Problems auto-mounting USB drives in Linux? Check your permissions!

I just had a bit of an issue on my Slackware laptop where my USB flash drive wouldn’t mount as a user. In KDE, plugging in the USB drive would have the notification pop-up come up, but it wouldn’t let me mount the device.

When I checked out /var/log/messages, I ended up seeing this particular error:

Jun 2 20:55:45 lappy dbus-daemon: [system] Rejected send message, 1
matched rules; type="method\_call", sender=":1.11" (uid=1000
pid=5137 comm="kdeinit4: kded4 [kdeinit])
interface="org.freedesktop.Hal.Device.Volume" member="Mount" error
name="(unset)" requested\_reply=0 destination="org.freedesktop.Hal"
(uid=0 pid=1886 comm="/usr/sbin/hald))

It looked liked a permissions issue. After checking /etc/dbus-1/system.d/hal.conf I could see that there was permissions set in place for the plugdev group to mount USB drives.

The fix was really simple. I just logged in as root and ran usermod -a -G plugdev $USER