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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.
9 Please see
10 http://protocolfreedom.org/ and
11 http://samba.org/samba/PFIF/
12 for more details.
15 For questions or bug reports please contact:
16 sfrench@samba.org (sfrench@us.ibm.com)
18 Build instructions:
19 ==================
20 For Linux 2.4:
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
37 4) save and exit
38 5) make dep
39 6) make modules (or "make" if CIFS VFS not to be built as a module)
41 For Linux 2.6:
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
47 4) save and exit
48 5) make
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.
82 Allowing User Mounts
83 ====================
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
90 unmount it e.g.
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.
128 Samba Considerations
129 ====================
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
136 the line:
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
142 Linux:
144 case sensitive = yes
145 delete readonly = yes
146 ea support = 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
160 "noacl" on mount.
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:
178 ln -s /mnt/foo bar
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.
189 Use instructions:
190 ================
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
193 servers:
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
200 are supported:
202 user=<username>
203 pass=<password>
204 domain=<domain name>
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
222 on the command line:
223 1) By including it in a credential file. Specify credentials=filename as one
224 of the mount options. Credential files contain two lines
225 username=someuser
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
234 Restrictions
235 ============
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
256 the CIFS session.
257 password The user password. If the mount helper is
258 installed, the user will be prompted for password
259 if not supplied.
260 ip The ip address of the target server
261 unc The target server Universal Network Name (export) to
262 mount.
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 based on the uid
266 passed in. 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. For the uid (gid) of newly
282 created files and directories, ie files created since
283 the last mount of the server share, the expected uid
284 (gid) is cached as long as the inode remains in
285 memory on the client. Also note that permission
286 checks (authorization checks) on accesses to a file occur
287 at the server, but there are cases in which an administrator
288 may want to restrict at the client as well. For those
289 servers which do not report a uid/gid owner
290 (such as Windows), permissions can also be checked at the
291 client, and a crude form of client side permission checking
292 can be enabled by specifying file_mode and dir_mode on
293 the client. Note that the mount.cifs helper must be
294 at version 1.10 or higher to support specifying the uid
295 (or gid) in non-numeric form.
296 forcegid (similar to above but for the groupid instead of uid)
297 uid Set the default uid for inodes, and indicate to the
298 cifs kernel driver which local user mounted . If the server
299 supports the unix extensions the default uid is
300 not used to fill in the owner fields of inodes (files)
301 unless the "forceuid" parameter is specified.
302 gid Set the default gid for inodes (similar to above).
303 file_mode If CIFS Unix extensions are not supported by the server
304 this overrides the default mode for file inodes.
305 dir_mode If CIFS Unix extensions are not supported by the server
306 this overrides the default mode for directory inodes.
307 port attempt to contact the server on this tcp port, before
308 trying the usual ports (port 445, then 139).
309 iocharset Codepage used to convert local path names to and from
310 Unicode. Unicode is used by default for network path
311 names if the server supports it. If iocharset is
312 not specified then the nls_default specified
313 during the local client kernel build will be used.
314 If server does not support Unicode, this parameter is
315 unused.
316 rsize default read size (usually 16K). The client currently
317 can not use rsize larger than CIFSMaxBufSize. CIFSMaxBufSize
318 defaults to 16K and may be changed (from 8K to the maximum
319 kmalloc size allowed by your kernel) at module install time
320 for cifs.ko. Setting CIFSMaxBufSize to a very large value
321 will cause cifs to use more memory and may reduce performance
322 in some cases. To use rsize greater than 127K (the original
323 cifs protocol maximum) also requires that the server support
324 a new Unix Capability flag (for very large read) which some
325 newer servers (e.g. Samba 3.0.26 or later) do. rsize can be
326 set from a minimum of 2048 to a maximum of 130048 (127K or
327 CIFSMaxBufSize, whichever is smaller)
328 wsize default write size (default 57344)
329 maximum wsize currently allowed by CIFS is 57344 (fourteen
330 4096 byte pages)
331 rw mount the network share read-write (note that the
332 server may still consider the share read-only)
333 ro mount network share read-only
334 version used to distinguish different versions of the
335 mount helper utility (not typically needed)
336 sep if first mount option (after the -o), overrides
337 the comma as the separator between the mount
338 parms. e.g.
339 -o user=myname,password=mypassword,domain=mydom
340 could be passed instead with period as the separator by
341 -o sep=.user=myname.password=mypassword.domain=mydom
342 this might be useful when comma is contained within username
343 or password or domain. This option is less important
344 when the cifs mount helper cifs.mount (version 1.1 or later)
345 is used.
346 nosuid Do not allow remote executables with the suid bit
347 program to be executed. This is only meaningful for mounts
348 to servers such as Samba which support the CIFS Unix Extensions.
349 If you do not trust the servers in your network (your mount
350 targets) it is recommended that you specify this option for
351 greater security.
352 exec Permit execution of binaries on the mount.
353 noexec Do not permit execution of binaries on the mount.
354 dev Recognize block devices on the remote mount.
355 nodev Do not recognize devices on the remote mount.
356 suid Allow remote files on this mountpoint with suid enabled to
357 be executed (default for mounts when executed as root,
358 nosuid is default for user mounts).
359 credentials Although ignored by the cifs kernel component, it is used by
360 the mount helper, mount.cifs. When mount.cifs is installed it
361 opens and reads the credential file specified in order
362 to obtain the userid and password arguments which are passed to
363 the cifs vfs.
364 guest Although ignored by the kernel component, the mount.cifs
365 mount helper will not prompt the user for a password
366 if guest is specified on the mount options. If no
367 password is specified a null password will be used.
368 perm Client does permission checks (vfs_permission check of uid
369 and gid of the file against the mode and desired operation),
370 Note that this is in addition to the normal ACL check on the
371 target machine done by the server software.
372 Client permission checking is enabled by default.
373 noperm Client does not do permission checks. This can expose
374 files on this mount to access by other users on the local
375 client system. It is typically only needed when the server
376 supports the CIFS Unix Extensions but the UIDs/GIDs on the
377 client and server system do not match closely enough to allow
378 access by the user doing the mount, but it may be useful with
379 non CIFS Unix Extension mounts for cases in which the default
380 mode is specified on the mount but is not to be enforced on the
381 client (e.g. perhaps when MultiUserMount is enabled)
382 Note that this does not affect the normal ACL check on the
383 target machine done by the server software (of the server
384 ACL against the user name provided at mount time).
385 serverino Use server's inode numbers instead of generating automatically
386 incrementing inode numbers on the client. Although this will
387 make it easier to spot hardlinked files (as they will have
388 the same inode numbers) and inode numbers may be persistent,
389 note that the server does not guarantee that the inode numbers
390 are unique if multiple server side mounts are exported under a
391 single share (since inode numbers on the servers might not
392 be unique if multiple filesystems are mounted under the same
393 shared higher level directory). Note that some older
394 (e.g. pre-Windows 2000) do not support returning UniqueIDs
395 or the CIFS Unix Extensions equivalent and for those
396 this mount option will have no effect. Exporting cifs mounts
397 under nfsd requires this mount option on the cifs mount.
398 This is now the default if server supports the
399 required network operation.
400 noserverino Client generates inode numbers (rather than using the actual one
401 from the server). These inode numbers will vary after
402 unmount or reboot which can confuse some applications,
403 but not all server filesystems support unique inode
404 numbers.
405 setuids If the CIFS Unix extensions are negotiated with the server
406 the client will attempt to set the effective uid and gid of
407 the local process on newly created files, directories, and
408 devices (create, mkdir, mknod). If the CIFS Unix Extensions
409 are not negotiated, for newly created files and directories
410 instead of using the default uid and gid specified on
411 the mount, cache the new file's uid and gid locally which means
412 that the uid for the file can change when the inode is
413 reloaded (or the user remounts the share).
414 nosetuids The client will not attempt to set the uid and gid on
415 on newly created files, directories, and devices (create,
416 mkdir, mknod) which will result in the server setting the
417 uid and gid to the default (usually the server uid of the
418 user who mounted the share). Letting the server (rather than
419 the client) set the uid and gid is the default. If the CIFS
420 Unix Extensions are not negotiated then the uid and gid for
421 new files will appear to be the uid (gid) of the mounter or the
422 uid (gid) parameter specified on the mount.
423 netbiosname When mounting to servers via port 139, specifies the RFC1001
424 source name to use to represent the client netbios machine
425 name when doing the RFC1001 netbios session initialize.
426 direct Do not do inode data caching on files opened on this mount.
427 This precludes mmaping files on this mount. In some cases
428 with fast networks and little or no caching benefits on the
429 client (e.g. when the application is doing large sequential
430 reads bigger than page size without rereading the same data)
431 this can provide better performance than the default
432 behavior which caches reads (readahead) and writes
433 (writebehind) through the local Linux client pagecache
434 if oplock (caching token) is granted and held. Note that
435 direct allows write operations larger than page size
436 to be sent to the server.
437 acl Allow setfacl and getfacl to manage posix ACLs if server
438 supports them. (default)
439 noacl Do not allow setfacl and getfacl calls on this mount
440 user_xattr Allow getting and setting user xattrs (those attributes whose
441 name begins with "user." or "os2.") as OS/2 EAs (extended
442 attributes) to the server. This allows support of the
443 setfattr and getfattr utilities. (default)
444 nouser_xattr Do not allow getfattr/setfattr to get/set/list xattrs
445 mapchars Translate six of the seven reserved characters (not backslash)
446 *?<>|:
447 to the remap range (above 0xF000), which also
448 allows the CIFS client to recognize files created with
449 such characters by Windows's POSIX emulation. This can
450 also be useful when mounting to most versions of Samba
451 (which also forbids creating and opening files
452 whose names contain any of these seven characters).
453 This has no effect if the server does not support
454 Unicode on the wire.
455 nomapchars Do not translate any of these seven characters (default).
456 nocase Request case insensitive path name matching (case
457 sensitive is the default if the server suports it).
458 (mount option "ignorecase" is identical to "nocase")
459 posixpaths If CIFS Unix extensions are supported, attempt to
460 negotiate posix path name support which allows certain
461 characters forbidden in typical CIFS filenames, without
462 requiring remapping. (default)
463 noposixpaths If CIFS Unix extensions are supported, do not request
464 posix path name support (this may cause servers to
465 reject creatingfile with certain reserved characters).
466 nounix Disable the CIFS Unix Extensions for this mount (tree
467 connection). This is rarely needed, but it may be useful
468 in order to turn off multiple settings all at once (ie
469 posix acls, posix locks, posix paths, symlink support
470 and retrieving uids/gids/mode from the server) or to
471 work around a bug in server which implement the Unix
472 Extensions.
473 nobrl Do not send byte range lock requests to the server.
474 This is necessary for certain applications that break
475 with cifs style mandatory byte range locks (and most
476 cifs servers do not yet support requesting advisory
477 byte range locks).
478 forcemandatorylock Even if the server supports posix (advisory) byte range
479 locking, send only mandatory lock requests. For some
480 (presumably rare) applications, originally coded for
481 DOS/Windows, which require Windows style mandatory byte range
482 locking, they may be able to take advantage of this option,
483 forcing the cifs client to only send mandatory locks
484 even if the cifs server would support posix advisory locks.
485 "forcemand" is accepted as a shorter form of this mount
486 option.
487 nostrictsync If this mount option is set, when an application does an
488 fsync call then the cifs client does not send an SMB Flush
489 to the server (to force the server to write all dirty data
490 for this file immediately to disk), although cifs still sends
491 all dirty (cached) file data to the server and waits for the
492 server to respond to the write. Since SMB Flush can be
493 very slow, and some servers may be reliable enough (to risk
494 delaying slightly flushing the data to disk on the server),
495 turning on this option may be useful to improve performance for
496 applications that fsync too much, at a small risk of server
497 crash. If this mount option is not set, by default cifs will
498 send an SMB flush request (and wait for a response) on every
499 fsync call.
500 nodfs Disable DFS (global name space support) even if the
501 server claims to support it. This can help work around
502 a problem with parsing of DFS paths with Samba server
503 versions 3.0.24 and 3.0.25.
504 remount remount the share (often used to change from ro to rw mounts
505 or vice versa)
506 cifsacl Report mode bits (e.g. on stat) based on the Windows ACL for
507 the file. (EXPERIMENTAL)
508 servern Specify the server 's netbios name (RFC1001 name) to use
509 when attempting to setup a session to the server.
510 This is needed for mounting to some older servers (such
511 as OS/2 or Windows 98 and Windows ME) since they do not
512 support a default server name. A server name can be up
513 to 15 characters long and is usually uppercased.
514 sfu When the CIFS Unix Extensions are not negotiated, attempt to
515 create device files and fifos in a format compatible with
516 Services for Unix (SFU). In addition retrieve bits 10-12
517 of the mode via the SETFILEBITS extended attribute (as
518 SFU does). In the future the bottom 9 bits of the
519 mode also will be emulated using queries of the security
520 descriptor (ACL).
521 sign Must use packet signing (helps avoid unwanted data modification
522 by intermediate systems in the route). Note that signing
523 does not work with lanman or plaintext authentication.
524 seal Must seal (encrypt) all data on this mounted share before
525 sending on the network. Requires support for Unix Extensions.
526 Note that this differs from the sign mount option in that it
527 causes encryption of data sent over this mounted share but other
528 shares mounted to the same server are unaffected.
529 locallease This option is rarely needed. Fcntl F_SETLEASE is
530 used by some applications such as Samba and NFSv4 server to
531 check to see whether a file is cacheable. CIFS has no way
532 to explicitly request a lease, but can check whether a file
533 is cacheable (oplocked). Unfortunately, even if a file
534 is not oplocked, it could still be cacheable (ie cifs client
535 could grant fcntl leases if no other local processes are using
536 the file) for cases for example such as when the server does not
537 support oplocks and the user is sure that the only updates to
538 the file will be from this client. Specifying this mount option
539 will allow the cifs client to check for leases (only) locally
540 for files which are not oplocked instead of denying leases
541 in that case. (EXPERIMENTAL)
542 sec Security mode. Allowed values are:
543 none attempt to connection as a null user (no name)
544 krb5 Use Kerberos version 5 authentication
545 krb5i Use Kerberos authentication and packet signing
546 ntlm Use NTLM password hashing (default)
547 ntlmi Use NTLM password hashing with signing (if
548 /proc/fs/cifs/PacketSigningEnabled on or if
549 server requires signing also can be the default)
550 ntlmv2 Use NTLMv2 password hashing
551 ntlmv2i Use NTLMv2 password hashing with packet signing
552 lanman (if configured in kernel config) use older
553 lanman hash
554 hard Retry file operations if server is not responding
555 soft Limit retries to unresponsive servers (usually only
556 one retry) before returning an error. (default)
558 The mount.cifs mount helper also accepts a few mount options before -o
559 including:
561 -S take password from stdin (equivalent to setting the environment
562 variable "PASSWD_FD=0"
563 -V print mount.cifs version
564 -? display simple usage information
566 With most 2.6 kernel versions of modutils, the version of the cifs kernel
567 module can be displayed via modinfo.
569 Misc /proc/fs/cifs Flags and Debug Info
570 =======================================
571 Informational pseudo-files:
572 DebugData Displays information about active CIFS sessions
573 and shares, as well as the cifs.ko version.
574 Stats Lists summary resource usage information as well as per
575 share statistics, if CONFIG_CIFS_STATS in enabled
576 in the kernel configuration.
578 Configuration pseudo-files:
579 MultiuserMount If set to one, more than one CIFS session to
580 the same server ip address can be established
581 if more than one uid accesses the same mount
582 point and if the uids user/password mapping
583 information is available. (default is 0)
584 PacketSigningEnabled If set to one, cifs packet signing is enabled
585 and will be used if the server requires
586 it. If set to two, cifs packet signing is
587 required even if the server considers packet
588 signing optional. (default 1)
589 SecurityFlags Flags which control security negotiation and
590 also packet signing. Authentication (may/must)
591 flags (e.g. for NTLM and/or NTLMv2) may be combined with
592 the signing flags. Specifying two different password
593 hashing mechanisms (as "must use") on the other hand
594 does not make much sense. Default flags are
595 0x07007
596 (NTLM, NTLMv2 and packet signing allowed). The maximum
597 allowable flags if you want to allow mounts to servers
598 using weaker password hashes is 0x37037 (lanman,
599 plaintext, ntlm, ntlmv2, signing allowed). Some
600 SecurityFlags require the corresponding menuconfig
601 options to be enabled (lanman and plaintext require
602 CONFIG_CIFS_WEAK_PW_HASH for example). Enabling
603 plaintext authentication currently requires also
604 enabling lanman authentication in the security flags
605 because the cifs module only supports sending
606 laintext passwords using the older lanman dialect
607 form of the session setup SMB. (e.g. for authentication
608 using plain text passwords, set the SecurityFlags
609 to 0x30030):
611 may use packet signing 0x00001
612 must use packet signing 0x01001
613 may use NTLM (most common password hash) 0x00002
614 must use NTLM 0x02002
615 may use NTLMv2 0x00004
616 must use NTLMv2 0x04004
617 may use Kerberos security 0x00008
618 must use Kerberos 0x08008
619 may use lanman (weak) password hash 0x00010
620 must use lanman password hash 0x10010
621 may use plaintext passwords 0x00020
622 must use plaintext passwords 0x20020
623 (reserved for future packet encryption) 0x00040
625 cifsFYI If set to non-zero value, additional debug information
626 will be logged to the system error log. This field
627 contains three flags controlling different classes of
628 debugging entries. The maximum value it can be set
629 to is 7 which enables all debugging points (default 0).
630 Some debugging statements are not compiled into the
631 cifs kernel unless CONFIG_CIFS_DEBUG2 is enabled in the
632 kernel configuration. cifsFYI may be set to one or
633 nore of the following flags (7 sets them all):
635 log cifs informational messages 0x01
636 log return codes from cifs entry points 0x02
637 log slow responses (ie which take longer than 1 second)
638 CONFIG_CIFS_STATS2 must be enabled in .config 0x04
641 traceSMB If set to one, debug information is logged to the
642 system error log with the start of smb requests
643 and responses (default 0)
644 LookupCacheEnable If set to one, inode information is kept cached
645 for one second improving performance of lookups
646 (default 1)
647 OplockEnabled If set to one, safe distributed caching enabled.
648 (default 1)
649 LinuxExtensionsEnabled If set to one then the client will attempt to
650 use the CIFS "UNIX" extensions which are optional
651 protocol enhancements that allow CIFS servers
652 to return accurate UID/GID information as well
653 as support symbolic links. If you use servers
654 such as Samba that support the CIFS Unix
655 extensions but do not want to use symbolic link
656 support and want to map the uid and gid fields
657 to values supplied at mount (rather than the
658 actual values, then set this to zero. (default 1)
659 Experimental When set to 1 used to enable certain experimental
660 features (currently enables multipage writes
661 when signing is enabled, the multipage write
662 performance enhancement was disabled when
663 signing turned on in case buffer was modified
664 just before it was sent, also this flag will
665 be used to use the new experimental directory change
666 notification code). When set to 2 enables
667 an additional experimental feature, "raw ntlmssp"
668 session establishment support (which allows
669 specifying "sec=ntlmssp" on mount). The Linux cifs
670 module will use ntlmv2 authentication encapsulated
671 in "raw ntlmssp" (not using SPNEGO) when
672 "sec=ntlmssp" is specified on mount.
673 This support also requires building cifs with
674 the CONFIG_CIFS_EXPERIMENTAL configuration flag.
676 These experimental features and tracing can be enabled by changing flags in
677 /proc/fs/cifs (after the cifs module has been installed or built into the
678 kernel, e.g. insmod cifs). To enable a feature set it to 1 e.g. to enable
679 tracing to the kernel message log type:
681 echo 7 > /proc/fs/cifs/cifsFYI
683 cifsFYI functions as a bit mask. Setting it to 1 enables additional kernel
684 logging of various informational messages. 2 enables logging of non-zero
685 SMB return codes while 4 enables logging of requests that take longer
686 than one second to complete (except for byte range lock requests).
687 Setting it to 4 requires defining CONFIG_CIFS_STATS2 manually in the
688 source code (typically by setting it in the beginning of cifsglob.h),
689 and setting it to seven enables all three. Finally, tracing
690 the start of smb requests and responses can be enabled via:
692 echo 1 > /proc/fs/cifs/traceSMB
694 Two other experimental features are under development. To test these
695 requires enabling CONFIG_CIFS_EXPERIMENTAL
697 cifsacl support needed to retrieve approximated mode bits based on
698 the contents on the CIFS ACL.
700 lease support: cifs will check the oplock state before calling into
701 the vfs to see if we can grant a lease on a file.
703 DNOTIFY fcntl: needed for support of directory change
704 notification and perhaps later for file leases)
706 Per share (per client mount) statistics are available in /proc/fs/cifs/Stats
707 if the kernel was configured with cifs statistics enabled. The statistics
708 represent the number of successful (ie non-zero return code from the server)
709 SMB responses to some of the more common commands (open, delete, mkdir etc.).
710 Also recorded is the total bytes read and bytes written to the server for
711 that share. Note that due to client caching effects this can be less than the
712 number of bytes read and written by the application running on the client.
713 The statistics for the number of total SMBs and oplock breaks are different in
714 that they represent all for that share, not just those for which the server
715 returned success.
717 Also note that "cat /proc/fs/cifs/DebugData" will display information about
718 the active sessions and the shares that are mounted.
720 Enabling Kerberos (extended security) works but requires version 1.2 or later
721 of the helper program cifs.upcall to be present and to be configured in the
722 /etc/request-key.conf file. The cifs.upcall helper program is from the Samba
723 project(http://www.samba.org). NTLM and NTLMv2 and LANMAN support do not
724 require this helper. Note that NTLMv2 security (which does not require the
725 cifs.upcall helper program), instead of using Kerberos, is sufficient for
726 some use cases.
728 DFS support allows transparent redirection to shares in an MS-DFS name space.
729 In addition, DFS support for target shares which are specified as UNC
730 names which begin with host names (rather than IP addresses) requires
731 a user space helper (such as cifs.upcall) to be present in order to
732 translate host names to ip address, and the user space helper must also
733 be configured in the file /etc/request-key.conf. Samba, Windows servers and
734 many NAS appliances support DFS as a way of constructing a global name
735 space to ease network configuration and improve reliability.
737 To use cifs Kerberos and DFS support, the Linux keyutils package should be
738 installed and something like the following lines should be added to the
739 /etc/request-key.conf file:
741 create cifs.spnego * * /usr/local/sbin/cifs.upcall %k
742 create dns_resolver * * /usr/local/sbin/cifs.upcall %k