.lockscreen UserPromptView.cpp:500 Failed to start the authentication process. Retrying for 1 time.
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 compiz[1877]: WARN 2018-01-06 17:15:42 unity.lockscreen UserPromptView.cpp:500 Failed to start the authentication process. Retrying for 2 time.
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 systemd[1411]: Starting Backing Service for the Unity Panel in Lockscreen mode...
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 compiz[1877]: WARN 2018-01-06 17:15:42 unity.glib.dbus.proxy GLibDBusProxy.cpp:487 Calling method "EmitEvent" on object path: "/com/ubuntu/Upstart" failed: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name com.canonical.Unity.Test.Upstart was not provided by any .service files
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 systemd-prestart-check[3804]: grep: /usr/share/gnome-session/sessions/ubuntu.session: Нет такого файла или каталога
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 systemd[1411]: Started Backing Service for the Unity Panel in Lockscreen mode.
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 systemd[1411]: Reached target A target that, when running, represents the screen being locked.
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 compiz[1877]: WARN 2018-01-06 17:15:42 unity.lockscreen UserPromptView.cpp:500 Failed to start the authentication process. Retrying for 3 time.
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 compiz[1877]: WARN 2018-01-06 17:15:42 unity.lockscreen UserPromptView.cpp:500 Failed to start the authentication process. Retrying for 4 time.
Jan 6 17:15:42 eugene-Lenovo-Flex-2-14 compiz[1877]: WARN 2018-01-06 17:15:42 unity.lockscreen UserPromptView.cpp:500 Failed to start the authentication process. Retrying for 5 time.

[Eugene Romanenko (eros2)]

Screenshot from virtualbox test install.

[Khurshid Alam (khurshid-alam)]

Something to do with pam. But this is only happening in 16.04...I can't reproduce on bionic (https://code.launchpad.net/~azzar1/unity/pam-logging-xenial)

[Garcia David (davidgfolch)]

For me, in an Ubuntu 16.04, happends every time I lock (or my laptot sleeps) and the login screen appears. It seems that it happends since I've installed virtualbox 5.4?

[Eugene Romanenko (eros2)]

> It seems that it happends since I've installed virtualbox 5.4?

Sure no, it just since latest unity update was landed in 16.04.

[Eugene Romanenko (eros2)]

> only happening in 16.04...I can't reproduce on bionic

In artful and bionic this issue reproduceable if lightdm used as display manager.

[Jonathan Eckstein (jonathan.eckstein)]

This just started happening to me in 16.04 LTS. Not fatal, but annoying.

FYI, I use a KVM switch on one of two monitors connected to Ubuntu.

[Georgi Tsenov (georgi-tsenov-90)]

This started happening to me after the following scenario:
- I had account for my wife, created on the machine, but she has not used it ever.
- today she logged in with her account.
- after she logged out the bug was present, when I attempted to log in.
Now when I Lock/Switch Account the bug is produced.

[Eugene Romanenko (eros2)]

Sometimes I think Unity developers never use Unity actually, as this issue immediately visible when you share home PC with wife and children (assuming they have separate accounts).

[Khurshid Alam (khurshid-alam)]

@Eugene

It depends on the hardware/graphics. But as I said, I can't reproduce it on bionic (bionic has different unity/lightdm version). Can you reproduce it in a live iso?

[Eugene Romanenko (eros2)]

> It depends on the hardware/graphics.

Sure, no. I tested and have this issue on home PC (16.04.3 after latest Unity update, AMD Phenom CPU/Nvidia GPU), work PC (17.10, Intel i7/Intel), Lenovo flex laptop (17.10, intel i5), and of course in VirtualBox (16.04.3 fresh install with latest updates, 18.04).

> But as I said, I can't reproduce it on bionic (bionic has different unity/lightdm version). Can you reproduce it in a live iso?

Not tried live iso, but I have test box with up-to-date 18.04. Just two days ago I tried:

Added second user account;
sudo apt install unity-session lightdm
sudo apt purge ubuntu-session gnome-shell gdm3

Reboot, login as first user, start second user session, end session, return to first user session, lock screen - issue here.

Bionic live iso does not have unity and lightdm preinstalled, so them will be downloaded from repository anyway.

[Garcia David (davidgfolch)]

In my case, I've installed virtualbox-dkms 32bits, in host "Ubuntu 16 64bits", instead than in the virtualbox hosted "Ubuntu 16 32bits"

When I've removed those 32bits libs the problem disappeared.

[Roberto Ribeiro de Avillez (roberto-avillez)]

It started to happen to my laptop today after I did an upgrade.

Ubuntu 16.04.

4.13.0-36-generic #40~16.04.1-Ubuntu SMP Fri Feb 16 23:25:58 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

Start-Date: 2018-02-24 14:43:33
Commandline: apt dist-upgrade
Requested-By: avillez (1000)
Upgrade: libpulsedsp:amd64 (1:8.0-0ubuntu3.7, 1:8.0-0ubuntu3.8), grub-common:amd
64 (2.02~beta2-36ubuntu3.16, 2.02~beta2-36ubuntu3.17), pulseaudio:amd64 (1:8.0-0
ubuntu3.7, 1:8.0-0ubuntu3.8), google-chrome-stable:amd64 (64.0.3282.167-1, 64.0.3282.186-1), python-apt-common:amd64 (1.1.0~beta1build1, 1.1.0~beta1ubuntu0.16.04.1), grub2-common:amd64 (2.02~beta2-36ubuntu3.16, 2.02~beta2-36ubuntu3.17), grub-pc:amd64 (2.02~beta2-36ubuntu3.16, 2.02~beta2-36ubuntu3.17), grub-pc-bin:amd64 (2.02~beta2-36ubuntu3.16, 2.02~beta2-36ubuntu3.17), ubuntu-drivers-common:amd64 (1:0.4.17.3, 1:0.4.17.6), python3-distupgrade:amd64 (1:16.04.23, 1:16.04.24), libpulse0:amd64 (1:8.0-0ubuntu3.7, 1:8.0-0ubuntu3.8), ubuntu-release-upgrader-core:amd64 (1:16.04.23, 1:16.04.24), libpulse-mainloop-glib0:amd64 (1:8.0-0ubuntu3.7, 1:8.0-0ubuntu3.8), pulseaudio-module-x11:amd64 (1:8.0-0ubuntu3.7, 1:8.0-0ubuntu3.8), ubuntu-release-upgrader-gtk:amd64 (1:16.04.23, 1:16.04.24), pulseaudio-module-bluetooth:amd64 (1:8.0-0ubuntu3.7, 1:8.0-0ubuntu3.8), pulseaudio-utils:amd64 (1:8.0-0ubuntu3.7, 1:8.0-0ubuntu3.8), python3-apt:amd64 (1.1.0~beta1build1, 1.1.0~beta1ubuntu0.16.04.1), base-files:amd64 (9.4ubuntu4.5, 9.4ubuntu4.6)
End-Date: 2018-02-24 14:44:44

[Hendri Schoeman (hendrisch)]

I can confirm the same is also happening on my notebook.
Everything was fine up to about 2-3 weeks ago.

```
hendri@neptune: ~$ cat /etc/issue
Ubuntu 16.04.4 LTS \n \l
```

OS: Ubuntu 16.04.4 ... all up to date
Hardware:
 Gigabyte P15 Notebook
 - Graphics - nVidida GTX 950M + Intel (Dual graphics)
 - Processor - i7-7700HQ
 - HDD 1 - Standard 1 TB HDD
 - HDD 2 - 950 Evo m.2 SSD
 - 8GB mem
Graphics driver - nVidia 384.111

I reckon it has something to do with the nVidia Driver.

[NULL (krush206)]

I can confirm this bug occurs with me aswell, though, I was doing some maintenance in my computer yesterday and after replugging the power cable of the monitor, instead of plugging it in my voltage stabilizer, I plugged it in the computer's power supply, after using Ubuntu for awhile, I locked the screen and noticed the bug was gone, Im not sure why this worked but this was the workaround I (mistakenly) found

[Nick Williams (rogwilco)]

I started encountering this issue also. My system was working fine up until yesterday when this started happening. I most often notice it when I connect my laptop to an external display (or make some other display related change that kicks me to the login prompt).

[Silvia (fichera-sil)]

I have this problem starting from today when I locked my laptop with win+L.

Description: Ubuntu 16.04.4 LTS
Release: 16.04
Codename: xenial

[Rubens (rhkina)]

Same issue!
Ubuntu: 16.04 LTS

[R_volkmann (r-volkmann)]

Same for me since last unity update and is very annoying

- CPU: i8700k
- Geforce 1060
- no Virtualbox installed
- multi-user
- English languade, German keyboard

[Bodinux (bodinux)]

I confirm the occurrence of this bug since yesterday.

[Alexander (azol)]

Confirming the same issue, Ubuntu: 16.04 LTS
Just began to experience it after last batch of system updates.

[P.Constantine (pconstantine)]

Mar 11 22:50:23 lenovo lightdm[1216]: ** (lightdm:1216): WARNING **: Error using VT_WAITACTIVE 7 on /dev/tty0: Interrupted system call
Mar 11 22:50:23 lenovo org.gtk.vfs.Daemon[11625]: A connection to the bus can't be made

[B@MB@M (bart-bamweb)]

I have the same issue.

I have Virtualbox running as well.
I'm not switching between users. Just standby and resume.

Here are some parts of several logfiles.

auth.log
======================================
Mar 12 16:36:33 BN pkexec: pam_systemd(polkit-1:session): Cannot create session: Already running in a session
Mar 12 16:36:33 BN pkexec[20336]: bart: Executing command [USER=root] [TTY=unknown] [CWD=/home/bart] [COMMAND=/usr/lib/unity-settings-daemon/usd-backlight-helper --set-brightness 7126]
Mar 12 16:36:45 BN lightdm: PAM unable to dlopen(pam_kwallet.so): /lib/security/pam_kwallet.so: cannot open shared object file: No such file or directory
Mar 12 16:36:45 BN lightdm: PAM adding faulty module: pam_kwallet.so
Mar 12 16:36:45 BN lightdm: PAM unable to dlopen(pam_kwallet5.so): /lib/security/pam_kwallet5.so: cannot open shared object file: No such file or directory
Mar 12 16:36:45 BN lightdm: PAM adding faulty module: pam_kwallet5.so
Mar 12 16:36:45 BN lightdm: pam_unix(lightdm-greeter:session): session opened for user lightdm by (uid=0)
Mar 12 16:36:45 BN systemd-logind[1178]: New session c32 of user lightdm.
Mar 12 16:36:45 BN lightdm: PAM unable to dlopen(pam_kwallet.so): /lib/security/pam_kwallet.so: cannot open shared object file: No such file or directory
Mar 12 16:36:45 BN lightdm: PAM adding faulty module: pam_kwallet.so
Mar 12 16:36:45 BN lightdm: PAM unable to dlopen(pam_kwallet5.so): /lib/security/pam_kwallet5.so: cannot open shared object file: No such file or directory
Mar 12 16:36:45 BN lightdm: PAM adding faulty module: pam_kwallet5.so
Mar 12 16:36:45 BN lightdm: pam_succeed_if(lightdm:auth): requirement "user ingroup nopasswdlogin" not met by user "bart"
Mar 12 16:36:49 BN lightdm: pam_unix(lightdm-greeter:session): session closed for user lightdm
Mar 12 16:36:49 BN dbus[1153]: [system] Rejected send message, 2 matched rules; type="method_call", sender=":1.498" (uid=109 pid=20527 comm="/usr/lib/x86_64-linux-gnu/indicator-bluetooth/indi") interface="org.freedesktop.DBus.Properties" member="GetAll" error name="(unset)" requested_reply="0" destination=":1.380" (uid=0 pid=10380 comm="/usr/lib/bluetooth/bluetoothd ")
Mar 12 16:36:49 BN dbus[1153]: [system] Rejected send message, 2 matched rules; type="method_call", sender=":1.498" (uid=109 pid=20527 comm="/usr/lib/x86_64-linux-gnu/indicator-bluetooth/indi") interface="org.freedesktop.DBus.ObjectManager" member="GetManagedObjects" error name="(unset)" requested_reply="0" destination="org.bluez" (uid=0 pid=10380 comm="/usr/lib/bluetooth/bluetoothd ")
Mar 12 16:37:15 BN sudo: bart : TTY=pts/22 ; PWD=/home/bart ; USER=root ; COMMAND=/usr/bin/zsh
Mar 12 16:37:15 BN sudo: pam_unix(sudo:session): session opened for user root by (uid=0)
Mar 12 16:38:58 BN pkexec: pam_unix(polkit-1:session): session opened for user root by (uid=1000)
Mar 12 16:38:58 BN pkexec: pam_systemd(polkit-1:session): Cannot create session: Already running in a session
Mar 12 16:38:58 BN pkexec[22237]: bart: Executing command [USER=root] [TTY=unknown] [CWD=/home/bart] [COMMAND=/usr/lib/update-notifier/package-system-locked]

Xorg.0.log
======================================
[ 23362.625] (II) AIGLX: Suspendi...

[B@MB@M (bart-bamweb)]

this is a 16.04 system

$ lsb_release -a
LSB Version: core-9.20160110ubuntu0.2-amd64:core-9.20160110ubuntu0.2-noarch:printing-9.20160110ubuntu0.2-amd64:printing-9.20160110ubuntu0.2-noarch:security-9.20160110ubuntu0.2-amd64:security-9.20160110ubuntu0.2-noarch
Distributor ID: Ubuntu
Description: Ubuntu 16.04.4 LTS
Release: 16.04
Codename: xenial

[DeltaLima (Marcus) (dlm274)]

same here, experiencing this until 2018-03-08 on my DellXPS 13 with latest i7 gen. (8.).
i have not done some debugging, but at this date the unity package was updated:

2018-03-08 09:35:13 upgrade unity:amd64 7.4.5+16.04.20171201.3 7.4.5+16.04.20180221-0ubuntu1

root@Atomrakete:~# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 16.04.4 LTS
Release: 16.04
Codename: xenial

It happens to me when i lock my screen with win+l

logfiles needed by someone?

[Edu (eduweb)]

Same issue in my laptop Lenovo G40-80 I think after some apt-get update/upgrade it has started. (Between 2 or 3 weeks ago)

I'm the only user of this computer. There is only my user and admin is disabled.
I use Virtual Box and it was upgraded recently to Version 5.1.34 r121010 (Qt5.5.1).

If I lock screen it don't happens immediately. It happens only after screen goes blank.
Then I have to click on "switch to greeter" in password field and wait some seconds to screen changes and I be able to insert password.

# lsb_release -a
LSB Version: core-9.20160110ubuntu0.2-amd64:core-9.20160110ubuntu0.2-noarch:printing-9.20160110ubuntu0.2-amd64:printing-9.20160110ubuntu0.2-noarch:security-9.20160110ubuntu0.2-amd64:security-9.20160110ubuntu0.2-noarch
Distributor ID: Ubuntu
Description: Ubuntu 16.04.4 LTS
Release: 16.04
Codename: xenial

[Axl Mattheus (axler8r)]

Replaced my hostname with ...hostname... and user name with ...user...

auth.log says:

Mar 13 16:59:10 ...hostname... lightdm: PAM unable to dlopen(pam_kwallet.so): /lib/security/pam_kwallet.so: cannot open shared object file: No such file or directory
Mar 13 16:59:10 ...hostname... lightdm: PAM adding faulty module: pam_kwallet.so
Mar 13 16:59:10 ...hostname... lightdm: PAM unable to dlopen(pam_kwallet5.so): /lib/security/pam_kwallet5.so: cannot open shared object file: No such file or directory
Mar 13 16:59:10 ...hostname... lightdm: PAM adding faulty module: pam_kwallet5.so
Mar 13 16:59:10 ...hostname... lightdm: pam_unix(lightdm-greeter:session): session opened for user lightdm by (uid=0)
Mar 13 16:59:10 ...hostname... systemd-logind[1033]: New session c6 of user lightdm.
Mar 13 16:59:10 ...hostname... lightdm: PAM unable to dlopen(pam_kwallet.so): /lib/security/pam_kwallet.so: cannot open shared object file: No such file or directory
Mar 13 16:59:10 ...hostname... lightdm: PAM adding faulty module: pam_kwallet.so
Mar 13 16:59:10 ...hostname... lightdm: PAM unable to dlopen(pam_kwallet5.so): /lib/security/pam_kwallet5.so: cannot open shared object file: No such file or directory
Mar 13 16:59:10 ...hostname... lightdm: PAM adding faulty module: pam_kwallet5.so
Mar 13 16:59:10 ...hostname... lightdm: pam_succeed_if(lightdm:auth): requirement "user ingroup nopasswdlogin" not met by user "...user..."
Mar 13 16:59:16 ...hostname... lightdm: pam_unix(lightdm-greeter:session): session closed for user lightdm

[Erik Meitner (e.meitner)]

I have this problem after installing updates yesterday. Looks like like how Eugene shows in comment #10.

The attachment contains the data logged in x-0.log, seat0-greeter.log, lightdm.log, and x-1.log in the /var/log/lightdm directory during a test. I pressed CTRL-ALT-L, waited 10 seconds, clicked "Switch to greeter...", waited 10 seconds, then logged in and stopped recording.

There is a DBus error, but not much else.

[WirelessMoves (gsmumts)]

Same here, happens since I installed updates on my 16.04 system yesterday. Never had this before. Uisng STRG-L to lock the screen frequently.

[WirelessMoves (gsmumts)]

Addition: Here are the packages that were updated. After this update the problem appeared on my 16.04 LTE system:

Log started: 2018-03-14 06:45:32
(Reading database ... 253390 files and directories currently installed.)
Preparing to unpack .../python-samba_2%3a4.3.11+dfsg-0ubuntu0.16.04.13_amd64.deb ...
Unpacking python-samba (2:4.3.11+dfsg-0ubuntu0.16.04.13) over (2:4.3.11+dfsg-0ubuntu0.16.04.12) ...
Preparing to unpack .../samba-common-bin_2%3a4.3.11+dfsg-0ubuntu0.16.04.13_amd64.deb ...
Unpacking samba-common-bin (2:4.3.11+dfsg-0ubuntu0.16.04.13) over (2:4.3.11+dfsg-0ubuntu0.16.04.12) ...
Preparing to unpack .../smbclient_2%3a4.3.11+dfsg-0ubuntu0.16.04.13_amd64.deb ...
Unpacking smbclient (2:4.3.11+dfsg-0ubuntu0.16.04.13) over (2:4.3.11+dfsg-0ubuntu0.16.04.12) ...
Preparing to unpack .../samba-libs_2%3a4.3.11+dfsg-0ubuntu0.16.04.13_amd64.deb ...
Unpacking samba-libs:amd64 (2:4.3.11+dfsg-0ubuntu0.16.04.13) over (2:4.3.11+dfsg-0ubuntu0.16.04.12) ...
Preparing to unpack .../libwbclient0_2%3a4.3.11+dfsg-0ubuntu0.16.04.13_amd64.deb ...
Unpacking libwbclient0:amd64 (2:4.3.11+dfsg-0ubuntu0.16.04.13) over (2:4.3.11+dfsg-0ubuntu0.16.04.12) ...
Preparing to unpack .../libsmbclient_2%3a4.3.11+dfsg-0ubuntu0.16.04.13_amd64.deb ...
Unpacking libsmbclient:amd64 (2:4.3.11+dfsg-0ubuntu0.16.04.13) over (2:4.3.11+dfsg-0ubuntu0.16.04.12) ...
Preparing to unpack .../samba-common_2%3a4.3.11+dfsg-0ubuntu0.16.04.13_all.deb ...
Unpacking samba-common (2:4.3.11+dfsg-0ubuntu0.16.04.13) over (2:4.3.11+dfsg-0ubuntu0.16.04.12) ...
Preparing to unpack .../update-notifier_3.168.8_amd64.deb ...
Unpacking update-notifier (3.168.8) over (3.168.7) ...
Preparing to unpack .../update-notifier-common_3.168.8_all.deb ...
Unpacking update-notifier-common (3.168.8) over (3.168.7) ...
Preparing to unpack .../libapparmor1_2.10.95-0ubuntu2.9_amd64.deb ...
Unpacking libapparmor1:amd64 (2.10.95-0ubuntu2.9) over (2.10.95-0ubuntu2.8) ...
Processing triggers for man-db (2.7.5-1) ...
Processing triggers for libc-bin (2.23-0ubuntu10) ...
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Processing triggers for libglib2.0-0:amd64 (2.48.2-0ubuntu1) ...
Setting up libapparmor1:amd64 (2.10.95-0ubuntu2.9) ...
Processing triggers for libc-bin (2.23-0ubuntu10) ...
(Reading database ... 253390 files and directories currently installed.)
Preparing to unpack .../libgcrypt20_1.6.5-2ubuntu0.4_amd64.deb ...
Unpacking libgcrypt20:amd64 (1.6.5-2ubuntu0.4) over (1.6.5-2ubuntu0.3) ...
Processing triggers for libc-bin (2.23-0ubuntu10) ...
Setting up libgcrypt20:amd64 (1.6.5-2ubuntu0.4) ...
Processing triggers for libc-bin (2.23-0ubuntu10) ...
(Reading database ... 253390 files and directories currently installed.)
Preparing to unpack .../libapparmor-perl_2.10.95-0ubuntu2.9_amd64.deb ...
Unpacking libapparmor-perl (2.10.95-0ubuntu2.9) over (2.10.95-0ubuntu2.8) ...
Preparing to unpack .../apparmor_2.10.95-0ubuntu2.9_amd64.deb ...
Unpacking apparmor (2.10.95-0ubuntu2.9) over (2.10.95-0ubuntu2.8) ...
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Unpacking friendly-recovery (0.2.31ubuntu1) over (0.2.31) ...
Preparing to unpack...

[john rogers (0-john-m)]

I had this on my 16.04 system and it was INFURIATING - was taking 30s or so to login after a lock screen.
I *think* I've found a workaround...
Changing the driver to neuveu reboot ( deal with the failure to detect resolution if needed )
change back to nvidia driver reboot
back to normal :) ( for the last 3 locks at least... fingers crossed!

[WirelessMoves (gsmumts)]

Update to #37 and #38 reporting the issue on 16.04 LTS: The issue went away as silently as it initially came. Ran another apt update/upgrade today, totally different packages updated and then rebooted. 'Authentication Failure' in the lock screen is now gone, even after several reboots.

For completeness here are the packages that updated, I don't see a comonality here.:

Start-Date: 2018-03-14 21:25:36
Commandline: apt upgrade
Requested-By: martin (1000)
Install: linux-image-extra-4.13.0-37-generic:amd64 (4.13.0-37.42~16.04.1, automatic), linux-headers-4.13.0-37-generic:amd64 (4.13.0-37.42~16.04.1, automatic), linux-headers-4.13.0-37:amd64 (4.13.0-37.42~16.04.1, automatic), linux-image-4.13.0-37-generic:amd64 (4.13.0-37.42~16.04.1, automatic)
Upgrade: unity-control-center-faces:amd64 (15.04.0+16.04.20170214-0ubuntu2, 15.04.0+16.04.20171130-0ubuntu1), linux-image-generic-hwe-16.04:amd64 (4.13.0.36.55, 4.13.0.37.56), linux-generic-hwe-16.04:amd64 (4.13.0.36.55, 4.13.0.37.56), unity-control-center:amd64 (15.04.0+16.04.20170214-0ubuntu2, 15.04.0+16.04.20171130-0ubuntu1), firefox-locale-en:amd64 (58.0.2+build1-0ubuntu0.16.04.1, 59.0+build5-0ubuntu0.16.04.1), libunity-control-center1:amd64 (15.04.0+16.04.20170214-0ubuntu2, 15.04.0+16.04.20171130-0ubuntu1), firefox:amd64 (58.0.2+build1-0ubuntu0.16.04.1, 59.0+build5-0ubuntu0.16.04.1), linux-headers-generic-hwe-16.04:amd64 (4.13.0.36.55, 4.13.0.37.56)
End-Date: 2018-03-14 21:26:48

[Khurshid Alam (khurshid-alam)]

From a fresh updated system run:

gdbus call -e -d com.canonical.indicator.session -o /com/canonical/indicator/session -m org.gtk.Actions.Activate "switch-to-greeter" "[]" "{}"

It will switch to greeter, login and then lock the screen (Ctrl+Alt+L). Does the lock-screen show the "Authentication Error" ?

[Magnus (magnusem)]

The lock-screen shows the "Authentication Error" for me after following your instructions.

[Igor (igorekz)]

To #41

No, in my case, lock screen doesn't show "Authentication Failure, Switch to Greeter" error after running the command you provided.

But it still shows this error if I just press Win+L to lock the computer or after it's being locked automatically.

This problem only happens when at least two users logged to computer even if one of them will logout later.

[hilault (lolo120916)]

Same bug appeared also on my home machine with two active accounts

[Jim Campbell (jwcampbell)]

I'm not certain that this is due to multiple user accounts.

This bug has appeared on a coworker's system which has only one user account. His session locked due to meeting the regular idle timeout threshold, and he saw this greeter message when going to log back in.

[Shlomo Bachar (shlomo-bachar)]

This bug started to appear to me today suddenly.
It appears every time that my laptop wakes up from suspend.
I didn't do anything special. Maybe some update to system.
I have Ubuntu 16.04.4 LTS with GNOME (together with Unity, although I don't use Unity so much).
My laptop is ASUS V301L.

[Konstantin Boyandin (7-det-g)]

Confirming the bug in Ubuntu 16.04.4 (64-bit). Started to happen approx. 2 days ago, after recent standard updates have been applied.

I do not switch user sessions/whatever, use single account. Yet after screensaver locks the screen, the "Authentication failure - Switch to greeter" is always shown, even if I didn't tried to unlock the screen.

Extremely annoying.

[Alex (phat0msp1ke)]

I use Ubuntu 16.04.4 LTS and have exactly the same problem.

I recently added a new user account and keep getting this message:

 "Authentication failure - Switch to greeter" upon log-in

Any tips how to resolve this will be greatly appreciated.

[Jim Campbell (jwcampbell)]

Users at my workplace who experienced this issue are reporting that updating all packages and restarting / rebooting has resolved the issue for them, even after repeated screen locks and login-logouts.

[Shlomo Bachar (shlomo-bachar)]

Update:
After restarting, the bug disappeared!

[Sam Stenvall (negge)]

I also started experiencing this issue some time ago. My dad was visiting and used the guest session and after that it started happening, although I'm not 100% sure if it was incidental or not.

Rebooting helps for some time, but after a day or two the issue is back.

[Shlomo Bachar (shlomo-bachar)]

After a few days without the bug, today it reappeared again.

[nrao (nagamalli-s)]

Facing the same issue for a week now. I am on Ubuntu 16.10.

[fagin (faginp)]

Same issue. It's been occurring for a couple of weeks. It's unrelated to me updating anything. I don't have Virtualbox, Playonlinux or anything. It comes and goes. This morning I step away from my computer, no anomolies when screen locks. This afternoon, it's happening again. I made no updates.

[Abdhul Lathif Riswan (malriswan)]

I am facing this issue too. It happened when I tried to lock my screen(Win+L).

I was using Chrome when the issue happened, the system would not respond to the above command initially. I clicked on the screen(the bookmark pop was open) a few times and tried the command again and it finally got locked.

When I tried to unlock my system I saw the terminal for a few seconds before the login screen. This happens everytime when I try to unlock the screen now.

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 16.04.4 LTS
Release: 16.04
Codename: xenial

[Nemanja V (vooxo)]

Experiencing the same thing on Ubuntu 16.04.4 LTS for some time (maybe a week) now.

I'm doing updates regularly.

[Nathan Fox (foxthatruns)]

This exact issue started happening to me a couple days ago. I didn't notice any apparent cause. When I click or press any key, the screen goes black for a second, then reloads with a system alert sound to the normal login screen. After a successful login, the screen flashes the "Switch to Greeter" screenshot that was attached to the original bug before successfully logging in.

__uname__
Kernel: Linux
Kernel Release: 4.13.0-38-generic
Kernel Version: #43~16.04.1-Ubuntu SMP Wed Mar 14 17:48:43 UTC 2018
Network Node Hostname: redgray
Machine Hardware Name: x86_64
Processor: x86_64
Hardware Platform: x86_64
Operating System: GNU/Linux 16.04.4 LTS

[Jorge (jorgarti)]

This went away after a reboot a few days ago but today it has appeared again. Yesterday it was working fine. No updates whatsoever between yesterday and today. Plus, the bug prevents me from login remotely through NoMachine NX.

[Edward Fjellskål (ebf0)]

This bug is really annoying!

btw, I run VMware® Workstation 12 Pro, 12.5.9 build-7535481.

My host:
Distributor ID: Ubuntu
Description: Ubuntu 16.04.4 LTS
Release: 16.04
Codename: xenial

Linux desktop 4.13.0-38-generic #43~16.04.1-Ubuntu SMP Wed Mar 14 17:48:43 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

The bug does not show it self before some days of uptime.

But then, every time the screen locks, I get this. At first, I could not find a work around, and all my VMs crashed hard, which costs me a lot of time, rebooting and booting all the VMs and starting all the apps I run and use daily.

For some reason, for me, hitting CTRL+ALT+ENTER gets me back to the original login screen, and I can unlock the screen, and continue.

Hope that upgrading to 18.04 soon might save the day!

[Antonin Chambolle (antonin-chambolle)]

Same as everyone, #12 for instance. Appears each time I lock.

But it hasn't occurred to anyone that this could be some kind of phishing technique?
Very often I start typing my password (or half of it) before realizing I have to click to switch to greeter, and in the meantime this screen is getting the input... There might well be some malicious code in one of the recent updates...

[sugunakar (sugunaker)]

I too have same problem. It just started in this week. I am using Ubuntu 16.04 version.

[Ibrahim Omar (ibom12)]

Same on 16.04 after updating Unity to latest proposed packages.

[Gunnar Grímsson (gunnar.grimsson)]

Same here, either after updating Ubuntu 16.04 or after installing Virtualbox. Just started this week.

[Matt Robinson (izoprene)]

Same here, Ubuntu 16.04.4. If I close the lid to put my DELL E6230 into sleep, upon opening the lid and bringing it out of sleep, it says 'Switch to greeter' message, same as OP.

Last system updates I actioned was installing security updates for the Wayland Compositor (Binary utilities & dev files). It also installed updates for Avahi (client library, common data files, common library & GObject library).

[Glide (gprod-net+ubuntu)]

Mostly same thing here with a brand new install.
It began to happen not long after I added an account for my wife.
The "Authentication failure" (on a separate login screen) systematically appears when I lock my screen with <Meta>+L (or selecting Lock/Switch Account...)

[Rael Gugelmin Cunha (rael-gc)]

Wondering if this issue is a side effect of fix for https://bugs.launchpad.net/ubuntu/+source/unity/+bug/1311316

[Gunnar Grímsson (gunnar.grimsson)]

Updated just now and rebooted and it seems to be fixed, just a normal login prompt. FYI :)

[sugunakar (sugunaker)]

I got the same problem. But now it is working fine after disabling guest account as mentioned in the below article

https://askubuntu.com/questions/62564/how-do-i-disable-the-guest-session

[Ismandra Eka Nugraha (icanhcorpse)]

Got the same issue. Disabling guest account seems not worked https://askubuntu.com/questions/62564/how-do-i-disable-the-guest-session

[Jim Campbell (jwcampbell)]

i don't think disabling the "guest session" session is part of the issue, as we have that disabled and are still experiencing the problem.

[Igor (igorekz)]

Kind of workaround until this annoying bug will be fixed.
This is for thouse who has this problem with multiple accounts.

1. Logout from all accounts or reboot the computer.
2. Login to first account.
3. Click the gear icon near clock in top-left corner of top bar, select second account in menu and login.

Never use the gear icon menu to change account again or you will get 'Authentication failure' error after next desktop locking.

Just switch between accounts pressing Ctrl-Alt-F7 and Ctrl-Alt-F8. You can lock the desktops with Ctrl-Alt-L or Win-L as usual.

Can you confirm that it works?

[Igor (igorekz)]

Sorry, top-right corner of the top bar of course.

[Alex Whitney (whitneyas)]

This seems to be happening to me when my screens locks from timeout and I come back.

[Tao Zhang (agmao)]

Same problem here. Sometimes after this occurs, I cannot even log in, have to restart the system.

[Aleksander Kamenik (aleksander.kamenik)]

> This seems to be happening to me when my screens locks from timeout and I come back.

Me too.

I started getting this problem about a week ago after the usual updates. Ubuntu 16.04 LTS. I have only one account I use, pretty much defaults everything. I do use Virtualbox though I get the problem without ever even starting the Virtualbox console after a restart.

unity 7.4.5+16.04.20180221-0ubuntu1
unity-greeter 16.04.2-0ubuntu1

However when I check apt history the last time unity packages were upgraded was 2018-03-06, at least a month earlier. (/var/log/apt/history.log*)

What packages could have caused this? I unfortunately don't have an exact date when this problem started and I think I postponed restarting the computer for many days when the updater was nagging me to restart last week.

[Rod Waltermann (roddw2)]

I have this problem, and found a thread here:
https://askubuntu.com/questions/584207/cannot-log-in-at-locked-screensaver-must-log-in-with-switch-user?utm_medium=organic&utm_source=google_rich_qa&utm_campaign=google_rich_qa

The fix that worked for me was a permission problem on /etc/shadow
$ ls -l /etc/shadow
-rw-r----- 1 root shadow 2202 Jun 23 12:39 /etc/shadow

For me the permission was:
$ ls -l /etc/shadow
-rw-r----- 1 root root 2202 Jun 23 12:39 /etc/shadow

When I changed the group to shadow and restarted the system. I was able to login from the lock screen again. The reason I believe that restarting is required is that the lightdm crashes if it cannot access the shadow file. and once it crashed, you get the message about authentication failure, switch to greeter.

The explanation was that the lockscreen runs in user context, whereas the greeter runs as root, so the shadow group allows lightdm to access it.

I tried the lock screen several times now, and it is solidly working. I did not change the group from shadow to root, so perhaps an update changed the file permission, or a patch changed the password utility. not sure.

[Aleksander Kamenik (aleksander.kamenik)]

My issue resolved itself. There was a kernel update with some other package updates and after restarting the problem was gone.

The shadow file permissions are OK now, I did not have a chance to check them before.

[Ethan Lamoreaux (hraefn)]

This bug has been bugging me for a while now, not sure exactly when it showed up but it was after an update a good while ago. When I lock my console, I get this "bug screen" immediately. When I want to unlock I have to click the "Switch to greeter" button which has mysteriously replaced my password entry blank. Typically my Xorg session is running on virtual terminal 7. When I click the "switch to greeter" button, the screen goes blank and a new Xorg session is started on VT8, which then displays the greeter. I can switch between the bug screen on VT7 and the greeter on VT8 using CTRL+ALT+(F7 or F8). After I log in, the Xorg session on VT8 shuts down and I am automatically switched back to VT7 which may show the bug screen for a flash before the screen unlocks.

After a reboot (which I typically do only after an update that requires it) this bug goes away for a while but just when I think it has been fixed, it shows up again.

My /etc/shadow permissions are:
-rw-r----- 1 root shadow 1924 Feb 18 02:53 /etc/shadow

[Erik Meitner (e.meitner)]

@Rael Gugelmin Cunha (rael-gc):
You are probably right. The changelog for the "unity" package says: "* Refactor the way UserAuthenticator is created and passed around. Handle failures to create new threads and fallback to a "Switch to greeter..." button in case of failure. (LP: #1311316)"

It seems that the initial bug from LP: #1311316 of "Sometimes (but not always) after locking the screen there is the situation not having any input field where I can type the password to unlock the session again." was addressed with a workaround, but this workaround has caused even more problems. I never had the issue of not having a password prompt.

[Adrienne (rykasimba)]

This happens to me on 16.04LTS about once a week. When it happens my login also changes to Kanji characters. the only way to fix it is to reboot. Then it comes right back.

[Suresh Krishnamoorthy (pattais)]

Same issue ubuntu 17.10 and auth.log looks exactly the same as reported in <a href=https://bugs.launchpad.net/ubuntu/+source/unity/+bug/1733557/comments/35> comment #35 </a> above.

[Suresh Krishnamoorthy (pattais)]

tail /var/log/auth.log output

[Abhay Mitra (abhaymitra)]

Same issue on Ubuntu 16.04.4 LTS (single user login).

[Pavel Slechta (paslechta)]

I can confirm the issue on 16.04.4 LTS. And I am not switching any sessions.

[amias (amias)]

this is happening to me on 18.04 upgraded all the way from 16.04 as the releases came out.

i don't have secure boot , i use an nvidia graphics card , i am running vmware workstation 14

[Ross Reedstrom (reedstrm)]

count me an additional sufferer - 16.04.4, upgraded as upgrades came out. I also see the behavior go away for a time, then come back after the computer has not rebooted for a period of time. I see it no matter how the computer is locked: crtl-alt-L, lid close to sleep, timeout, the . Once the authentication error shows up, it doesn't go away until a full reboot. Single user/session

Dell XPS 15 (9550) intel/nvidia, stock everything, except kernel updated to 4.15.0-20-generic #21~16.04.1-Ubuntu

[Archit Kumar (architkumar)]

Same error : 16.04lts , single user, dual boot.
kernel 4.13.0-39-generic

[Robert Clayton (rnctx)]

Same error here with me on 16.04 (+ latest updates from security). Also using virtualbox as a plain ole non-root user.

[Lex_Dysia (johnkirk)]

I've experienced the same problem on a fully patched 16.04 LTS.
This issue only occurred in the last few weeks & may have corresponded to when I added 3 new users to the machine.
I have previously used the first option in https://askubuntu.com/questions/859581/how-to-change-the-unity-lockscreen-wallpaper to modify my lock screen wallpaper.
After this recent "Authentication failure" issue occurred I recompiled the Greeter Schema as per the link above (sudo glib-compile-schemas /usr/share/glib-2.0/schemas) which has cured the problem on my machine at least.

[Sam (shf42)]

I updated snapd (along with many other packages) and now the message is gone. Maybe snapd was at fault, but I am not sure.

[Rael Gugelmin Cunha (rael-gc)]

This bug happens in Bionic (18.04) too.

[Playing With (afulldeck)]

^ Crap. I was hoping the upgrade to 18.04 would remove it. I have the same bug with 16.04. This is been going on for some time. Does anyone know what is causing it???

[bx1 (abx1)]

The extra "Enter" to take me to the login screen is killing couple of seconds of my work. I am not sure if this is related to Xorg. Ping me if I need to dig in more. Here's the log

[ 40206.697] (II) AIGLX: Suspending AIGLX clients for VT switch
[ 40206.751] (EE) modeset(0): failed to set mode: Permission denied
[ 40212.065] (II) AIGLX: Resuming AIGLX clients after VT switch
[ 40212.131] (II) modeset(0): EDID vendor "AUO", prod id 8685
[ 40212.131] (II) modeset(0): Printing DDC gathered Modelines:
[ 40212.131] (II) modeset(0): Modeline "1920x1080"x0.0 141.00 1920 2028 2076 2086 1080 1090 1100 1126 -hsync -vsync (67.6 kHz eP)
[ 40212.148] (--) synaptics: ELAN1300:00 04F3:3057 Touchpad: touchpad found

[DocWilco (k-ubuntuone-m)]

A full reboot did fix this for me on 16.04

[Rolf Leggewie (r0lf)]

I doubt this is a regression due to the fix for bug 1311316, simply for the fact that this problem was reported last November while the fix for bug 1311316 was only uploaded to the archive in February.

[ptah (brett-h-l)]

I can confirm this problem running Ubuntu 16.04 on Lenovo Carbon X1. Started ~4 months ago. Lock, close lid, open lid, "ubuntu authentication failure switch to greeter", hit enter and return to normal login screen. Single user.

[Rael Gugelmin Cunha (rael-gc)]

@Rolf: this issue is not new. But it started to happen everytime a second user logs in after https://bugs.launchpad.net/ubuntu/+source/unity/+bug/1311316 fix. I helped to test that fix.

[Peter Smith (l-peter-v)]

FWIW this has been happening to me for some time.
Single user on this laptop.
Ubuntu 16.04
It doesn't happen all the time, but it occurs sooner if I have been using a large number of tabs in Chrome.
Hope that might help. :)

[Erik Meitner (e.meitner)]

I upgraded from 16.04 to 18.04. Same problem with the exception that I can't switch to the login screen from the lock screen by hitting a key. I need to press CTRL-ALT-F1 to get to the login screen. Then I can log in to get back to my session.

[Rael Gugelmin Cunha (rael-gc)]

Usually after click to switch to greeter and got able to login, if I restart compiz (compiz --replace &), this will stop.

[Rael Gugelmin Cunha (rael-gc)]

God, this bug is so annoying... I faced it several times in a day!

[inactivist (inactivist)]

Recompiling the greeter schemas as mentioned in #89[1] worked for me (Ubuntu 16.04 x64) -- haven't seen the failure in weeks, was seeing it every day or so before. I have no idea why it works, but so far so good. Wish I had time to dig deeper.

$ sudo glib-compile-schemas /usr/share/glib-2.0/schemas

[1]https://bugs.launchpad.net/ubuntu/+source/unity/+bug/1733557/comments/89 worked for me.

[Rael Gugelmin Cunha (rael-gc)]

Recompile the greeter schemas made nothing here: after the second user login/logout, the first one will continue to see the message.

[Szilárd Páll (sin-pecado)]

As many others, after a recent update, whenever on return to any of the three machines I have with up-to-date 16.04.5, I am met with the "Authentication failure message" and am forced to switch to the greeter which on some boxes (e.g. my workstation with multiple NVIDIA GPUs) takes >5 sec.

[Rael Gugelmin Cunha (rael-gc)]

I think this is the related diff: https://code.launchpad.net/~azzar1/unity/fix-missing-entry-lockscreen/+merge/330801/+preview-diff/804854/+files/preview.diff

If someone can test reverting those changes...

[Michael Engelbrecht (mikee13)]

Hi. I also have this problem on my DELL Optiplex AIO 9010 running Ubuntu 16.04.5 LTS.

And "Yes I know that 16.04 is no longer supported" ... however it seems that if you upgrade to 18.04, it does not solve the problem and in fact makes it worse !! At the moment, I get this message after my desktop has been sleeping, click on it and the usual login prompt appears whereas with 18.04 it seems that we cannot switch to the login screen without pressing CTRL-ALT-F1.

[Rick Harris (rickfharris)]

In reply to #105

Have tested reverting that fix and it just re-introduces the bug
"After locking screen there is no input field to type password for unlock"

Having no input field is worse.

[angela (malaikazoe)]

I solved it with this:

https://medium.com/@5XvYrLT7/fix-ubuntus-switch-to-greeter-bug-715d05520f46

[Rael Gugelmin Cunha (rael-gc)]

@angela: I tested and it doesn't work. It had the same effect as restart or restart unity/compiz plugin: it'll work only until log with second user and suspend, then error is back.

[Shlomo Bachar (shlomo-bachar)]

This bug happens to me also. I had this problem in my laptop during a few months. But it disappeared after a while. Now it suddenly appeared on my desktop. 16.04 LTS. I dont have other users in my computers as others mentioned. It happened after a few weeks of a fresh Ubuntu installation. Annoying but not serious. It happens after returning from screen lock or restart. Disappears after doing "ESC".

[pommm (pommm)]

I 've got this bug after "apt-get dist-upgrade" on my system too.

System before bug:
Ubuntu 16.04.1 LTS
Kernel 4.4.0-45-generic #66-Ubuntu SMP

After upgrade:
Ubuntu 16.04.5 LTS
Kernel 4.4.0-131-generic #157-Ubuntu SMP

User A logged in
User A lock screen
User B logged in
User B logged out
User A try to login.

Message:
Authentication failure
Swith to Greeter

If click Swith to Greeter it witll allow you to login and then it is back.

[Tobias (tobias-welti)]

I also experience the same problem on a fresh Ubuntu 16.04.5 LTS install. Fresh meaning: installed 6 days ago, in the meantime had to do 'sudo apt install --reinstall ubuntu-desktop'. Since then, I'm having this issue every time I lock my screen.

[c4pp4 (c4pp4)]

Single user desktop - steps to reproduce:
1) restart computer or log out user
2) log into user session from LightDM
3) use the gear icon menu to lock the screen
4) use the gear icon menu to switch the account
5) now we are switched into LightDM
6) log into user session again
7) use the gear icon menu to lock the screen
8) Authentication failure - Switch to greeter

[Rael Gugelmin Cunha (rael-gc)]

@c4pp4 is the attached patch file a solution?

[c4pp4 (c4pp4)]

@Rael Gugelmin Cunha

My knowledge is not PAM friendly but I think it's something like this - when the screen is locked, PAM transaction is started via pam_start and after authentication (entered a password) it's closed via pam_end. But if we switch user from the locked screen, PAM transaction is not terminated via pam_end and pam_handle_ is still presented. When we return into the session and lock the screen again, the following code will cause the issue:

unity/lockscreen/UserAuthenticatorPam.cpp

if (pam_handle_)
  {
    LOG_ERROR(logger) << "Unable to start authentication because another one has already been started";
    return false;
  }

It will try 5 times to authenticate but it always returns false as pam_handle_ is still present, then the following code shows "Authentication failure" with "Switch to greeter" button:

unity/lockscreen/UserPromptView.cpp

if (num_retry_auth_ <= 5)
  {
    LOG_WARNING(logger) << "Failed to start the authentication process. Retrying for " << num_retry_auth_ << " time.";
    source_manager_.AddTimeout(100, [this] {
      StartAuthentication();
      return false;
    });
  }
  else
  {
    AddMessage(_("Authentication failure"), nux::color::Red);
    AddButton(_("Switch to greeter…"), [this] {
      session_manager_->SwitchToGreeter();
    });

My solution is to terminate the PAM transaction and let it try to init the new one. I have tested it in my case and it works without problem.
I wonder why there is the case of error - "Unable to start authentication because another one has already been started". I don't know what case it's related to.

[Ubuntu Foundations Team Bug Bot (crichton)]

The attachment "authentication.patch" seems to be a patch. If it isn't, please remove the "patch" flag from the attachment, remove the "patch" tag, and if you are a member of the ~ubuntu-reviewers, unsubscribe the team.

[This is an automated message performed by a Launchpad user owned by ~brian-murray, for any issues please contact him.]

[Roland (roland-breedveld)]

Same issue, sometimes, with Ubuntu 18.10
switching user isn working
workarround is to switch to another console (ctr-alt-F1) after loggin in get my session back
if it occours, itś every time the screen locks also with the lock-screen button

[Khurshid Alam (khurshid-alam)]

@@c4pp4

Please test if it works with multiple users. If it does it's better to attach a git patch with proper header.

commit your local changes using

git commit -a -m "<your specific message>"

then generate a patch using

git format-patch -s -n -1 HEAD

Then you will have a 0001-*.patch in root project dir.

[c4pp4 (c4pp4)]

@Khurshid Alam

I have tested it with multiple users without problem. I have tweaked it little bit.

[Krzysztof Ostaszewski (ostaszewski-k)]

@c4pp4

How can I apply the patch? Or should I wait for it to be upstream and available via apt upgrade? I am on Ubuntu 18.04 and 18.10 with same multi-user problem.

[c4pp4 (c4pp4)]

@Krzysztof Ostaszewski

Test build:
https://launchpad.net/~c4pp4/+archive/ubuntu/ppa

[Rael Gugelmin Cunha (rael-gc)]

I'm adding the PPA to my install in order to test.

[Rael Gugelmin Cunha (rael-gc)]

Now almost 2 days using: I've resumed from suspend, switched users, and still working fine! Hope we can get this published soon! Thank you @c4pp4!

[Rael Gugelmin Cunha (rael-gc)]

Ok, after install the PPA, this issue is gone. No reboot since 19th, and several users used my box, I've suspend and resumed: working like a charm.

Now how can we get this patch as an official update?

[Khurshid Alam (khurshid-alam)]

@Rael

As of now Unityshell compiz plugin is crashing in disco (bug 1812964), once that's fixed I will open a merge.

[Krzysztof Ostaszewski (ostaszewski-k)]

@c4pp4 any chance providing a ppa for cosmic?

[c4pp4 (c4pp4)]

@Krzysztof Ostaszewski

As you wish, it's ready now.

[Andrej Shadura (andrew.sh)]

Submitted https://code.launchpad.net/~andrew.sh/unity/+git/unity/+merge/362414.

[Krzysztof Ostaszewski (ostaszewski-k)]

@c4pp4 Than you for the trouble. I installed your PPA and after update I can confirm the patch solved my issue. I no longer see "authentication failure" dialog. Unity 7.5.0 on Ubuntu 18.10

[Krzysztof Ostaszewski (ostaszewski-k)]

@c4pp4 because of other issues I had in my system (Firefox acting weird with recent 64 and 65 releases on 18.10) i rolled back to 18.04 (using LVM and backups) and installed your PPA - it also solved my long lasting issue with multiple logged-in accounts. Thanks!

[Launchpad Janitor (janitor)]

This bug was fixed in the package unity - 7.5.0+19.04.20190217-0ubuntu1

---------------
unity (7.5.0+19.04.20190217-0ubuntu1) disco; urgency=medium

  [ Andrea Azzarone ]
  * locksreen: cancel authentication if externally unlocked (LP:
    #1733557)

 -- Dmitry Shachnev <email address hidden> Sun, 17 Feb 2019 19:14:19 +0000

[Krzysztof Ostaszewski (ostaszewski-k)]

Perfect! Is it backported to 18.04 and 18.10?

[Rael Gugelmin Cunha (rael-gc)]

A friendly reminder it affects 16.04 too (aside 18.04 and 18.10).

[Steve Langasek (vorlon)]

Hello Andrew, or anyone else affected,

Accepted unity into cosmic-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/unity/7.5.0+18.10.20190304-0ubuntu1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested and change the tag from verification-needed-cosmic to verification-done-cosmic. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-cosmic. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

[Krzysztof Ostaszewski (ostaszewski-k)]

That's great news! Does it mean it will be backported into bionic after it will be accepted from proposed? Is there a way to enable proposed for 18.04?

[Andrea Azzarone (azzar1)]

I can no longer reproduce the problem in Cosmic following the steps in [Test Case]. I'm running Unity 7.5.0+18.10.20190304-0ubuntu1. Marking as verification-done.

[Launchpad Janitor (janitor)]

This bug was fixed in the package unity - 7.5.0+18.10.20190304-0ubuntu1

---------------
unity (7.5.0+18.10.20190304-0ubuntu1) cosmic; urgency=medium

  * lockscreen: cancel authentication if externally unlocked (LP:
    #1733557)

 -- Andrea Azzarone <email address hidden> Mon, 04 Mar 2019 11:03:23 +0000

[Łukasz Zemczak (sil2100)]

The verification of the Stable Release Update for unity has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.

[Rael Gugelmin Cunha (rael-gc)]

@sil2100 Any chance we get a build for Xenial and Bionic?

[Vasya Pupkin (shadowlmd)]

I've started seeing this bug in Ubuntu 16.04 recently.

[Łukasz Zemczak (sil2100)]

Hello Andrew, or anyone else affected,

Accepted unity into bionic-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/unity/7.5.0+18.04.20190304-0ubuntu1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested and change the tag from verification-needed-bionic to verification-done-bionic. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-bionic. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

[Łukasz Zemczak (sil2100)]

Hello Andrew, or anyone else affected,

Accepted unity into xenial-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/unity/7.4.5+16.04.20190312-0ubuntu1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested and change the tag from verification-needed-xenial to verification-done-xenial. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-xenial. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

[Łukasz Zemczak (sil2100)]

I have accepted Andrea's fixes to both xenial-proposed and bionic-proposed - could you please perform validation? Thank you!

[Simon Quigley (tsimonq2)]

Unsubscribing the sponsors team, as there is nothing left to sponsor.

[Andrea Azzarone (azzar1)]

I can no longer reproduce the issue in xenial installing unity from proposed (7.4.5+16.04.20190312-0ubuntu1).

[Andrea Azzarone (azzar1)]

I can no longer reproduce the issue in bionic installing unity from proposed 7.5.0+18.04.20190304-0ubuntu1. Please note that if you're running gdm3 in order to reproduce (or not reproduce) the problem you need the follow steps:
1. Lock the screen
2. Switch to gdm using ctrl + alt + f1
3. Use gdm to unlock the session
4. The session should be unlocked
5. Lock again the session
6. Depending on the unity version you are running you should be able to reproduce (not reproduce the bug)

[Launchpad Janitor (janitor)]

This bug was fixed in the package unity - 7.5.0+18.04.20190304-0ubuntu1

---------------
unity (7.5.0+18.04.20190304-0ubuntu1) bionic; urgency=medium

  * lockscreen: cancel authentication if externally unlocked (LP:
    #1733557)

 -- Andrea Azzarone <email address hidden> Mon, 04 Mar 2019 11:03:45 +0000

[Launchpad Janitor (janitor)]

This bug was fixed in the package unity - 7.4.5+16.04.20190312-0ubuntu1

---------------
unity (7.4.5+16.04.20190312-0ubuntu1) xenial; urgency=medium

  * lockscreen: cancel authentication if externally unlocked (LP:
    #1733557)

 -- Andrea Azzarone <email address hidden> Tue, 12 Mar 2019 17:54:13 +0000