casper toram doesn't free /dev/loop0 after copy

[Alex Roper]

When booting Ubuntu 12.04 livecd using the "toram" option to copy the CD image into RAM before proceeding, casper mounts the imstallation media at /isodevice at boot. This device is no longer necessary once the image copy is complete, and therefore unmounting it should work if requested by the user.

However, attempting to umount it fails claiming it is busy, yet fuser -m provides nothing. It turns out that /dev/loop0 is still bound to the image stored on /isodevice.

I agree it's perfectly reasonable to keep /isodevice mounted after boot toram in case the user wants something on there, but it should be easy via gui or cli to umount it, and since the loopback doesn't show in lsof or fuser -m, many intermediate users are going to be stumped by this.

Since yanking the device anyway doesn't cause any problems, I would consider this a minor bug concerned primarily with user friendliness.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Bob/Paul (ubuntu-launchpad-bobpaul)]

I believe this is a regression, as I reported it working correctly on 11.04 in an edit I made to the wiki (https://wiki.ubuntu.com/BootToRAM) I'm downloading 11.04 and 11.10 to confirm.

>I agree it's perfectly reasonable to keep /isodevice mounted after boot toram in case the user wants something on there,

No, that's not really good. It's better to clean things up fully. If the user unplugs and replugs, it'll show up in /media/FS_LABEL (/media/CORSAIR in my case). This is where the user should expect to find thumbdrives, not in /isodevice. After booting with toram, the device should be unmounted so it can be safetly pulled. If the user wants something on it, they should plug it back in.

>Since yanking the device anyway doesn't cause any problems,

Presumably the filesystem on your thumbdrive is FAT32. Other filesystems might not be so friendly without a clean unmount, but even FAT32 will be marked as dirty and request an fsck when next mounted. This can sometimes interfere with automount systems on various OSs/distros (had issues with this in the past on both WinXP and freebsd for sure, though not necessarily related to this bug).

[Stéphane Graber (stgraber)]

/dev/loop0 is used for the loop mounted squashfs image it can't be unmounted as that'd mean loosing access to all the files.