[Bug 1080701] Re: After 'Preparing to install Ubuntu' screen, raring installation hangs

[codeslinger]

the follwoing is a follow up to a discussion with cjwatson on #ubuntu-installer
--------------------------------------------

fresh boot from flash drive or DVD

swap is mounted
no other partitions are mounted

partman is not running/hung

Start Install
select English
[continue]

[x] Install this third party software
[continue]

At this point partman is launched.

result: partman.failed.r2.txt


========================

Analysis: Fundamentally there are multiple seperate bugs here, and they all interact to 
create the very erratic behavior that has been widely observed.


The primary issue is that if partman fails for any reason, then instead of exiting, it hangs.

When the installer gets run again, it will start a new partman process, the new partman process
will also hang because of the existance of the previously hung partman process.  This will occur
even if the original error condition has been cleared.  

By starting the installer multiple times, you will get multiple hung partman processes, one for 
each invocation.  The presence of any hung partman process will cause the new partman process 
to hang.  This accounts for a lot of the erratic behavior that people are seeing.


Partman has two modes.  The first mode is that it requires the partitons to be unmounted.
The second mode is that it will ignore(allow) the fact that partitions are mounted.

When partman is initially invoked, it checks to see if there are any partitions mounted.  If it 
finds any mounted partitions, it prompts the user to see if they would like to unmount the partitons
or to ignore the fact that the partitions are mounted.

For mode one, partman will attempt to unmount the mounted partitions.  If for any reason  -- 
such as a file that is in use --  that partman fails to unmount the partitons, then partman will hang.
Once partman is hung, the behavior is as described above.

For mode two, if the user chooses to continue while allowing the partitons to remain mounted, then partman
will work as expected.  This is why users are able to coax partman into working by both having a mounted 
partiton and by telling partman to ignore the mounted partitions.


now for the tricky bug...  if the swap file is mounted, partman does not prompt the user about the fact 
that it is mounted.  Neither does partman attempt to unmount the swap partition.  Instead partman will 
hang when it later realizes that the swap partiton is mounted.

If on the other hand, another partition is mounted, then partman will prompt as above, and if the user 
chooses to ignore the mounted partitions, then partman will also ignore the mounted swap partition.  
This is the crux of the observed erratic behavior.  Once partman decides to ignore the swap it will 
function as expected.

Partman will work if the swap partition is not mounted and no other partition is mounted.  Partman will 
also work if the swap partiton is mounted and at least one other partition is mounted... which causes 
partman to prompt about the partitions, AND the user chooses to ignore them.  In all other scenarios 
partman will fail.


Summary: Partman fails to turn off the swap file.  Partman fails to prompt the user about the presence 
of the swap file.  Partman can fail to unmount a partiton that is in use, after prompting the user.  Any 
failure will cause partman to hang. Once partman is hung, it stays hung even after quiting the installer.  
The presence of a hung partman process will cause subsequent install attempts to also fail.  They must 
either be killed manually or the computer rebooted.

It may be that under some circuimstances, partman does succeed in turning off the swap file, or for 
some other reason the swap file is not activated.  When this happens then partman works as expected.


===========================

When partman is hung, it looks like this:

root      8364  0.0  0.0   6436   396 ?        S    03:35   0:00 log-output -t ubiquity --pass-stdout sh -c /usr/share/ubiquity/activate-dmraid && /bin/partman
root      8365  0.0  0.0   4440   624 ?        S    03:35   0:00 sh -c /usr/share/ubiquity/activate-dmraid && /bin/partman
root      8371  0.0  0.0   4572   892 ?        S    03:35   0:00 /bin/sh /bin/partman
root      8496  0.1  0.0  24628  1112 ?        S    03:35   0:00 parted_server
root      9485  0.0  0.0   4572   880 ?        S    03:35   0:00 /bin/sh /lib/partman/display.d/10initial_auto
root     10634  0.0  0.0   4572   592 ?        S    03:36   0:00 /bin/sh /lib/partman/display.d/10initial_auto
root     10730  0.0  0.0   4572   896 ?        S    03:36   0:00 /bin/sh /lib/partman/automatically_partition/15reuse/choices


============================


** Attachment added: "partman log of failure when swap file is active"
   https://bugs.launchpad.net/ubuntu/+source/ubiquity/+bug/1080701/+attachment/3619695/+files/partman.failed.r2a.txt

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Title:
  After 'Preparing to install Ubuntu' screen, raring installation hangs

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