I have wrote an Ubuntu ISO image to an USB pen-drive.

I think Ubuntu is loaded in RAM, and nothing is wrote on my USB. I need to be 100% sure that nothing is wrote onto the USB pen-drive. I am asking you, is it?

If some files are wrote onto the USB pendrive and then deleted from the OS it would be a problem for me.


Nothing will be stored persistently on the drive.

Any modification to any file / folder performed during the usage of the system will be stored in the filesystem loaded into the memory, and not in the filesystem stored into the drive.

If you want proofs, here's a comparison of the MD5 sums of the Ubuntu Desktop 15.04 64 bit ISO and of the USB drive to which I wrote it and from which I've been regularily booting for weeks:

ubuntu@ubuntu /media/ubuntu/DATA/Transmission
 % md5sum ubuntu-15.04-desktop-amd64.iso 
53c869eba8686007239a650d903847fd  ubuntu-15.04-desktop-amd64.iso
ubuntu@ubuntu /media/ubuntu/DATA/Transmission
 % ls -l ubuntu-15.04-desktop-amd64.iso 
-rwxrwxrwx 1 ubuntu ubuntu 1150844928 Aug 13 17:27 ubuntu-15.04-desktop-amd64.iso
ubuntu@ubuntu /media/ubuntu/DATA/Transmission
 % sudo dd if=/dev/sdb iflag=fullblock bs=8192 count=$((1150844928/8192)) | md5sum -
140484+0 records in
140484+0 records out
1150844928 bytes (1.2 GB) copied, 100.541 s, 11.4 MB/s
53c869eba8686007239a650d903847fd  -
  • 1
    And now 10.000 :) – A.B. Sep 12 '15 at 7:35

You can write files on the USB if it is not write-protected. But this action has to be user-approved. The LIVE system itself will not write anything on it. But to be 100% sure in your case, try to install some program from Software center and you will see, if it persists after rebooting.

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