I believe that this comment:
https://code.launchpad.net/~noorez-kassam/ubuntu/utopic/initramfs-tools
/fix-for-1317437/+merge/219927/comments/592175
""""
This is the way I understand this is and my testing is shown below:
Mounting and creating the loop device in the same step with the readonly
option, makes it impossible to remount the loop device later as read-
write.
By creating the loop device separately (which defaults to read-write
capable unless the -r option is supplied), the loop device can then be
mounted readonly, and later remounted as read-write.
This change is needed since release 14.04, which - for unknown reasons -
now won't let the loop device be remounted read-write (perhaps it's
passing the -r option to losetup internally and it's losetup which has
started enforcing this?).
The end result is that Wubi installs cannot boot, because the remount
read-write fails.
My tests confirm this:
Setup:
1. Create a file, format as ext4.
bcbc@neptune:~$ dd if=/dev/zero of=new.disk bs=1MB count=100
bcbc@neptune:~$ mkfs.ext4 -F new.disk
2. Old method, mount and create loop device as read only, then try to remount
bcbc@neptune:~$ sudo mount -r -t ext4 -o loop new.disk /mnt
bcbc@neptune:~$ sudo touch /mnt/test
touch: impossible de faire un touch «/mnt/test»: Système de fichiers accessible
en lecture seulement
bcbc@neptune:~$ sudo mount -o remount,rw /mnt
mount : impossible de remonter périphérique bloc /dev/loop0 en
lecture/écriture, est protégé en écriture
bcbc@neptune:~$ sudo umount /mnt
3. New method, first create loop device (defaults to read-write capable), then
mount as read only, then try to remount read-write
bcbc@neptune:~$ sudo losetup /dev/loop0 new.disk
bcbc@neptune:~$ sudo mount -r -t ext4 /dev/loop0 /mnt
bcbc@neptune:~$ sudo touch /mnt/test
touch: impossible de faire un touch «/mnt/test»: Système de fichiers accessible
en lecture seulement
bcbc@neptune:~$ sudo mount -o remount,rw /mnt
bcbc@neptune:~$ sudo touch /mnt/test
bcbc@neptune:~$ sudo umount /mnt
bcbc@neptune:~$ sudo losetup -d /dev/loop0
4. To confirm it's probably passing -r to losetup
bcbc@neptune:~$ sudo losetup -r /dev/loop0 new.disk
bcbc@neptune:~$ sudo mount -r -t ext4 /dev/loop0 /mnt
bcbc@neptune:~$ sudo touch /mnt/test
touch: impossible de faire un touch «/mnt/test»: Système de fichiers accessible
en lecture seulement
bcbc@neptune:~$ sudo mount -o remount,rw /mnt
mount : impossible de remonter périphérique bloc /dev/loop0 en
lecture/écriture, est protégé en écriture
bcbc@neptune:~$ sudo umount /mnt
bcbc@neptune:~$ sudo losetup -d /dev/loop0
Conclusion:
This fix is appropriate and required for loop mounted installs
""""
>From "bcbc" is what this bug is all about.
** Changed in: initramfs-tools (Ubuntu)
Assignee: (unassigned) => Rafael David Tinoco (inaddy)
** Changed in: initramfs-tools (Ubuntu)
Status: Confirmed => In Progress
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https://bugs.launchpad.net/bugs/1317437
Title:
wubi kernel option "rw" required
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