Android devices typically require you to use MTP to read and write files, instead of using USB mass storage. Wondering why? A lot of other people have wondered the same thing. This post (from here, the XDA developer forum) provides an explanation:
“MTP is a big improvement over USB mass storage — for devices with lots of internal memory, a manufacturer no longer needs to come up with some hard partition between the USB mass storage and internal storage. Instead, they are all in one partition, with MTP providing access to the directory of media files that would normally be available through USB mass storage. This means there is no longer a need for apps on SD card for such devices, because what used to be the ‘internal SD card’ is in the same partition as where applications are stored. The storage on your device can be used for either applications or media, depending on what you want to put on it. You aren’t stuck with how much space the manufacturer decided to leave for the two areas.[…Also,] this means that the media storage doesn’t need to be unmounted from Android when it is being accessed through the PC”
Problem is, Linux MTP is a little problematic. For example, the Nook I bought recently doesn’t work out of the box on my Slackware-current install despite having the latest libmtp – the device turned out to be read-only. Initially I had to use ADB to copy files onto it, but we found a simple solution. If your MTP devices turn out to be read-only on Linux, then there’s a strong possibility that the problem is with libMTP. Specifically, the devices may need to be listed in this file – music-players.h. For this you need the vendor number and the device ID. To get these, plug the device in via USB and type ‘lsusb’. Find the relevant line:
Bus 001 Device 036: ID 2080:0006 Barnes & Noble
The first of those (2080) is the vendor ID. The second is the device ID. Adding these to libmtp and recompiling resolved the Nook HD issue for me; maybe it will work for you too. Pretty soon libmtp will contain these devices as standard (the HD+ is already in there), but then there’ll be another crop of Android devices with similar MTP problems around in a minute, so it’s worth remembering the trick anyway.