mounting ntsf drive in fstab , unsure of fmask and dmask values

plisken · 04-17-2013, 03:44 PM

I've created a mount point and an entry in my fstab which is as follows:

Code:

/dev/sdc1   /DATA   ntfs-3g  fmask=111,dmask=000   1   0

Now, I'm unsure what values I should have for fmask and dmask

From googling, I believe the above is full access to all, which I'm not wanting.
The other options I tried were

Code:

 fmask=133,dmask=022

I wish only 1 user and root to be able to have full access, none else.

All help appreciated...

thanks

alkk · 04-17-2013, 04:00 PM

Mount it with options "umask=022,dmask=022,uid=1000", where "1000" is id of the user allowed to acces. You can check your user id with command "id"

More information on umask: http://en.wikipedia.org/wiki/Umask

chrism01 · 04-17-2013, 11:57 PM

Actually, if you read that link carefully and this http://linux.die.net/man/8/mount, dmask+fmask are for (V)FAT filesytems.
For NTFS its just umask.

alkk · 04-18-2013, 04:46 AM

Quote:

Originally Posted by chrism01

Actually, if you read that link carefully and this http://linux.die.net/man/8/mount, dmask+fmask are for (V)FAT filesytems.
For NTFS its just umask.

You are wrong, dmask+fmask is supported by ntfs3g (but can be replaces with ulimit, yes): http://linux.die.net/man/8/ntfs-3g

chrism01 · 04-18-2013, 08:44 AM

I'm surprised those other links don't mention it.

plisken · 04-18-2013, 01:14 PM

I found the following text quite informative, I take no responsability for it and unfortunately, can not remember from where it came.

Code:

fmask, dmask, and umask taken together pertain only to Windows filetypes ( NTFS and FAT32 ) whereas umask alone pertains to both windows and Linux filetypes but are implemented 2 different ways.

On Linux Filesystems

At the moment of birth every file has permissions of 666 and every directory has permissions of 777. A system wide umask is created to modify these permissions immediately after birth and it's currently set at 002. So when you create a new file it's permissions are:

666
002 <-- minus the umask
==
664

And every new directory has permissions of:

777
002 <-- minus the umask
==
775

On Windows Filesystems

Windows fileystems have no Linux file permission attributes so a virtual filesystem is used to create a "view" to give them the appearance that they do have them. The system wide umask has no affect on these filesystems nor does a chmod or a chown. They can only be set when the "view" is created in fstab.

At the moment of birth NTFS files and folders start out with exactly the same permissions: 777. If you were to set up in fstab a umask of 002 for these partitions then the result would be different from a Linux filesystem:

File: 777 - 002 = 775
Folder: 777 - 002 = 775

The folder setting is fine and that's the way you want them to be but the files have all been made executable - every single one of them. You can change that by separating umask into it's constituent parts: fmask and dmask:

So if you set up fstab this way for an NTFS partition: dmask=002,fmask=113

File: 777 - 113 = 664
Folder: 777 - 002 = 775

All that said, I have opted for the folling line to be added to my fstab:

Code:

/dev/sdc1        /DATA            ntfs-3g     fmask=113,dmask=002,uid=1000    1   0

which seems to be working for me just now.

giving root and myself (1000) rw access to files and rwx access to folders
other users r access to files and rx access to folders.

This was based on a standard Slack install setting fmask to 133 and dmask to 022 based on root having read/write access to the ntfs partition.