[Bug 1489855] Re: Change to mount sequence order breaks persistence on casper-rw partitions

[Akeo]

> the ones that matter are in the initrd (casper/initrd in this case).

D'oh! Of course they are... The way I was trying to test your changes
was indeed pointless.

> OK, that wasn't so bad:
https://code.launchpad.net/~mwhudson/ubuntu/+source/casper/+git/casper/+merge/370351

Awesome.

I just tested your changes, by simply updating scripts/casper-helpers
from the 2018.07.15 eoan-desktop-amd64.iso in http://cdimage.ubuntu.com
/daily-live/current/ with your proposed ones (the instructions on how to
recreate initrd were very helpful btw), and I too can confirm that the
case I have been testing (vfat partition with copy of the ISO content +
casper-rw partition) is fixed. Persistent partitions now seem to work
beautifully with Ubuntu Live. Great work!!

Btw, I should point out that, the reason I've been pushing for this
issue to be fixed is that I am the developer of Rufus, which (currently
[1]) is the application Ubuntu recommends when creating a bootable
Ubuntu USB Flash Drive on Windows. And because this has been requested
by a quite few users, I very recently added the ability to create
persistent partitions. However, this bug made it a bit vexing to not be
able to properly use that feature with Ubuntu (which is why, at the
moment, Rufus does not automatically add 'persistent' to the kernel
options when creating the drive -- I'm planning to add that once Eoan is
out). So I really appreciate the effort spent on fixing this. Many, many
thanks!

/Pete

[1] https://tutorials.ubuntu.com/tutorial/tutorial-create-a-usb-stick-
on-windows#1

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https://bugs.launchpad.net/bugs/1489855

Title:
  Change to mount sequence order breaks persistence on casper-rw
  partitions

Status in casper package in Ubuntu:
  In Progress

Bug description:
  the system boots fine when using a casper-rw FILE but drops to a
  busybox when using a partition

  
  the short log would be:
  ___________________________________________________
  Begin: Running /scripts/casper-premount ... done.
  done.
  umount: can't umount /cdrom: Device or resource busy
  Warning: Unable to find the persistent home medium
  umount: can't umount /cdrom: Device or resource busy
  Warning: Impossible to include the casper-sn Snapshot
  umount: can't umount /cdrom: Device or resource busy
  Warning: Impossible to include the home-sn Snapshot
  done.
  ___________________________________________________

  removing the "persistence" keyword from the syslinux.cfg works and the live usb drive boots just fine.
  using a persistence file instead of the partition and the usb drive boots just fine.

  i found older bug reports concerning the same problem but the fix
  proposed in 2010 is already integrated into the script "casper".

  so i started the flashdrive with the casper debug= option and i see
  the following (after probing several other devices it finally finds
  the right device and partition (sdb3)

  ___________________________________________________

  + cow_backing_mp=/cdrom
  + [ -e /cdrom/casper-rw ]
  + umount /cdrom
  + sys2dev /sys/block/sdb/sdb3
  + sysdev=/block/sdb/sdb3
  + udevadm info -q name -p /block/sdb/sdb3
  + echo /dev/sdb3
  + devname=/dev/sdb3
  + /sbin/blkid -s LABEL -o value /dev/sdb3
  + [ casper-rw = casper-rw ]
  + echo /dev/sdb3
  + return
  + cowprobe=/dev/sdb3
  + [ -b /dev/sdb3 ]
  + cowdevice=/dev/sdb3
  + get_fstype /dev/sdb3
  + local FSTYPE
  + local FSSIZE
  + fstype
  + eval FSTYPE=ext4 FSSIZE=8458862592
  + FSTYPE=ext4 FSSIZE=8458862592
  + [ ext4 != unknown ]
  + echo ext4
  + return 0
  + cow_fstype=ext4
  + cow_mountopt=rw,noatime
  + mount -t ext4 -o rw,noatime /dev/sdb3 /cow
  + [ ! -d /cow/upper ]
  + mkdir -p /cow/upper
  + continue
  + continue
  + mkdir -p /cow/work
  + [ -f /cow/format ]
  + [ DEFAULT = DEFAULT ]
  + modprobe -q -b overlay
  + grep -q ^overlay$
  + cut -f2 /proc/filesystems
  + UNIONFS=overlay
  + break
  ___________________________________________________

  this looks fine to me.. it looks like it recognizes everything .. it's
  ext4 .. label casper-rw.. it's mounting it...

  a little bit further down in the loooong log file it states the
  following:

  ______________________________________________

  + cow_backing_mp=/home-rw-backing
  + [ -e /home-rw-backing/home-rw ]
  + umount /home-rw-backing
  + sys2dev /sys/block/sdb/sdb3
  + sysdev=/block/sdb/sdb3
  + udevadm info -q name -p /block/sdb/sdb3
  + echo /dev/sdb3
  + devname=/dev/sdb3
  + /sbin/blkid -s LABEL -o value /dev/sdb3
  + [ casper-rw = home-rw ]
  + get_fstype /dev/sdb3
  + local FSTYPE
  + local FSSIZE
  + fstype
  + eval FSTYPE=ext4 FSSIZE=8458862592
  + FSTYPE=ext4 FSSIZE=8458862592
  + [ ext4 != unknown ]
  + echo ext4
  + return 0
  + [ ext4 = vfat ]
  + homecow=
  + [ -b ]
  + [ n != y ]
  + log_warning_msg Unable to find the persistent home medium
  + _log_msg Warning: Unable to find the persistent home medium\n
  + [ n = y ]
  + printf Warning: Unable to find the persistent home medium\n
  Warning: Unable to find the persistent home medium
  __________________________________________________________

  
  a warning about the home medium is shown in both cases (file and partition) but the persistence file works never the less..

  
  my system:  

  kubuntu linux 15.10 beta1

  uname -a
  Linux wald 4.1.0-3-generic #3-Ubuntu SMP Tue Jul 28 12:25:10 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

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