I'm running Ubuntu from a "Try Ubuntu" file that I downloaded to my USB stick and booted from. Can I mount that very USB stick and write to it while running Ubuntu from it? If so, how?

Edit to clarify: It's not important that settings of applications and such are saved; I'm just looking to save some specific data.

Another edit: I restarted and booted again. This time the USB stick is found (/dev/sdb1) but it is already mounted (read-only) to /cdrom, so I can't mount it again. A file called "README.diskdefines" on the USB stick says that it's Ubuntu 10.10 i386.

  • 1
    You can try remounting rw with sudo mount -o remount,rw /cdrom
    – enzotib
    Jul 26, 2011 at 19:02
  • 2
    @enzotib: That did it. Thanks! Please put it as an answer.
    – Andy
    Jul 26, 2011 at 19:26
  • ok I put it in an answer
    – enzotib
    Jul 26, 2011 at 19:43
  • The USB stick is always already mounted, as you use it (in /cdrom). If you want to mount things again, you have to unmount them first.
    – Quidam
    Apr 26, 2020 at 14:11

4 Answers 4


You can remount in read-write mode the partition mounted on /cdrom with the following command:

sudo mount -o remount,rw /cdrom
  • I did this, and the command completed successfully, and I can sudo touch a file onto it. However, it's still not writable with the GUI file manager. Everything is owned by root. I tried chmod to 777 and that did nothing. I also get "Operation not permitted" when trying to chown it to the xubuntu live session user. Jul 17, 2018 at 5:53
  • That's easy to be root in a live-CD session, run " sudo -i ", so they won't ask you for your root password. I edit the answer to add that.
    – Quidam
    Apr 26, 2020 at 14:15

I have tried to write to my cdrom drive but it requires root permission, which is not really practical as every time I need to write to the folder its mounted to, I have to use sudo/gksu.

After some researching to make the cdrom folder writeable, I realized that the problem here is simple. Data need to be easily shared (both read and write) on both Windows and Ubuntu. So I have changed my approach and use following technique.

  1. Use GParted to have following partition layout on my 8GB USB stick:

    • [ Primary 4GB fat32 label Data flag lba ]
    • [ Logical 710MB fat32 label LiveUSB flag boot/lba ]
    • [ Logical 3.29GB ext4 label casper-rw ] ]

    After I created all partitions, I had to unplug and re-plug the stick so that Ubuntu would remount all partition. I am not sure about the lba flag but I keep it just to be in safer side.

  2. Use usb-creator to put Live USB to 2nd partition which is labeled LiveUSB. I also followed the instructions here and added the word persistent after append in order for the stick to become a real Live USB device.

After booting from the newly created Live USB stick, a mount point Data show up, and I can write to that easily. After booting Windows and putting in the USB stick, I also have a drive labeled Data for me to write to. This fitted my need.


Yes. If you want to, you can make your USB-stick persistent when you create it, which allows you to save settings and save files within Ubuntu. If you are looking to be able to access the files you write to the stick, while NOT running from the stick, you'll need to partition the stick.

More information on both can be found at https://wiki.ubuntu.com/LiveUsbPendrivePersistent

  • 1
    I've already created the stick and am currently running from it (on a computer without net connection). I don't think it's persistent. I can use it to read/write files while not running Ubuntu from it, both on Windows and Ubuntu. Is it possible in this situation, without creating a new stick?
    – Andy
    Jul 26, 2011 at 18:35
  • I don't need to store fancy things like keyboard layout and settings, just a single file.
    – Andy
    Jul 26, 2011 at 18:35
  • Someone knows why I can only have one persistant storage when I use multiboot, (like with Multisystem)?
    – Quidam
    Apr 26, 2020 at 14:12

Persistent partitions on syslinux type bootable flash drives do not work since 14.04, (SDC, UNetbootin, Universal).

Persistent partitions do work on grub2 type bootable flash drives,(mkusb, grub-n-iso).

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