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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 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
324 unused.
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
339 4096 byte pages)
340 rw mount the network share read-write (note that the
341 server may still consider the share read-only)
342 ro mount network share read-only
343 version used to distinguish different versions of the
344 mount helper utility (not typically needed)
345 sep if first mount option (after the -o), overrides
346 the comma as the separator between the mount
347 parms. e.g.
348 -o user=myname,password=mypassword,domain=mydom
349 could be passed instead with period as the separator by
350 -o sep=.user=myname.password=mypassword.domain=mydom
351 this might be useful when comma is contained within username
352 or password or domain. This option is less important
353 when the cifs mount helper cifs.mount (version 1.1 or later)
354 is used.
355 nosuid Do not allow remote executables with the suid bit
356 program to be executed. This is only meaningful for mounts
357 to servers such as Samba which support the CIFS Unix Extensions.
358 If you do not trust the servers in your network (your mount
359 targets) it is recommended that you specify this option for
360 greater security.
361 exec Permit execution of binaries on the mount.
362 noexec Do not permit execution of binaries on the mount.
363 dev Recognize block devices on the remote mount.
364 nodev Do not recognize devices on the remote mount.
365 suid Allow remote files on this mountpoint with suid enabled to
366 be executed (default for mounts when executed as root,
367 nosuid is default for user mounts).
368 credentials Although ignored by the cifs kernel component, it is used by
369 the mount helper, mount.cifs. When mount.cifs is installed it
370 opens and reads the credential file specified in order
371 to obtain the userid and password arguments which are passed to
372 the cifs vfs.
373 guest Although ignored by the kernel component, the mount.cifs
374 mount helper will not prompt the user for a password
375 if guest is specified on the mount options. If no
376 password is specified a null password will be used.
377 perm Client does permission checks (vfs_permission check of uid
378 and gid of the file against the mode and desired operation),
379 Note that this is in addition to the normal ACL check on the
380 target machine done by the server software.
381 Client permission checking is enabled by default.
382 noperm Client does not do permission checks. This can expose
383 files on this mount to access by other users on the local
384 client system. It is typically only needed when the server
385 supports the CIFS Unix Extensions but the UIDs/GIDs on the
386 client and server system do not match closely enough to allow
387 access by the user doing the mount, but it may be useful with
388 non CIFS Unix Extension mounts for cases in which the default
389 mode is specified on the mount but is not to be enforced on the
390 client (e.g. perhaps when MultiUserMount is enabled)
391 Note that this does not affect the normal ACL check on the
392 target machine done by the server software (of the server
393 ACL against the user name provided at mount time).
394 serverino Use server's inode numbers instead of generating automatically
395 incrementing inode numbers on the client. Although this will
396 make it easier to spot hardlinked files (as they will have
397 the same inode numbers) and inode numbers may be persistent,
398 note that the server does not guarantee that the inode numbers
399 are unique if multiple server side mounts are exported under a
400 single share (since inode numbers on the servers might not
401 be unique if multiple filesystems are mounted under the same
402 shared higher level directory). Note that some older
403 (e.g. pre-Windows 2000) do not support returning UniqueIDs
404 or the CIFS Unix Extensions equivalent and for those
405 this mount option will have no effect. Exporting cifs mounts
406 under nfsd requires this mount option on the cifs mount.
407 This is now the default if server supports the
408 required network operation.
409 noserverino Client generates inode numbers (rather than using the actual one
410 from the server). These inode numbers will vary after
411 unmount or reboot which can confuse some applications,
412 but not all server filesystems support unique inode
413 numbers.
414 setuids If the CIFS Unix extensions are negotiated with the server
415 the client will attempt to set the effective uid and gid of
416 the local process on newly created files, directories, and
417 devices (create, mkdir, mknod). If the CIFS Unix Extensions
418 are not negotiated, for newly created files and directories
419 instead of using the default uid and gid specified on
420 the mount, cache the new file's uid and gid locally which means
421 that the uid for the file can change when the inode is
422 reloaded (or the user remounts the share).
423 nosetuids The client will not attempt to set the uid and gid on
424 on newly created files, directories, and devices (create,
425 mkdir, mknod) which will result in the server setting the
426 uid and gid to the default (usually the server uid of the
427 user who mounted the share). Letting the server (rather than
428 the client) set the uid and gid is the default. If the CIFS
429 Unix Extensions are not negotiated then the uid and gid for
430 new files will appear to be the uid (gid) of the mounter or the
431 uid (gid) parameter specified on the mount.
432 netbiosname When mounting to servers via port 139, specifies the RFC1001
433 source name to use to represent the client netbios machine
434 name when doing the RFC1001 netbios session initialize.
435 direct Do not do inode data caching on files opened on this mount.
436 This precludes mmapping files on this mount. In some cases
437 with fast networks and little or no caching benefits on the
438 client (e.g. when the application is doing large sequential
439 reads bigger than page size without rereading the same data)
440 this can provide better performance than the default
441 behavior which caches reads (readahead) and writes
442 (writebehind) through the local Linux client pagecache
443 if oplock (caching token) is granted and held. Note that
444 direct allows write operations larger than page size
445 to be sent to the server.
446 acl Allow setfacl and getfacl to manage posix ACLs if server
447 supports them. (default)
448 noacl Do not allow setfacl and getfacl calls on this mount
449 user_xattr Allow getting and setting user xattrs (those attributes whose
450 name begins with "user." or "os2.") as OS/2 EAs (extended
451 attributes) to the server. This allows support of the
452 setfattr and getfattr utilities. (default)
453 nouser_xattr Do not allow getfattr/setfattr to get/set/list xattrs
454 mapchars Translate six of the seven reserved characters (not backslash)
455 *?<>|:
456 to the remap range (above 0xF000), which also
457 allows the CIFS client to recognize files created with
458 such characters by Windows's POSIX emulation. This can
459 also be useful when mounting to most versions of Samba
460 (which also forbids creating and opening files
461 whose names contain any of these seven characters).
462 This has no effect if the server does not support
463 Unicode on the wire.
464 nomapchars Do not translate any of these seven characters (default).
465 nocase Request case insensitive path name matching (case
466 sensitive is the default if the server suports it).
467 (mount option "ignorecase" is identical to "nocase")
468 posixpaths If CIFS Unix extensions are supported, attempt to
469 negotiate posix path name support which allows certain
470 characters forbidden in typical CIFS filenames, without
471 requiring remapping. (default)
472 noposixpaths If CIFS Unix extensions are supported, do not request
473 posix path name support (this may cause servers to
474 reject creatingfile with certain reserved characters).
475 nounix Disable the CIFS Unix Extensions for this mount (tree
476 connection). This is rarely needed, but it may be useful
477 in order to turn off multiple settings all at once (ie
478 posix acls, posix locks, posix paths, symlink support
479 and retrieving uids/gids/mode from the server) or to
480 work around a bug in server which implement the Unix
481 Extensions.
482 nobrl Do not send byte range lock requests to the server.
483 This is necessary for certain applications that break
484 with cifs style mandatory byte range locks (and most
485 cifs servers do not yet support requesting advisory
486 byte range locks).
487 forcemandatorylock Even if the server supports posix (advisory) byte range
488 locking, send only mandatory lock requests. For some
489 (presumably rare) applications, originally coded for
490 DOS/Windows, which require Windows style mandatory byte range
491 locking, they may be able to take advantage of this option,
492 forcing the cifs client to only send mandatory locks
493 even if the cifs server would support posix advisory locks.
494 "forcemand" is accepted as a shorter form of this mount
495 option.
496 nostrictsync If this mount option is set, when an application does an
497 fsync call then the cifs client does not send an SMB Flush
498 to the server (to force the server to write all dirty data
499 for this file immediately to disk), although cifs still sends
500 all dirty (cached) file data to the server and waits for the
501 server to respond to the write. Since SMB Flush can be
502 very slow, and some servers may be reliable enough (to risk
503 delaying slightly flushing the data to disk on the server),
504 turning on this option may be useful to improve performance for
505 applications that fsync too much, at a small risk of server
506 crash. If this mount option is not set, by default cifs will
507 send an SMB flush request (and wait for a response) on every
508 fsync call.
509 nodfs Disable DFS (global name space support) even if the
510 server claims to support it. This can help work around
511 a problem with parsing of DFS paths with Samba server
512 versions 3.0.24 and 3.0.25.
513 remount remount the share (often used to change from ro to rw mounts
514 or vice versa)
515 cifsacl Report mode bits (e.g. on stat) based on the Windows ACL for
516 the file. (EXPERIMENTAL)
517 servern Specify the server 's netbios name (RFC1001 name) to use
518 when attempting to setup a session to the server.
519 This is needed for mounting to some older servers (such
520 as OS/2 or Windows 98 and Windows ME) since they do not
521 support a default server name. A server name can be up
522 to 15 characters long and is usually uppercased.
523 sfu When the CIFS Unix Extensions are not negotiated, attempt to
524 create device files and fifos in a format compatible with
525 Services for Unix (SFU). In addition retrieve bits 10-12
526 of the mode via the SETFILEBITS extended attribute (as
527 SFU does). In the future the bottom 9 bits of the
528 mode also will be emulated using queries of the security
529 descriptor (ACL).
530 mfsymlinks Enable support for Minshall+French symlinks
531 (see http://wiki.samba.org/index.php/UNIX_Extensions#Minshall.2BFrench_symlinks)
532 This option is ignored when specified together with the
533 'sfu' option. Minshall+French symlinks are used even if
534 the server supports the CIFS Unix Extensions.
535 sign Must use packet signing (helps avoid unwanted data modification
536 by intermediate systems in the route). Note that signing
537 does not work with lanman or plaintext authentication.
538 seal Must seal (encrypt) all data on this mounted share before
539 sending on the network. Requires support for Unix Extensions.
540 Note that this differs from the sign mount option in that it
541 causes encryption of data sent over this mounted share but other
542 shares mounted to the same server are unaffected.
543 locallease This option is rarely needed. Fcntl F_SETLEASE is
544 used by some applications such as Samba and NFSv4 server to
545 check to see whether a file is cacheable. CIFS has no way
546 to explicitly request a lease, but can check whether a file
547 is cacheable (oplocked). Unfortunately, even if a file
548 is not oplocked, it could still be cacheable (ie cifs client
549 could grant fcntl leases if no other local processes are using
550 the file) for cases for example such as when the server does not
551 support oplocks and the user is sure that the only updates to
552 the file will be from this client. Specifying this mount option
553 will allow the cifs client to check for leases (only) locally
554 for files which are not oplocked instead of denying leases
555 in that case. (EXPERIMENTAL)
556 sec Security mode. Allowed values are:
557 none attempt to connection as a null user (no name)
558 krb5 Use Kerberos version 5 authentication
559 krb5i Use Kerberos authentication and packet signing
560 ntlm Use NTLM password hashing (default)
561 ntlmi Use NTLM password hashing with signing (if
562 /proc/fs/cifs/PacketSigningEnabled on or if
563 server requires signing also can be the default)
564 ntlmv2 Use NTLMv2 password hashing
565 ntlmv2i Use NTLMv2 password hashing with packet signing
566 lanman (if configured in kernel config) use older
567 lanman hash
568 hard Retry file operations if server is not responding
569 soft Limit retries to unresponsive servers (usually only
570 one retry) before returning an error. (default)
572 The mount.cifs mount helper also accepts a few mount options before -o
573 including:
575 -S take password from stdin (equivalent to setting the environment
576 variable "PASSWD_FD=0"
577 -V print mount.cifs version
578 -? display simple usage information
580 With most 2.6 kernel versions of modutils, the version of the cifs kernel
581 module can be displayed via modinfo.
583 Misc /proc/fs/cifs Flags and Debug Info
584 =======================================
585 Informational pseudo-files:
586 DebugData Displays information about active CIFS sessions and
587 shares, features enabled as well as the cifs.ko
588 version.
589 Stats Lists summary resource usage information as well as per
590 share statistics, if CONFIG_CIFS_STATS in enabled
591 in the kernel configuration.
593 Configuration pseudo-files:
594 MultiuserMount If set to one, more than one CIFS session to
595 the same server ip address can be established
596 if more than one uid accesses the same mount
597 point and if the uids user/password mapping
598 information is available. (default is 0)
599 PacketSigningEnabled If set to one, cifs packet signing is enabled
600 and will be used if the server requires
601 it. If set to two, cifs packet signing is
602 required even if the server considers packet
603 signing optional. (default 1)
604 SecurityFlags Flags which control security negotiation and
605 also packet signing. Authentication (may/must)
606 flags (e.g. for NTLM and/or NTLMv2) may be combined with
607 the signing flags. Specifying two different password
608 hashing mechanisms (as "must use") on the other hand
609 does not make much sense. Default flags are
610 0x07007
611 (NTLM, NTLMv2 and packet signing allowed). The maximum
612 allowable flags if you want to allow mounts to servers
613 using weaker password hashes is 0x37037 (lanman,
614 plaintext, ntlm, ntlmv2, signing allowed). Some
615 SecurityFlags require the corresponding menuconfig
616 options to be enabled (lanman and plaintext require
617 CONFIG_CIFS_WEAK_PW_HASH for example). Enabling
618 plaintext authentication currently requires also
619 enabling lanman authentication in the security flags
620 because the cifs module only supports sending
621 laintext passwords using the older lanman dialect
622 form of the session setup SMB. (e.g. for authentication
623 using plain text passwords, set the SecurityFlags
624 to 0x30030):
626 may use packet signing 0x00001
627 must use packet signing 0x01001
628 may use NTLM (most common password hash) 0x00002
629 must use NTLM 0x02002
630 may use NTLMv2 0x00004
631 must use NTLMv2 0x04004
632 may use Kerberos security 0x00008
633 must use Kerberos 0x08008
634 may use lanman (weak) password hash 0x00010
635 must use lanman password hash 0x10010
636 may use plaintext passwords 0x00020
637 must use plaintext passwords 0x20020
638 (reserved for future packet encryption) 0x00040
640 cifsFYI If set to non-zero value, additional debug information
641 will be logged to the system error log. This field
642 contains three flags controlling different classes of
643 debugging entries. The maximum value it can be set
644 to is 7 which enables all debugging points (default 0).
645 Some debugging statements are not compiled into the
646 cifs kernel unless CONFIG_CIFS_DEBUG2 is enabled in the
647 kernel configuration. cifsFYI may be set to one or
648 nore of the following flags (7 sets them all):
650 log cifs informational messages 0x01
651 log return codes from cifs entry points 0x02
652 log slow responses (ie which take longer than 1 second)
653 CONFIG_CIFS_STATS2 must be enabled in .config 0x04
656 traceSMB If set to one, debug information is logged to the
657 system error log with the start of smb requests
658 and responses (default 0)
659 LookupCacheEnable If set to one, inode information is kept cached
660 for one second improving performance of lookups
661 (default 1)
662 OplockEnabled If set to one, safe distributed caching enabled.
663 (default 1)
664 LinuxExtensionsEnabled If set to one then the client will attempt to
665 use the CIFS "UNIX" extensions which are optional
666 protocol enhancements that allow CIFS servers
667 to return accurate UID/GID information as well
668 as support symbolic links. If you use servers
669 such as Samba that support the CIFS Unix
670 extensions but do not want to use symbolic link
671 support and want to map the uid and gid fields
672 to values supplied at mount (rather than the
673 actual values, then set this to zero. (default 1)
674 Experimental When set to 1 used to enable certain experimental
675 features (currently enables multipage writes
676 when signing is enabled, the multipage write
677 performance enhancement was disabled when
678 signing turned on in case buffer was modified
679 just before it was sent, also this flag will
680 be used to use the new experimental directory change
681 notification code). When set to 2 enables
682 an additional experimental feature, "raw ntlmssp"
683 session establishment support (which allows
684 specifying "sec=ntlmssp" on mount). The Linux cifs
685 module will use ntlmv2 authentication encapsulated
686 in "raw ntlmssp" (not using SPNEGO) when
687 "sec=ntlmssp" is specified on mount.
688 This support also requires building cifs with
689 the CONFIG_CIFS_EXPERIMENTAL configuration flag.
691 These experimental features and tracing can be enabled by changing flags in
692 /proc/fs/cifs (after the cifs module has been installed or built into the
693 kernel, e.g. insmod cifs). To enable a feature set it to 1 e.g. to enable
694 tracing to the kernel message log type:
696 echo 7 > /proc/fs/cifs/cifsFYI
698 cifsFYI functions as a bit mask. Setting it to 1 enables additional kernel
699 logging of various informational messages. 2 enables logging of non-zero
700 SMB return codes while 4 enables logging of requests that take longer
701 than one second to complete (except for byte range lock requests).
702 Setting it to 4 requires defining CONFIG_CIFS_STATS2 manually in the
703 source code (typically by setting it in the beginning of cifsglob.h),
704 and setting it to seven enables all three. Finally, tracing
705 the start of smb requests and responses can be enabled via:
707 echo 1 > /proc/fs/cifs/traceSMB
709 Two other experimental features are under development. To test these
710 requires enabling CONFIG_CIFS_EXPERIMENTAL
712 cifsacl support needed to retrieve approximated mode bits based on
713 the contents on the CIFS ACL.
715 lease support: cifs will check the oplock state before calling into
716 the vfs to see if we can grant a lease on a file.
718 DNOTIFY fcntl: needed for support of directory change
719 notification and perhaps later for file leases)
721 Per share (per client mount) statistics are available in /proc/fs/cifs/Stats
722 if the kernel was configured with cifs statistics enabled. The statistics
723 represent the number of successful (ie non-zero return code from the server)
724 SMB responses to some of the more common commands (open, delete, mkdir etc.).
725 Also recorded is the total bytes read and bytes written to the server for
726 that share. Note that due to client caching effects this can be less than the
727 number of bytes read and written by the application running on the client.
728 The statistics for the number of total SMBs and oplock breaks are different in
729 that they represent all for that share, not just those for which the server
730 returned success.
732 Also note that "cat /proc/fs/cifs/DebugData" will display information about
733 the active sessions and the shares that are mounted.
735 Enabling Kerberos (extended security) works but requires version 1.2 or later
736 of the helper program cifs.upcall to be present and to be configured in the
737 /etc/request-key.conf file. The cifs.upcall helper program is from the Samba
738 project(http://www.samba.org). NTLM and NTLMv2 and LANMAN support do not
739 require this helper. Note that NTLMv2 security (which does not require the
740 cifs.upcall helper program), instead of using Kerberos, is sufficient for
741 some use cases.
743 DFS support allows transparent redirection to shares in an MS-DFS name space.
744 In addition, DFS support for target shares which are specified as UNC
745 names which begin with host names (rather than IP addresses) requires
746 a user space helper (such as cifs.upcall) to be present in order to
747 translate host names to ip address, and the user space helper must also
748 be configured in the file /etc/request-key.conf. Samba, Windows servers and
749 many NAS appliances support DFS as a way of constructing a global name
750 space to ease network configuration and improve reliability.
752 To use cifs Kerberos and DFS support, the Linux keyutils package should be
753 installed and something like the following lines should be added to the
754 /etc/request-key.conf file:
756 create cifs.spnego * * /usr/local/sbin/cifs.upcall %k
757 create dns_resolver * * /usr/local/sbin/cifs.upcall %k