Handling complete failure in the installer

[Carl Karsten]

On Fri, Nov 27, 2009 at 9:48 AM, Matthew Paul Thomas <mpt at canonical.com> wrote:
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> Colin Watson wrote on 27/11/09 14:12:
>>...
>> On Thu, Nov 26, 2009 at 09:33:16PM +0000, Matthew Paul Thomas wrote:
>>>
>>> Evan Dandrea wrote on 12/11/09 14:18:
>>...
>>>>    <s>The installation medium could be faulty.  It is reccomended
>>>>    that you run the "Check CD for defects" option you saw when
>>>>    booting this CD/DVD. This may rule out the possibility of a bad
>>>>    CD burn.
>>>
>>> With a button to click to do that, if possible.
>>
>> Quite often, what's happened here is that the kernel encountered a
>> read error, and then squashfs decided to fall over in a messy heap.
>> The result is usually a downward spiral in quite short order; there's
>> generally enough in cache to be able to display an error message, I
>> think, but in many cases we aren't going to be able to launch an
>> application.

Would a 2nd squashfs file help?  It could hold the files needed to
gracefully deal with a read error in the first.

Of course a read error in the 2nd is then just as bad, but the smaller
footprint means less chance.

I am assuming that the files already exist in the first, so it would
be a matter of moving (not copying) them into the 2nd.  So this should
not take up much more space on the CD.  I am also assuming unionfs can
deal with 2 squashfs+ram.

if ram is over some threshold, preload the shutdown apps.  There are
probably enough 500mb machines that most would benefit from this.

>>
>> The most practical option here is probably a button to cause an
>> immediate reboot (after which we've told them what to select).
>>...
>
> Yes, that's what I meant -- a "Restart" button, not a button that tries
> to launch a standalone CD check.
>

kexec could load/launch the cd check.

Not sure if this is a good idea, given it might fail.  "your CD may be
damaged.  we will attempt to run the test, but the damage may cause
this to fail.  reboot and try from the menu"  yeah, too wordy.



-- 
Carl K