Trying to boot from USB "Scanning disc for index files..."

Question

I'm trying to boot an Ubuntu 14.04.1 LTS USB stick, and it seems it will never enter the Desktop.

I'm stuck on the bootscreen, and here are the lines when I press "ESC" :

stdin: Not a typewriter
umount: can't umount /cdrom: Device or resource busy
/init: line 7: can't open /dev/sr0: No medium found
stdin: Not a typewriter
/init: line 7: can't open /dev/sr0: No medium found
stdin: Not a typewriter
umount: can't umount /cdrom: Device or resource busy
/init: line 7: can't open /dev/sr0: No medium found
stdin: Not a typewriter
/init: line 7: can't open /dev/sr0: No medium found
stdin: Not a typewriter
umount: can't umount /cdrom: Device or resource busy
/init: line 7: can't open /dev/sr0: No medium found
Generating locales...
  fr_FR.UTF-8... done
Generation complete.
pwconv: failed to change the mode of /etc/passwd- to 0600
Using CD-ROM mount point /cdrom
Identifying... [d0f03a23b18ebd55964c351e853c5b6f-2]
Scanning disc for index files...
stdin: Not a typewriter
stdin: Not a typewriter
stdin: Not a typewriter
stdin: Not a typewriter
umount: can't umount /cdrom: Device or resource busy
/init: line 7: can't open /dev/sr0: No medium found
stdin: Not a typewriter
/init: line 7: can't open /dev/sr0: No medium found
stdin: Not a typewriter
umount: can't umount /cdrom: Device or resource busy
/init: line 7: can't open /dev/sr0: No medium found
stdin: Not a typewriter
/init: line 7: can't open /dev/sr0: No medium found
stdin: Not a typewriter
umount: can't umount /cdrom: Device or resource busy
/init: line 7: can't open /dev/sr0: No medium found
Generating locales...
  fr_FR.UTF-8... done
Generation complete.
pwconv: failed to change the mode of /etc/passwd- to 0600
Using CD-ROM mount point /cdrom
Identifying... [d0f03a23b18ebd55964c351e853c5b6f-2]
Scanning disc for index files...

It blocks a long while on "Scanning disc for index files...", then writes all the following and re-blocks on next Scanning disc for index files....

I used the usb-creator-gtk program to build my USB stick, with persistent data enabled.

As somebody seemed to have the same problem (http://www.reddit.com/r/linuxquestions/comments/2dsgd5/cant_boot_from_cdusb_to_install_ubuntu/) I tried the solution from there (adding nomodeset), but I still have the same results: blocked at the bootscreen (not really hanged because the little dots are still "alive")...

Does somebody have an idea what happens ?

Solution

I finally found a workaround: I created an usb stick with persistent data disabled, and I finally managed to boot correctly!

I was inspired by comment 15 of the bug chapuzzo point me out.

Comments

[Anthony O.]

I tried that but it didn't work better :(