Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 870 insertions, 0 deletions

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+=====
+Usage
+=====
+
+This module supports the SMB3 family of advanced network protocols (as well
+as older dialects, originally called "CIFS" or SMB1).
+
+The CIFS VFS module for Linux supports many advanced network filesystem
+features such as hierarchical DFS like namespace, hardlinks, locking and more.
+It was designed to comply with the SNIA CIFS Technical Reference (which
+supersedes the 1992 X/Open SMB Standard) as well as to perform best practice
+practical interoperability with Windows 2000, Windows XP, Samba and equivalent
+servers.  This code was developed in participation with the Protocol Freedom
+Information Foundation.  CIFS and now SMB3 has now become a defacto
+standard for interoperating between Macs and Windows and major NAS appliances.
+
+Please see
+MS-SMB2 (for detailed SMB2/SMB3/SMB3.1.1 protocol specification)
+or https://samba.org/samba/PFIF/
+for more details.
+
+
+For questions or bug reports please contact:
+
+    smfrench@gmail.com
+
+See the project page at: https://wiki.samba.org/index.php/LinuxCIFS_utils
+
+Build instructions
+==================
+
+For Linux:
+
+1) Download the kernel (e.g. from https://www.kernel.org)
+   and change directory into the top of the kernel directory tree
+   (e.g. /usr/src/linux-2.5.73)
+2) make menuconfig (or make xconfig)
+3) select cifs from within the network filesystem choices
+4) save and exit
+5) make
+
+
+Installation instructions
+=========================
+
+If you have built the CIFS vfs as module (successfully) simply
+type ``make modules_install`` (or if you prefer, manually copy the file to
+the modules directory e.g. /lib/modules/6.3.0-060300-generic/kernel/fs/smb/client/cifs.ko).
+
+If you have built the CIFS vfs into the kernel itself, follow the instructions
+for your distribution on how to install a new kernel (usually you
+would simply type ``make install``).
+
+If you do not have the utility mount.cifs (in the Samba 4.x source tree and on
+the CIFS VFS web site) copy it to the same directory in which mount helpers
+reside (usually /sbin).  Although the helper software is not
+required, mount.cifs is recommended.  Most distros include a ``cifs-utils``
+package that includes this utility so it is recommended to install this.
+
+Note that running the Winbind pam/nss module (logon service) on all of your
+Linux clients is useful in mapping Uids and Gids consistently across the
+domain to the proper network user.  The mount.cifs mount helper can be
+found at cifs-utils.git on git.samba.org
+
+If cifs is built as a module, then the size and number of network buffers
+and maximum number of simultaneous requests to one server can be configured.
+Changing these from their defaults is not recommended. By executing modinfo::
+
+	modinfo <path to cifs.ko>
+
+on kernel/fs/smb/client/cifs.ko the list of configuration changes that can be made
+at module initialization time (by running insmod cifs.ko) can be seen.
+
+Recommendations
+===============
+
+To improve security the SMB2.1 dialect or later (usually will get SMB3.1.1) is now
+the new default. To use old dialects (e.g. to mount Windows XP) use "vers=1.0"
+on mount (or vers=2.0 for Windows Vista).  Note that the CIFS (vers=1.0) is
+much older and less secure than the default dialect SMB3 which includes
+many advanced security features such as downgrade attack detection
+and encrypted shares and stronger signing and authentication algorithms.
+There are additional mount options that may be helpful for SMB3 to get
+improved POSIX behavior (NB: can use vers=3.0 to force only SMB3, never 2.1):
+
+   ``mfsymlinks`` and either ``cifsacl`` or ``modefromsid`` (usually with ``idsfromsid``)
+
+Allowing User Mounts
+====================
+
+To permit users to mount and unmount over directories they own is possible
+with the cifs vfs.  A way to enable such mounting is to mark the mount.cifs
+utility as suid (e.g. ``chmod +s /sbin/mount.cifs``). To enable users to
+umount shares they mount requires
+
+1) mount.cifs version 1.4 or later
+2) an entry for the share in /etc/fstab indicating that a user may
+   unmount it e.g.::
+
+     //server/usersharename  /mnt/username cifs user 0 0
+
+Note that when the mount.cifs utility is run suid (allowing user mounts),
+in order to reduce risks, the ``nosuid`` mount flag is passed in on mount to
+disallow execution of an suid program mounted on the remote target.
+When mount is executed as root, nosuid is not passed in by default,
+and execution of suid programs on the remote target would be enabled
+by default. This can be changed, as with nfs and other filesystems,
+by simply specifying ``nosuid`` among the mount options. For user mounts
+though to be able to pass the suid flag to mount requires rebuilding
+mount.cifs with the following flag: CIFS_ALLOW_USR_SUID
+
+There is a corresponding manual page for cifs mounting in the Samba 3.0 and
+later source tree in docs/manpages/mount.cifs.8
+
+Allowing User Unmounts
+======================
+
+To permit users to unmount directories that they have user mounted (see above),
+the utility umount.cifs may be used.  It may be invoked directly, or if
+umount.cifs is placed in /sbin, umount can invoke the cifs umount helper
+(at least for most versions of the umount utility) for umount of cifs
+mounts, unless umount is invoked with -i (which will avoid invoking a umount
+helper). As with mount.cifs, to enable user unmounts umount.cifs must be marked
+as suid (e.g. ``chmod +s /sbin/umount.cifs``) or equivalent (some distributions
+allow adding entries to a file to the /etc/permissions file to achieve the
+equivalent suid effect).  For this utility to succeed the target path
+must be a cifs mount, and the uid of the current user must match the uid
+of the user who mounted the resource.
+
+Also note that the customary way of allowing user mounts and unmounts is
+(instead of using mount.cifs and unmount.cifs as suid) to add a line
+to the file /etc/fstab for each //server/share you wish to mount, but
+this can become unwieldy when potential mount targets include many
+or  unpredictable UNC names.
+
+Samba Considerations
+====================
+
+Most current servers support SMB2.1 and SMB3 which are more secure,
+but there are useful protocol extensions for the older less secure CIFS
+dialect, so to get the maximum benefit if mounting using the older dialect
+(CIFS/SMB1), we recommend using a server that supports the SNIA CIFS
+Unix Extensions standard (e.g. almost any  version of Samba ie version
+2.2.5 or later) but the CIFS vfs works fine with a wide variety of CIFS servers.
+Note that uid, gid and file permissions will display default values if you do
+not have a server that supports the Unix extensions for CIFS (such as Samba
+2.2.5 or later).  To enable the Unix CIFS Extensions in the Samba server, add
+the line::
+
+	unix extensions = yes
+
+to your smb.conf file on the server.  Note that the following smb.conf settings
+are also useful (on the Samba server) when the majority of clients are Unix or
+Linux::
+
+	case sensitive = yes
+	delete readonly = yes
+	ea support = yes
+
+Note that server ea support is required for supporting xattrs from the Linux
+cifs client, and that EA support is present in later versions of Samba (e.g.
+3.0.6 and later (also EA support works in all versions of Windows, at least to
+shares on NTFS filesystems).  Extended Attribute (xattr) support is an optional
+feature of most Linux filesystems which may require enabling via
+make menuconfig. Client support for extended attributes (user xattr) can be
+disabled on a per-mount basis by specifying ``nouser_xattr`` on mount.
+
+The CIFS client can get and set POSIX ACLs (getfacl, setfacl) to Samba servers
+version 3.10 and later.  Setting POSIX ACLs requires enabling both XATTR and
+then POSIX support in the CIFS configuration options when building the cifs
+module.  POSIX ACL support can be disabled on a per mount basic by specifying
+``noacl`` on mount.
+
+Some administrators may want to change Samba's smb.conf ``map archive`` and
+``create mask`` parameters from the default.  Unless the create mask is changed
+newly created files can end up with an unnecessarily restrictive default mode,
+which may not be what you want, although if the CIFS Unix extensions are
+enabled on the server and client, subsequent setattr calls (e.g. chmod) can
+fix the mode.  Note that creating special devices (mknod) remotely
+may require specifying a mkdev function to Samba if you are not using
+Samba 3.0.6 or later.  For more information on these see the manual pages
+(``man smb.conf``) on the Samba server system.  Note that the cifs vfs,
+unlike the smbfs vfs, does not read the smb.conf on the client system
+(the few optional settings are passed in on mount via -o parameters instead).
+Note that Samba 2.2.7 or later includes a fix that allows the CIFS VFS to delete
+open files (required for strict POSIX compliance).  Windows Servers already
+supported this feature. Samba server does not allow symlinks that refer to files
+outside of the share, so in Samba versions prior to 3.0.6, most symlinks to
+files with absolute paths (ie beginning with slash) such as::
+
+	 ln -s /mnt/foo bar
+
+would be forbidden. Samba 3.0.6 server or later includes the ability to create
+such symlinks safely by converting unsafe symlinks (ie symlinks to server
+files that are outside of the share) to a samba specific format on the server
+that is ignored by local server applications and non-cifs clients and that will
+not be traversed by the Samba server).  This is opaque to the Linux client
+application using the cifs vfs. Absolute symlinks will work to Samba 3.0.5 or
+later, but only for remote clients using the CIFS Unix extensions, and will
+be invisible to Windows clients and typically will not affect local
+applications running on the same server as Samba.
+
+Use instructions
+================
+
+Once the CIFS VFS support is built into the kernel or installed as a module
+(cifs.ko), you can use mount syntax like the following to access Samba or
+Mac or Windows servers::
+
+  mount -t cifs //9.53.216.11/e$ /mnt -o username=myname,password=mypassword
+
+Before -o the option -v may be specified to make the mount.cifs
+mount helper display the mount steps more verbosely.
+After -o the following commonly used cifs vfs specific options
+are supported::
+
+  username=<username>
+  password=<password>
+  domain=<domain name>
+
+Other cifs mount options are described below.  Use of TCP names (in addition to
+ip addresses) is available if the mount helper (mount.cifs) is installed. If
+you do not trust the server to which are mounted, or if you do not have
+cifs signing enabled (and the physical network is insecure), consider use
+of the standard mount options ``noexec`` and ``nosuid`` to reduce the risk of
+running an altered binary on your local system (downloaded from a hostile server
+or altered by a hostile router).
+
+Although mounting using format corresponding to the CIFS URL specification is
+not possible in mount.cifs yet, it is possible to use an alternate format
+for the server and sharename (which is somewhat similar to NFS style mount
+syntax) instead of the more widely used UNC format (i.e. \\server\share)::
+
+  mount -t cifs tcp_name_of_server:share_name /mnt -o user=myname,pass=mypasswd
+
+When using the mount helper mount.cifs, passwords may be specified via alternate
+mechanisms, instead of specifying it after -o using the normal ``pass=`` syntax
+on the command line:
+1) By including it in a credential file. Specify credentials=filename as one
+of the mount options. Credential files contain two lines::
+
+	username=someuser
+	password=your_password
+
+2) By specifying the password in the PASSWD environment variable (similarly
+   the user name can be taken from the USER environment variable).
+3) By specifying the password in a file by name via PASSWD_FILE
+4) By specifying the password in a file by file descriptor via PASSWD_FD
+
+If no password is provided, mount.cifs will prompt for password entry
+
+Restrictions
+============
+
+Servers must support either "pure-TCP" (port 445 TCP/IP CIFS connections) or RFC
+1001/1002 support for "Netbios-Over-TCP/IP." This is not likely to be a
+problem as most servers support this.
+
+Valid filenames differ between Windows and Linux.  Windows typically restricts
+filenames which contain certain reserved characters (e.g.the character :
+which is used to delimit the beginning of a stream name by Windows), while
+Linux allows a slightly wider set of valid characters in filenames. Windows
+servers can remap such characters when an explicit mapping is specified in
+the Server's registry.  Samba starting with version 3.10 will allow such
+filenames (ie those which contain valid Linux characters, which normally
+would be forbidden for Windows/CIFS semantics) as long as the server is
+configured for Unix Extensions (and the client has not disabled
+/proc/fs/cifs/LinuxExtensionsEnabled). In addition the mount option
+``mapposix`` can be used on CIFS (vers=1.0) to force the mapping of
+illegal Windows/NTFS/SMB characters to a remap range (this mount parameter
+is the default for SMB3). This remap (``mapposix``) range is also
+compatible with Mac (and "Services for Mac" on some older Windows).
+
+CIFS VFS Mount Options
+======================
+A partial list of the supported mount options follows:
+
+  username
+		The user name to use when trying to establish
+		the CIFS session.
+  password
+		The user password.  If the mount helper is
+		installed, the user will be prompted for password
+		if not supplied.
+  ip
+		The ip address of the target server
+  unc
+		The target server Universal Network Name (export) to
+		mount.
+  domain
+		Set the SMB/CIFS workgroup name prepended to the
+		username during CIFS session establishment
+  forceuid
+		Set the default uid for inodes to the uid
+		passed in on mount. For mounts to servers
+		which do support the CIFS Unix extensions, such as a
+		properly configured Samba server, the server provides
+		the uid, gid and mode so this parameter should not be
+		specified unless the server and clients uid and gid
+		numbering differ.  If the server and client are in the
+		same domain (e.g. running winbind or nss_ldap) and
+		the server supports the Unix Extensions then the uid
+		and gid can be retrieved from the server (and uid
+		and gid would not have to be specified on the mount.
+		For servers which do not support the CIFS Unix
+		extensions, the default uid (and gid) returned on lookup
+		of existing files will be the uid (gid) of the person
+		who executed the mount (root, except when mount.cifs
+		is configured setuid for user mounts) unless the ``uid=``
+		(gid) mount option is specified. Also note that permission
+		checks (authorization checks) on accesses to a file occur
+		at the server, but there are cases in which an administrator
+		may want to restrict at the client as well.  For those
+		servers which do not report a uid/gid owner
+		(such as Windows), permissions can also be checked at the
+		client, and a crude form of client side permission checking
+		can be enabled by specifying file_mode and dir_mode on
+		the client.  (default)
+  forcegid
+		(similar to above but for the groupid instead of uid) (default)
+  noforceuid
+		Fill in file owner information (uid) by requesting it from
+		the server if possible. With this option, the value given in
+		the uid= option (on mount) will only be used if the server
+		can not support returning uids on inodes.
+  noforcegid
+		(similar to above but for the group owner, gid, instead of uid)
+  uid
+		Set the default uid for inodes, and indicate to the
+		cifs kernel driver which local user mounted. If the server
+		supports the unix extensions the default uid is
+		not used to fill in the owner fields of inodes (files)
+		unless the ``forceuid`` parameter is specified.
+  gid
+		Set the default gid for inodes (similar to above).
+  file_mode
+		If CIFS Unix extensions are not supported by the server
+		this overrides the default mode for file inodes.
+  fsc
+		Enable local disk caching using FS-Cache (off by default). This
+		option could be useful to improve performance on a slow link,
+		heavily loaded server and/or network where reading from the
+		disk is faster than reading from the server (over the network).
+		This could also impact scalability positively as the
+		number of calls to the server are reduced. However, local
+		caching is not suitable for all workloads for e.g. read-once
+		type workloads. So, you need to consider carefully your
+		workload/scenario before using this option. Currently, local
+		disk caching is functional for CIFS files opened as read-only.
+  dir_mode
+		If CIFS Unix extensions are not supported by the server
+		this overrides the default mode for directory inodes.
+  port
+		attempt to contact the server on this tcp port, before
+		trying the usual ports (port 445, then 139).
+  iocharset
+		Codepage used to convert local path names to and from
+		Unicode. Unicode is used by default for network path
+		names if the server supports it.  If iocharset is
+		not specified then the nls_default specified
+		during the local client kernel build will be used.
+		If server does not support Unicode, this parameter is
+		unused.
+  rsize
+		default read size (usually 16K). The client currently
+		can not use rsize larger than CIFSMaxBufSize. CIFSMaxBufSize
+		defaults to 16K and may be changed (from 8K to the maximum
+		kmalloc size allowed by your kernel) at module install time
+		for cifs.ko. Setting CIFSMaxBufSize to a very large value
+		will cause cifs to use more memory and may reduce performance
+		in some cases.  To use rsize greater than 127K (the original
+		cifs protocol maximum) also requires that the server support
+		a new Unix Capability flag (for very large read) which some
+		newer servers (e.g. Samba 3.0.26 or later) do. rsize can be
+		set from a minimum of 2048 to a maximum of 130048 (127K or
+		CIFSMaxBufSize, whichever is smaller)
+  wsize
+		default write size (default 57344)
+		maximum wsize currently allowed by CIFS is 57344 (fourteen
+		4096 byte pages)
+  actimeo=n
+		attribute cache timeout in seconds (default 1 second).
+		After this timeout, the cifs client requests fresh attribute
+		information from the server. This option allows to tune the
+		attribute cache timeout to suit the workload needs. Shorter
+		timeouts mean better the cache coherency, but increased number
+		of calls to the server. Longer timeouts mean reduced number
+		of calls to the server at the expense of less stricter cache
+		coherency checks (i.e. incorrect attribute cache for a short
+		period of time).
+  rw
+		mount the network share read-write (note that the
+		server may still consider the share read-only)
+  ro
+		mount network share read-only
+  version
+		used to distinguish different versions of the
+		mount helper utility (not typically needed)
+  sep
+		if first mount option (after the -o), overrides
+		the comma as the separator between the mount
+		parameters. e.g.::
+
+			-o user=myname,password=mypassword,domain=mydom
+
+		could be passed instead with period as the separator by::
+
+			-o sep=.user=myname.password=mypassword.domain=mydom
+
+		this might be useful when comma is contained within username
+		or password or domain. This option is less important
+		when the cifs mount helper cifs.mount (version 1.1 or later)
+		is used.
+  nosuid
+		Do not allow remote executables with the suid bit
+		program to be executed.  This is only meaningful for mounts
+		to servers such as Samba which support the CIFS Unix Extensions.
+		If you do not trust the servers in your network (your mount
+		targets) it is recommended that you specify this option for
+		greater security.
+  exec
+		Permit execution of binaries on the mount.
+  noexec
+		Do not permit execution of binaries on the mount.
+  dev
+		Recognize block devices on the remote mount.
+  nodev
+		Do not recognize devices on the remote mount.
+  suid
+		Allow remote files on this mountpoint with suid enabled to
+		be executed (default for mounts when executed as root,
+		nosuid is default for user mounts).
+  credentials
+		Although ignored by the cifs kernel component, it is used by
+		the mount helper, mount.cifs. When mount.cifs is installed it
+		opens and reads the credential file specified in order
+		to obtain the userid and password arguments which are passed to
+		the cifs vfs.
+  guest
+		Although ignored by the kernel component, the mount.cifs
+		mount helper will not prompt the user for a password
+		if guest is specified on the mount options.  If no
+		password is specified a null password will be used.
+  perm
+		Client does permission checks (vfs_permission check of uid
+		and gid of the file against the mode and desired operation),
+		Note that this is in addition to the normal ACL check on the
+		target machine done by the server software.
+		Client permission checking is enabled by default.
+  noperm
+		Client does not do permission checks.  This can expose
+		files on this mount to access by other users on the local
+		client system. It is typically only needed when the server
+		supports the CIFS Unix Extensions but the UIDs/GIDs on the
+		client and server system do not match closely enough to allow
+		access by the user doing the mount, but it may be useful with
+		non CIFS Unix Extension mounts for cases in which the default
+		mode is specified on the mount but is not to be enforced on the
+		client (e.g. perhaps when MultiUserMount is enabled)
+		Note that this does not affect the normal ACL check on the
+		target machine done by the server software (of the server
+		ACL against the user name provided at mount time).
+  serverino
+		Use server's inode numbers instead of generating automatically
+		incrementing inode numbers on the client.  Although this will
+		make it easier to spot hardlinked files (as they will have
+		the same inode numbers) and inode numbers may be persistent,
+		note that the server does not guarantee that the inode numbers
+		are unique if multiple server side mounts are exported under a
+		single share (since inode numbers on the servers might not
+		be unique if multiple filesystems are mounted under the same
+		shared higher level directory).  Note that some older
+		(e.g. pre-Windows 2000) do not support returning UniqueIDs
+		or the CIFS Unix Extensions equivalent and for those
+		this mount option will have no effect.  Exporting cifs mounts
+		under nfsd requires this mount option on the cifs mount.
+		This is now the default if server supports the
+		required network operation.
+  noserverino
+		Client generates inode numbers (rather than using the actual one
+		from the server). These inode numbers will vary after
+		unmount or reboot which can confuse some applications,
+		but not all server filesystems support unique inode
+		numbers.
+  setuids
+		If the CIFS Unix extensions are negotiated with the server
+		the client will attempt to set the effective uid and gid of
+		the local process on newly created files, directories, and
+		devices (create, mkdir, mknod).  If the CIFS Unix Extensions
+		are not negotiated, for newly created files and directories
+		instead of using the default uid and gid specified on
+		the mount, cache the new file's uid and gid locally which means
+		that the uid for the file can change when the inode is
+		reloaded (or the user remounts the share).
+  nosetuids
+		The client will not attempt to set the uid and gid on
+		on newly created files, directories, and devices (create,
+		mkdir, mknod) which will result in the server setting the
+		uid and gid to the default (usually the server uid of the
+		user who mounted the share).  Letting the server (rather than
+		the client) set the uid and gid is the default. If the CIFS
+		Unix Extensions are not negotiated then the uid and gid for
+		new files will appear to be the uid (gid) of the mounter or the
+		uid (gid) parameter specified on the mount.
+  netbiosname
+		When mounting to servers via port 139, specifies the RFC1001
+		source name to use to represent the client netbios machine
+		name when doing the RFC1001 netbios session initialize.
+  direct
+		Do not do inode data caching on files opened on this mount.
+		This precludes mmapping files on this mount. In some cases
+		with fast networks and little or no caching benefits on the
+		client (e.g. when the application is doing large sequential
+		reads bigger than page size without rereading the same data)
+		this can provide better performance than the default
+		behavior which caches reads (readahead) and writes
+		(writebehind) through the local Linux client pagecache
+		if oplock (caching token) is granted and held. Note that
+		direct allows write operations larger than page size
+		to be sent to the server.
+  strictcache
+		Use for switching on strict cache mode. In this mode the
+		client read from the cache all the time it has Oplock Level II,
+		otherwise - read from the server. All written data are stored
+		in the cache, but if the client doesn't have Exclusive Oplock,
+		it writes the data to the server.
+  rwpidforward
+		Forward pid of a process who opened a file to any read or write
+		operation on that file. This prevent applications like WINE
+		from failing on read and write if we use mandatory brlock style.
+  acl
+		Allow setfacl and getfacl to manage posix ACLs if server
+		supports them.  (default)
+  noacl
+		Do not allow setfacl and getfacl calls on this mount
+  user_xattr
+		Allow getting and setting user xattrs (those attributes whose
+		name begins with ``user.`` or ``os2.``) as OS/2 EAs (extended
+		attributes) to the server.  This allows support of the
+		setfattr and getfattr utilities. (default)
+  nouser_xattr
+		Do not allow getfattr/setfattr to get/set/list xattrs
+  mapchars
+		Translate six of the seven reserved characters (not backslash)::
+
+			*?<>|:
+
+		to the remap range (above 0xF000), which also
+		allows the CIFS client to recognize files created with
+		such characters by Windows's POSIX emulation. This can
+		also be useful when mounting to most versions of Samba
+		(which also forbids creating and opening files
+		whose names contain any of these seven characters).
+		This has no effect if the server does not support
+		Unicode on the wire.
+  nomapchars
+		Do not translate any of these seven characters (default).
+  nocase
+		Request case insensitive path name matching (case
+		sensitive is the default if the server supports it).
+		(mount option ``ignorecase`` is identical to ``nocase``)
+  posixpaths
+		If CIFS Unix extensions are supported, attempt to
+		negotiate posix path name support which allows certain
+		characters forbidden in typical CIFS filenames, without
+		requiring remapping. (default)
+  noposixpaths
+		If CIFS Unix extensions are supported, do not request
+		posix path name support (this may cause servers to
+		reject creatingfile with certain reserved characters).
+  nounix
+		Disable the CIFS Unix Extensions for this mount (tree
+		connection). This is rarely needed, but it may be useful
+		in order to turn off multiple settings all at once (ie
+		posix acls, posix locks, posix paths, symlink support
+		and retrieving uids/gids/mode from the server) or to
+		work around a bug in server which implement the Unix
+		Extensions.
+  nobrl
+		Do not send byte range lock requests to the server.
+		This is necessary for certain applications that break
+		with cifs style mandatory byte range locks (and most
+		cifs servers do not yet support requesting advisory
+		byte range locks).
+  forcemandatorylock
+		Even if the server supports posix (advisory) byte range
+		locking, send only mandatory lock requests.  For some
+		(presumably rare) applications, originally coded for
+		DOS/Windows, which require Windows style mandatory byte range
+		locking, they may be able to take advantage of this option,
+		forcing the cifs client to only send mandatory locks
+		even if the cifs server would support posix advisory locks.
+		``forcemand`` is accepted as a shorter form of this mount
+		option.
+  nostrictsync
+		If this mount option is set, when an application does an
+		fsync call then the cifs client does not send an SMB Flush
+		to the server (to force the server to write all dirty data
+		for this file immediately to disk), although cifs still sends
+		all dirty (cached) file data to the server and waits for the
+		server to respond to the write.  Since SMB Flush can be
+		very slow, and some servers may be reliable enough (to risk
+		delaying slightly flushing the data to disk on the server),
+		turning on this option may be useful to improve performance for
+		applications that fsync too much, at a small risk of server
+		crash.  If this mount option is not set, by default cifs will
+		send an SMB flush request (and wait for a response) on every
+		fsync call.
+  nodfs
+		Disable DFS (global name space support) even if the
+		server claims to support it.  This can help work around
+		a problem with parsing of DFS paths with Samba server
+		versions 3.0.24 and 3.0.25.
+  remount
+		remount the share (often used to change from ro to rw mounts
+		or vice versa)
+  cifsacl
+		Report mode bits (e.g. on stat) based on the Windows ACL for
+		the file. (EXPERIMENTAL)
+  servern
+		Specify the server 's netbios name (RFC1001 name) to use
+		when attempting to setup a session to the server.
+		This is needed for mounting to some older servers (such
+		as OS/2 or Windows 98 and Windows ME) since they do not
+		support a default server name.  A server name can be up
+		to 15 characters long and is usually uppercased.
+  sfu
+		When the CIFS Unix Extensions are not negotiated, attempt to
+		create device files and fifos in a format compatible with
+		Services for Unix (SFU).  In addition retrieve bits 10-12
+		of the mode via the SETFILEBITS extended attribute (as
+		SFU does).  In the future the bottom 9 bits of the
+		mode also will be emulated using queries of the security
+		descriptor (ACL).
+  mfsymlinks
+		Enable support for Minshall+French symlinks
+		(see http://wiki.samba.org/index.php/UNIX_Extensions#Minshall.2BFrench_symlinks)
+		This option is ignored when specified together with the
+		'sfu' option. Minshall+French symlinks are used even if
+		the server supports the CIFS Unix Extensions.
+  sign
+		Must use packet signing (helps avoid unwanted data modification
+		by intermediate systems in the route).  Note that signing
+		does not work with lanman or plaintext authentication.
+  seal
+		Must seal (encrypt) all data on this mounted share before
+		sending on the network.  Requires support for Unix Extensions.
+		Note that this differs from the sign mount option in that it
+		causes encryption of data sent over this mounted share but other
+		shares mounted to the same server are unaffected.
+  locallease
+		This option is rarely needed. Fcntl F_SETLEASE is
+		used by some applications such as Samba and NFSv4 server to
+		check to see whether a file is cacheable.  CIFS has no way
+		to explicitly request a lease, but can check whether a file
+		is cacheable (oplocked).  Unfortunately, even if a file
+		is not oplocked, it could still be cacheable (ie cifs client
+		could grant fcntl leases if no other local processes are using
+		the file) for cases for example such as when the server does not
+		support oplocks and the user is sure that the only updates to
+		the file will be from this client. Specifying this mount option
+		will allow the cifs client to check for leases (only) locally
+		for files which are not oplocked instead of denying leases
+		in that case. (EXPERIMENTAL)
+  sec
+		Security mode.  Allowed values are:
+
+			none
+				attempt to connection as a null user (no name)
+			krb5
+				Use Kerberos version 5 authentication
+			krb5i
+				Use Kerberos authentication and packet signing
+			ntlm
+				Use NTLM password hashing (default)
+			ntlmi
+				Use NTLM password hashing with signing (if
+				/proc/fs/cifs/PacketSigningEnabled on or if
+				server requires signing also can be the default)
+			ntlmv2
+				Use NTLMv2 password hashing
+			ntlmv2i
+				Use NTLMv2 password hashing with packet signing
+			lanman
+				(if configured in kernel config) use older
+				lanman hash
+  hard
+		Retry file operations if server is not responding
+  soft
+		Limit retries to unresponsive servers (usually only
+		one retry) before returning an error.  (default)
+
+The mount.cifs mount helper also accepts a few mount options before -o
+including:
+
+=============== ===============================================================
+	-S      take password from stdin (equivalent to setting the environment
+		variable ``PASSWD_FD=0``
+	-V      print mount.cifs version
+	-?      display simple usage information
+=============== ===============================================================
+
+With most 2.6 kernel versions of modutils, the version of the cifs kernel
+module can be displayed via modinfo.
+
+Misc /proc/fs/cifs Flags and Debug Info
+=======================================
+
+Informational pseudo-files:
+
+======================= =======================================================
+DebugData		Displays information about active CIFS sessions and
+			shares, features enabled as well as the cifs.ko
+			version.
+Stats			Lists summary resource usage information as well as per
+			share statistics.
+open_files		List all the open file handles on all active SMB sessions.
+======================= =======================================================
+
+Configuration pseudo-files:
+
+======================= =======================================================
+SecurityFlags		Flags which control security negotiation and
+			also packet signing. Authentication (may/must)
+			flags (e.g. for NTLM and/or NTLMv2) may be combined with
+			the signing flags.  Specifying two different password
+			hashing mechanisms (as "must use") on the other hand
+			does not make much sense. Default flags are::
+
+				0x07007
+
+			(NTLM, NTLMv2 and packet signing allowed).  The maximum
+			allowable flags if you want to allow mounts to servers
+			using weaker password hashes is 0x37037 (lanman,
+			plaintext, ntlm, ntlmv2, signing allowed).  Some
+			SecurityFlags require the corresponding menuconfig
+			options to be enabled.  Enabling plaintext
+			authentication currently requires also enabling
+			lanman authentication in the security flags
+			because the cifs module only supports sending
+			laintext passwords using the older lanman dialect
+			form of the session setup SMB.  (e.g. for authentication
+			using plain text passwords, set the SecurityFlags
+			to 0x30030)::
+
+			  may use packet signing			0x00001
+			  must use packet signing			0x01001
+			  may use NTLM (most common password hash)	0x00002
+			  must use NTLM					0x02002
+			  may use NTLMv2				0x00004
+			  must use NTLMv2				0x04004
+			  may use Kerberos security			0x00008
+			  must use Kerberos				0x08008
+			  may use lanman (weak) password hash		0x00010
+			  must use lanman password hash			0x10010
+			  may use plaintext passwords			0x00020
+			  must use plaintext passwords			0x20020
+			  (reserved for future packet encryption)	0x00040
+
+cifsFYI			If set to non-zero value, additional debug information
+			will be logged to the system error log.  This field
+			contains three flags controlling different classes of
+			debugging entries.  The maximum value it can be set
+			to is 7 which enables all debugging points (default 0).
+			Some debugging statements are not compiled into the
+			cifs kernel unless CONFIG_CIFS_DEBUG2 is enabled in the
+			kernel configuration. cifsFYI may be set to one or
+			more of the following flags (7 sets them all)::
+
+			  +-----------------------------------------------+------+
+			  | log cifs informational messages		  | 0x01 |
+			  +-----------------------------------------------+------+
+			  | log return codes from cifs entry points	  | 0x02 |
+			  +-----------------------------------------------+------+
+			  | log slow responses				  | 0x04 |
+			  | (ie which take longer than 1 second)	  |      |
+			  |                                               |      |
+			  | CONFIG_CIFS_STATS2 must be enabled in .config |      |
+			  +-----------------------------------------------+------+
+
+traceSMB		If set to one, debug information is logged to the
+			system error log with the start of smb requests
+			and responses (default 0)
+LookupCacheEnable	If set to one, inode information is kept cached
+			for one second improving performance of lookups
+			(default 1)
+LinuxExtensionsEnabled	If set to one then the client will attempt to
+			use the CIFS "UNIX" extensions which are optional
+			protocol enhancements that allow CIFS servers
+			to return accurate UID/GID information as well
+			as support symbolic links. If you use servers
+			such as Samba that support the CIFS Unix
+			extensions but do not want to use symbolic link
+			support and want to map the uid and gid fields
+			to values supplied at mount (rather than the
+			actual values, then set this to zero. (default 1)
+dfscache		List the content of the DFS cache.
+			If set to 0, the client will clear the cache.
+======================= =======================================================
+
+These experimental features and tracing can be enabled by changing flags in
+/proc/fs/cifs (after the cifs module has been installed or built into the
+kernel, e.g.  insmod cifs).  To enable a feature set it to 1 e.g.  to enable
+tracing to the kernel message log type::
+
+	echo 7 > /proc/fs/cifs/cifsFYI
+
+cifsFYI functions as a bit mask. Setting it to 1 enables additional kernel
+logging of various informational messages.  2 enables logging of non-zero
+SMB return codes while 4 enables logging of requests that take longer
+than one second to complete (except for byte range lock requests).
+Setting it to 4 requires CONFIG_CIFS_STATS2 to be set in kernel configuration
+(.config). Setting it to seven enables all three.  Finally, tracing
+the start of smb requests and responses can be enabled via::
+
+	echo 1 > /proc/fs/cifs/traceSMB
+
+Per share (per client mount) statistics are available in /proc/fs/cifs/Stats.
+Additional information is available if CONFIG_CIFS_STATS2 is enabled in the
+kernel configuration (.config).  The statistics returned include counters which
+represent the number of attempted and failed (ie non-zero return code from the
+server) SMB3 (or cifs) requests grouped by request type (read, write, close etc.).
+Also recorded is the total bytes read and bytes written to the server for
+that share.  Note that due to client caching effects this can be less than the
+number of bytes read and written by the application running on the client.
+Statistics can be reset to zero by ``echo 0 > /proc/fs/cifs/Stats`` which may be
+useful if comparing performance of two different scenarios.
+
+Also note that ``cat /proc/fs/cifs/DebugData`` will display information about
+the active sessions and the shares that are mounted.
+
+Enabling Kerberos (extended security) works but requires version 1.2 or later
+of the helper program cifs.upcall to be present and to be configured in the
+/etc/request-key.conf file.  The cifs.upcall helper program is from the Samba
+project(https://www.samba.org). NTLM and NTLMv2 and LANMAN support do not
+require this helper. Note that NTLMv2 security (which does not require the
+cifs.upcall helper program), instead of using Kerberos, is sufficient for
+some use cases.
+
+DFS support allows transparent redirection to shares in an MS-DFS name space.
+In addition, DFS support for target shares which are specified as UNC
+names which begin with host names (rather than IP addresses) requires
+a user space helper (such as cifs.upcall) to be present in order to
+translate host names to ip address, and the user space helper must also
+be configured in the file /etc/request-key.conf.  Samba, Windows servers and
+many NAS appliances support DFS as a way of constructing a global name
+space to ease network configuration and improve reliability.
+
+To use cifs Kerberos and DFS support, the Linux keyutils package should be
+installed and something like the following lines should be added to the
+/etc/request-key.conf file::
+
+  create cifs.spnego * * /usr/local/sbin/cifs.upcall %k
+  create dns_resolver * * /usr/local/sbin/cifs.upcall %k
+
+CIFS kernel module parameters
+=============================
+These module parameters can be specified or modified either during the time of
+module loading or during the runtime by using the interface::
+
+	/sys/module/cifs/parameters/<param>
+
+i.e.::
+
+    echo "value" > /sys/module/cifs/parameters/<param>
+
+================= ==========================================================
+1. enable_oplocks Enable or disable oplocks. Oplocks are enabled by default.
+		  [Y/y/1]. To disable use any of [N/n/0].
+================= ==========================================================