[Solved] - Tower's 1st [no, 3rd] Hard-Reset since clean-reinstall.

[kdemeoz]

Obviously i'm "interested" [wild understatement] in why my 1/1/17-clean-reinstalled Nouveau-drivered Maui 2.1 P5.8.4 has suffered these multiple freezes needing hard resets. 

However, i'm also interested in understanding why REISUB has not worked any of these 2017 times, despite working in my original 2016 installation of Maui [not clean, was on top of Mint 17.3 KDE4], & also working back when i did use said Mint.

I wondered if maybe the Ubuntu 16.04, or Maui, Devs had chosen to disable it, but it seems partly not, if i'm understanding "176" correctly as enabling "S U B" in /etc/sysctl.d/10-magic-sysrq.conf...

Code:

# The magic SysRq key enables certain keyboard combinations to be
# interpreted by the kernel to help with debugging. The kernel will respond
# to these keys regardless of the current running applications.
#
# In general, the magic SysRq key is not needed for the average Ubuntu
# system, and having it enabled by default can lead to security issues on
# the console such as being able to dump memory or to kill arbitrary
# processes including the running screen lock.
#
# Here is the list of possible values:
#   0 - disable sysrq completely
#   1 - enable all functions of sysrq
#  >1 - enable certain functions by adding up the following values:
#          2 - enable control of console logging level
#          4 - enable control of keyboard (SAK, unraw)
#          8 - enable debugging dumps of processes etc.
#         16 - enable sync command
#         32 - enable remount read-only
#         64 - enable signalling of processes (term, kill, oom-kill)
#        128 - allow reboot/poweroff
#        256 - allow nicing of all RT tasks
#
#   For example, to enable both control of console logging level and
#   debugging dumps of processes: kernel.sysrq = 10
#
kernel.sysrq = 176

SUB [= 16 + 32 + 128] is only half of REISUB. What are the Maui Devs' opinions about me editing this file to make the value "1" (ie, uncomment the "1" line], or otherwise deducing what the new number should be to add the REI to the existing SUB [maybe 244, according to my deduction from https://askubuntu.com/questions/11002/al...ptop#11194]?

[rocky7x]

When you get into such a state, have you tried Ctrl+Alt+Backspace? It restarts X server, always helps for me. But I don't know if it's enabled by default - check in System Setting -> Input Devices -> Keyboard -> Advanced and there find the option Key sequence to kill X server. When you open it, there shouldbe just 1 option Ctrl+Alt+Backspace - enabled it and hit Apply. The next time you have the screen stuck, just hit Ctrl+Alt+Backspace and it will restart the X server and present you with a login screen as if you would have restarted. It's much quicker than waiting to reboot

[leszek]

If REISUB is not working that means the kernel froze which is very bad as you cannot do anything then but restart

[rocky7x]

If REISUB is not working that means the kernel froze which is very bad as you cannot do anything then but restart

I'm not really sure the kernel could have frozen if she could hear the thunderbird refreshing mails... If kernel froze, everything would stop, wouldn't it?

[leszek]

Yeah but why are the magic sysrq keys not working then? If the kernel is not frozen it should have done something.

[kdemeoz]

Thanks both rocky & leszek

Ctrl+Alt+Backspace --> how excellent that you told me how to enable it [now done]. This had never ever worked for me since i left Mint 17.3 KDE4 for Maui, & i stupidly assumed it was "omitted" from Ubuntu 16.04. I dunno why i never thought of looking in this part of Settings for it. Next freeze i shall use this... but it would be kinda nice if i have no more freezes!

Re your kernel possible freeze debate, i also had wondered that this morning, but had also concluded same as rocky, given that TB was definitely still working, & thus obviously so still was Network Manager etc.

I'm using kernel 4.4.0-59-generic btw, ie, nothing "radical".

Even though i now have Ctrl+Alt+Backspace available again, i'm still interested in activating REISUB, not just SUB... should i / can i just use either the 1 or 244 value, do you think?

[leszek]

I forgot that magic sysrq keys are disabled by default in ubuntu based systems.
See this on how to activate them: http://askubuntu.com/questions/11002/alt...-my-laptop

[kdemeoz]

Um, are we going around in circles? That's the link that i already gave you, in my earlier post above... & i've been asking you about setting it to 1 or retaining the current 176 or using 244...? Ie, i do know how to enable it, but it's a question of what setting is best? My inclination is just to make it 1, which enables everything, but first i value your expert advice. 

[leszek]

Yeah enable it with 1

[kdemeoz]

Thanks, will do. Is a reboot needed to make the new setting "active"?