I'm running Slackware64 15
I do not understand what the fmask and dmask are doing
the doc I have found says
"fmask=177,dmask=077" "Root has read/write access, users have no access (ntfs-3g)"
"fmask=333,dmask=222" "Everyone has read only access (built-in kernel ntfs driver)"
"fmask=133,dmask=022" "Everyone has read access, but only root can write (ntfs-3g)"
"fmask=111,dmask=000" "All users can read/write to any file (ntfs-3g)" .
my fstab was
/dev/nvme0n1p3 /mnt/ntfs-c ntfs3 fmask=333,dmask=222,uid=500,gid=500 1 0
and yet as root I can still use mkdir on the ntfs partition ?
the mount command says
/dev/nvme0n1p3 on /mnt/ntfs-c type ntfs3 (rw,relatime,uid=500,gid=500,fmask=37777600333,dmask=37777600222,iocharset=utf8)
these mask numbers look strange ?
if I change my fstab to
/dev/nvme0n1p3 /mnt/ntfs-c ntfs3 ro,fmask=333,dmask=222,uid=500,gid=500 1 0
I cannot do mkdir on the ntfs partition as expected
so why does fmask=333 and dmask=222 not prevent root from writing into the NTFS partition ?

I tried fmask=133 and dmask=022 (which is what I want)
but ended up having to run chkdsk on the NTFS partition to repair it.
I had used dolphin to drag and drop some files and directories to the NTFS partition as a user by mistake.

Also the vfat defaults seem to be fmask=0022 and dmask=0022.
what does this mean ?

probably this helps a bit: https://en.wikipedia.org/wiki/Umask

thanks
that explains what 0022 means.u=rwx,g=rx,o=rx
but not why my mount command shows strange fmask and dmask values
/dev/nvme0n1p3 on /mnt/ntfs-c type ntfs3 (rw,relatime,uid=500,gid=500,fmask=37777600333,dmask=37777600222,iocharset=utf8)
is the dmask/fmask suppose to be 3 digits or 4 digits long

I didn't like what was going on with fmask and dmask so I removed them from fstab
my fstab now looks like this
/dev/nvme0n1p3 /mnt/ntfs-c ntfs3 ro,uid=500,gid=500 1 0
my mount command now shows this
/dev/nvme0n1p3 on /mnt/ntfs-c type ntfs3 (ro,relatime,uid=500,gid=500,iocharset=utf8)
using a usb stick to move files from slackware to windows isn't a big deal for me.

what is the difference between ntfs3 and ntfs-3g
on my slackware15 system there is a "man ntfs-3g" but no "man ntfs3"

https://www.kernel.org/doc/html/late...ems/ntfs3.html
https://github.com/tuxera/ntfs-3g/wiki
https://www.paragon-software.com/home/ntfs3-driver-faq/

what is the difference between ntfs3 and ntfs-3g
on my slackware15 system there is a "man ntfs-3g" but no "man ntfs3"

What do you think? Should I repeat my post too? That is explained on those pages and I also quoted the most relevant part.

thanks
that explains what is going on with NTFS3
only thing not explained is why
when my fstab was
/dev/nvme0n1p3 /mnt/ntfs-c ntfs3 fmask=333,dmask=222 1 0 (this should be read only)
the mount command shows
/dev/nvme0n1p3 on /mnt/ntfs-c type ntfs3 (rw,relatime,fmask=37777600333,dmask=37777600222,iocharset=utf8)
where did those strange fmask and dmask numbers come from ?
and as root I was still able to use mkdir on the ntfs partition ?

At least you are not the only one seeing these "3777760" prefixes before your fmask and dmask values.
If you search for "dmask 37777600022" which is a more normal value for a dmask (0022 meaning writable for the owner), you'll find several discussions involving multiple Linux distributions. And no explanation to be found.

probably this: https://www.spinics.net/lists/ntfs3/msg00693.html

OK
so the funny numbers are only a display problem (we think)
but
dev/nvme0n1p3 /mnt/ntfs-c ntfs3 fmask=333,dmask=222 1 0
"fmask=333,dmask=222" "Everyone has read only access (built-in kernel ntfs driver)"
as root I was still able to use mkdir on the ntfs partition ?
is root not part of "Everyone" ?

no, root has special rights. But anyway umask does not restrict users, just modifies the permissions (see the man page I sent): the mask acts as a last-stage filter that strips away permissions as a file (or dir) is created

1 members found this post helpful.

looking at the NTFS3 manual it says
umask Controls the default permissions for files/directories created after the NTFS volume is mounted
so my concept of what these masks do is completely wrong.
I believe I got this misconception from the wording in the Slackware install.
I'm not going to run the install again but what I remember I was given several choices
on how to mount the NTFS on my machine . I was under the impression it had to do with restricting users.
No wonder I messed up my NTFS.
Thanks

I figured out what happened to my NTFS
if I remove the line
/dev/nvme0n1p3 /mnt/ntfs-c ntfs3 fmask=133,dmask=022 1 0
from fstab and reboot I get
bash-5.1$ pwd
/mnt
ls -l
drwxr-xr-x 2 root root 4096 Feb 27 06:51 ntfs-c
which is great
if I put the line
/dev/nvme0n1p3 /mnt/ntfs-c ntfs3 fmask=133,dmask=022 1 0
back in I get
bash-5.1$ pwd
/mnt
ls -l
drwxrwxrwx 1 root root 8192 Apr 10 12:31 ntfs-c
this is bad news
the root of my NTFS partition is wide open
not sure how to fix this so i'm going back mounting it read only.