VFS_ACL_XATTR(8) System Administration tools VFS_ACL_XATTR(8)

NAME

vfs_acl_xattr - Save NTFS-ACLs in Extended Attributes (EAs)

SYNOPSIS

vfs objects = acl_xattr

DESCRIPTION

This VFS module is part of the samba(7) suite.

This module is made for systems which do not support standardized
NFS4 ACLs but only a deprecated POSIX ACL draft implementation. This
is usually the case on Linux systems. Systems that do support just
use NFSv4 ACLs directly instead of this module. Such support is
usually provided by the filesystem VFS module specific to the
underlying filesystem that supports NFS4 ACLs

The vfs_acl_xattr VFS module stores NTFS Access Control Lists (ACLs)
in Extended Attributes (EAs). This enables the full mapping of
Windows ACLs on Samba servers even if the ACL implementation is not
capable of doing so.

The NT ACLs are stored in the security.NTACL extended attribute of
files and directories in a form containing the Windows SID
representing the users and groups in the ACL. This is different from
the uid and gids stored in local filesystem ACLs and the mapping from
users and groups to Windows SIDs must be consistent in order to
maintain the meaning of the stored NT ACL That extended attribute is
not listed by the Linux command getfattr -d filename. To show the
current value, the name of the EA must be specified (e.g. getfattr
-n security.NTACL filename).

This module forces the following parameters:

+o inherit acls = true

+o dos filemode = true

+o force unknown acl user = true


This module is stackable.

OPTIONS

acl_xattr:security_acl_name = NAME
This option allows to redefine the default location for the NTACL
extended attribute (xattr). If not set, NTACL xattrs are written
to security.NTACL which is a protected location, which means the
content of the security.NTACL attribute is not accessible from
normal users outside of Samba. When this option is set to use a
user-defined value, e.g. user.NTACL then any user can potentially
access and overwrite this information. The module prevents access
to this xattr over SMB, but the xattr may still be accessed by
other means (eg local access, SSH, NFS). This option must only be
used when this consequence is clearly understood and when
specific precautions are taken to avoid compromising the ACL
content.

acl_xattr:ignore system acls = [yes|no]
When set to yes, a best effort mapping from/to the POSIX draft
ACL layer will not be done by this module. The default is no,
which means that Samba keeps setting and evaluating both the
system ACLs and the NT ACLs. This is better if you need your
system ACLs be set for local or NFS file access, too. If you only
access the data via Samba you might set this to yes to achieve
better NT ACL compatibility.

If acl_xattr:ignore system acls is set to yes, the following
additional settings will be enforced:

+o create mask = 0666

+o directory mask = 0777

+o map archive = no

+o map hidden = no

+o map readonly = no

+o map system = no

+o store dos attributes = yes


acl_xattr:default acl style = [posix|windows|everyone]
This parameter determines the type of ACL that is synthesized in
case a file or directory lacks an security.NTACL xattr.

When set to posix, an ACL will be synthesized based on the POSIX
mode permissions for user, group and others, with an additional
ACE for NT Authority\SYSTEM will full rights.

When set to windows, an ACL is synthesized the same way Windows
does it, only including permissions for the owner and NT
Authority\SYSTEM.

When set to everyone, an ACL is synthesized giving full
permissions to everyone (S-1-1-0).

The default for this option is posix.

AUTHOR

The original Samba software and related utilities were created by
Andrew Tridgell. Samba is now developed by the Samba Team as an Open
Source project similar to the way the Linux kernel is developed.

Samba 4.18.11 03/13/2024 VFS_ACL_XATTR(8)