Run nautilus with root permissions and go into the properties of the drive/partitions, check the tabs for 'share this folder' and 'allow others to create and delete files.' Lastly create 3 samba users and passwords.
When you first create a share from nautilus in the way you described it above it will automatically install the correct samba package. When you are done you can run the following command to check your share definitions:
Code:
net usershare info --long
BTW, not sure why you are using "gksu nautilus" to share these partitions unless you are setting these up as not being owned by you.
EDIT: If you run into any problems posting the output of the following commands will tell people how you are set up:
Code:
testparm -s
net usershare info --long
smbtree
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