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The CIFS VFS support 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.

For questions or bug reports please contact:

    sfrench@samba.org (sfrench@us.ibm.com)

Build instructions:

==================

For Linux 2.4:

1) Get the kernel source (e.g.from http://www.kernel.org)

and download the cifs vfs source (see the project page

at http://us1.samba.org/samba/Linux_CIFS_client.html)

and change directory into the top of the kernel directory

then patch the kernel (e.g. "patch -p1 < cifs_24.patch")

to add the cifs vfs to your kernel configure options if

it has not already been added (e.g. current SuSE and UL

users do not need to apply the cifs_24.patch since the cifs vfs is

already in the kernel configure menu) and then

mkdir linux/fs/cifs and then copy the current cifs vfs files from

the cifs download to your kernel build directory e.g.

        cp /fs/cifs/* to /fs/cifs

2) make menuconfig (or make xconfig)

3) select cifs from within the network filesystem choices

4) save and exit

5) make dep

6) make modules (or "make" if CIFS VFS not to be built as a module)

For Linux 2.6:

1) Download the kernel (e.g. from http://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/2.4.10-4GB/kernel/fs/cifs/cifs.o).

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 3.0 source tree and on

the CIFS VFS web site) copy it to the same directory in which mount.smbfs and

similar files reside (usually /sbin).  Although the helper software is not

required, mount.cifs is recommended.  Eventually the Samba 3.0 utility program

"net" may also be helpful since it may someday provide easier mount syntax for

users who are used to Windows e.g.  net use  

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

trivially built from Samba 3.0 or later source e.g. by executing:

        gcc samba/source/client/mount.cifs.c -o mount.cifs

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 kernel/fs/cifs/cifs.ko

on kernel/fs/cifs/cifs.ko the list of configuration changes that can be made

at module initialization time (by running insmod cifs.ko) can be seen.

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:

        gcc samba/source/client/mount.cifs.c -DCIFS_ALLOW_USR_SUID -o mount.cifs

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 ummount 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

====================

To get the maximum benefit from the CIFS VFS, we recommend using a server that

supports the SNIA CIFS Unix Extensions standard (e.g.  Samba 2.2.5 or later or

Samba 3.0) 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 invisbile 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.o), you can use mount syntax like the following to access Samba or Windows

servers:

  mount -t cifs //9.53.216.11/e$ /mnt -o user=myname,pass=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:

  user=

  pass=

  domain=

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).

CIFS VFS Mount Options

======================

A partial list of the supported mount options follows:

  user          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 it is 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

  uid           Set the default uid for inodes. 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 specifed 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.  For the uid (gid) of newly

                created files and directories, ie files created since

                the last mount of the server share, the expected uid

                (gid) is cached as long as the inode remains in

                memory on the client.   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.  Note that the mount.cifs helper must be

                at version 1.10 or higher to support specifying the uid

                (or gid) in non-numberic form.

  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.

  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)

  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

                parms. 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.

  noserverino   Client generates inode numbers (rather than using the actual one

                from the server) by default.

  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 mmaping 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.

  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 as OS/2 EAs (extended

                attributes) to the server (default) e.g. via setfattr

                and getfattr utilities.

  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 suports it).

 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).

 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

                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).

 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.

 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

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, as well as the cifs.ko version.

Stats                   Lists summary resource usage information as well as per

                        share statistics, if CONFIG_CIFS_STATS in enabled

                        in the kernel configuration.

Configuration pseudo-files:

MultiuserMount          If set to one, more than one CIFS session to

                        the same server ip address can be established

                        if more than one uid accesses the same mount

                        point and if the uids user/password mapping

                        information is available. (default is 0)

PacketSigningEnabled    If set to one, cifs packet signing is enabled

                        and will be used if the server requires

                        it.  If set to two, cifs packet signing is

                        required even if the server considers packet

                        signing optional. (default 1)

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).  Maximum

                        allowable flags if you want to allow mounts to servers

                        using weaker password hashes is 0x37037 (lanman,

                        plaintext, ntlm, ntlmv2, signing allowed):

                        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 (not implemented yet) 0x00008

                        must use Kerberos (not implemented yet)         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

                        nore of the following flags (7 sets them all):

                        log cifs informational messages                 0x01

                        log return codes from cifs entry points         0x02

                        log slow responses (ie which take longer than 1 second)

                          CONFIG_CIFS_STATS2 must be enabled in .config 0x04

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)

OplockEnabled           If set to one, safe distributed caching enabled.

                        (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)

Experimental            When set to 1 used to enable certain experimental

                        features (currently enables multipage writes

                        when signing is enabled, the multipage write

                        performance enhancement was disabled when

                        signing turned on in case buffer was modified

                        just before it was sent, also this flag will

                        be used to use the new experimental directory change

                        notification code).

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 defining CONFIG_CIFS_STATS2 manually in the

source code (typically by setting it in the beginning of cifsglob.h),

and 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

Two other experimental features are under development. To test these

requires enabling CONFIG_CIFS_EXPERIMENTAL

        cifsacl support needed to retrieve approximated mode bits based on

                the contents on the CIFS ACL.

        DNOTIFY fcntl: needed for support of directory change

                            notification and perhaps later for file leases)

Per share (per client mount) statistics are available in /proc/fs/cifs/Stats

if the kernel was configured with cifs statistics enabled.  The statistics

represent the number of successful (ie non-zero return code from the server)

SMB responses to some of the more common commands (open, delete, mkdir 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.

The statistics for the number of total SMBs and oplock breaks are different in

that they represent all for that share, not just those for which the server

returned success.

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 when CONFIG_CIFS_EXPERIMENTAL is enabled

but requires a user space helper (from the Samba project). NTLM and NTLMv2 and

LANMAN support do not require this helpr.