How UNIX permissions are affected when files are edited using Windows applications

Many Windows applications incorrectly interpret the ACLs when reading files that have UNIX security. When the application saves the file, the original UNIX permissions are lost. Using the cifs.preserve_unix_security option avoids this problem.

You should set the cifs.preserve_unix_security option to on if you serve files under the following conditions:

The files have UNIX permissions (that is, mode bits are set using the chmod or umask commands).
NFS v4 Access Control Lists (ACLs) are not applied to the files.
The files are in a qtree with UNIX or mixed security.
The files are edited using Windows applications.

Note: When this option is enabled, a UNIX style qtree appears as an NTFS volume instead of a FAT volume when viewed from a Windows client.

When the cifs.preserve_unix_security option is set, you can view and edit UNIX permissions using the Security tab in the Windows Properties dialog box . However, you cannot modify permissions from a Windows client if the operation is not permitted by the UNIX system. For example, you cannot change the ownership of a file you do not own, because the UNIX system does not permit this operation. This restriction prevents Windows clients from bypassing UNIX permissions set on the storage system.

When the cifs.preserve_unix_security option is set, you can view and edit UNIX permissions using the Security tab in the Windows Properties dialog box.

For more information about the cifs.preserve_unix_security option, see the options(1) man page.

Parent topic: How security styles affect access to your data