Cannot copy files from external USB HDD to computer
Solution 1:
You can take ownership of the whole /media/usb0/ directory: sudo chown -R $USER:$USER /media/mnt
If you are using a desktop environment, it's automount daemon should take care of mounting the volume with correct permissions. Just make sure to remove /media/usbX lines from /etc/fstab
If the volume is NTFS, make sure you have ntfs-3g installed.