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Linus Torvalds1da177e2005-04-16 15:20:36 -07001The CIFS VFS support for Linux supports many advanced network filesystem
Uwe Kleine-König1b3c3712007-02-17 19:23:03 +01002features such as hierarchical dfs like namespace, hardlinks, locking and more.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003It was designed to comply with the SNIA CIFS Technical Reference (which
4supersedes the 1992 X/Open SMB Standard) as well as to perform best practice
5practical interoperability with Windows 2000, Windows XP, Samba and equivalent
Steve French675c4672008-04-17 23:41:01 +00006servers. This code was developed in participation with the Protocol Freedom
7Information Foundation.
8
9Please see
10 http://protocolfreedom.org/ and
11 http://samba.org/samba/PFIF/
12for more details.
13
Linus Torvalds1da177e2005-04-16 15:20:36 -070014
15For questions or bug reports please contact:
16 sfrench@samba.org (sfrench@us.ibm.com)
17
18Build instructions:
19==================
20For Linux 2.4:
211) Get the kernel source (e.g.from http://www.kernel.org)
22and download the cifs vfs source (see the project page
23at http://us1.samba.org/samba/Linux_CIFS_client.html)
24and change directory into the top of the kernel directory
25then patch the kernel (e.g. "patch -p1 < cifs_24.patch")
26to add the cifs vfs to your kernel configure options if
27it has not already been added (e.g. current SuSE and UL
28users do not need to apply the cifs_24.patch since the cifs vfs is
29already in the kernel configure menu) and then
30mkdir linux/fs/cifs and then copy the current cifs vfs files from
31the cifs download to your kernel build directory e.g.
32
33 cp <cifs_download_dir>/fs/cifs/* to <kernel_download_dir>/fs/cifs
34
352) make menuconfig (or make xconfig)
363) select cifs from within the network filesystem choices
374) save and exit
385) make dep
396) make modules (or "make" if CIFS VFS not to be built as a module)
40
41For Linux 2.6:
Adrian Bunkdfc1e142005-05-05 16:15:51 -0700421) Download the kernel (e.g. from http://www.kernel.org)
43and change directory into the top of the kernel directory tree
44(e.g. /usr/src/linux-2.5.73)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700452) make menuconfig (or make xconfig)
463) select cifs from within the network filesystem choices
474) save and exit
485) make
49
50
51Installation instructions:
52=========================
53If you have built the CIFS vfs as module (successfully) simply
54type "make modules_install" (or if you prefer, manually copy the file to
55the modules directory e.g. /lib/modules/2.4.10-4GB/kernel/fs/cifs/cifs.o).
56
57If you have built the CIFS vfs into the kernel itself, follow the instructions
58for your distribution on how to install a new kernel (usually you
59would simply type "make install").
60
61If you do not have the utility mount.cifs (in the Samba 3.0 source tree and on
62the CIFS VFS web site) copy it to the same directory in which mount.smbfs and
63similar files reside (usually /sbin). Although the helper software is not
64required, 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
Steve Frenchf6d09982008-01-08 23:18:22 +000066users who are used to Windows e.g.
67 net use <mount point> <UNC name or cifs URL>
Linus Torvalds1da177e2005-04-16 15:20:36 -070068Note that running the Winbind pam/nss module (logon service) on all of your
69Linux clients is useful in mapping Uids and Gids consistently across the
70domain to the proper network user. The mount.cifs mount helper can be
71trivially built from Samba 3.0 or later source e.g. by executing:
72
73 gcc samba/source/client/mount.cifs.c -o mount.cifs
74
75If cifs is built as a module, then the size and number of network buffers
76and maximum number of simultaneous requests to one server can be configured.
77Changing these from their defaults is not recommended. By executing modinfo
78 modinfo kernel/fs/cifs/cifs.ko
79on kernel/fs/cifs/cifs.ko the list of configuration changes that can be made
80at module initialization time (by running insmod cifs.ko) can be seen.
81
82Allowing User Mounts
83====================
84To permit users to mount and unmount over directories they own is possible
85with the cifs vfs. A way to enable such mounting is to mark the mount.cifs
Steve French099a58f2005-04-28 22:41:07 -070086utility as suid (e.g. "chmod +s /sbin/mount.cifs). To enable users to
Linus Torvalds1da177e2005-04-16 15:20:36 -070087umount shares they mount requires
881) mount.cifs version 1.4 or later
892) an entry for the share in /etc/fstab indicating that a user may
90unmount it e.g.
91//server/usersharename /mnt/username cifs user 0 0
92
93Note that when the mount.cifs utility is run suid (allowing user mounts),
94in order to reduce risks, the "nosuid" mount flag is passed in on mount to
95disallow execution of an suid program mounted on the remote target.
96When mount is executed as root, nosuid is not passed in by default,
97and execution of suid programs on the remote target would be enabled
98by default. This can be changed, as with nfs and other filesystems,
99by simply specifying "nosuid" among the mount options. For user mounts
100though to be able to pass the suid flag to mount requires rebuilding
101mount.cifs with the following flag:
102
103 gcc samba/source/client/mount.cifs.c -DCIFS_ALLOW_USR_SUID -o mount.cifs
104
105There is a corresponding manual page for cifs mounting in the Samba 3.0 and
106later source tree in docs/manpages/mount.cifs.8
107
Steve French099a58f2005-04-28 22:41:07 -0700108Allowing User Unmounts
109======================
110To permit users to ummount directories that they have user mounted (see above),
111the utility umount.cifs may be used. It may be invoked directly, or if
Steve French0cb766a2005-04-28 22:41:11 -0700112umount.cifs is placed in /sbin, umount can invoke the cifs umount helper
Steve French099a58f2005-04-28 22:41:07 -0700113(at least for most versions of the umount utility) for umount of cifs
Steve French0cb766a2005-04-28 22:41:11 -0700114mounts, unless umount is invoked with -i (which will avoid invoking a umount
115helper). As with mount.cifs, to enable user unmounts umount.cifs must be marked
116as suid (e.g. "chmod +s /sbin/umount.cifs") or equivalent (some distributions
117allow adding entries to a file to the /etc/permissions file to achieve the
118equivalent suid effect). For this utility to succeed the target path
119must be a cifs mount, and the uid of the current user must match the uid
120of the user who mounted the resource.
Steve French099a58f2005-04-28 22:41:07 -0700121
122Also 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
124to the file /etc/fstab for each //server/share you wish to mount, but
125this can become unwieldy when potential mount targets include many
126or unpredictable UNC names.
127
Linus Torvalds1da177e2005-04-16 15:20:36 -0700128Samba Considerations
129====================
130To get the maximum benefit from the CIFS VFS, we recommend using a server that
131supports the SNIA CIFS Unix Extensions standard (e.g. Samba 2.2.5 or later or
132Samba 3.0) but the CIFS vfs works fine with a wide variety of CIFS servers.
133Note that uid, gid and file permissions will display default values if you do
134not have a server that supports the Unix extensions for CIFS (such as Samba
1352.2.5 or later). To enable the Unix CIFS Extensions in the Samba server, add
136the line:
137
138 unix extensions = yes
139
140to your smb.conf file on the server. Note that the following smb.conf settings
141are also useful (on the Samba server) when the majority of clients are Unix or
142Linux:
143
144 case sensitive = yes
145 delete readonly = yes
146 ea support = yes
147
148Note that server ea support is required for supporting xattrs from the Linux
149cifs client, and that EA support is present in later versions of Samba (e.g.
1503.0.6 and later (also EA support works in all versions of Windows, at least to
151shares on NTFS filesystems). Extended Attribute (xattr) support is an optional
152feature of most Linux filesystems which may require enabling via
153make menuconfig. Client support for extended attributes (user xattr) can be
154disabled on a per-mount basis by specifying "nouser_xattr" on mount.
155
156The CIFS client can get and set POSIX ACLs (getfacl, setfacl) to Samba servers
157version 3.10 and later. Setting POSIX ACLs requires enabling both XATTR and
158then POSIX support in the CIFS configuration options when building the cifs
159module. POSIX ACL support can be disabled on a per mount basic by specifying
160"noacl" on mount.
161
162Some 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
164newly created files can end up with an unnecessarily restrictive default mode,
165which may not be what you want, although if the CIFS Unix extensions are
166enabled on the server and client, subsequent setattr calls (e.g. chmod) can
167fix the mode. Note that creating special devices (mknod) remotely
168may require specifying a mkdev function to Samba if you are not using
169Samba 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,
171unlike 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).
173Note that Samba 2.2.7 or later includes a fix that allows the CIFS VFS to delete
174open files (required for strict POSIX compliance). Windows Servers already
175supported this feature. Samba server does not allow symlinks that refer to files
176outside of the share, so in Samba versions prior to 3.0.6, most symlinks to
177files with absolute paths (ie beginning with slash) such as:
178 ln -s /mnt/foo bar
179would be forbidden. Samba 3.0.6 server or later includes the ability to create
180such symlinks safely by converting unsafe symlinks (ie symlinks to server
181files that are outside of the share) to a samba specific format on the server
182that is ignored by local server applications and non-cifs clients and that will
183not be traversed by the Samba server). This is opaque to the Linux client
184application using the cifs vfs. Absolute symlinks will work to Samba 3.0.5 or
185later, but only for remote clients using the CIFS Unix extensions, and will
186be invisbile to Windows clients and typically will not affect local
187applications running on the same server as Samba.
188
189Use instructions:
190================
191Once 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
193servers:
194
195 mount -t cifs //9.53.216.11/e$ /mnt -o user=myname,pass=mypassword
196
197Before -o the option -v may be specified to make the mount.cifs
198mount helper display the mount steps more verbosely.
199After -o the following commonly used cifs vfs specific options
200are supported:
201
202 user=<username>
203 pass=<password>
204 domain=<domain name>
205
206Other cifs mount options are described below. Use of TCP names (in addition to
207ip addresses) is available if the mount helper (mount.cifs) is installed. If
208you do not trust the server to which are mounted, or if you do not have
209cifs signing enabled (and the physical network is insecure), consider use
210of the standard mount options "noexec" and "nosuid" to reduce the risk of
211running an altered binary on your local system (downloaded from a hostile server
212or altered by a hostile router).
213
214Although mounting using format corresponding to the CIFS URL specification is
215not possible in mount.cifs yet, it is possible to use an alternate format
216for the server and sharename (which is somewhat similar to NFS style mount
217syntax) 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
219
220When using the mount helper mount.cifs, passwords may be specified via alternate
221mechanisms, instead of specifying it after -o using the normal "pass=" syntax
222on the command line:
2231) By including it in a credential file. Specify credentials=filename as one
224of the mount options. Credential files contain two lines
225 username=someuser
226 password=your_password
2272) By specifying the password in the PASSWD environment variable (similarly
228the user name can be taken from the USER environment variable).
2293) By specifying the password in a file by name via PASSWD_FILE
2304) By specifying the password in a file by file descriptor via PASSWD_FD
231
232If no password is provided, mount.cifs will prompt for password entry
233
234Restrictions
235============
Linus Torvalds1da177e2005-04-16 15:20:36 -0700236Servers must support either "pure-TCP" (port 445 TCP/IP CIFS connections) or RFC
Jeff Laytoncea21802007-11-20 23:19:03 +00002371001/1002 support for "Netbios-Over-TCP/IP." This is not likely to be a
238problem as most servers support this.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700239
240Valid filenames differ between Windows and Linux. Windows typically restricts
241filenames which contain certain reserved characters (e.g.the character :
242which is used to delimit the beginning of a stream name by Windows), while
243Linux allows a slightly wider set of valid characters in filenames. Windows
244servers can remap such characters when an explicit mapping is specified in
245the Server's registry. Samba starting with version 3.10 will allow such
246filenames (ie those which contain valid Linux characters, which normally
247would be forbidden for Windows/CIFS semantics) as long as the server is
248configured for Unix Extensions (and the client has not disabled
249/proc/fs/cifs/LinuxExtensionsEnabled).
250
251
252CIFS VFS Mount Options
253======================
254A 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
Steve Frenchf6d09982008-01-08 23:18:22 +0000259 if not supplied.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700260 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
Steve Frenchd0985642009-08-04 03:53:28 +0000265 forceuid Set the default uid for inodes to the uid
266 passed in on mount. For mounts to servers
Steve French4523cc32007-04-30 20:13:06 +0000267 which do support the CIFS Unix extensions, such as a
268 properly configured Samba server, the server provides
Steve Frenchd0985642009-08-04 03:53:28 +0000269 the uid, gid and mode so this parameter should not be
Steve French4523cc32007-04-30 20:13:06 +0000270 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
Linus Torvalds1da177e2005-04-16 15:20:36 -0700279 who executed the mount (root, except when mount.cifs
280 is configured setuid for user mounts) unless the "uid="
Steve Frenchd0985642009-08-04 03:53:28 +0000281 (gid) mount option is specified. Also note that permission
Linus Torvalds1da177e2005-04-16 15:20:36 -0700282 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
Steve Frenchd0985642009-08-04 03:53:28 +0000289 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)
Steve Frenchf0472d02009-06-06 21:09:39 +0000296 uid Set the default uid for inodes, and indicate to the
Steve Frenchd0985642009-08-04 03:53:28 +0000297 cifs kernel driver which local user mounted. If the server
Steve Frenchf0472d02009-06-06 21:09:39 +0000298 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.
Steve French4523cc32007-04-30 20:13:06 +0000301 gid Set the default gid for inodes (similar to above).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700302 file_mode If CIFS Unix extensions are not supported by the server
303 this overrides the default mode for file inodes.
Suresh Jayaraman3694b912010-08-05 18:52:21 +0530304 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.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700314 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.
Steve French75865f8c2007-06-24 18:30:48 +0000325 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)
Suresh Jayaraman6d20e842010-12-01 14:42:28 +0530340 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
348 period of time).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700349 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
356 parms. e.g.
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)
363 is used.
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
369 greater security.
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
381 the cifs vfs.
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
Steve French6473a552005-11-29 20:20:10 -0800396 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)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700400 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).
Steve French7521a3c2007-07-11 18:30:34 +0000403 serverino Use server's inode numbers instead of generating automatically
Linus Torvalds1da177e2005-04-16 15:20:36 -0700404 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
Steve French7521a3c2007-07-11 18:30:34 +0000411 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.
Steve Frenchc5077ec2009-05-28 15:09:04 +0000416 This is now the default if server supports the
417 required network operation.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700418 noserverino Client generates inode numbers (rather than using the actual one
Steve Frenchc5077ec2009-05-28 15:09:04 +0000419 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
422 numbers.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700423 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
Steve French6473a552005-11-29 20:20:10 -0800426 devices (create, mkdir, mknod). If the CIFS Unix Extensions
427 are not negotiated, for newly created files and directories
Matt LaPlantecab00892006-10-03 22:36:44 +0200428 instead of using the default uid and gid specified on
Steve French6473a552005-11-29 20:20:10 -0800429 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).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700432 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
Steve French67594fe2005-05-17 13:04:49 -0500436 user who mounted the share). Letting the server (rather than
Steve French6473a552005-11-29 20:20:10 -0800437 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.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700441 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.
André Goddard Rosaaf901ca2009-11-14 13:09:05 -0200445 This precludes mmapping files on this mount. In some cases
Linus Torvalds1da177e2005-04-16 15:20:36 -0700446 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
Steve French67594fe2005-05-17 13:04:49 -0500450 behavior which caches reads (readahead) and writes
Linus Torvalds1da177e2005-04-16 15:20:36 -0700451 (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 acl Allow setfacl and getfacl to manage posix ACLs if server
456 supports them. (default)
457 noacl Do not allow setfacl and getfacl calls on this mount
Steve Frenchf6d09982008-01-08 23:18:22 +0000458 user_xattr Allow getting and setting user xattrs (those attributes whose
459 name begins with "user." or "os2.") as OS/2 EAs (extended
460 attributes) to the server. This allows support of the
461 setfattr and getfattr utilities. (default)
Steve Frenchea4c07d2006-08-16 19:44:25 +0000462 nouser_xattr Do not allow getfattr/setfattr to get/set/list xattrs
Steve French737b7582005-04-28 22:41:06 -0700463 mapchars Translate six of the seven reserved characters (not backslash)
464 *?<>|:
Steve French6a0b4822005-04-28 22:41:05 -0700465 to the remap range (above 0xF000), which also
466 allows the CIFS client to recognize files created with
467 such characters by Windows's POSIX emulation. This can
468 also be useful when mounting to most versions of Samba
469 (which also forbids creating and opening files
470 whose names contain any of these seven characters).
471 This has no effect if the server does not support
472 Unicode on the wire.
473 nomapchars Do not translate any of these seven characters (default).
Steve Frenchc46fa8a2005-08-18 20:49:57 -0700474 nocase Request case insensitive path name matching (case
475 sensitive is the default if the server suports it).
Steve Frenchf6d09982008-01-08 23:18:22 +0000476 (mount option "ignorecase" is identical to "nocase")
Steve French82940a42006-03-02 03:24:57 +0000477 posixpaths If CIFS Unix extensions are supported, attempt to
478 negotiate posix path name support which allows certain
479 characters forbidden in typical CIFS filenames, without
480 requiring remapping. (default)
481 noposixpaths If CIFS Unix extensions are supported, do not request
482 posix path name support (this may cause servers to
483 reject creatingfile with certain reserved characters).
Steve Frencha403a0a2007-07-26 15:54:16 +0000484 nounix Disable the CIFS Unix Extensions for this mount (tree
485 connection). This is rarely needed, but it may be useful
486 in order to turn off multiple settings all at once (ie
487 posix acls, posix locks, posix paths, symlink support
488 and retrieving uids/gids/mode from the server) or to
489 work around a bug in server which implement the Unix
490 Extensions.
Steve Frenchc46fa8a2005-08-18 20:49:57 -0700491 nobrl Do not send byte range lock requests to the server.
492 This is necessary for certain applications that break
493 with cifs style mandatory byte range locks (and most
494 cifs servers do not yet support requesting advisory
495 byte range locks).
Steve French13a6e422008-12-02 17:24:33 +0000496 forcemandatorylock Even if the server supports posix (advisory) byte range
497 locking, send only mandatory lock requests. For some
498 (presumably rare) applications, originally coded for
499 DOS/Windows, which require Windows style mandatory byte range
500 locking, they may be able to take advantage of this option,
501 forcing the cifs client to only send mandatory locks
502 even if the cifs server would support posix advisory locks.
503 "forcemand" is accepted as a shorter form of this mount
504 option.
Steve Frenchbe652442009-02-23 15:21:59 +0000505 nostrictsync If this mount option is set, when an application does an
506 fsync call then the cifs client does not send an SMB Flush
507 to the server (to force the server to write all dirty data
508 for this file immediately to disk), although cifs still sends
509 all dirty (cached) file data to the server and waits for the
510 server to respond to the write. Since SMB Flush can be
511 very slow, and some servers may be reliable enough (to risk
512 delaying slightly flushing the data to disk on the server),
513 turning on this option may be useful to improve performance for
514 applications that fsync too much, at a small risk of server
515 crash. If this mount option is not set, by default cifs will
516 send an SMB flush request (and wait for a response) on every
517 fsync call.
Steve French2c1b8612008-10-16 18:35:21 +0000518 nodfs Disable DFS (global name space support) even if the
519 server claims to support it. This can help work around
Steve French13a6e422008-12-02 17:24:33 +0000520 a problem with parsing of DFS paths with Samba server
521 versions 3.0.24 and 3.0.25.
Steve French0cb766a2005-04-28 22:41:11 -0700522 remount remount the share (often used to change from ro to rw mounts
523 or vice versa)
Jeff Laytoncea21802007-11-20 23:19:03 +0000524 cifsacl Report mode bits (e.g. on stat) based on the Windows ACL for
525 the file. (EXPERIMENTAL)
Cyrill Gorcunov5e6e6232007-08-18 00:15:20 +0000526 servern Specify the server 's netbios name (RFC1001 name) to use
Steve Frenchad7a2922008-02-07 23:25:02 +0000527 when attempting to setup a session to the server.
Cyrill Gorcunov5e6e6232007-08-18 00:15:20 +0000528 This is needed for mounting to some older servers (such
529 as OS/2 or Windows 98 and Windows ME) since they do not
530 support a default server name. A server name can be up
531 to 15 characters long and is usually uppercased.
Steve French6473a552005-11-29 20:20:10 -0800532 sfu When the CIFS Unix Extensions are not negotiated, attempt to
533 create device files and fifos in a format compatible with
534 Services for Unix (SFU). In addition retrieve bits 10-12
535 of the mode via the SETFILEBITS extended attribute (as
Matt LaPlantecab00892006-10-03 22:36:44 +0200536 SFU does). In the future the bottom 9 bits of the
Steve French6473a552005-11-29 20:20:10 -0800537 mode also will be emulated using queries of the security
538 descriptor (ACL).
Stefan Metzmacher736a3322010-07-30 14:56:00 +0200539 mfsymlinks Enable support for Minshall+French symlinks
540 (see http://wiki.samba.org/index.php/UNIX_Extensions#Minshall.2BFrench_symlinks)
541 This option is ignored when specified together with the
542 'sfu' option. Minshall+French symlinks are used even if
543 the server supports the CIFS Unix Extensions.
Steve French750d1152006-06-27 06:28:30 +0000544 sign Must use packet signing (helps avoid unwanted data modification
545 by intermediate systems in the route). Note that signing
546 does not work with lanman or plaintext authentication.
Steve French95b1cb92008-05-15 16:44:38 +0000547 seal Must seal (encrypt) all data on this mounted share before
548 sending on the network. Requires support for Unix Extensions.
549 Note that this differs from the sign mount option in that it
550 causes encryption of data sent over this mounted share but other
551 shares mounted to the same server are unaffected.
Steve French84210e92008-10-23 04:42:37 +0000552 locallease This option is rarely needed. Fcntl F_SETLEASE is
553 used by some applications such as Samba and NFSv4 server to
554 check to see whether a file is cacheable. CIFS has no way
555 to explicitly request a lease, but can check whether a file
556 is cacheable (oplocked). Unfortunately, even if a file
557 is not oplocked, it could still be cacheable (ie cifs client
558 could grant fcntl leases if no other local processes are using
559 the file) for cases for example such as when the server does not
560 support oplocks and the user is sure that the only updates to
561 the file will be from this client. Specifying this mount option
562 will allow the cifs client to check for leases (only) locally
563 for files which are not oplocked instead of denying leases
564 in that case. (EXPERIMENTAL)
Steve French750d1152006-06-27 06:28:30 +0000565 sec Security mode. Allowed values are:
Steve Frenchbf820672005-12-01 22:32:42 -0800566 none attempt to connection as a null user (no name)
567 krb5 Use Kerberos version 5 authentication
568 krb5i Use Kerberos authentication and packet signing
569 ntlm Use NTLM password hashing (default)
570 ntlmi Use NTLM password hashing with signing (if
571 /proc/fs/cifs/PacketSigningEnabled on or if
572 server requires signing also can be the default)
573 ntlmv2 Use NTLMv2 password hashing
574 ntlmv2i Use NTLMv2 password hashing with packet signing
Steve French189acaa2006-06-23 02:33:48 +0000575 lanman (if configured in kernel config) use older
576 lanman hash
Steve Frenchf6d09982008-01-08 23:18:22 +0000577hard Retry file operations if server is not responding
578soft Limit retries to unresponsive servers (usually only
579 one retry) before returning an error. (default)
Steve Frenchbf820672005-12-01 22:32:42 -0800580
Linus Torvalds1da177e2005-04-16 15:20:36 -0700581The mount.cifs mount helper also accepts a few mount options before -o
582including:
583
584 -S take password from stdin (equivalent to setting the environment
585 variable "PASSWD_FD=0"
586 -V print mount.cifs version
587 -? display simple usage information
588
Jeff Layton8426c392007-05-05 03:27:49 +0000589With most 2.6 kernel versions of modutils, the version of the cifs kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -0700590module can be displayed via modinfo.
591
592Misc /proc/fs/cifs Flags and Debug Info
593=======================================
594Informational pseudo-files:
Suresh Jayaraman95c99902010-07-30 18:01:17 +0530595DebugData Displays information about active CIFS sessions and
596 shares, features enabled as well as the cifs.ko
597 version.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700598Stats Lists summary resource usage information as well as per
599 share statistics, if CONFIG_CIFS_STATS in enabled
600 in the kernel configuration.
601
602Configuration pseudo-files:
603MultiuserMount If set to one, more than one CIFS session to
604 the same server ip address can be established
605 if more than one uid accesses the same mount
606 point and if the uids user/password mapping
607 information is available. (default is 0)
608PacketSigningEnabled If set to one, cifs packet signing is enabled
609 and will be used if the server requires
610 it. If set to two, cifs packet signing is
611 required even if the server considers packet
612 signing optional. (default 1)
Steve French254e55e2006-06-04 05:53:15 +0000613SecurityFlags Flags which control security negotiation and
614 also packet signing. Authentication (may/must)
615 flags (e.g. for NTLM and/or NTLMv2) may be combined with
616 the signing flags. Specifying two different password
617 hashing mechanisms (as "must use") on the other hand
618 does not make much sense. Default flags are
619 0x07007
Steve French2e655022008-08-28 15:30:06 +0000620 (NTLM, NTLMv2 and packet signing allowed). The maximum
Steve French254e55e2006-06-04 05:53:15 +0000621 allowable flags if you want to allow mounts to servers
622 using weaker password hashes is 0x37037 (lanman,
Steve French2e655022008-08-28 15:30:06 +0000623 plaintext, ntlm, ntlmv2, signing allowed). Some
624 SecurityFlags require the corresponding menuconfig
625 options to be enabled (lanman and plaintext require
626 CONFIG_CIFS_WEAK_PW_HASH for example). Enabling
627 plaintext authentication currently requires also
628 enabling lanman authentication in the security flags
629 because the cifs module only supports sending
630 laintext passwords using the older lanman dialect
631 form of the session setup SMB. (e.g. for authentication
632 using plain text passwords, set the SecurityFlags
633 to 0x30030):
Steve French254e55e2006-06-04 05:53:15 +0000634
635 may use packet signing 0x00001
636 must use packet signing 0x01001
637 may use NTLM (most common password hash) 0x00002
638 must use NTLM 0x02002
639 may use NTLMv2 0x00004
640 must use NTLMv2 0x04004
Steve Frenchf6d09982008-01-08 23:18:22 +0000641 may use Kerberos security 0x00008
642 must use Kerberos 0x08008
Steve French254e55e2006-06-04 05:53:15 +0000643 may use lanman (weak) password hash 0x00010
644 must use lanman password hash 0x10010
645 may use plaintext passwords 0x00020
646 must use plaintext passwords 0x20020
647 (reserved for future packet encryption) 0x00040
648
Jeff Layton8426c392007-05-05 03:27:49 +0000649cifsFYI If set to non-zero value, additional debug information
650 will be logged to the system error log. This field
651 contains three flags controlling different classes of
652 debugging entries. The maximum value it can be set
653 to is 7 which enables all debugging points (default 0).
654 Some debugging statements are not compiled into the
655 cifs kernel unless CONFIG_CIFS_DEBUG2 is enabled in the
656 kernel configuration. cifsFYI may be set to one or
657 nore of the following flags (7 sets them all):
658
659 log cifs informational messages 0x01
660 log return codes from cifs entry points 0x02
Steve French0ec54aa2007-05-05 22:08:06 +0000661 log slow responses (ie which take longer than 1 second)
662 CONFIG_CIFS_STATS2 must be enabled in .config 0x04
Jeff Layton8426c392007-05-05 03:27:49 +0000663
664
Linus Torvalds1da177e2005-04-16 15:20:36 -0700665traceSMB If set to one, debug information is logged to the
666 system error log with the start of smb requests
667 and responses (default 0)
668LookupCacheEnable If set to one, inode information is kept cached
669 for one second improving performance of lookups
670 (default 1)
671OplockEnabled If set to one, safe distributed caching enabled.
672 (default 1)
673LinuxExtensionsEnabled If set to one then the client will attempt to
674 use the CIFS "UNIX" extensions which are optional
675 protocol enhancements that allow CIFS servers
676 to return accurate UID/GID information as well
677 as support symbolic links. If you use servers
678 such as Samba that support the CIFS Unix
679 extensions but do not want to use symbolic link
680 support and want to map the uid and gid fields
681 to values supplied at mount (rather than the
682 actual values, then set this to zero. (default 1)
Steve French60808232006-04-22 15:53:05 +0000683Experimental When set to 1 used to enable certain experimental
684 features (currently enables multipage writes
685 when signing is enabled, the multipage write
686 performance enhancement was disabled when
687 signing turned on in case buffer was modified
688 just before it was sent, also this flag will
Jeff Laytoncea21802007-11-20 23:19:03 +0000689 be used to use the new experimental directory change
Steve Frenchac683922009-05-06 04:16:04 +0000690 notification code). When set to 2 enables
691 an additional experimental feature, "raw ntlmssp"
692 session establishment support (which allows
693 specifying "sec=ntlmssp" on mount). The Linux cifs
694 module will use ntlmv2 authentication encapsulated
695 in "raw ntlmssp" (not using SPNEGO) when
696 "sec=ntlmssp" is specified on mount.
697 This support also requires building cifs with
698 the CONFIG_CIFS_EXPERIMENTAL configuration flag.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700699
700These experimental features and tracing can be enabled by changing flags in
701/proc/fs/cifs (after the cifs module has been installed or built into the
702kernel, e.g. insmod cifs). To enable a feature set it to 1 e.g. to enable
703tracing to the kernel message log type:
704
Steve French1047abc2005-10-11 19:58:06 -0700705 echo 7 > /proc/fs/cifs/cifsFYI
Linus Torvalds1da177e2005-04-16 15:20:36 -0700706
Steve French1047abc2005-10-11 19:58:06 -0700707cifsFYI functions as a bit mask. Setting it to 1 enables additional kernel
708logging of various informational messages. 2 enables logging of non-zero
709SMB return codes while 4 enables logging of requests that take longer
710than one second to complete (except for byte range lock requests).
711Setting it to 4 requires defining CONFIG_CIFS_STATS2 manually in the
712source code (typically by setting it in the beginning of cifsglob.h),
713and setting it to seven enables all three. Finally, tracing
714the start of smb requests and responses can be enabled via:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700715
716 echo 1 > /proc/fs/cifs/traceSMB
717
Steve French75865f8c2007-06-24 18:30:48 +0000718Two other experimental features are under development. To test these
719requires enabling CONFIG_CIFS_EXPERIMENTAL
Linus Torvalds1da177e2005-04-16 15:20:36 -0700720
Jeff Laytoncea21802007-11-20 23:19:03 +0000721 cifsacl support needed to retrieve approximated mode bits based on
722 the contents on the CIFS ACL.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700723
Steve French84210e92008-10-23 04:42:37 +0000724 lease support: cifs will check the oplock state before calling into
725 the vfs to see if we can grant a lease on a file.
726
Linus Torvalds1da177e2005-04-16 15:20:36 -0700727 DNOTIFY fcntl: needed for support of directory change
728 notification and perhaps later for file leases)
729
730Per share (per client mount) statistics are available in /proc/fs/cifs/Stats
731if the kernel was configured with cifs statistics enabled. The statistics
732represent the number of successful (ie non-zero return code from the server)
733SMB responses to some of the more common commands (open, delete, mkdir etc.).
734Also recorded is the total bytes read and bytes written to the server for
735that share. Note that due to client caching effects this can be less than the
736number of bytes read and written by the application running on the client.
737The statistics for the number of total SMBs and oplock breaks are different in
738that they represent all for that share, not just those for which the server
739returned success.
740
Steve French3d2af342008-08-19 20:51:09 +0000741Also note that "cat /proc/fs/cifs/DebugData" will display information about
Jeff Laytoncea21802007-11-20 23:19:03 +0000742the active sessions and the shares that are mounted.
Steve French3d2af342008-08-19 20:51:09 +0000743
744Enabling Kerberos (extended security) works but requires version 1.2 or later
745of the helper program cifs.upcall to be present and to be configured in the
746/etc/request-key.conf file. The cifs.upcall helper program is from the Samba
747project(http://www.samba.org). NTLM and NTLMv2 and LANMAN support do not
748require this helper. Note that NTLMv2 security (which does not require the
749cifs.upcall helper program), instead of using Kerberos, is sufficient for
750some use cases.
751
Steve Frenchbe652442009-02-23 15:21:59 +0000752DFS support allows transparent redirection to shares in an MS-DFS name space.
753In addition, DFS support for target shares which are specified as UNC
Steve French3d2af342008-08-19 20:51:09 +0000754names which begin with host names (rather than IP addresses) requires
755a user space helper (such as cifs.upcall) to be present in order to
756translate host names to ip address, and the user space helper must also
Steve Frenchbe652442009-02-23 15:21:59 +0000757be configured in the file /etc/request-key.conf. Samba, Windows servers and
758many NAS appliances support DFS as a way of constructing a global name
759space to ease network configuration and improve reliability.
Steve French3d2af342008-08-19 20:51:09 +0000760
761To use cifs Kerberos and DFS support, the Linux keyutils package should be
762installed and something like the following lines should be added to the
763/etc/request-key.conf file:
764
765create cifs.spnego * * /usr/local/sbin/cifs.upcall %k
766create dns_resolver * * /usr/local/sbin/cifs.upcall %k
767
768