Unable to mount ISO file on vboxsf Virtualbox shared folder

[ctgreybeard]

This is likely something I'm trying to do that can't be done ... but ...

I'm running Ubuntu 18.04 under VirtualBox and I'm trying to write the Ubuntu ISO to an SDcard for later use. Here's what I get:

╰─➤  ./bootiso --device /dev/sdc /media/sf_ISO/ubuntu-18.04-live-server-amd64.iso
Granting root privileges for bootiso.
Provided file `/media/sf_ISO/ubuntu-18.04-live-server-amd64.iso' seems to have a loose mime-type `application/octet-stream'.
It's possible that it is corrupted and you should control its integrity with a checksum tool.
The selected device `/dev/sdc' is connected through USB.
Created ISO mount point at `/tmp/iso.xvF'
mount: /tmp/iso.xvF: can't read superblock on /dev/loop1.
Could not mount ISO file.
Exiting bootiso...
umount: /tmp/iso.xvF: not mounted.
Could not unmount ISO mount point.

Is this something that I should be able to do?

[jsamr]

@ctgreybeard Given the log, it's actually the .iso file which cannot be mounted. I don't think it's related to a peculiar handling of SD interface.
Did you checksum the ISO ?

[jsamr]

@ctgreybeard could you also dump the output of file /media/sf_ISO/ubuntu-18.04-live-server-amd64.iso ?

Locally (DL through torrent) I have:

ubuntu-18.04-desktop-amd64.iso: DOS/MBR boot sector; partition 2 : ID=0xef, start-CHS (0x3ff,254,63), end-CHS (0x3ff,254,63), startsector 3672780, 4672 sectors

[ctgreybeard]

Hmmm, I checked the MD5SUM and it verifies but my file output is different. Are you looking at the server iso?

ubuntu-18.04-live-server-amd64.iso: DOS/MBR boot sector; partition 2 : ID=0xef, start-CHS (0x3ff,254,63), end-CHS (0x3ff,254,63), startsector 1575508, 4672 sectors

[jsamr]

@ctgreybeard You are right, I had the desktop file. So I downloaded the server ISO and had no issue with mounting it.

$ bootiso -ya ubuntu-18.04-live-server-amd64.iso 
Granting root privileges for bootiso.
[sudo] password for jsamr: 
Provided file `ubuntu-18.04-live-server-amd64.iso' seems to have a loose mime-type `application/octet-stream'.
It's possible that it is corrupted and you should control its integrity with a checksum tool.
Listing USB drives available in your system:
NAME           HOTPLUG   SIZE STATE   TYPE
sdd                  1  14.7G running disk
Autoselecting `sdd' (only USB device candidate)
The selected device `/dev/sdd' is connected through USB.
Created ISO mount point at `/tmp/iso.WS8'
`bootiso' is about to wipe out the content of device `/dev/sdd'.
Bypassing confirmation with `-y' option.
Erasing contents of /dev/sdd...
Partition #1 contains a vfat signature.
Creating FAT32 partition on `/dev/sdd1'...
Created USB device mount point at `/tmp/usb.An5'
Copying files from ISO to USB device with `rsync'    
Synchronizing writes on device `/dev/sdd'    
`bootiso' took 81 seconds to write ISO to USB device with `rsync' method.
ISO succesfully unmounted.
USB device succesfully unmounted.
USB device succesfully ejected.
You can safely remove it !

Perhaps Ubuntu team have replaced the ISO upstream due to a bug ; you might want to download a new one and hopefully it should work.

[ctgreybeard]

Because I checked against the latest MD5SUM I don't think it has changed.

Let me try some other things.

[ctgreybeard]

OK. Apparently a virtualbox mounted drive doesn't support what the script is attempting. I copied the iso to /tmp and it works.

Thanks!

Bill

[jsamr]

@ctgreybeard Interesting! Glad it works for you. Could you dump your fstab file with the aforementioned mount point? I could therefore add an entry to a "Known issues" section.

[ctgreybeard]

It's not in the fstab. The mount is made by the VirtualBox Guest Additions

[ctgreybeard]

The line in the mtab is:

ISO /media/sf_ISO vboxsf rw,nodev,relatime 0 0

[jsamr]

@ctgreybeard I think I spot the bug in Virtualbox issue tracker: Cannot mount loop device from within shared folder on 5.2.x. Feel free to give them feedback :-)

[ctgreybeard]

Good sleuthing there ... I've put my 2 cents in.