NTFS-3G usermapping permission issues

I use the command

Code:ntfsusermap /dev/sda1in order to generate a mapping file to use a NTFS usb external drive (that has already many files written under Windows in it) with debian based linux distro. When I launch this command, I see a prompt line Quote:

User:

so I input 1000 that is my linux account UID and I get the message:

Quote:

You have defined no group, this can cause problems Do you accept defining a standard group ?

I don't know why, since it hasn't appeared any step where input the group GID, and apparently seems I have no choice to click enter to continue the mapping file creation with no group or abort the procedure. The generated mapping file has the following structure:

Code:# Generated by ntfsusermap for Linux, v 1.2.0
:p1:S-1-5-21-7726005000-258166423-2201256221-513
p1:p1:S-1-5-21-7726005000-258166423-2201256221-1001And last line Code:S-1-5-21-7726005000-258166423-2201256221-1001match exactly the SID of the Windows user account used to write the files already present on the external hard drive.

Now, If I use the mapping file generated in this way and add in fstab the line Code:UUID=<MYDISKUID> /home/<mymountpoint> ntfs-3g defaults,dmode=770,fmode=660 0 0,when I try to mount the drive I get the warning message:

Quote:

There were no valid user or no valid group

and with some server applications I get the error message

Quote:

Your data directory is readable by other users Please change the permissions to 0770 so that the directory cannot be listed by other users.

How should I map the drive to avoid similar problems?