I need some help trying to figure out how to restrict the reading and writing access of usb devices. There are two groups on my system:

  • usbreaders: only should have rights to access and read the usb content.
  • usbwriters: should have reading and writing rights on the usb content.

I configured the following udev rule to create a symbolic link of the storage device attached:



Then I configured autofs to mount the usb content with different permissions to two different folders:


MY_USB       -fstype=auto    :/dev/USB_MASS_STORAGE1


/USBRO  /etc/auto.master.d/auto-USB.autofs --timeout=10,noexec,nosuid,uid=root,gid=usbreaders,fmask=127,dmask=027
/USBRW  /etc/auto.master.d/auto-USB.autofs --timeout=10,noexec,nosuid,uid=root,gid=usbwriters,fmask=007,dmask=007

But something weird happens. Permissions changes automatically, sometimes owns to usbwriters and sometimes to usbreaders o both folders... really weird.

Could anybody give me ha hand with this? Thank you, really aprecciated!

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.