1 The CIFS VFS support for Linux supports many advanced network filesystem
2 features such as hierarchical dfs like namespace, hardlinks, locking and more.
3 It was designed to comply with the SNIA CIFS Technical Reference (which
4 supersedes the 1992 X/Open SMB Standard) as well as to perform best practice
5 practical interoperability with Windows 2000, Windows XP, Samba and equivalent
6 servers. This code was developed in participation with the Protocol Freedom
7 Information Foundation.
10 http://protocolfreedom.org/ and
11 http://samba.org/samba/PFIF/
15 For questions or bug reports please contact:
16 sfrench@samba.org (sfrench@us.ibm.com)
21 1) Get the kernel source (e.g.from http://www.kernel.org)
22 and download the cifs vfs source (see the project page
23 at http://us1.samba.org/samba/Linux_CIFS_client.html)
24 and change directory into the top of the kernel directory
25 then patch the kernel (e.g. "patch -p1 < cifs_24.patch")
26 to add the cifs vfs to your kernel configure options if
27 it has not already been added (e.g. current SuSE and UL
28 users do not need to apply the cifs_24.patch since the cifs vfs is
29 already in the kernel configure menu) and then
30 mkdir linux/fs/cifs and then copy the current cifs vfs files from
31 the cifs download to your kernel build directory e.g.
33 cp <cifs_download_dir>/fs/cifs/* to <kernel_download_dir>/fs/cifs
35 2) make menuconfig (or make xconfig)
36 3) select cifs from within the network filesystem choices
39 6) make modules (or "make" if CIFS VFS not to be built as a module)
42 1) Download the kernel (e.g. from http://www.kernel.org)
43 and change directory into the top of the kernel directory tree
44 (e.g. /usr/src/linux-2.5.73)
45 2) make menuconfig (or make xconfig)
46 3) select cifs from within the network filesystem choices
51 Installation instructions:
52 =========================
53 If you have built the CIFS vfs as module (successfully) simply
54 type "make modules_install" (or if you prefer, manually copy the file to
55 the modules directory e.g. /lib/modules/2.4.10-4GB/kernel/fs/cifs/cifs.o).
57 If you have built the CIFS vfs into the kernel itself, follow the instructions
58 for your distribution on how to install a new kernel (usually you
59 would simply type "make install").
61 If you do not have the utility mount.cifs (in the Samba 3.0 source tree and on
62 the CIFS VFS web site) copy it to the same directory in which mount.smbfs and
63 similar files reside (usually /sbin). Although the helper software is not
64 required, mount.cifs is recommended. Eventually the Samba 3.0 utility program
65 "net" may also be helpful since it may someday provide easier mount syntax for
66 users who are used to Windows e.g.
67 net use <mount point> <UNC name or cifs URL>
68 Note that running the Winbind pam/nss module (logon service) on all of your
69 Linux clients is useful in mapping Uids and Gids consistently across the
70 domain to the proper network user. The mount.cifs mount helper can be
71 trivially built from Samba 3.0 or later source e.g. by executing:
73 gcc samba/source/client/mount.cifs.c -o mount.cifs
75 If cifs is built as a module, then the size and number of network buffers
76 and maximum number of simultaneous requests to one server can be configured.
77 Changing these from their defaults is not recommended. By executing modinfo
78 modinfo kernel/fs/cifs/cifs.ko
79 on kernel/fs/cifs/cifs.ko the list of configuration changes that can be made
80 at module initialization time (by running insmod cifs.ko) can be seen.
84 To permit users to mount and unmount over directories they own is possible
85 with the cifs vfs. A way to enable such mounting is to mark the mount.cifs
86 utility as suid (e.g. "chmod +s /sbin/mount.cifs). To enable users to
87 umount shares they mount requires
88 1) mount.cifs version 1.4 or later
89 2) an entry for the share in /etc/fstab indicating that a user may
91 //server/usersharename /mnt/username cifs user 0 0
93 Note that when the mount.cifs utility is run suid (allowing user mounts),
94 in order to reduce risks, the "nosuid" mount flag is passed in on mount to
95 disallow execution of an suid program mounted on the remote target.
96 When mount is executed as root, nosuid is not passed in by default,
97 and execution of suid programs on the remote target would be enabled
98 by default. This can be changed, as with nfs and other filesystems,
99 by simply specifying "nosuid" among the mount options. For user mounts
100 though to be able to pass the suid flag to mount requires rebuilding
101 mount.cifs with the following flag:
103 gcc samba/source/client/mount.cifs.c -DCIFS_ALLOW_USR_SUID -o mount.cifs
105 There is a corresponding manual page for cifs mounting in the Samba 3.0 and
106 later source tree in docs/manpages/mount.cifs.8
108 Allowing User Unmounts
109 ======================
110 To permit users to ummount directories that they have user mounted (see above),
111 the utility umount.cifs may be used. It may be invoked directly, or if
112 umount.cifs is placed in /sbin, umount can invoke the cifs umount helper
113 (at least for most versions of the umount utility) for umount of cifs
114 mounts, unless umount is invoked with -i (which will avoid invoking a umount
115 helper). As with mount.cifs, to enable user unmounts umount.cifs must be marked
116 as suid (e.g. "chmod +s /sbin/umount.cifs") or equivalent (some distributions
117 allow adding entries to a file to the /etc/permissions file to achieve the
118 equivalent suid effect). For this utility to succeed the target path
119 must be a cifs mount, and the uid of the current user must match the uid
120 of the user who mounted the resource.
122 Also note that the customary way of allowing user mounts and unmounts is
123 (instead of using mount.cifs and unmount.cifs as suid) to add a line
124 to the file /etc/fstab for each //server/share you wish to mount, but
125 this can become unwieldy when potential mount targets include many
126 or unpredictable UNC names.
130 To get the maximum benefit from the CIFS VFS, we recommend using a server that
131 supports the SNIA CIFS Unix Extensions standard (e.g. Samba 2.2.5 or later or
132 Samba 3.0) but the CIFS vfs works fine with a wide variety of CIFS servers.
133 Note that uid, gid and file permissions will display default values if you do
134 not have a server that supports the Unix extensions for CIFS (such as Samba
135 2.2.5 or later). To enable the Unix CIFS Extensions in the Samba server, add
138 unix extensions = yes
140 to your smb.conf file on the server. Note that the following smb.conf settings
141 are also useful (on the Samba server) when the majority of clients are Unix or
145 delete readonly = yes
148 Note that server ea support is required for supporting xattrs from the Linux
149 cifs client, and that EA support is present in later versions of Samba (e.g.
150 3.0.6 and later (also EA support works in all versions of Windows, at least to
151 shares on NTFS filesystems). Extended Attribute (xattr) support is an optional
152 feature of most Linux filesystems which may require enabling via
153 make menuconfig. Client support for extended attributes (user xattr) can be
154 disabled on a per-mount basis by specifying "nouser_xattr" on mount.
156 The CIFS client can get and set POSIX ACLs (getfacl, setfacl) to Samba servers
157 version 3.10 and later. Setting POSIX ACLs requires enabling both XATTR and
158 then POSIX support in the CIFS configuration options when building the cifs
159 module. POSIX ACL support can be disabled on a per mount basic by specifying
162 Some administrators may want to change Samba's smb.conf "map archive" and
163 "create mask" parameters from the default. Unless the create mask is changed
164 newly created files can end up with an unnecessarily restrictive default mode,
165 which may not be what you want, although if the CIFS Unix extensions are
166 enabled on the server and client, subsequent setattr calls (e.g. chmod) can
167 fix the mode. Note that creating special devices (mknod) remotely
168 may require specifying a mkdev function to Samba if you are not using
169 Samba 3.0.6 or later. For more information on these see the manual pages
170 ("man smb.conf") on the Samba server system. Note that the cifs vfs,
171 unlike the smbfs vfs, does not read the smb.conf on the client system
172 (the few optional settings are passed in on mount via -o parameters instead).
173 Note that Samba 2.2.7 or later includes a fix that allows the CIFS VFS to delete
174 open files (required for strict POSIX compliance). Windows Servers already
175 supported this feature. Samba server does not allow symlinks that refer to files
176 outside of the share, so in Samba versions prior to 3.0.6, most symlinks to
177 files with absolute paths (ie beginning with slash) such as:
179 would be forbidden. Samba 3.0.6 server or later includes the ability to create
180 such symlinks safely by converting unsafe symlinks (ie symlinks to server
181 files that are outside of the share) to a samba specific format on the server
182 that is ignored by local server applications and non-cifs clients and that will
183 not be traversed by the Samba server). This is opaque to the Linux client
184 application using the cifs vfs. Absolute symlinks will work to Samba 3.0.5 or
185 later, but only for remote clients using the CIFS Unix extensions, and will
186 be invisbile to Windows clients and typically will not affect local
187 applications running on the same server as Samba.
191 Once the CIFS VFS support is built into the kernel or installed as a module
192 (cifs.o), you can use mount syntax like the following to access Samba or Windows
195 mount -t cifs //9.53.216.11/e$ /mnt -o user=myname,pass=mypassword
197 Before -o the option -v may be specified to make the mount.cifs
198 mount helper display the mount steps more verbosely.
199 After -o the following commonly used cifs vfs specific options
206 Other cifs mount options are described below. Use of TCP names (in addition to
207 ip addresses) is available if the mount helper (mount.cifs) is installed. If
208 you do not trust the server to which are mounted, or if you do not have
209 cifs signing enabled (and the physical network is insecure), consider use
210 of the standard mount options "noexec" and "nosuid" to reduce the risk of
211 running an altered binary on your local system (downloaded from a hostile server
212 or altered by a hostile router).
214 Although mounting using format corresponding to the CIFS URL specification is
215 not possible in mount.cifs yet, it is possible to use an alternate format
216 for the server and sharename (which is somewhat similar to NFS style mount
217 syntax) instead of the more widely used UNC format (i.e. \\server\share):
218 mount -t cifs tcp_name_of_server:share_name /mnt -o user=myname,pass=mypasswd
220 When using the mount helper mount.cifs, passwords may be specified via alternate
221 mechanisms, instead of specifying it after -o using the normal "pass=" syntax
223 1) By including it in a credential file. Specify credentials=filename as one
224 of the mount options. Credential files contain two lines
226 password=your_password
227 2) By specifying the password in the PASSWD environment variable (similarly
228 the user name can be taken from the USER environment variable).
229 3) By specifying the password in a file by name via PASSWD_FILE
230 4) By specifying the password in a file by file descriptor via PASSWD_FD
232 If no password is provided, mount.cifs will prompt for password entry
236 Servers must support either "pure-TCP" (port 445 TCP/IP CIFS connections) or RFC
237 1001/1002 support for "Netbios-Over-TCP/IP." This is not likely to be a
238 problem as most servers support this.
240 Valid filenames differ between Windows and Linux. Windows typically restricts
241 filenames which contain certain reserved characters (e.g.the character :
242 which is used to delimit the beginning of a stream name by Windows), while
243 Linux allows a slightly wider set of valid characters in filenames. Windows
244 servers can remap such characters when an explicit mapping is specified in
245 the Server's registry. Samba starting with version 3.10 will allow such
246 filenames (ie those which contain valid Linux characters, which normally
247 would be forbidden for Windows/CIFS semantics) as long as the server is
248 configured for Unix Extensions (and the client has not disabled
249 /proc/fs/cifs/LinuxExtensionsEnabled).
252 CIFS VFS Mount Options
253 ======================
254 A partial list of the supported mount options follows:
255 user The user name to use when trying to establish
257 password The user password. If the mount helper is
258 installed, the user will be prompted for password
260 ip The ip address of the target server
261 unc The target server Universal Network Name (export) to
263 domain Set the SMB/CIFS workgroup name prepended to the
264 username during CIFS session establishment
265 forceuid Set the default uid for inodes to the uid
266 passed in on mount. For mounts to servers
267 which do support the CIFS Unix extensions, such as a
268 properly configured Samba server, the server provides
269 the uid, gid and mode so this parameter should not be
270 specified unless the server and clients uid and gid
271 numbering differ. If the server and client are in the
272 same domain (e.g. running winbind or nss_ldap) and
273 the server supports the Unix Extensions then the uid
274 and gid can be retrieved from the server (and uid
275 and gid would not have to be specifed on the mount.
276 For servers which do not support the CIFS Unix
277 extensions, the default uid (and gid) returned on lookup
278 of existing files will be the uid (gid) of the person
279 who executed the mount (root, except when mount.cifs
280 is configured setuid for user mounts) unless the "uid="
281 (gid) mount option is specified. Also note that permission
282 checks (authorization checks) on accesses to a file occur
283 at the server, but there are cases in which an administrator
284 may want to restrict at the client as well. For those
285 servers which do not report a uid/gid owner
286 (such as Windows), permissions can also be checked at the
287 client, and a crude form of client side permission checking
288 can be enabled by specifying file_mode and dir_mode on
289 the client. (default)
290 forcegid (similar to above but for the groupid instead of uid) (default)
291 noforceuid Fill in file owner information (uid) by requesting it from
292 the server if possible. With this option, the value given in
293 the uid= option (on mount) will only be used if the server
294 can not support returning uids on inodes.
295 noforcegid (similar to above but for the group owner, gid, instead of uid)
296 uid Set the default uid for inodes, and indicate to the
297 cifs kernel driver which local user mounted. If the server
298 supports the unix extensions the default uid is
299 not used to fill in the owner fields of inodes (files)
300 unless the "forceuid" parameter is specified.
301 gid Set the default gid for inodes (similar to above).
302 file_mode If CIFS Unix extensions are not supported by the server
303 this overrides the default mode for file inodes.
304 fsc Enable local disk caching using FS-Cache (off by default). This
305 option could be useful to improve performance on a slow link,
306 heavily loaded server and/or network where reading from the
307 disk is faster than reading from the server (over the network).
308 This could also impact scalability positively as the
309 number of calls to the server are reduced. However, local
310 caching is not suitable for all workloads for e.g. read-once
311 type workloads. So, you need to consider carefully your
312 workload/scenario before using this option. Currently, local
313 disk caching is functional for CIFS files opened as read-only.
314 dir_mode If CIFS Unix extensions are not supported by the server
315 this overrides the default mode for directory inodes.
316 port attempt to contact the server on this tcp port, before
317 trying the usual ports (port 445, then 139).
318 iocharset Codepage used to convert local path names to and from
319 Unicode. Unicode is used by default for network path
320 names if the server supports it. If iocharset is
321 not specified then the nls_default specified
322 during the local client kernel build will be used.
323 If server does not support Unicode, this parameter is
325 rsize default read size (usually 16K). The client currently
326 can not use rsize larger than CIFSMaxBufSize. CIFSMaxBufSize
327 defaults to 16K and may be changed (from 8K to the maximum
328 kmalloc size allowed by your kernel) at module install time
329 for cifs.ko. Setting CIFSMaxBufSize to a very large value
330 will cause cifs to use more memory and may reduce performance
331 in some cases. To use rsize greater than 127K (the original
332 cifs protocol maximum) also requires that the server support
333 a new Unix Capability flag (for very large read) which some
334 newer servers (e.g. Samba 3.0.26 or later) do. rsize can be
335 set from a minimum of 2048 to a maximum of 130048 (127K or
336 CIFSMaxBufSize, whichever is smaller)
337 wsize default write size (default 57344)
338 maximum wsize currently allowed by CIFS is 57344 (fourteen
340 actimeo=n attribute cache timeout in seconds (default 1 second).
341 After this timeout, the cifs client requests fresh attribute
342 information from the server. This option allows to tune the
343 attribute cache timeout to suit the workload needs. Shorter
344 timeouts mean better the cache coherency, but increased number
345 of calls to the server. Longer timeouts mean reduced number
346 of calls to the server at the expense of less stricter cache
347 coherency checks (i.e. incorrect attribute cache for a short
349 rw mount the network share read-write (note that the
350 server may still consider the share read-only)
351 ro mount network share read-only
352 version used to distinguish different versions of the
353 mount helper utility (not typically needed)
354 sep if first mount option (after the -o), overrides
355 the comma as the separator between the mount
357 -o user=myname,password=mypassword,domain=mydom
358 could be passed instead with period as the separator by
359 -o sep=.user=myname.password=mypassword.domain=mydom
360 this might be useful when comma is contained within username
361 or password or domain. This option is less important
362 when the cifs mount helper cifs.mount (version 1.1 or later)
364 nosuid Do not allow remote executables with the suid bit
365 program to be executed. This is only meaningful for mounts
366 to servers such as Samba which support the CIFS Unix Extensions.
367 If you do not trust the servers in your network (your mount
368 targets) it is recommended that you specify this option for
370 exec Permit execution of binaries on the mount.
371 noexec Do not permit execution of binaries on the mount.
372 dev Recognize block devices on the remote mount.
373 nodev Do not recognize devices on the remote mount.
374 suid Allow remote files on this mountpoint with suid enabled to
375 be executed (default for mounts when executed as root,
376 nosuid is default for user mounts).
377 credentials Although ignored by the cifs kernel component, it is used by
378 the mount helper, mount.cifs. When mount.cifs is installed it
379 opens and reads the credential file specified in order
380 to obtain the userid and password arguments which are passed to
382 guest Although ignored by the kernel component, the mount.cifs
383 mount helper will not prompt the user for a password
384 if guest is specified on the mount options. If no
385 password is specified a null password will be used.
386 perm Client does permission checks (vfs_permission check of uid
387 and gid of the file against the mode and desired operation),
388 Note that this is in addition to the normal ACL check on the
389 target machine done by the server software.
390 Client permission checking is enabled by default.
391 noperm Client does not do permission checks. This can expose
392 files on this mount to access by other users on the local
393 client system. It is typically only needed when the server
394 supports the CIFS Unix Extensions but the UIDs/GIDs on the
395 client and server system do not match closely enough to allow
396 access by the user doing the mount, but it may be useful with
397 non CIFS Unix Extension mounts for cases in which the default
398 mode is specified on the mount but is not to be enforced on the
399 client (e.g. perhaps when MultiUserMount is enabled)
400 Note that this does not affect the normal ACL check on the
401 target machine done by the server software (of the server
402 ACL against the user name provided at mount time).
403 serverino Use server's inode numbers instead of generating automatically
404 incrementing inode numbers on the client. Although this will
405 make it easier to spot hardlinked files (as they will have
406 the same inode numbers) and inode numbers may be persistent,
407 note that the server does not guarantee that the inode numbers
408 are unique if multiple server side mounts are exported under a
409 single share (since inode numbers on the servers might not
410 be unique if multiple filesystems are mounted under the same
411 shared higher level directory). Note that some older
412 (e.g. pre-Windows 2000) do not support returning UniqueIDs
413 or the CIFS Unix Extensions equivalent and for those
414 this mount option will have no effect. Exporting cifs mounts
415 under nfsd requires this mount option on the cifs mount.
416 This is now the default if server supports the
417 required network operation.
418 noserverino Client generates inode numbers (rather than using the actual one
419 from the server). These inode numbers will vary after
420 unmount or reboot which can confuse some applications,
421 but not all server filesystems support unique inode
423 setuids If the CIFS Unix extensions are negotiated with the server
424 the client will attempt to set the effective uid and gid of
425 the local process on newly created files, directories, and
426 devices (create, mkdir, mknod). If the CIFS Unix Extensions
427 are not negotiated, for newly created files and directories
428 instead of using the default uid and gid specified on
429 the mount, cache the new file's uid and gid locally which means
430 that the uid for the file can change when the inode is
431 reloaded (or the user remounts the share).
432 nosetuids The client will not attempt to set the uid and gid on
433 on newly created files, directories, and devices (create,
434 mkdir, mknod) which will result in the server setting the
435 uid and gid to the default (usually the server uid of the
436 user who mounted the share). Letting the server (rather than
437 the client) set the uid and gid is the default. If the CIFS
438 Unix Extensions are not negotiated then the uid and gid for
439 new files will appear to be the uid (gid) of the mounter or the
440 uid (gid) parameter specified on the mount.
441 netbiosname When mounting to servers via port 139, specifies the RFC1001
442 source name to use to represent the client netbios machine
443 name when doing the RFC1001 netbios session initialize.
444 direct Do not do inode data caching on files opened on this mount.
445 This precludes mmapping files on this mount. In some cases
446 with fast networks and little or no caching benefits on the
447 client (e.g. when the application is doing large sequential
448 reads bigger than page size without rereading the same data)
449 this can provide better performance than the default
450 behavior which caches reads (readahead) and writes
451 (writebehind) through the local Linux client pagecache
452 if oplock (caching token) is granted and held. Note that
453 direct allows write operations larger than page size
454 to be sent to the server.
455 strictcache Use for switching on strict cache mode. In this mode the
456 client read from the cache all the time it has Oplock Level II,
457 otherwise - read from the server. All written data are stored
458 in the cache, but if the client doesn't have Exclusive Oplock,
459 it writes the data to the server.
460 acl Allow setfacl and getfacl to manage posix ACLs if server
461 supports them. (default)
462 noacl Do not allow setfacl and getfacl calls on this mount
463 user_xattr Allow getting and setting user xattrs (those attributes whose
464 name begins with "user." or "os2.") as OS/2 EAs (extended
465 attributes) to the server. This allows support of the
466 setfattr and getfattr utilities. (default)
467 nouser_xattr Do not allow getfattr/setfattr to get/set/list xattrs
468 mapchars Translate six of the seven reserved characters (not backslash)
470 to the remap range (above 0xF000), which also
471 allows the CIFS client to recognize files created with
472 such characters by Windows's POSIX emulation. This can
473 also be useful when mounting to most versions of Samba
474 (which also forbids creating and opening files
475 whose names contain any of these seven characters).
476 This has no effect if the server does not support
478 nomapchars Do not translate any of these seven characters (default).
479 nocase Request case insensitive path name matching (case
480 sensitive is the default if the server suports it).
481 (mount option "ignorecase" is identical to "nocase")
482 posixpaths If CIFS Unix extensions are supported, attempt to
483 negotiate posix path name support which allows certain
484 characters forbidden in typical CIFS filenames, without
485 requiring remapping. (default)
486 noposixpaths If CIFS Unix extensions are supported, do not request
487 posix path name support (this may cause servers to
488 reject creatingfile with certain reserved characters).
489 nounix Disable the CIFS Unix Extensions for this mount (tree
490 connection). This is rarely needed, but it may be useful
491 in order to turn off multiple settings all at once (ie
492 posix acls, posix locks, posix paths, symlink support
493 and retrieving uids/gids/mode from the server) or to
494 work around a bug in server which implement the Unix
496 nobrl Do not send byte range lock requests to the server.
497 This is necessary for certain applications that break
498 with cifs style mandatory byte range locks (and most
499 cifs servers do not yet support requesting advisory
501 forcemandatorylock Even if the server supports posix (advisory) byte range
502 locking, send only mandatory lock requests. For some
503 (presumably rare) applications, originally coded for
504 DOS/Windows, which require Windows style mandatory byte range
505 locking, they may be able to take advantage of this option,
506 forcing the cifs client to only send mandatory locks
507 even if the cifs server would support posix advisory locks.
508 "forcemand" is accepted as a shorter form of this mount
510 nostrictsync If this mount option is set, when an application does an
511 fsync call then the cifs client does not send an SMB Flush
512 to the server (to force the server to write all dirty data
513 for this file immediately to disk), although cifs still sends
514 all dirty (cached) file data to the server and waits for the
515 server to respond to the write. Since SMB Flush can be
516 very slow, and some servers may be reliable enough (to risk
517 delaying slightly flushing the data to disk on the server),
518 turning on this option may be useful to improve performance for
519 applications that fsync too much, at a small risk of server
520 crash. If this mount option is not set, by default cifs will
521 send an SMB flush request (and wait for a response) on every
523 nodfs Disable DFS (global name space support) even if the
524 server claims to support it. This can help work around
525 a problem with parsing of DFS paths with Samba server
526 versions 3.0.24 and 3.0.25.
527 remount remount the share (often used to change from ro to rw mounts
529 cifsacl Report mode bits (e.g. on stat) based on the Windows ACL for
530 the file. (EXPERIMENTAL)
531 servern Specify the server 's netbios name (RFC1001 name) to use
532 when attempting to setup a session to the server.
533 This is needed for mounting to some older servers (such
534 as OS/2 or Windows 98 and Windows ME) since they do not
535 support a default server name. A server name can be up
536 to 15 characters long and is usually uppercased.
537 sfu When the CIFS Unix Extensions are not negotiated, attempt to
538 create device files and fifos in a format compatible with
539 Services for Unix (SFU). In addition retrieve bits 10-12
540 of the mode via the SETFILEBITS extended attribute (as
541 SFU does). In the future the bottom 9 bits of the
542 mode also will be emulated using queries of the security
544 mfsymlinks Enable support for Minshall+French symlinks
545 (see http://wiki.samba.org/index.php/UNIX_Extensions#Minshall.2BFrench_symlinks)
546 This option is ignored when specified together with the
547 'sfu' option. Minshall+French symlinks are used even if
548 the server supports the CIFS Unix Extensions.
549 sign Must use packet signing (helps avoid unwanted data modification
550 by intermediate systems in the route). Note that signing
551 does not work with lanman or plaintext authentication.
552 seal Must seal (encrypt) all data on this mounted share before
553 sending on the network. Requires support for Unix Extensions.
554 Note that this differs from the sign mount option in that it
555 causes encryption of data sent over this mounted share but other
556 shares mounted to the same server are unaffected.
557 locallease This option is rarely needed. Fcntl F_SETLEASE is
558 used by some applications such as Samba and NFSv4 server to
559 check to see whether a file is cacheable. CIFS has no way
560 to explicitly request a lease, but can check whether a file
561 is cacheable (oplocked). Unfortunately, even if a file
562 is not oplocked, it could still be cacheable (ie cifs client
563 could grant fcntl leases if no other local processes are using
564 the file) for cases for example such as when the server does not
565 support oplocks and the user is sure that the only updates to
566 the file will be from this client. Specifying this mount option
567 will allow the cifs client to check for leases (only) locally
568 for files which are not oplocked instead of denying leases
569 in that case. (EXPERIMENTAL)
570 sec Security mode. Allowed values are:
571 none attempt to connection as a null user (no name)
572 krb5 Use Kerberos version 5 authentication
573 krb5i Use Kerberos authentication and packet signing
574 ntlm Use NTLM password hashing (default)
575 ntlmi Use NTLM password hashing with signing (if
576 /proc/fs/cifs/PacketSigningEnabled on or if
577 server requires signing also can be the default)
578 ntlmv2 Use NTLMv2 password hashing
579 ntlmv2i Use NTLMv2 password hashing with packet signing
580 lanman (if configured in kernel config) use older
582 hard Retry file operations if server is not responding
583 soft Limit retries to unresponsive servers (usually only
584 one retry) before returning an error. (default)
586 The mount.cifs mount helper also accepts a few mount options before -o
589 -S take password from stdin (equivalent to setting the environment
590 variable "PASSWD_FD=0"
591 -V print mount.cifs version
592 -? display simple usage information
594 With most 2.6 kernel versions of modutils, the version of the cifs kernel
595 module can be displayed via modinfo.
597 Misc /proc/fs/cifs Flags and Debug Info
598 =======================================
599 Informational pseudo-files:
600 DebugData Displays information about active CIFS sessions and
601 shares, features enabled as well as the cifs.ko
603 Stats Lists summary resource usage information as well as per
604 share statistics, if CONFIG_CIFS_STATS in enabled
605 in the kernel configuration.
607 Configuration pseudo-files:
608 MultiuserMount If set to one, more than one CIFS session to
609 the same server ip address can be established
610 if more than one uid accesses the same mount
611 point and if the uids user/password mapping
612 information is available. (default is 0)
613 PacketSigningEnabled If set to one, cifs packet signing is enabled
614 and will be used if the server requires
615 it. If set to two, cifs packet signing is
616 required even if the server considers packet
617 signing optional. (default 1)
618 SecurityFlags Flags which control security negotiation and
619 also packet signing. Authentication (may/must)
620 flags (e.g. for NTLM and/or NTLMv2) may be combined with
621 the signing flags. Specifying two different password
622 hashing mechanisms (as "must use") on the other hand
623 does not make much sense. Default flags are
625 (NTLM, NTLMv2 and packet signing allowed). The maximum
626 allowable flags if you want to allow mounts to servers
627 using weaker password hashes is 0x37037 (lanman,
628 plaintext, ntlm, ntlmv2, signing allowed). Some
629 SecurityFlags require the corresponding menuconfig
630 options to be enabled (lanman and plaintext require
631 CONFIG_CIFS_WEAK_PW_HASH for example). Enabling
632 plaintext authentication currently requires also
633 enabling lanman authentication in the security flags
634 because the cifs module only supports sending
635 laintext passwords using the older lanman dialect
636 form of the session setup SMB. (e.g. for authentication
637 using plain text passwords, set the SecurityFlags
640 may use packet signing 0x00001
641 must use packet signing 0x01001
642 may use NTLM (most common password hash) 0x00002
643 must use NTLM 0x02002
644 may use NTLMv2 0x00004
645 must use NTLMv2 0x04004
646 may use Kerberos security 0x00008
647 must use Kerberos 0x08008
648 may use lanman (weak) password hash 0x00010
649 must use lanman password hash 0x10010
650 may use plaintext passwords 0x00020
651 must use plaintext passwords 0x20020
652 (reserved for future packet encryption) 0x00040
654 cifsFYI If set to non-zero value, additional debug information
655 will be logged to the system error log. This field
656 contains three flags controlling different classes of
657 debugging entries. The maximum value it can be set
658 to is 7 which enables all debugging points (default 0).
659 Some debugging statements are not compiled into the
660 cifs kernel unless CONFIG_CIFS_DEBUG2 is enabled in the
661 kernel configuration. cifsFYI may be set to one or
662 nore of the following flags (7 sets them all):
664 log cifs informational messages 0x01
665 log return codes from cifs entry points 0x02
666 log slow responses (ie which take longer than 1 second)
667 CONFIG_CIFS_STATS2 must be enabled in .config 0x04
670 traceSMB If set to one, debug information is logged to the
671 system error log with the start of smb requests
672 and responses (default 0)
673 LookupCacheEnable If set to one, inode information is kept cached
674 for one second improving performance of lookups
676 OplockEnabled If set to one, safe distributed caching enabled.
678 LinuxExtensionsEnabled If set to one then the client will attempt to
679 use the CIFS "UNIX" extensions which are optional
680 protocol enhancements that allow CIFS servers
681 to return accurate UID/GID information as well
682 as support symbolic links. If you use servers
683 such as Samba that support the CIFS Unix
684 extensions but do not want to use symbolic link
685 support and want to map the uid and gid fields
686 to values supplied at mount (rather than the
687 actual values, then set this to zero. (default 1)
689 These experimental features and tracing can be enabled by changing flags in
690 /proc/fs/cifs (after the cifs module has been installed or built into the
691 kernel, e.g. insmod cifs). To enable a feature set it to 1 e.g. to enable
692 tracing to the kernel message log type:
694 echo 7 > /proc/fs/cifs/cifsFYI
696 cifsFYI functions as a bit mask. Setting it to 1 enables additional kernel
697 logging of various informational messages. 2 enables logging of non-zero
698 SMB return codes while 4 enables logging of requests that take longer
699 than one second to complete (except for byte range lock requests).
700 Setting it to 4 requires defining CONFIG_CIFS_STATS2 manually in the
701 source code (typically by setting it in the beginning of cifsglob.h),
702 and setting it to seven enables all three. Finally, tracing
703 the start of smb requests and responses can be enabled via:
705 echo 1 > /proc/fs/cifs/traceSMB
707 Two other experimental features are under development. To test these
708 requires enabling CONFIG_CIFS_EXPERIMENTAL
710 cifsacl support needed to retrieve approximated mode bits based on
711 the contents on the CIFS ACL.
713 lease support: cifs will check the oplock state before calling into
714 the vfs to see if we can grant a lease on a file.
716 DNOTIFY fcntl: needed for support of directory change
717 notification and perhaps later for file leases)
719 Per share (per client mount) statistics are available in /proc/fs/cifs/Stats
720 if the kernel was configured with cifs statistics enabled. The statistics
721 represent the number of successful (ie non-zero return code from the server)
722 SMB responses to some of the more common commands (open, delete, mkdir etc.).
723 Also recorded is the total bytes read and bytes written to the server for
724 that share. Note that due to client caching effects this can be less than the
725 number of bytes read and written by the application running on the client.
726 The statistics for the number of total SMBs and oplock breaks are different in
727 that they represent all for that share, not just those for which the server
730 Also note that "cat /proc/fs/cifs/DebugData" will display information about
731 the active sessions and the shares that are mounted.
733 Enabling Kerberos (extended security) works but requires version 1.2 or later
734 of the helper program cifs.upcall to be present and to be configured in the
735 /etc/request-key.conf file. The cifs.upcall helper program is from the Samba
736 project(http://www.samba.org). NTLM and NTLMv2 and LANMAN support do not
737 require this helper. Note that NTLMv2 security (which does not require the
738 cifs.upcall helper program), instead of using Kerberos, is sufficient for
741 DFS support allows transparent redirection to shares in an MS-DFS name space.
742 In addition, DFS support for target shares which are specified as UNC
743 names which begin with host names (rather than IP addresses) requires
744 a user space helper (such as cifs.upcall) to be present in order to
745 translate host names to ip address, and the user space helper must also
746 be configured in the file /etc/request-key.conf. Samba, Windows servers and
747 many NAS appliances support DFS as a way of constructing a global name
748 space to ease network configuration and improve reliability.
750 To use cifs Kerberos and DFS support, the Linux keyutils package should be
751 installed and something like the following lines should be added to the
752 /etc/request-key.conf file:
754 create cifs.spnego * * /usr/local/sbin/cifs.upcall %k
755 create dns_resolver * * /usr/local/sbin/cifs.upcall %k
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