When I connect my Kindle, it shows up as an usb0 media, which I can read but not write (owner = root).

However, if I do sudo umount /media/usb0, usb0 gets unmounted and a Kindle media gets mounted properly (is writable etc.).

What can cause such strange behavior? It's not only with Kindle, but with Flash drives etc. as well.

My /etc/fstab:

# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
proc            /proc           proc    nodev,noexec,nosuid 0       0
# / was on /dev/sda2 during installation
UUID=595815c2-d882-4ec8-a2cd-cce70471167c /               ext4    errors=remount-ro 0       1
# /boot was on /dev/sda6 during installation
#UUID=1340a336-66ca-4743-a6e4-41a307af2dda /boot           ext4    defaults        0       3
# swap was on /dev/sda5 during installation
UUID=afa49f1d-d505-4166-82a2-2f44548a48c6 none            swap    sw              0       0

UUID=deb86039-528a-45f3-b5f9-ce528740c94e /data_hdd ext4    defaults    0   2

My groups:

petr@sova:~$ groups petr
petr : petr adm cdrom sudo dip plugdev fuse lpadmin sambashare bumblebee