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Thread: display-manager.service fails, boot hangs, no login screen

  1. #1
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    Default display-manager.service fails, boot hangs, no login screen

    This is random, but appears to happen a little more often past few days. So far, the only solution I have used is Ctrl-Alt-Del to force shutdown/reboot and hope the next run-up succeeds.

    Usually, this forced reboot is only required once, though sometimes it can take 2 or 3 tries, then all works as it should and the Login Greeter shows up.

    Scanning through the boot logs, I find this output for the time it fails, when it does. These same lines are the only lines I do not see in a successfull boot:
    Code:
    Aug 29 16:54:34 MyHostName.MyDomain systemd[1]: display-manager.service: Main process exited, code=exited, status=1/FAILURE
    Aug 29 16:54:34 MyHostName.MyDomain display-manager[1631]: ..done
    Aug 29 16:54:34 MyHostName.MyDomain systemd[1]: display-manager.service: Unit entered failed state.
    Aug 29 16:54:34 MyHostName.MyDomain systemd[1]: display-manager.service: Failed with result 'exit-code'.
    My next step, the next time it happens, will be to switch to a console on one of the other ttys, login, and try:
    Code:
    su systemctl start display-manager
    to see what happens. Or, alternately, log into the console as root and just try:
    Code:
    systemctl start display-manager
    Today I tried logging into the console as root and issued:
    Code:
    startx
    but that immediately logged me into the GUI desktop as root without further asking for the root password. NOT Good!

    Quickly logged right back out, as we know the risks associated with logging into the GUI as root!

    This just put me back to the console, where I logged out of root. No more time to play, then, so ran no further tests.

    I would like to know if anyone else is experiencing this issue. As I said, it is a random act, and so far since installing 42.2 in May, I have only had it happen now and then.

    Otherwise, almost everything else is running flawlessly.

    For now, I want to gather a little more information, if I can, and confirmation from any other users, before filing a bug report.

    Display Manager is lightdm

    Desktop is Xfce
    "Take a Walk on a Sunny Day, Greet everyone along the way, and Make Somebody Smile, Today"
    Gerry Jack Macks"Walk On A Sunny Day" GerryJackMacks.net

  2. #2
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    Default Re: display-manager.service fails, boot hangs, no login screen

    When the display-manager.service fails any useful error messages logged?
    Code:
    sudo journalctl -e -u lightdm
    Or following a successful boot, examine the previous boot for lightdm messages perhaps...
    Code:
    sudo journalctl -b1 |grep lightdm

  3. #3
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    Default Re: display-manager.service fails, boot hangs, no login screen

    Sorry, for previous boot that should have been...
    Code:
    sudo journalctl -b -1 |grep lightdm

  4. #4
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    Default Re: display-manager.service fails, boot hangs, no login screen

    Quote Originally Posted by deano_ferrari View Post
    Sorry, for previous boot that should have been...
    Code:
    sudo journalctl -b -1 |grep lightdm
    Thanks, deano.

    However, I used
    Code:
    journalctl -S "2017-08-28 14:35" |grep lightdm
    since I know the exact times of the failed and successfull boots.

    As I mentioned in the first post, the output I showed above is the only output that differs between a successfull invocation of the greeter and no greeter showing up.

    I could find no other differences in various journalctl options, so had I output the full boot output of the journal up the the point of success or failure, then manually scanned each line looking for clues -- now, that is a tedious task, I tell ya -- and could find nothing else in the failed boot that does not also appear in a successfull login.

    There is an error, of sorts (does not come up with the ERROR option, btw), as you will see in the output below, but it shows up in the successfull bootup and login records, as well, so I doubt it is the answer.

    However, since we should always show what the person offering to help asked (how is that for a subtle hint to others seeking help?), here is the output I get for lightdm, 5 boots, 3 of which were successfull, 2 which weren't.

    SUCCESSFULL BOOT:
    Code:
    Aug 30 13:10:29 MyHostName.MyDomain display-manager[1316]: Starting service lightdm..done
    Aug 30 13:10:29 MyHostName.MyDomain display-manager[1316]: (lightdm:1521): GLib-GObject-CRITICAL **: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
    Aug 30 13:10:30 MyHostName.MyDomain lightdm[1615]: pam_unix(lightdm-greeter:session): session opened for user lightdm by (uid=0)
    Aug 30 13:10:30 MyHostName.MyDomain systemd[1]: Created slice User Slice of lightdm.
    Aug 30 13:10:30 MyHostName.MyDomain systemd[1]: Started Session 1 of user lightdm.
    Aug 30 13:10:30 MyHostName.MyDomain systemd-logind[813]: New session 1 of user lightdm.
    Aug 30 13:10:30 MyHostName.MyDomain systemd[1626]: pam_unix(systemd-user:session): session opened for user lightdm by (uid=0)
    Aug 30 13:10:36 MyHostName.MyDomain lightdm[1615]: pam_unix(lightdm-greeter:session): session closed for user lightdm
    Aug 30 13:10:36 MyHostName.MyDomain lightdm[1640]: pam_unix(lightdm:session): session opened for user gerry by (uid=0)
    Aug 30 13:10:36 MyHostName.MyDomain display-manager[1316]: (lightdm:1521): GLib-GObject-CRITICAL **: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
    Aug 30 13:10:36 MyHostName.MyDomain systemd[1629]: pam_unix(systemd-user:session): session closed for user lightdm
    Aug 30 13:10:36 MyHostName.MyDomain systemd[1]: Removed slice User Slice of lightdm.
    SUCCESSFULL BOOT:
    Code:
    Aug 30 18:15:51 MyHostName.MyDomain display-manager[1083]: Starting service lightdm..done
    Aug 30 18:15:52 MyHostName.MyDomain display-manager[1083]: (lightdm:1512): GLib-GObject-CRITICAL **: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
    Aug 30 18:15:52 MyHostName.MyDomain lightdm[1616]: pam_unix(lightdm-greeter:session): session opened for user lightdm by (uid=0)
    Aug 30 18:15:52 MyHostName.MyDomain systemd[1]: Created slice User Slice of lightdm.
    Aug 30 18:15:52 MyHostName.MyDomain systemd[1]: Started Session 1 of user lightdm.
    Aug 30 18:15:52 MyHostName.MyDomain systemd-logind[817]: New session 1 of user lightdm.
    Aug 30 18:15:52 MyHostName.MyDomain systemd[1627]: pam_unix(systemd-user:session): session opened for user lightdm by (uid=0)
    Aug 30 18:16:01 MyHostName.MyDomain lightdm[1616]: pam_unix(lightdm-greeter:session): session closed for user lightdm
    Aug 30 18:16:01 MyHostName.MyDomain display-manager[1083]: (lightdm:1512): GLib-GObject-CRITICAL **: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
    Aug 30 18:16:01 MyHostName.MyDomain lightdm[1642]: pam_unix(lightdm:session): session opened for user gerry by (uid=0)
    Aug 30 18:16:01 MyHostName.MyDomain systemd[1630]: pam_unix(systemd-user:session): session closed for user lightdm
    Aug 30 18:16:01 MyHostName.MyDomain systemd[1]: Removed slice User Slice of lightdm.
    FAILED BOOT:
    Code:
    Aug 28 14:35:56 MyHostName.MyDomain display-manager[983]: Starting service lightdm..done
    Aug 28 14:35:57 MyHostName.MyDomain display-manager[983]: (lightdm:1467): GLib-GObject-CRITICAL **: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
    Aug 28 14:35:57 MyHostName.MyDomain lightdm[1529]: pam_unix(lightdm-greeter:session): session opened for user lightdm by (uid=0)
    Aug 28 14:35:57 MyHostName.MyDomain systemd[1]: Created slice User Slice of lightdm.
    Aug 28 14:35:57 MyHostName.MyDomain systemd-logind[746]: New session 1 of user lightdm.
    Aug 28 14:35:57 MyHostName.MyDomain systemd[1]: Started Session 1 of user lightdm.
    Aug 28 14:35:57 MyHostName.MyDomain systemd[1587]: pam_unix(systemd-user:session): session opened for user lightdm by (uid=0)
    Aug 28 14:35:57 MyHostName.MyDomain lightdm[1529]: pam_unix(lightdm-greeter:session): session closed for user lightdm
    Aug 28 14:35:58 MyHostName.MyDomain systemd[1590]: pam_unix(systemd-user:session): session closed for user lightdm
    Aug 28 14:35:58 MyHostName.MyDomain systemd[1]: Removed slice User Slice of lightdm.
    FAILED BOOT (2nd in a row):
    Code:
    Aug 28 14:37:50 MyHostName.MyDomain display-manager[1044]: Starting service lightdm..done
    Aug 28 14:37:50 MyHostName.MyDomain display-manager[1044]: (lightdm:1482): GLib-GObject-CRITICAL **: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
    Aug 28 14:37:51 MyHostName.MyDomain lightdm[1541]: pam_unix(lightdm-greeter:session): session opened for user lightdm by (uid=0)
    Aug 28 14:37:51 MyHostName.MyDomain systemd[1]: Created slice User Slice of lightdm.
    Aug 28 14:37:51 MyHostName.MyDomain systemd-logind[761]: New session 1 of user lightdm.
    Aug 28 14:37:51 MyHostName.MyDomain systemd[1599]: pam_unix(systemd-user:session): session opened for user lightdm by (uid=0)
    Aug 28 14:37:51 MyHostName.MyDomain systemd[1]: Started Session 1 of user lightdm.
    Aug 28 14:37:51 MyHostName.MyDomain lightdm[1541]: pam_unix(lightdm-greeter:session): session closed for user lightdm
    Aug 28 14:37:51 MyHostName.MyDomain systemd[1602]: pam_unix(systemd-user:session): session closed for user lightdm
    Aug 28 14:37:51 MyHostName.MyDomain systemd[1]: Removed slice User Slice of lightdm.
    SUCCESSFULL BOOT after LATTER FAILED BOOT:
    Code:
    Aug 28 14:40:16 MyHostName.MyDomain display-manager[1106]: Starting service lightdm..done
    Aug 28 14:40:17 MyHostName.MyDomain display-manager[1106]: (lightdm:1446): GLib-GObject-CRITICAL **: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
    Aug 28 14:40:17 MyHostName.MyDomain lightdm[1497]: pam_unix(lightdm-greeter:session): session opened for user lightdm by (uid=0)
    Aug 28 14:40:17 MyHostName.MyDomain systemd[1]: Created slice User Slice of lightdm.
    Aug 28 14:40:17 MyHostName.MyDomain systemd-logind[764]: New session 1 of user lightdm.
    Aug 28 14:40:17 MyHostName.MyDomain systemd[1]: Started Session 1 of user lightdm.
    Aug 28 14:40:17 MyHostName.MyDomain systemd[1558]: pam_unix(systemd-user:session): session opened for user lightdm by (uid=0)
    Aug 28 14:40:25 MyHostName.MyDomain lightdm[1497]: pam_unix(lightdm-greeter:session): session closed for user lightdm
    Aug 28 14:40:25 MyHostName.MyDomain systemd[1561]: pam_unix(systemd-user:session): session closed for user lightdm
    Aug 28 14:40:25 MyHostName.MyDomain display-manager[1106]: (lightdm:1446): GLib-GObject-CRITICAL **: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
    Aug 28 14:40:25 MyHostName.MyDomain lightdm[1572]: pam_unix(lightdm:session): session opened for user gerry by (uid=0)
    Aug 28 14:40:25 MyHostName.MyDomain systemd[1]: Removed slice User Slice of lightdm.
    "Take a Walk on a Sunny Day, Greet everyone along the way, and Make Somebody Smile, Today"
    Gerry Jack Macks"Walk On A Sunny Day" GerryJackMacks.net

  5. #5
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    Default Re: display-manager.service fails, boot hangs, no login screen

    Once consistent observation: I note that when it succeeds a user session is opened eg
    Code:
     pam_unix(lightdm:session): session opened for user gerry by (uid=0)
    but when it fails there is no such session opened. It might be worth examining the pam_unix authentication output a bit more.

  6. #6
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    Default Re: display-manager.service fails, boot hangs, no login screen

    Quote Originally Posted by deano_ferrari View Post
    Once consistent observation: I note that when it succeeds a user session is opened eg
    Code:
     pam_unix(lightdm:session): session opened for user gerry by (uid=0)
    but when it fails there is no such session opened. It might be worth examining the pam_unix authentication output a bit more.
    ... well, yes. The User session is opened because I get a login screen, the greeter, so I can successfully log in. That just shows my successfull login.

    This does not show when the greeter does not show, because I therefore cannot login to the GUI. Since I do not log in, the session does not attempt to open.

    When it fails, I could get the same (rather, very similar) line by switching to another tty and log into the CLI.

    So, no, that is not a clue. But, thanks.

    BTW: That line is the one I use to determine where it fails or succeeds in the journal.

    These are the last lines before success or failure:
    Code:
    Aug 28 14:37:51 MyHostName.MyDomain systemd[1599]: Startup finished in 27ms.
    Aug 28 14:37:51 MyHostName.MyDomain systemd[1]: Started User Manager for UID 479.
    Aug 28 14:37:51 MyHostName.MyDomain lightdm[1541]: pam_unix(lightdm-greeter:session): session closed for user lightdm
    Aug 28 14:37:51 MyHostName.MyDomain systemd-logind[761]: Removed session 1.
    Aug 28 14:37:51 MyHostName.MyDomain systemd[1]: Stopping User Manager for UID 479...
    Aug 28 14:37:51 MyHostName.MyDomain systemd[1599]: Stopped target Default.
    Aug 28 14:37:51 MyHostName.MyDomain systemd[1599]: Stopped target Basic System.
    Aug 28 14:37:51 MyHostName.MyDomain systemd[1599]: Stopped target Paths.
    Aug 28 14:37:51 MyHostName.MyDomain systemd[1599]: Stopped target Timers.
    Aug 28 14:37:51 MyHostName.MyDomain systemd[1599]: Stopped target Sockets.
    Aug 28 14:37:51 MyHostName.MyDomain systemd[1599]: Reached target Shutdown.
    Aug 28 14:37:51 MyHostName.MyDomain systemd[1599]: Starting Exit the Session...
    Aug 28 14:37:51 MyHostName.MyDomain systemd[1599]: Received SIGRTMIN+24 from PID 1609 (kill).
    Aug 28 14:37:51 MyHostName.MyDomain systemd[1602]: pam_unix(systemd-user:session): session closed for user lightdm
    Aug 28 14:37:51 MyHostName.MyDomain systemd[1]: Stopped User Manager for UID 479.
    Aug 28 14:37:51 MyHostName.MyDomain systemd[1]: Removed slice User Slice of lightdm.
    When it fails (ie: no greeter comes up and the system just sits waiting), the next four lines will be:

    Code:
    Aug 28 14:37:52 MyHostName.MyDomain systemd[1]: display-manager.service: Main process exited, code=exited, status=1/FAILURE
    Aug 28 14:37:52 MyHostName.MyDomain display-manager[1616]: ..done
    Aug 28 14:37:52 MyHostName.MyDomain systemd[1]: display-manager.service: Unit entered failed state.
    Aug 28 14:37:52 MyHostName.MyDomain systemd[1]: display-manager.service: Failed with result 'exit-code'.
    When it succeeds, the greeter comes up, and I enter my login credentials, the next lines will instead be:
    Code:
    Aug 30 18:16:01 MyHostName.MyDomain systemd[1627]: Reached target Shutdown.
    Aug 30 18:16:01 MyHostName.MyDomain display-manager[1083]: (lightdm:1512): GLib-GObject-CRITICAL **: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
    Aug 30 18:16:01 MyHostName.MyDomain lightdm[1642]: pam_unix(lightdm:session): session opened for user gerry by (uid=0)
    ... and AFAICS these are the only differences.

    PS: Note that CRITICAL message is not always in the same position, and the movement of it does not appear to be related to whether there is a Greeter or No Greeter and Sit with empty black screen (with just a couple of the last boot output lines showing, no errors).
    "Take a Walk on a Sunny Day, Greet everyone along the way, and Make Somebody Smile, Today"
    Gerry Jack Macks"Walk On A Sunny Day" GerryJackMacks.net

  7. #7
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    Default Re: display-manager.service fails, boot hangs, no login screen

    FWIW, similar intermittent behaviour discussed in this Ubuntu bug report. Race condition of some sort?

  8. #8
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    Default Re: display-manager.service fails, boot hangs, no login screen

    BTW: For additional clarity, I can easily switch terminals with the F keys, all other terminals are sitting at a CLI login prompt. Logging in just gets me into the CLI. startx fails as user (of course), and as root goes directly into the GUI..

    Also, the reason the fail logs are 08/28 is because it has not happened during boots the last couple days. As I said, it is quite random.
    "Take a Walk on a Sunny Day, Greet everyone along the way, and Make Somebody Smile, Today"
    Gerry Jack Macks"Walk On A Sunny Day" GerryJackMacks.net

  9. #9
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    Default Re: display-manager.service fails, boot hangs, no login screen

    Quote Originally Posted by deano_ferrari View Post
    FWIW, similar intermittent behaviour discussed in this Ubuntu bug report. Race condition of some sort?
    Hmmm. Thanks for the link, will look into it.
    "Take a Walk on a Sunny Day, Greet everyone along the way, and Make Somebody Smile, Today"
    Gerry Jack Macks"Walk On A Sunny Day" GerryJackMacks.net

  10. #10
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    Default Re: display-manager.service fails, boot hangs, no login screen

    Quote Originally Posted by Fraser_Bell View Post
    Also, the reason the fail logs are 08/28 is because it has not happened during boots the last couple days. As I said, it is quite random.
    Yep, got that

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