Fixing a missing taskbar on the x86 image


24 posts
by spl23 » Sat Dec 24, 2016 11:40 am
Several people have reported that the x86 image boots and then shows just a desktop and wastebasket without a taskbar. This seems to be caused by either some incompatibility with the on-board sound device in the target machine and the Linux ALSA sound architecture, causing the volume control plugin on the taskbar to crash, or the CPU monitor plugin crashing due to some incompatibility with the host machine. We'll investigate these and hopefully find fixes for the next release, but in the meantime, the workaround is to remove the plugins from the panel.

To do this, here are the steps. (You'll need to be running with a persistence partition for the changes to be saved.)

Open a terminal (Ctrl-Alt-T)

Launch Geany to open the lxpanel configuration file - geany ~/.config/lxpanel/LXDE-pi/panels/panel

There are two sections which might cause the problem. The volume control is:

Code: Select all
Plugin {
  type=volumealsa
  Config {
  }
}

The CPU monitor is:

Code: Select all
Plugin {
  type=cpu
  Config {
    ShowPercent=1
    Foreground=#a9a9a9a9a9a9
    Background=#d3d3d3d3d3d3
  }
}

Try deleting each in turn, and see if it fixes the problem for you.

If you do find that one or the other of these fixes the problem, it would be much appreciated if you could please post here and let us know!
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by carvellw » Wed Dec 28, 2016 3:51 pm
I removed the lines you listed and the taskbar is still missing.
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by nipponese » Wed Dec 28, 2016 10:23 pm
Same experience as @carvellw. Commenting out these lines did not fix the issue.
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by ShiftPlusOne » Wed Dec 28, 2016 10:37 pm
Is persistence working? Does the change remain in the file after you reboot?
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by nipponese » Thu Dec 29, 2016 12:07 am
ShiftPlusOne wrote:Is persistence working? Does the change remain in the file after you reboot?


Yes, just booted the machine from off. The lines were still commented out. I have another theory: The taskbar seems to flash when the wifi drops or switches to another network, so that may be the reason.
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by ShiftPlusOne » Thu Dec 29, 2016 1:25 am
I don't remember the command off the top of my head, but you can try running lxpanel with the LXDE-pi(?) profile to see what went wrong. Simon should be able to provide the exact command. That should tell you why it's crashing. There is also a .log file that contains that information, but I don't have the path to that right now either.
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by spl23 » Thu Dec 29, 2016 8:45 am
ShiftPlusOne wrote:I don't remember the command off the top of my head, but you can try running lxpanel with the LXDE-pi(?) profile to see what went wrong. Simon should be able to provide the exact command. That should tell you why it's crashing. There is also a .log file that contains that information, but I don't have the path to that right now either.


Code: Select all
lxpanel -p LXDE-pi
is what you need - run that from a terminal (Ctrl-Alt-T to open one from the desktop) and see what happens.
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by bensimmo » Thu Dec 29, 2016 3:16 pm
Just for some feedback

DISC worked fine (MagPi cover)
PenDrive written from downloaded ISO, booted up and no Taskbar.
switching out (C-A-F1) and killing ( sudo pkill lxsession), logging back in did not help (as per MAgPi, pg76)
Though a reboot worked and it's showing now.
(since you mention ALSA, that is HDA NVidia (Alsa Mixer on this))
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by billis2020 » Thu Dec 29, 2016 7:09 pm
I have this problem too and i need HELP!
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by nipponese » Thu Dec 29, 2016 9:16 pm
spl23 wrote:
ShiftPlusOne wrote:I don't remember the command off the top of my head, but you can try running lxpanel with the LXDE-pi(?) profile to see what went wrong. Simon should be able to provide the exact command. That should tell you why it's crashing. There is also a .log file that contains that information, but I don't have the path to that right now either.


Code: Select all
lxpanel -p LXDE-pi
is what you need - run that from a terminal (Ctrl-Alt-T to open one from the desktop) and see what happens.


Strangely, the taskbar re-appears again after running this command, but then disappears when I kill the command.

Here's the output:

Code: Select all
pi@raspberrypi:~ $ lxpanel -p LXDE-pi
** Message: x-terminal-emulator has very limited support, consider choose another terminal
** Message: Connecting ...
** Message: Status changed to down
** Message: Status changed to opened
** Message: Connected to dhcpcd-6.7.1
** Message: Status changed to connected
** Message: wlan0: Associated with <my SSID>
** Message: wlan0: Configured 192.168.1.<x>/24
** Message: wlan0: WPA status connected
** Message: wlan0: Received scan results
** Message: bt: Name org.bluez owned on DBus
** Message: bt: New agent manager found
** Message: bt: No adapter found
** Message: wlan0: Received scan results
** Message: wlan0: Received scan results
** Message: wlan0: Received scan results
** Message: wlan0: Received scan results
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by ShiftPlusOne » Thu Dec 29, 2016 10:06 pm
Could you post your ~/.cache/lxsession/LXDE-pi/run.log ?
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by spl23 » Thu Dec 29, 2016 10:10 pm
nipponese wrote:Strangely, the taskbar re-appears again after running this command, but then disappears when I kill the command.

Here's the output:

Code: Select all
pi@raspberrypi:~ $ lxpanel -p LXDE-pi
** Message: x-terminal-emulator has very limited support, consider choose another terminal
** Message: Connecting ...
** Message: Status changed to down
** Message: Status changed to opened
** Message: Connected to dhcpcd-6.7.1
** Message: Status changed to connected
** Message: wlan0: Associated with <my SSID>
** Message: wlan0: Configured 192.168.1.<x>/24
** Message: wlan0: WPA status connected
** Message: wlan0: Received scan results
** Message: bt: Name org.bluez owned on DBus
** Message: bt: New agent manager found
** Message: bt: No adapter found
** Message: wlan0: Received scan results
** Message: wlan0: Received scan results
** Message: wlan0: Received scan results
** Message: wlan0: Received scan results


That's exactly what should happen - including the taskbar vanishing when you kill the command. It looks as if something is causing the taskbar to crash at first boot, but whatever it is goes away later on. I've actually seen something similar on my Mac mini - I get a taskbar crash on boot but can then restart it later and have it work fine. We'll carry on investigating, but if you could provide the log file ShiftPlusOne suggests above, that would be helpful.
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by nipponese » Fri Dec 30, 2016 7:37 am
ShiftPlusOne wrote:Could you post your ~/.cache/lxsession/LXDE-pi/run.log ?


Couldn't attach a .log or .txt, and file was too big to paste directly into post, so here's the pastebin:
https://pastebin.com/reZPefvv
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by spl23 » Fri Dec 30, 2016 11:33 am
That's really helpful, thank you.

It looks as if the CPU monitor crashed, rather than the volume control. We've seen this happen occasionally in the past, but have never been able to repeat it - looks like it may be a bigger problem on x86 builds. (Which would make sense.)

To confirm that this is indeed the issue, you could try removing the CPU monitor from the taskbar instead of the volume control. Follow the directions in the post at the top of this thread, but remove this section of the panel file instead:

Code: Select all
Plugin {
  type=cpu
  Config {
    ShowPercent=1
    Foreground=#a9a9a9a9a9a9
    Background=#d3d3d3d3d3d3
  }
}
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by bensimmo » Fri Dec 30, 2016 12:40 pm
Is there any way the taskbar can ignore the crash and carry on regardless? (Which seems the sensible way to me) Or is it just the way the taskbar works?
(Interested over actually trying to help :oops: )
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by spl23 » Fri Dec 30, 2016 12:46 pm
bensimmo wrote:Is there any way the taskbar can ignore the crash and carry on regardless? (Which seems the sensible way to me) Or is it just the way the taskbar works?
(Interested over actually trying to help :oops: )


Unfortunately not - the plugins are shared code libraries which are loaded by the taskbar at startup, and if any one of them segfaults, it invariably takes the taskbar down with it. The only exceptions to this are applications which show icons in the system tray, which are completely separate applications that just provide an icon to a specific part of the taskbar - it might be possible to rewrite all plugins to work like this, but then you'd lose the ability to choose the order they appear, nicely space them out, etc. It'd be a lot of work to try, and I don't think the results would be entirely satisfactory. (I'm not saying crashing plugins taking the taskbar down is satisfactory either, but it's probably the lesser of two evils at present...)
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by billis2020 » Fri Dec 30, 2016 2:38 pm
When i delete the lines they return back after reboot and i use persistence (i have usb stick)
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by nipponese » Fri Dec 30, 2016 7:20 pm
spl23 wrote:That's really helpful, thank you.
To confirm that this is indeed the issue, you could try removing the CPU monitor from the taskbar instead of the volume control


Ok, gave this try and it seemed to work. I ran it through my "test" (compiling ruby 2.2 via RVM) and the taskbar didn't disappear or flicker as it normally does.
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by spl23 » Fri Dec 30, 2016 8:38 pm
nipponese wrote:
spl23 wrote:That's really helpful, thank you.
To confirm that this is indeed the issue, you could try removing the CPU monitor from the taskbar instead of the volume control


Ok, gave this try and it seemed to work. I ran it through my "test" (compiling ruby 2.2 via RVM) and the taskbar didn't disappear or flicker as it normally does.


Thank you very much for the confirmation - I'll have another look through that plugin and see if I can see any likely failure modes.
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by fos » Mon Jan 02, 2017 4:53 pm
I was experiencing an intermittent missing menu when using Raspbian PIXEL on my 2007 vintage Dell Inspiron and a usb memory chip. After setting the audio device settings, I have not had the menu disappear for several days.

YMMV. I will report further is the menu problem returns.

v/r
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by carvellw » Tue Jan 03, 2017 2:13 pm
So i didn't try the removing of the CPU monitor line. But I did unplug the ethernet cable then reboot. After the reboot the taskbar came back and working just fine. I then reboot with the ethernet cable in and the taskbar does not come up. I confirmed that it does not show up when ethernet cable is plugged in.
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by harmen » Tue Jan 03, 2017 10:09 pm
On my HP Elitebook 8440p, I #-ed out:

Plugin {
type=cpu
Config {
ShowPercent=1
Foreground=#a9a9a9a9a9a9
Background=#d3d3d3d3d3d3
}
}

in the config file, did a reboot and I have a taskbar on top of my screen.
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by billis2020 » Thu Jan 05, 2017 11:51 am
Deleted CPU plugin and now my taskbar is back!
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by dgordon42 » Tue Jan 10, 2017 11:57 am
I also have had problems with the Task Bar intermittently disappearing for 10 to 20 seconds, then usually but not always reappearing. It tends to do this when there is lots of activity on the USB Memory Stick I'm booting from.
I can always reproduce the snag by running 'sudo apt-get update'. The Task Bar will always cycle once or twice while apt-get runs.

I'm running PIXEL with persistence on a 10 year old Dell Inspiron 1501 laptop with (unusually) an AMD Athlon processor.

I can confirm that commenting out the CPU activity app entry in '~/.config/lxpanel/LXDE-pi/panels/panel' has 100% fixed my problem, I've been running for the last day or so without a problem, before I would be lucky to get past 20 minutes.

Hope this helps,
Dave.
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