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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:

/etc/udev/rules.d/99-usb.rules

SUBSYSTEMS=="usb",DRIVERS=="usb-storage",SYMLINK+="USB_MASS_STORAGE%n"

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

/etc/auto.master.d/auto-USB.autofs

MY_USB       -fstype=auto    :/dev/USB_MASS_STORAGE1

/etc/auto.master

/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
+auto.master

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!

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