Merge ~crass/casper:fix-toram into casper:main

[Glenn Washburn]

This is a fix for LP: #684280 and in doing so makes the /isodevice mount user accessible again from overlayfs root if "toram" is on the kernel commandline. This brings back behavior that some people have comes to rely on (that /isodevice is user accessible) and when "toram" is used allows for removing devices that contain the backing iso while the live system is running.

To test, first boot via loopback without "toram" on the kernel commandline and verify that /isodevice exists after boot is complete. Then boot with "toram" on the kernel commandline and verify that the iso file does not exist in the list of loopback devices listed via losetup.

[Steve Langasek (vorlon)]

> This brings back behavior that some people have comes to rely on

But that cannot be bug #684280, which was reported in 2010 and affects all supported releases of Ubuntu for several years now.

Perhaps there has been some mismarking of other bugs as duplicates?

review: Needs Information

[Glenn Washburn (crass)]

> > This brings back behavior that some people have comes to rely on
>
> But that cannot be bug #684280, which was reported in 2010 and affects all
> supported releases of Ubuntu for several years now.
>
> Perhaps there has been some mismarking of other bugs as duplicates?

What people have been doing is working around the bug as mentioned in the comments of that bug. You can see consistently through the years people working around it. Regardless, this merge request fixes that bug.

[Glenn Washburn (crass)]

Its unclear to me what other information is needed. Could you please be specific in what more information is required?

[scmarko (scmarko)]

This bug should get fixed as it seems to affect all current Ubuntu based distributions. Currently when you boot an ISO file from the hard drive using the "toram" option, Ubuntu loads fine into RAM, but the problems start when you try to repartition and install Ubuntu from RAM to the hard drive.

Because the hard drive is left mounted after Ubuntu has loaded into RAM, you can't repartition the hard drive if you started the ISO file from the same hard drive partition.

There are a lot of cases when Ubuntu should be able to boot completely to RAM, allowing unmounting of the hard drive and let it repartition the hard drive, but this bug prevents that. This bug adds a lot complexity when users need to modify their initrds in Ubuntu installations manually.

Unmerged commits

4f0556e... by Glenn Washburn on 2023-10-04

Allow device with loopback loaded iso to be removed when toram is specified

When running from ram, the iso's backing device should be unused by the
livecd. The expected use case is that a user is loading the iso from a
removable device (eg. usb stick) and wants to start the livecd and remove
the device while the livecd system is running.

LP: #684280

d6b5560... by Glenn Washburn on 2023-10-04

Make /isodevice accessible from overlay root again

This functionality appears to have been inadvertently removed during
the merging of lupin-casper. To quote from an issue comment[1]:"The problem
without these lines of code is that the partition remains mounted but the
mount point is lost, it can not be unmounted, it locks the partition
(avoiding changes in the disk when toram option is used)".

[1] https://bugs.launchpad.net/ubuntu/+source/lupin/+bug/1960457/comments/34

diff --git a/scripts/casper-bottom/05mountpoints b/scripts/casper-bottom/05mountpoints
index bce0b1f..ecdcc53 100755
--- a/scripts/casper-bottom/05mountpoints
+++ b/scripts/casper-bottom/05mountpoints
@@ -28,4 +28,11 @@ mount -n -o move /cdrom /root/cdrom
 mkdir -p /root/media
 ln -s /cdrom /root/media/cdrom
 
+# Move the mount point for the filesystem containing the ISO when loopback
+# booting.
+if grep -q '^[^ ]* /isodevice ' /proc/mounts; then
+        mkdir -p ${rootmnt}/isodevice
+        mount -n -o move /isodevice ${rootmnt}/isodevice
+fi
+
 log_end_msg
diff --git a/scripts/casper-bottom/99casperboot b/scripts/casper-bottom/99casperboot
index da4909f..aa1575a 100755
--- a/scripts/casper-bottom/99casperboot
+++ b/scripts/casper-bottom/99casperboot
@@ -16,3 +16,8 @@ prereqs)
 esac
 
 touch /run/.casper-boot
+
+if [ "$TORAM" ] && [ -e "${rootmnt}/isodevice" ]; then
+        umount -l ${rootmnt}/isodevice
+        losetup -d /dev/loop0
+fi