Extract footer from dump

[lukes1582]

Good morning I have a question. I'm using Sandy, but it shows me this mistake. Where am I wrong?
This is the error:
"Name of the parameter or ENTER to continue: image_file
Set new value for [ image_file ]:
/media/user/userdata/userdata.dd
Name of the parameter or ENTER to continue: out_dir
Set new value for [ out_dir ]:
/home/user/sandy
Name of the parameter or ENTER to continue:
[ INFO ]: Opening the dd image file: /home/user/sandy//media/user/userdata/userdata.dd...
[ ERROR ]: I/O error(2): No such file or directory /home/user/sandy//media/user/userdata/userdata.dd "
Other Informations:

• The userdata is maybe 25Gig.
• The distro is Linux ubuntu 3.13.0-119-generic #166-Ubuntu SMP x86_64 x86_64 x86_64 GNU/Linux.
• I ran Sandy in normal mode and in su mode.