System Update froze - UbuntuMATE 16-04

[Gene Heskett]

On Thursday 21 June 2018 04:43:16 Colin Law wrote:

> On 21 June 2018 at 09:32, Bret Busby <bret.busby at gmail.com> wrote:
> > On 21/06/2018, Colin Law <clanlaw at gmail.com> wrote:
> >> ...
> >> sync
> >
> > After about fifteen minutes, no displayed response - cursor goes
> > onto next line after the line in which the command is entered, an
> > the cursor sits there flashing at me, in an otherwise blank line.
> >
> > So, the command "sync" also appears to have been hanged (and, yes, I
> > do know the difference between hanged and hung :) ).
>
> So it is that bug that you are hitting.  The update runs sync to flush
> data to disc and that cannot complete for some reason.
>
> > It surprises me that this bug original report is apparently 16
> > months old, and, apparently a critical bug, and, since then, two
> > "point releases" and a new version (18.04) have been released, with
> > this critical bug not being fixed, with the bug appearing to take
> > 16.04 from being a "stasle" release, to a status equivalent to
> > Debian sid, with all that that name involves.
> >
> > I am now concerned that the bug may also apply to 18.04, as the bug
> > has apparently not been fixed.
>
> Yes I believe it does.  I guess the reason it has not been fixed is
> that it is extraordinarily rare, as can be seen from the small number
> of reports compared to, I guess, many many millions of times kernel
> updates have been run.  The issue now is to find the problem on your
> machine.  It could be hardware I imagine, being an issue with the disc
> interface or disc itself in which case you are probably stuck.
> Otherwise some process is hanging onto it and the only option is
> probably to kill that process.  Someone may know how to identify which
> process it is, but I don't.
>
> Colin

My approach would be to see if the machine is sluggish or snappy, if its 
sluggish then the process will like be waving its hand in a pee dance to 
htop. If its installed. htop, when sorting display order by cpu usage is 
handy at finding that sort of thing.

In extreme cases, one might have to scan down the process list killing 
anything that could be disk related except the first synch. At some 
point you should hit the blocker (write each one down in the order 
you've killed them) and that first synch should then finish. You will of 
course have to reboot but your written notes will be helpfull the next 
time it occurs. Then you kill the last entry to see if it unblocks 
things, to confirm that is where its at. And to be what the bug report 
should be looking at.

Thats my best shot at a start to find it procedure, Bret. Intermittent 
bugs are the worst kind.


-- 
Cheers, Gene Heskett
--
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