Auto-mounted USB thumb drive only has user write permission if FAT16 or FAT32

Bug #121900 reported by Michael E. Adams
This bug affects 2 people
Affects Status Importance Assigned to Milestone

Bug Description

If I prepare a USB thumb drive (memory stick) with either FAT16 or FAT32 file systems, it will auto-mount and user write access is granted (i.e. user can drag from Home folder to USB drive folder to write to the device).

However, if I prepare the same thumb drive with an ext3 file system, the device will still auto-mount correctly, but user write access is denied.

I have demonstrated this on two different USB memory devices (old Memorex 128M Thumb Drive and a 5GB Pleomax Drive).

I used gparted to partition and format the devices.

Feisty Fawn Ubuntu 7.04 completely up to date as of 06/23/07

I followed many web search threads about people having trouble getting user write access to USB devices, but I haven't seen it trouble shot to this specific observation. I was originally trying to get user write access on my Pleomax re-formated to ext3 and notice that my Memorex was formated as FAT16 and worked just fine. So, I played around re-formating both devices to find this.

Revision history for this message
jcfp (jcfp) wrote :

This is likely to be a permission problem. Many filesystems commonly used on flash drives (like vfat) do not have support for file permission/ownership themselves. On modern distributions like Ubuntu, fake permissions are put on top of these filesystems in such a way that normal users have read and write permissions.

Ext3 on the other hand does have full support for unix style file permissions (usb drive or not), and these will be respected by the operating system. As a result you may well have insufficient rights by default to write to the filesystem as a normal user after formatting. Please mount the usb drive and then change the permissions and/or ownership in order to make the drive writable (using sudo when needed).

Revision history for this message
Juan Simón (simonbcn) wrote :

I also have he himself problem. It is normal that ubuntu respects the file permission/ownership in a hard disk ext3. In fact, I have formated my hard disk USB with ext3 therefore. But the system of auto-mount does not allow me to indicate to him that that device has right of rw for certain user because always mounts it with root. How I can change this by defect? For my, this it is a failure of the auto-mount system.

Revision history for this message
Launchpad Janitor (janitor) wrote :

[Expired for Ubuntu because there has been no activity for 60 days.]

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