Fmask

The following is copy pasted from "man mount". umask=value Set the umask (the bitmask of the permissions that are not present). The default is the umask of the current process. The value is given in octal. dmask=value Set the umask applied to directories only. The default is the umask of the current process. The value is given in octal. fmask=value Set the umask applied to regular files only. The default is the umask of the current process. The value is given in octal.

Examples

The following is an example of a user's "/etc/fstab" file. # /etc/fstab: static file system information. # /dev/hda1 /media/win ntfs rw,suid,dev,exec,auto,user,async,fmask=113,dmask=002,gid=46 0 1 /dev/hda2 /media/big vfat rw,suid,dev,exec,auto,user,async,fmask=113,dmask=002,gid=46,utf8 0 1 /dev/hdb1 /media/old vfat rw,suid,dev,exec,auto,user,async,fmask=113,dmask=002,gid=46,utf8 0 1The meanig of dmask and fmask is as follows.
The directories will have rwx rwx r-x (775) permissions,
while the files will have rw- rw- r-- (664) permissions.
To know how the values are calculated read ahead.

Directories

Full access for directories is 777. 777 AND NOT 002 = 775 in detail: 777₈ = 111 111 111₂ 002₈ = 000 000 010₂ NOT 000 000 010₂ = 111 111 101₂ 111 111 111₂ (777) AND 111 111 101₂ (775) 111 111 101₂ (775)

Files

Full access for files is 666. 666 AND NOT 113 = 664 in detail: 666₈ = 110 110 110₂ 113₈ = 001 001 011₂ NOT 001 001 011₂ = 110 110 100₂ 110 110 110₂ (666) AND 110 110 100₂ (664) 110 110 100₂ (664)

See also

* fstab
* umask
* dmask