Switching to TTY7 after 'service lightdm stop' hangs machine

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tedrogers
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Switching to TTY7 after 'service lightdm stop' hangs machine

Unread post by tedrogers » Fri Dec 07, 2018 8:03 am

Running Debian Stretch on my Odroid XU4, and by default it doesn't boot into lightdm (by my choice).

To start lightdm (for configuration / maintenance / ease / a nice change) I issue at the console TTY1:

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sudo service lightdm start
Great! It starts. I do my stuff and then some annoying things happen when I want to go back to console entirely.

Firstly, I can CTRL + ALT + DEL to kill X. But this just hangs my machine. I think it's stuck on TTY7 with nothing there, and the whole system is unresponsive. Reeboot required. I have since disabled CTRL + ALT + DEL by re-running setup-odroid as root back at TTY1.

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su <enter password>
setup-odroid
Second option is to switch from TTY7 running lightdm, to say TTY1, and issues the following:

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sudo service lightdm stop
This is fine until I switch to TTY7 (for curiosity), which then instantly hangs my machine. Reboot time!

Interestingly, if I don't let my curiosity get the better of me and I don't flip to TTY7 inbetween STOPPING and (RE)STARTING lightdm, then I can go in and out as I see fit.

I just wondered why this is happening?

It might be worth noting, that on a clean boot TTY7 doesn't exist at all. Only TTY 1 > 6 exist.

Also, I am unable to manually create a console at TTY7 with the following command:

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sudo /sbin/getty -8 38400 tty7 &
It simply doesn't appear to do much of anything, certainly there is no console / login at TTY7, although the output it produces strongly suggests that it is doing something useful and meaningful, albeit quite cryptic.

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[1]   890
Any advice from more learned folk?

Thanks all.

tedrogers
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Re: Switching to TTY7 after 'service lightdm stop' hangs machine

Unread post by tedrogers » Fri Dec 28, 2018 8:29 am

* bump *

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mad_ady
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Re: Switching to TTY7 after 'service lightdm stop' hangs machine

Unread post by mad_ady » Fri Dec 28, 2018 3:12 pm

890 should be the pid of the getty process.
When you say "it hangs" do you mean the unit can't be accessed through ssh either?

tedrogers
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Re: Switching to TTY7 after 'service lightdm stop' hangs machine

Unread post by tedrogers » Fri Dec 28, 2018 8:52 pm

mad_ady wrote:890 should be the pid of the getty process.
When you say "it hangs" do you mean the unit can't be accessed through ssh either?
The whole machine becomes dead. Forced restart is the only way. No SSH, no direct control. This only happens if I switch the TTY7 where there was previously a GUI session. If I simply don't go back to TTY7 then all is fine, but if I go there by accident, boom, total system hang.

Thank you for being the first to try and help me out with this. I appreciate it.

Sent from my Lenovo P2a42 using Tapatalk



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mad_ady
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Re: Switching to TTY7 after 'service lightdm stop' hangs machine

Unread post by mad_ady » Fri Dec 28, 2018 10:39 pm

Ok, try this: connect to the odroid via ssh and run a dmesg -w
Then start lightdm and switch consoles to reproduce the issue and see if you get anything in the dmesg log.
Try also switching consoles with chvt.
What OS/desktop environment are you running?

tedrogers
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Re: Switching to TTY7 after 'service lightdm stop' hangs machine

Unread post by tedrogers » Sat Dec 29, 2018 12:14 am

Thanks. I'll give this a go this evening. I could do it now remotely, but the ODROID is busy doing some critical things, so I'd rather be on site to fix it.

I'm on Debian Stretch / LXDE.

Mostly it runs headless, but naturally it's good to have GUI for certain admin tasks.

I can and have been using x2go instead of manually starting lightdm, which doesn't cause any hanging issues and uptime has been unaffected by any normal usage, like switching TTY sessions in console.

Sent from my Lenovo P2a42 using Tapatalk


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