[Bug 1087915] Re: Can't combine -o permissions with -o uid=UUU, gid=GGG

[Dan Muresan]

"id; touch newfile; stat newfile"

OK, you are right "-o permissions" alone accurately preserves owners and
permissions, which is sort of what I needed. I was confused by some
experiments I did with memory sticks accessed from Windows.

"Yes, that should be expected. You cannot both define the owner of a
file both as the current user and a forced user. See
http://www.tuxera.com/community/ntfs-3g-advanced/ownership-and-
permissions/#options"

Ownership and permission are orthogonal settings. You could force
ownership while leaving permissions alone.

This would be useful when working with memory sticks that are accessed
both in Windows and Linux (because sometimes directories created in
Windows will appear owned by root and unwritable).

The permissions/conditions table is actually quite confusing. It's
trying to represent a decision tree. I don't have better suggestions
though, other than switching the column order, i.e. Condition first,
Results second.

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https://bugs.launchpad.net/bugs/1087915

Title:
  Can't combine -o permissions with -o uid=UUU,gid=GGG

Status in “ntfs-3g” package in Ubuntu:
  New

Bug description:
  At the moment, it seems that mount.ntfs-3g disables -o permissions if
  -o uid=UUU and/or uid=GGG are also specified. This (combined with
  Ubuntu's compilation options disallowing user mounts for NTFS-3g)
  prevents unprivileged users from easily accessing NTFS systems while
  preserving standard Unix permissions.

  root# mount -o uid=500,gid=500,umask=000 /dev/sdb1 /vol/exthd/
  root# touch /vol/exthd/x
  root# ls -al /vol/exthd/x
  -rwxrwxrwx 1 muresan muresan 0 Dec 8 00:29 /vol/exthd/x
  root# chmod u-x /vol/exthd/x
  root# ls -al /vol/exthd/x
  -rwxrwxrwx 1 muresan muresan 0 Dec 8 00:29 /vol/exthd/x

  So chmod is ignored and all permissions are fixed to rwx.

  With "mount -o permissions", permissions ARE preserved, but all files
  are owned by root:

  root# mount -o permissions /dev/sdb1 /vol/exthd
  Using default user mapping
  root# touch /vol/exthd/x
  root# ls -al /vol/exthd/x
  -rw--w--w- 1 root root 0 Dec 8 00:29 /vol/exthd/x
  root# chmod u+x /vol/exthd/x
  root# ls -al /vol/exthd/x
  -rwx-w--w- 1 root root 0 Dec 8 00:29 /vol/exthd/x
  root# rm /vol/exthd/x

  root# ls -al /bin/bash
  -rwxr-xr-x 1 root root 920788 Apr 3 2012 /bin/bash
  root# cp -a /bin/bash /vol/exthd/
  root# ls -al /vol/exthd/bash
  -rwxr-xr-x 1 root root 920788 Apr 3 2012 /vol/exthd/bash
  root# umount /vol/exthd

  Trying to mount the filesystem as an unprivileged user results in:

  Either mount the volume as root, or rebuild NTFS-3G with integrated
  FUSE support and make it setuid root. Please see more information at
  http://tuxera.com/community/ntfs-3g-faq/#unprivileged

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