How to unmount a live DVD/USB?

Question

I need to burn a new live DVD (Debian 8.0) from an Ubuntu 16.04 live DVD.

• the live DVD is the device /dev/sr0 mounted on /cdrom
• the blank DVD to be burnt is also located at /dev/sr0
• Changing the DVD does not umount the live DVD on /cdrom

How can I umount my live DVD in order to burn my new live DVD?

RAM drive

If there is enough RAM in your computer, it should be possible to detach the DVD disk, if you add the boot option toram, because it means that the system will write the content of the DVD disk into RAM, and use that image instead of reading files from the disk.

A. When you boot with syslinux you can add boot options like this:

1. As the CD boots, the user can gain access to the advanced page and its options by pressing any key when the small logo appears at the bottom of your screen.

2. After selecting language you arrive at the main menu of the installer.

3. Select 'Try Ubuntu without installing'

4. Press F6.

5. A menu with a number of options appears. The option toram is not there, so press Escape to close the list.

6. Now a string of options is visible, often with 'quiet' or 'quiet splash ---' at the end. Add toram to the string surrounded by spaces before the dashes.

   ... toram ---
   

7. Press return, and booting the live session 'Try Ubuntu' continues ...

See this link for more details, Syslinux boot options

B. When you boot with grub you can add boot options like this:

When a live drive boots to grub, you will see the grub menu (white text on black background). 'Try Ubuntu without installing' is selected, and should be used in this case.

1. The automatic countdown may be stopped by pressing any key other than the ENTER key.

2. Press the 'e' key to reveal the selection's settings.

3. Use the UP/DN/Left/Right cursor keys to navigate to the desired point for editing. Do not use ENTER to move between lines.

4. Move the cursor to the space before the dashes at the end of the 'linux' line. Add toram to the line surrounded by spaces before the dashes.

   ... toram ---
   

5. When editing is complete, Press CTRL-x or F10 - and booting continues.

See this link for more details, Editing the GRUB 2 Menu During Boot

-o-

Workarounds

1. Boot from DVD, write to a USB pendrive or memory card.

2. Boot from USB pendrive or memory card, write to a DVD disk.

Comments

[SamWN]

Just to make sure I fully understand the situation: - You have 1 disk drive. - You are trying to run Ubuntu off of a live disk (using the disk drive). - And want to know how to eject the live disk so that you can use the disk drive. Considering that the OS is running off of the disk, I can't imagine that ejecting it is safe to do... A bit like amputating your own head... Someone may be able to help you figure out a way to instruct the system to read the OS from a ram disk (i.e. /dev/shm ), but that's still risky if you're not using ECC memory. I would suggest simply avoiding the issue entirely

[Pandya]

I think in case of usb, it should be /isodevice which can be lazy unmounted by umount -l

[Mark Kirby]

Why see the link for adding boot options? Would it not be better to have that (the main info of the answer) here? This is borderline link only, please edit.

[sudodus]

There are two options, one for syslinux and one for grub, so the answer will be long. Anyway, I will try to make a good description here.

[Mark Kirby]

Don't get me wrong, I think this answer is right but the links can be unreliable and that would invalidate the answer, just copy some info from the link to flesh it out a bit, only the grub one would do IMO.

[sudodus]

I intend to create pictures via booting in VBox ...

[Mark Kirby]

Don't worry about images, this is great +1

[sudodus]

OK, but I want to add two screenshots :-)

[Mark Kirby]

That is up to you, I won't stop you making it better :)