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igorzwx

Member

Registered: 2024-05-06

Posts: 105  

Automounting USB Drives (NTFS, exFAT) with dmask=022,fmask=133

System: Devuan, Mate Desktop

$ cat /etc/*-release | grep PRETTY
PRETTY_NAME="Devuan GNU/Linux 5 (daedalus)" 

$ inxi -S
System:
  Host: devuan Kernel: 6.1.0-25-amd64 arch: x86_64 bits: 64 Desktop: MATE
    v: 1.26.0 Distro: Devuan GNU/Linux 5 (daedalus)

When you insert a USB drive, it is automatically mounted to a directory under /media
However, if your USB drive has a Windows file system (e.g. NTFS, or exFAT), all your text files (and all other files: *.jpg, *.wav, etc.) on the USB drive become executable (777 - 022 = 755).
If you copy such files to your home folder, you have to fix permissions, for example:

$ chmod -Rv -x+X -- ./ 

_https://unix.stackexchange.com/questions/296967/how-to-recursively-remove-execute-permissions-from-files-without-touching-folder

It seems that this problem can be easily fixed with /etc/udisks2/mount_options.conf

$ ls -1 /etc/udisks2/
mount_options.conf.example
udisks2.conf 

$ sudo nano /etc/udisks2/mount_options.conf
 
$ cat /etc/udisks2/mount_options.conf
[defaults]
vfat_defaults=uid=$UID,gid=$GID,shortname=mixed,utf8=1,showexec,dmask=022,fmask=133
exfat_defaults=uid=$UID,gid=$GID,iocharset=utf8,errors=remount-ro,dmask=022,fmask=133
ntfs_defaults=uid=$UID,gid=$GID,dmask=022,fmask=133 

NOTE: /etc/udisks2/mount_options.conf is enabled automatically (a reboot is not required).
You can simply insert your USB drive and check file permissions:

$ touch file.txt
$ stat -c %a file.txt
644
$ mkdir folder1
$ stat -c %a folder1
755 

See:
_https://chmodcommand.com/chmod-644/
_https://chmodcommand.com/chmod-755/

Perhaps, this mount_options.conf can be somehow improved, or there is a better solution.

Last edited by igorzwx (2024-09-09 14:36:02)

PedroReina

Member

From: Madrid, Spain

Registered: 2019-01-13

Posts: 268  

Website

Re: Automounting USB Drives (NTFS, exFAT) with dmask=022,fmask=133

After 20 years, at last I know how to fix this annoying behaviour. Thanks a lot!

igorzwx

Member

Registered: 2024-05-06

Posts: 105  

Re: Automounting USB Drives (NTFS, exFAT) with dmask=022,fmask=133

Hope it works for you.

After 20 years, at last I know how to fix this annoying behaviour.

I thought that it is a special feature of Devuan.
If it is "annoying behaviour" for you, it does not mean that it is also annoying for others.
Since nobody complains, it might be the normal way of things for pulseaudio users.
Although, of course, it might be a security problem.

The /etc/udisks2/mount_options.conf should be tested and verified.

Umask
_https://en.wikipedia.org/wiki/Umask
_https://wiki.archlinux.org/title/Umask

$ umask
0022 

_https://www.linuxquestions.org/questions/linux-general-1/mounting-ntsf-drive-in-fstab-unsure-of-fmask-and-dmask-values-4175458533/#post4934200

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 

_https://thelinuxcode.com/automount-usb-ubuntu/
_https://www.freedesktop.org/wiki/Software/udisks/
_https://storaged.org/doc/udisks2-api/latest/mount_options.html
_https://www.kernel.org/doc/Documentation/filesystems/vfat.txt

ArchWiki
_https://wiki.archlinux.org/title/Udisks#NTFS_mount_failing
_https://wiki.archlinux.org/title/Udisks#NTFS_file_creation_failing_(filename-dependent)

$ locate udisksd
/usr/libexec/udisks2/udisksd
/usr/share/man/man8/udisksd.8.gz

$ man udisksd
$ man udisksctl 

Last edited by igorzwx (2024-09-10 14:47:50)