1 This module supports the SMB3 family of advanced network protocols (as well
2 as older dialects, originally called "CIFS" or SMB1).
4 The CIFS VFS module for Linux supports many advanced network filesystem
5 features such as hierarchical DFS like namespace, hardlinks, locking and more.
6 It was designed to comply with the SNIA CIFS Technical Reference (which
7 supersedes the 1992 X/Open SMB Standard) as well as to perform best practice
8 practical interoperability with Windows 2000, Windows XP, Samba and equivalent
9 servers. This code was developed in participation with the Protocol Freedom
10 Information Foundation. CIFS and now SMB3 has now become a defacto
11 standard for interoperating between Macs and Windows and major NAS appliances.
14 MS-SMB2 (for detailed SMB2/SMB3/SMB3.1.1 protocol specification)
15 http://protocolfreedom.org/ and
16 http://samba.org/samba/PFIF/
20 For questions or bug reports please contact:
23 See the project page at: https://wiki.samba.org/index.php/LinuxCIFS_utils
28 1) Download the kernel (e.g. from http://www.kernel.org)
29 and change directory into the top of the kernel directory tree
30 (e.g. /usr/src/linux-2.5.73)
31 2) make menuconfig (or make xconfig)
32 3) select cifs from within the network filesystem choices
37 Installation instructions:
38 =========================
39 If you have built the CIFS vfs as module (successfully) simply
40 type "make modules_install" (or if you prefer, manually copy the file to
41 the modules directory e.g. /lib/modules/2.4.10-4GB/kernel/fs/cifs/cifs.ko).
43 If you have built the CIFS vfs into the kernel itself, follow the instructions
44 for your distribution on how to install a new kernel (usually you
45 would simply type "make install").
47 If you do not have the utility mount.cifs (in the Samba 4.x source tree and on
48 the CIFS VFS web site) copy it to the same directory in which mount helpers
49 reside (usually /sbin). Although the helper software is not
50 required, mount.cifs is recommended. Most distros include a "cifs-utils"
51 package that includes this utility so it is recommended to install this.
53 Note that running the Winbind pam/nss module (logon service) on all of your
54 Linux clients is useful in mapping Uids and Gids consistently across the
55 domain to the proper network user. The mount.cifs mount helper can be
56 found at cifs-utils.git on git.samba.org
58 If cifs is built as a module, then the size and number of network buffers
59 and maximum number of simultaneous requests to one server can be configured.
60 Changing these from their defaults is not recommended. By executing modinfo
61 modinfo kernel/fs/cifs/cifs.ko
62 on kernel/fs/cifs/cifs.ko the list of configuration changes that can be made
63 at module initialization time (by running insmod cifs.ko) can be seen.
67 To improve security the SMB2.1 dialect or later (usually will get SMB3) is now
68 the new default. To use old dialects (e.g. to mount Windows XP) use "vers=1.0"
69 on mount (or vers=2.0 for Windows Vista). Note that the CIFS (vers=1.0) is
70 much older and less secure than the default dialect SMB3 which includes
71 many advanced security features such as downgrade attack detection
72 and encrypted shares and stronger signing and authentication algorithms.
73 There are additional mount options that may be helpful for SMB3 to get
74 improved POSIX behavior (NB: can use vers=3.0 to force only SMB3, never 2.1):
75 "mfsymlinks" and "cifsacl" and "idsfromsid"
79 To permit users to mount and unmount over directories they own is possible
80 with the cifs vfs. A way to enable such mounting is to mark the mount.cifs
81 utility as suid (e.g. "chmod +s /sbin/mount.cifs). To enable users to
82 umount shares they mount requires
83 1) mount.cifs version 1.4 or later
84 2) an entry for the share in /etc/fstab indicating that a user may
86 //server/usersharename /mnt/username cifs user 0 0
88 Note that when the mount.cifs utility is run suid (allowing user mounts),
89 in order to reduce risks, the "nosuid" mount flag is passed in on mount to
90 disallow execution of an suid program mounted on the remote target.
91 When mount is executed as root, nosuid is not passed in by default,
92 and execution of suid programs on the remote target would be enabled
93 by default. This can be changed, as with nfs and other filesystems,
94 by simply specifying "nosuid" among the mount options. For user mounts
95 though to be able to pass the suid flag to mount requires rebuilding
96 mount.cifs with the following flag: CIFS_ALLOW_USR_SUID
98 There is a corresponding manual page for cifs mounting in the Samba 3.0 and
99 later source tree in docs/manpages/mount.cifs.8
101 Allowing User Unmounts
102 ======================
103 To permit users to ummount directories that they have user mounted (see above),
104 the utility umount.cifs may be used. It may be invoked directly, or if
105 umount.cifs is placed in /sbin, umount can invoke the cifs umount helper
106 (at least for most versions of the umount utility) for umount of cifs
107 mounts, unless umount is invoked with -i (which will avoid invoking a umount
108 helper). As with mount.cifs, to enable user unmounts umount.cifs must be marked
109 as suid (e.g. "chmod +s /sbin/umount.cifs") or equivalent (some distributions
110 allow adding entries to a file to the /etc/permissions file to achieve the
111 equivalent suid effect). For this utility to succeed the target path
112 must be a cifs mount, and the uid of the current user must match the uid
113 of the user who mounted the resource.
115 Also note that the customary way of allowing user mounts and unmounts is
116 (instead of using mount.cifs and unmount.cifs as suid) to add a line
117 to the file /etc/fstab for each //server/share you wish to mount, but
118 this can become unwieldy when potential mount targets include many
119 or unpredictable UNC names.
123 Most current servers support SMB2.1 and SMB3 which are more secure,
124 but there are useful protocol extensions for the older less secure CIFS
125 dialect, so to get the maximum benefit if mounting using the older dialect
126 (CIFS/SMB1), we recommend using a server that supports the SNIA CIFS
127 Unix Extensions standard (e.g. almost any version of Samba ie version
128 2.2.5 or later) but the CIFS vfs works fine with a wide variety of CIFS servers.
129 Note that uid, gid and file permissions will display default values if you do
130 not have a server that supports the Unix extensions for CIFS (such as Samba
131 2.2.5 or later). To enable the Unix CIFS Extensions in the Samba server, add
134 unix extensions = yes
136 to your smb.conf file on the server. Note that the following smb.conf settings
137 are also useful (on the Samba server) when the majority of clients are Unix or
141 delete readonly = yes
144 Note that server ea support is required for supporting xattrs from the Linux
145 cifs client, and that EA support is present in later versions of Samba (e.g.
146 3.0.6 and later (also EA support works in all versions of Windows, at least to
147 shares on NTFS filesystems). Extended Attribute (xattr) support is an optional
148 feature of most Linux filesystems which may require enabling via
149 make menuconfig. Client support for extended attributes (user xattr) can be
150 disabled on a per-mount basis by specifying "nouser_xattr" on mount.
152 The CIFS client can get and set POSIX ACLs (getfacl, setfacl) to Samba servers
153 version 3.10 and later. Setting POSIX ACLs requires enabling both XATTR and
154 then POSIX support in the CIFS configuration options when building the cifs
155 module. POSIX ACL support can be disabled on a per mount basic by specifying
158 Some administrators may want to change Samba's smb.conf "map archive" and
159 "create mask" parameters from the default. Unless the create mask is changed
160 newly created files can end up with an unnecessarily restrictive default mode,
161 which may not be what you want, although if the CIFS Unix extensions are
162 enabled on the server and client, subsequent setattr calls (e.g. chmod) can
163 fix the mode. Note that creating special devices (mknod) remotely
164 may require specifying a mkdev function to Samba if you are not using
165 Samba 3.0.6 or later. For more information on these see the manual pages
166 ("man smb.conf") on the Samba server system. Note that the cifs vfs,
167 unlike the smbfs vfs, does not read the smb.conf on the client system
168 (the few optional settings are passed in on mount via -o parameters instead).
169 Note that Samba 2.2.7 or later includes a fix that allows the CIFS VFS to delete
170 open files (required for strict POSIX compliance). Windows Servers already
171 supported this feature. Samba server does not allow symlinks that refer to files
172 outside of the share, so in Samba versions prior to 3.0.6, most symlinks to
173 files with absolute paths (ie beginning with slash) such as:
175 would be forbidden. Samba 3.0.6 server or later includes the ability to create
176 such symlinks safely by converting unsafe symlinks (ie symlinks to server
177 files that are outside of the share) to a samba specific format on the server
178 that is ignored by local server applications and non-cifs clients and that will
179 not be traversed by the Samba server). This is opaque to the Linux client
180 application using the cifs vfs. Absolute symlinks will work to Samba 3.0.5 or
181 later, but only for remote clients using the CIFS Unix extensions, and will
182 be invisbile to Windows clients and typically will not affect local
183 applications running on the same server as Samba.
187 Once the CIFS VFS support is built into the kernel or installed as a module
188 (cifs.ko), you can use mount syntax like the following to access Samba or
189 Mac or Windows servers:
191 mount -t cifs //9.53.216.11/e$ /mnt -o username=myname,password=mypassword
193 Before -o the option -v may be specified to make the mount.cifs
194 mount helper display the mount steps more verbosely.
195 After -o the following commonly used cifs vfs specific options
202 Other cifs mount options are described below. Use of TCP names (in addition to
203 ip addresses) is available if the mount helper (mount.cifs) is installed. If
204 you do not trust the server to which are mounted, or if you do not have
205 cifs signing enabled (and the physical network is insecure), consider use
206 of the standard mount options "noexec" and "nosuid" to reduce the risk of
207 running an altered binary on your local system (downloaded from a hostile server
208 or altered by a hostile router).
210 Although mounting using format corresponding to the CIFS URL specification is
211 not possible in mount.cifs yet, it is possible to use an alternate format
212 for the server and sharename (which is somewhat similar to NFS style mount
213 syntax) instead of the more widely used UNC format (i.e. \\server\share):
214 mount -t cifs tcp_name_of_server:share_name /mnt -o user=myname,pass=mypasswd
216 When using the mount helper mount.cifs, passwords may be specified via alternate
217 mechanisms, instead of specifying it after -o using the normal "pass=" syntax
219 1) By including it in a credential file. Specify credentials=filename as one
220 of the mount options. Credential files contain two lines
222 password=your_password
223 2) By specifying the password in the PASSWD environment variable (similarly
224 the user name can be taken from the USER environment variable).
225 3) By specifying the password in a file by name via PASSWD_FILE
226 4) By specifying the password in a file by file descriptor via PASSWD_FD
228 If no password is provided, mount.cifs will prompt for password entry
232 Servers must support either "pure-TCP" (port 445 TCP/IP CIFS connections) or RFC
233 1001/1002 support for "Netbios-Over-TCP/IP." This is not likely to be a
234 problem as most servers support this.
236 Valid filenames differ between Windows and Linux. Windows typically restricts
237 filenames which contain certain reserved characters (e.g.the character :
238 which is used to delimit the beginning of a stream name by Windows), while
239 Linux allows a slightly wider set of valid characters in filenames. Windows
240 servers can remap such characters when an explicit mapping is specified in
241 the Server's registry. Samba starting with version 3.10 will allow such
242 filenames (ie those which contain valid Linux characters, which normally
243 would be forbidden for Windows/CIFS semantics) as long as the server is
244 configured for Unix Extensions (and the client has not disabled
245 /proc/fs/cifs/LinuxExtensionsEnabled). In addition the mount option
246 "mapposix" can be used on CIFS (vers=1.0) to force the mapping of
247 illegal Windows/NTFS/SMB characters to a remap range (this mount parm
248 is the default for SMB3). This remap ("mapposix") range is also
249 compatible with Mac (and "Services for Mac" on some older Windows).
251 CIFS VFS Mount Options
252 ======================
253 A partial list of the supported mount options follows:
254 username The user name to use when trying to establish
256 password The user password. If the mount helper is
257 installed, the user will be prompted for password
259 ip The ip address of the target server
260 unc The target server Universal Network Name (export) to
262 domain Set the SMB/CIFS workgroup name prepended to the
263 username during CIFS session establishment
264 forceuid Set the default uid for inodes to the uid
265 passed in on mount. For mounts to servers
266 which do support the CIFS Unix extensions, such as a
267 properly configured Samba server, the server provides
268 the uid, gid and mode so this parameter should not be
269 specified unless the server and clients uid and gid
270 numbering differ. If the server and client are in the
271 same domain (e.g. running winbind or nss_ldap) and
272 the server supports the Unix Extensions then the uid
273 and gid can be retrieved from the server (and uid
274 and gid would not have to be specified on the mount.
275 For servers which do not support the CIFS Unix
276 extensions, the default uid (and gid) returned on lookup
277 of existing files will be the uid (gid) of the person
278 who executed the mount (root, except when mount.cifs
279 is configured setuid for user mounts) unless the "uid="
280 (gid) mount option is specified. Also note that permission
281 checks (authorization checks) on accesses to a file occur
282 at the server, but there are cases in which an administrator
283 may want to restrict at the client as well. For those
284 servers which do not report a uid/gid owner
285 (such as Windows), permissions can also be checked at the
286 client, and a crude form of client side permission checking
287 can be enabled by specifying file_mode and dir_mode on
288 the client. (default)
289 forcegid (similar to above but for the groupid instead of uid) (default)
290 noforceuid Fill in file owner information (uid) by requesting it from
291 the server if possible. With this option, the value given in
292 the uid= option (on mount) will only be used if the server
293 can not support returning uids on inodes.
294 noforcegid (similar to above but for the group owner, gid, instead of uid)
295 uid Set the default uid for inodes, and indicate to the
296 cifs kernel driver which local user mounted. If the server
297 supports the unix extensions the default uid is
298 not used to fill in the owner fields of inodes (files)
299 unless the "forceuid" parameter is specified.
300 gid Set the default gid for inodes (similar to above).
301 file_mode If CIFS Unix extensions are not supported by the server
302 this overrides the default mode for file inodes.
303 fsc Enable local disk caching using FS-Cache (off by default). This
304 option could be useful to improve performance on a slow link,
305 heavily loaded server and/or network where reading from the
306 disk is faster than reading from the server (over the network).
307 This could also impact scalability positively as the
308 number of calls to the server are reduced. However, local
309 caching is not suitable for all workloads for e.g. read-once
310 type workloads. So, you need to consider carefully your
311 workload/scenario before using this option. Currently, local
312 disk caching is functional for CIFS files opened as read-only.
313 dir_mode If CIFS Unix extensions are not supported by the server
314 this overrides the default mode for directory inodes.
315 port attempt to contact the server on this tcp port, before
316 trying the usual ports (port 445, then 139).
317 iocharset Codepage used to convert local path names to and from
318 Unicode. Unicode is used by default for network path
319 names if the server supports it. If iocharset is
320 not specified then the nls_default specified
321 during the local client kernel build will be used.
322 If server does not support Unicode, this parameter is
324 rsize default read size (usually 16K). The client currently
325 can not use rsize larger than CIFSMaxBufSize. CIFSMaxBufSize
326 defaults to 16K and may be changed (from 8K to the maximum
327 kmalloc size allowed by your kernel) at module install time
328 for cifs.ko. Setting CIFSMaxBufSize to a very large value
329 will cause cifs to use more memory and may reduce performance
330 in some cases. To use rsize greater than 127K (the original
331 cifs protocol maximum) also requires that the server support
332 a new Unix Capability flag (for very large read) which some
333 newer servers (e.g. Samba 3.0.26 or later) do. rsize can be
334 set from a minimum of 2048 to a maximum of 130048 (127K or
335 CIFSMaxBufSize, whichever is smaller)
336 wsize default write size (default 57344)
337 maximum wsize currently allowed by CIFS is 57344 (fourteen
339 actimeo=n attribute cache timeout in seconds (default 1 second).
340 After this timeout, the cifs client requests fresh attribute
341 information from the server. This option allows to tune the
342 attribute cache timeout to suit the workload needs. Shorter
343 timeouts mean better the cache coherency, but increased number
344 of calls to the server. Longer timeouts mean reduced number
345 of calls to the server at the expense of less stricter cache
346 coherency checks (i.e. incorrect attribute cache for a short
348 rw mount the network share read-write (note that the
349 server may still consider the share read-only)
350 ro mount network share read-only
351 version used to distinguish different versions of the
352 mount helper utility (not typically needed)
353 sep if first mount option (after the -o), overrides
354 the comma as the separator between the mount
356 -o user=myname,password=mypassword,domain=mydom
357 could be passed instead with period as the separator by
358 -o sep=.user=myname.password=mypassword.domain=mydom
359 this might be useful when comma is contained within username
360 or password or domain. This option is less important
361 when the cifs mount helper cifs.mount (version 1.1 or later)
363 nosuid Do not allow remote executables with the suid bit
364 program to be executed. This is only meaningful for mounts
365 to servers such as Samba which support the CIFS Unix Extensions.
366 If you do not trust the servers in your network (your mount
367 targets) it is recommended that you specify this option for
369 exec Permit execution of binaries on the mount.
370 noexec Do not permit execution of binaries on the mount.
371 dev Recognize block devices on the remote mount.
372 nodev Do not recognize devices on the remote mount.
373 suid Allow remote files on this mountpoint with suid enabled to
374 be executed (default for mounts when executed as root,
375 nosuid is default for user mounts).
376 credentials Although ignored by the cifs kernel component, it is used by
377 the mount helper, mount.cifs. When mount.cifs is installed it
378 opens and reads the credential file specified in order
379 to obtain the userid and password arguments which are passed to
381 guest Although ignored by the kernel component, the mount.cifs
382 mount helper will not prompt the user for a password
383 if guest is specified on the mount options. If no
384 password is specified a null password will be used.
385 perm Client does permission checks (vfs_permission check of uid
386 and gid of the file against the mode and desired operation),
387 Note that this is in addition to the normal ACL check on the
388 target machine done by the server software.
389 Client permission checking is enabled by default.
390 noperm Client does not do permission checks. This can expose
391 files on this mount to access by other users on the local
392 client system. It is typically only needed when the server
393 supports the CIFS Unix Extensions but the UIDs/GIDs on the
394 client and server system do not match closely enough to allow
395 access by the user doing the mount, but it may be useful with
396 non CIFS Unix Extension mounts for cases in which the default
397 mode is specified on the mount but is not to be enforced on the
398 client (e.g. perhaps when MultiUserMount is enabled)
399 Note that this does not affect the normal ACL check on the
400 target machine done by the server software (of the server
401 ACL against the user name provided at mount time).
402 serverino Use server's inode numbers instead of generating automatically
403 incrementing inode numbers on the client. Although this will
404 make it easier to spot hardlinked files (as they will have
405 the same inode numbers) and inode numbers may be persistent,
406 note that the server does not guarantee that the inode numbers
407 are unique if multiple server side mounts are exported under a
408 single share (since inode numbers on the servers might not
409 be unique if multiple filesystems are mounted under the same
410 shared higher level directory). Note that some older
411 (e.g. pre-Windows 2000) do not support returning UniqueIDs
412 or the CIFS Unix Extensions equivalent and for those
413 this mount option will have no effect. Exporting cifs mounts
414 under nfsd requires this mount option on the cifs mount.
415 This is now the default if server supports the
416 required network operation.
417 noserverino Client generates inode numbers (rather than using the actual one
418 from the server). These inode numbers will vary after
419 unmount or reboot which can confuse some applications,
420 but not all server filesystems support unique inode
422 setuids If the CIFS Unix extensions are negotiated with the server
423 the client will attempt to set the effective uid and gid of
424 the local process on newly created files, directories, and
425 devices (create, mkdir, mknod). If the CIFS Unix Extensions
426 are not negotiated, for newly created files and directories
427 instead of using the default uid and gid specified on
428 the mount, cache the new file's uid and gid locally which means
429 that the uid for the file can change when the inode is
430 reloaded (or the user remounts the share).
431 nosetuids The client will not attempt to set the uid and gid on
432 on newly created files, directories, and devices (create,
433 mkdir, mknod) which will result in the server setting the
434 uid and gid to the default (usually the server uid of the
435 user who mounted the share). Letting the server (rather than
436 the client) set the uid and gid is the default. If the CIFS
437 Unix Extensions are not negotiated then the uid and gid for
438 new files will appear to be the uid (gid) of the mounter or the
439 uid (gid) parameter specified on the mount.
440 netbiosname When mounting to servers via port 139, specifies the RFC1001
441 source name to use to represent the client netbios machine
442 name when doing the RFC1001 netbios session initialize.
443 direct Do not do inode data caching on files opened on this mount.
444 This precludes mmapping files on this mount. In some cases
445 with fast networks and little or no caching benefits on the
446 client (e.g. when the application is doing large sequential
447 reads bigger than page size without rereading the same data)
448 this can provide better performance than the default
449 behavior which caches reads (readahead) and writes
450 (writebehind) through the local Linux client pagecache
451 if oplock (caching token) is granted and held. Note that
452 direct allows write operations larger than page size
453 to be sent to the server.
454 strictcache Use for switching on strict cache mode. In this mode the
455 client read from the cache all the time it has Oplock Level II,
456 otherwise - read from the server. All written data are stored
457 in the cache, but if the client doesn't have Exclusive Oplock,
458 it writes the data to the server.
459 rwpidforward Forward pid of a process who opened a file to any read or write
460 operation on that file. This prevent applications like WINE
461 from failing on read and write if we use mandatory brlock style.
462 acl Allow setfacl and getfacl to manage posix ACLs if server
463 supports them. (default)
464 noacl Do not allow setfacl and getfacl calls on this mount
465 user_xattr Allow getting and setting user xattrs (those attributes whose
466 name begins with "user." or "os2.") as OS/2 EAs (extended
467 attributes) to the server. This allows support of the
468 setfattr and getfattr utilities. (default)
469 nouser_xattr Do not allow getfattr/setfattr to get/set/list xattrs
470 mapchars Translate six of the seven reserved characters (not backslash)
472 to the remap range (above 0xF000), which also
473 allows the CIFS client to recognize files created with
474 such characters by Windows's POSIX emulation. This can
475 also be useful when mounting to most versions of Samba
476 (which also forbids creating and opening files
477 whose names contain any of these seven characters).
478 This has no effect if the server does not support
480 nomapchars Do not translate any of these seven characters (default).
481 nocase Request case insensitive path name matching (case
482 sensitive is the default if the server supports it).
483 (mount option "ignorecase" is identical to "nocase")
484 posixpaths If CIFS Unix extensions are supported, attempt to
485 negotiate posix path name support which allows certain
486 characters forbidden in typical CIFS filenames, without
487 requiring remapping. (default)
488 noposixpaths If CIFS Unix extensions are supported, do not request
489 posix path name support (this may cause servers to
490 reject creatingfile with certain reserved characters).
491 nounix Disable the CIFS Unix Extensions for this mount (tree
492 connection). This is rarely needed, but it may be useful
493 in order to turn off multiple settings all at once (ie
494 posix acls, posix locks, posix paths, symlink support
495 and retrieving uids/gids/mode from the server) or to
496 work around a bug in server which implement the Unix
498 nobrl Do not send byte range lock requests to the server.
499 This is necessary for certain applications that break
500 with cifs style mandatory byte range locks (and most
501 cifs servers do not yet support requesting advisory
503 forcemandatorylock Even if the server supports posix (advisory) byte range
504 locking, send only mandatory lock requests. For some
505 (presumably rare) applications, originally coded for
506 DOS/Windows, which require Windows style mandatory byte range
507 locking, they may be able to take advantage of this option,
508 forcing the cifs client to only send mandatory locks
509 even if the cifs server would support posix advisory locks.
510 "forcemand" is accepted as a shorter form of this mount
512 nostrictsync If this mount option is set, when an application does an
513 fsync call then the cifs client does not send an SMB Flush
514 to the server (to force the server to write all dirty data
515 for this file immediately to disk), although cifs still sends
516 all dirty (cached) file data to the server and waits for the
517 server to respond to the write. Since SMB Flush can be
518 very slow, and some servers may be reliable enough (to risk
519 delaying slightly flushing the data to disk on the server),
520 turning on this option may be useful to improve performance for
521 applications that fsync too much, at a small risk of server
522 crash. If this mount option is not set, by default cifs will
523 send an SMB flush request (and wait for a response) on every
525 nodfs Disable DFS (global name space support) even if the
526 server claims to support it. This can help work around
527 a problem with parsing of DFS paths with Samba server
528 versions 3.0.24 and 3.0.25.
529 remount remount the share (often used to change from ro to rw mounts
531 cifsacl Report mode bits (e.g. on stat) based on the Windows ACL for
532 the file. (EXPERIMENTAL)
533 servern Specify the server 's netbios name (RFC1001 name) to use
534 when attempting to setup a session to the server.
535 This is needed for mounting to some older servers (such
536 as OS/2 or Windows 98 and Windows ME) since they do not
537 support a default server name. A server name can be up
538 to 15 characters long and is usually uppercased.
539 sfu When the CIFS Unix Extensions are not negotiated, attempt to
540 create device files and fifos in a format compatible with
541 Services for Unix (SFU). In addition retrieve bits 10-12
542 of the mode via the SETFILEBITS extended attribute (as
543 SFU does). In the future the bottom 9 bits of the
544 mode also will be emulated using queries of the security
546 mfsymlinks Enable support for Minshall+French symlinks
547 (see http://wiki.samba.org/index.php/UNIX_Extensions#Minshall.2BFrench_symlinks)
548 This option is ignored when specified together with the
549 'sfu' option. Minshall+French symlinks are used even if
550 the server supports the CIFS Unix Extensions.
551 sign Must use packet signing (helps avoid unwanted data modification
552 by intermediate systems in the route). Note that signing
553 does not work with lanman or plaintext authentication.
554 seal Must seal (encrypt) all data on this mounted share before
555 sending on the network. Requires support for Unix Extensions.
556 Note that this differs from the sign mount option in that it
557 causes encryption of data sent over this mounted share but other
558 shares mounted to the same server are unaffected.
559 locallease This option is rarely needed. Fcntl F_SETLEASE is
560 used by some applications such as Samba and NFSv4 server to
561 check to see whether a file is cacheable. CIFS has no way
562 to explicitly request a lease, but can check whether a file
563 is cacheable (oplocked). Unfortunately, even if a file
564 is not oplocked, it could still be cacheable (ie cifs client
565 could grant fcntl leases if no other local processes are using
566 the file) for cases for example such as when the server does not
567 support oplocks and the user is sure that the only updates to
568 the file will be from this client. Specifying this mount option
569 will allow the cifs client to check for leases (only) locally
570 for files which are not oplocked instead of denying leases
571 in that case. (EXPERIMENTAL)
572 sec Security mode. Allowed values are:
573 none attempt to connection as a null user (no name)
574 krb5 Use Kerberos version 5 authentication
575 krb5i Use Kerberos authentication and packet signing
576 ntlm Use NTLM password hashing (default)
577 ntlmi Use NTLM password hashing with signing (if
578 /proc/fs/cifs/PacketSigningEnabled on or if
579 server requires signing also can be the default)
580 ntlmv2 Use NTLMv2 password hashing
581 ntlmv2i Use NTLMv2 password hashing with packet signing
582 lanman (if configured in kernel config) use older
584 hard Retry file operations if server is not responding
585 soft Limit retries to unresponsive servers (usually only
586 one retry) before returning an error. (default)
588 The mount.cifs mount helper also accepts a few mount options before -o
591 -S take password from stdin (equivalent to setting the environment
592 variable "PASSWD_FD=0"
593 -V print mount.cifs version
594 -? display simple usage information
596 With most 2.6 kernel versions of modutils, the version of the cifs kernel
597 module can be displayed via modinfo.
599 Misc /proc/fs/cifs Flags and Debug Info
600 =======================================
601 Informational pseudo-files:
602 DebugData Displays information about active CIFS sessions and
603 shares, features enabled as well as the cifs.ko
605 Stats Lists summary resource usage information as well as per
608 Configuration pseudo-files:
609 SecurityFlags Flags which control security negotiation and
610 also packet signing. Authentication (may/must)
611 flags (e.g. for NTLM and/or NTLMv2) may be combined with
612 the signing flags. Specifying two different password
613 hashing mechanisms (as "must use") on the other hand
614 does not make much sense. Default flags are
616 (NTLM, NTLMv2 and packet signing allowed). The maximum
617 allowable flags if you want to allow mounts to servers
618 using weaker password hashes is 0x37037 (lanman,
619 plaintext, ntlm, ntlmv2, signing allowed). Some
620 SecurityFlags require the corresponding menuconfig
621 options to be enabled (lanman and plaintext require
622 CONFIG_CIFS_WEAK_PW_HASH for example). Enabling
623 plaintext authentication currently requires also
624 enabling lanman authentication in the security flags
625 because the cifs module only supports sending
626 laintext passwords using the older lanman dialect
627 form of the session setup SMB. (e.g. for authentication
628 using plain text passwords, set the SecurityFlags
631 may use packet signing 0x00001
632 must use packet signing 0x01001
633 may use NTLM (most common password hash) 0x00002
634 must use NTLM 0x02002
635 may use NTLMv2 0x00004
636 must use NTLMv2 0x04004
637 may use Kerberos security 0x00008
638 must use Kerberos 0x08008
639 may use lanman (weak) password hash 0x00010
640 must use lanman password hash 0x10010
641 may use plaintext passwords 0x00020
642 must use plaintext passwords 0x20020
643 (reserved for future packet encryption) 0x00040
645 cifsFYI If set to non-zero value, additional debug information
646 will be logged to the system error log. This field
647 contains three flags controlling different classes of
648 debugging entries. The maximum value it can be set
649 to is 7 which enables all debugging points (default 0).
650 Some debugging statements are not compiled into the
651 cifs kernel unless CONFIG_CIFS_DEBUG2 is enabled in the
652 kernel configuration. cifsFYI may be set to one or
653 nore of the following flags (7 sets them all):
655 log cifs informational messages 0x01
656 log return codes from cifs entry points 0x02
657 log slow responses (ie which take longer than 1 second)
658 CONFIG_CIFS_STATS2 must be enabled in .config 0x04
661 traceSMB If set to one, debug information is logged to the
662 system error log with the start of smb requests
663 and responses (default 0)
664 LookupCacheEnable If set to one, inode information is kept cached
665 for one second improving performance of lookups
667 LinuxExtensionsEnabled If set to one then the client will attempt to
668 use the CIFS "UNIX" extensions which are optional
669 protocol enhancements that allow CIFS servers
670 to return accurate UID/GID information as well
671 as support symbolic links. If you use servers
672 such as Samba that support the CIFS Unix
673 extensions but do not want to use symbolic link
674 support and want to map the uid and gid fields
675 to values supplied at mount (rather than the
676 actual values, then set this to zero. (default 1)
678 These experimental features and tracing can be enabled by changing flags in
679 /proc/fs/cifs (after the cifs module has been installed or built into the
680 kernel, e.g. insmod cifs). To enable a feature set it to 1 e.g. to enable
681 tracing to the kernel message log type:
683 echo 7 > /proc/fs/cifs/cifsFYI
685 cifsFYI functions as a bit mask. Setting it to 1 enables additional kernel
686 logging of various informational messages. 2 enables logging of non-zero
687 SMB return codes while 4 enables logging of requests that take longer
688 than one second to complete (except for byte range lock requests).
689 Setting it to 4 requires CONFIG_CIFS_STATS2 to be set in kernel configuration
690 (.config). Setting it to seven enables all three. Finally, tracing
691 the start of smb requests and responses can be enabled via:
693 echo 1 > /proc/fs/cifs/traceSMB
695 Per share (per client mount) statistics are available in /proc/fs/cifs/Stats.
696 Additional information is available if CONFIG_CIFS_STATS2 is enabled in the
697 kernel configuration (.config). The statistics returned include counters which
698 represent the number of attempted and failed (ie non-zero return code from the
699 server) SMB3 (or cifs) requests grouped by request type (read, write, close etc.).
700 Also recorded is the total bytes read and bytes written to the server for
701 that share. Note that due to client caching effects this can be less than the
702 number of bytes read and written by the application running on the client.
703 Statistics can be reset to zero by "echo 0 > /proc/fs/cifs/Stats" which may be
704 useful if comparing performance of two different scenarios.
706 Also note that "cat /proc/fs/cifs/DebugData" will display information about
707 the active sessions and the shares that are mounted.
709 Enabling Kerberos (extended security) works but requires version 1.2 or later
710 of the helper program cifs.upcall to be present and to be configured in the
711 /etc/request-key.conf file. The cifs.upcall helper program is from the Samba
712 project(http://www.samba.org). NTLM and NTLMv2 and LANMAN support do not
713 require this helper. Note that NTLMv2 security (which does not require the
714 cifs.upcall helper program), instead of using Kerberos, is sufficient for
717 DFS support allows transparent redirection to shares in an MS-DFS name space.
718 In addition, DFS support for target shares which are specified as UNC
719 names which begin with host names (rather than IP addresses) requires
720 a user space helper (such as cifs.upcall) to be present in order to
721 translate host names to ip address, and the user space helper must also
722 be configured in the file /etc/request-key.conf. Samba, Windows servers and
723 many NAS appliances support DFS as a way of constructing a global name
724 space to ease network configuration and improve reliability.
726 To use cifs Kerberos and DFS support, the Linux keyutils package should be
727 installed and something like the following lines should be added to the
728 /etc/request-key.conf file:
730 create cifs.spnego * * /usr/local/sbin/cifs.upcall %k
731 create dns_resolver * * /usr/local/sbin/cifs.upcall %k
733 CIFS kernel module parameters
734 =============================
735 These module parameters can be specified or modified either during the time of
736 module loading or during the runtime by using the interface
737 /proc/module/cifs/parameters/<param>
739 i.e. echo "value" > /sys/module/cifs/parameters/<param>
741 1. enable_oplocks - Enable or disable oplocks. Oplocks are enabled by default.
742 [Y/y/1]. To disable use any of [N/n/0].
git.samba.org / sfrench / cifs-2.6.git / blob