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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.
304 dir_mode If CIFS Unix extensions are not supported by the server
305 this overrides the default mode for directory inodes.
306 port attempt to contact the server on this tcp port, before
307 trying the usual ports (port 445, then 139).
308 iocharset Codepage used to convert local path names to and from
309 Unicode. Unicode is used by default for network path
310 names if the server supports it. If iocharset is
311 not specified then the nls_default specified
312 during the local client kernel build will be used.
313 If server does not support Unicode, this parameter is
314 unused.
Steve French75865f82007-06-24 18:30:48 +0000315 rsize default read size (usually 16K). The client currently
316 can not use rsize larger than CIFSMaxBufSize. CIFSMaxBufSize
317 defaults to 16K and may be changed (from 8K to the maximum
318 kmalloc size allowed by your kernel) at module install time
319 for cifs.ko. Setting CIFSMaxBufSize to a very large value
320 will cause cifs to use more memory and may reduce performance
321 in some cases. To use rsize greater than 127K (the original
322 cifs protocol maximum) also requires that the server support
323 a new Unix Capability flag (for very large read) which some
324 newer servers (e.g. Samba 3.0.26 or later) do. rsize can be
325 set from a minimum of 2048 to a maximum of 130048 (127K or
326 CIFSMaxBufSize, whichever is smaller)
327 wsize default write size (default 57344)
328 maximum wsize currently allowed by CIFS is 57344 (fourteen
329 4096 byte pages)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700330 rw mount the network share read-write (note that the
331 server may still consider the share read-only)
332 ro mount network share read-only
333 version used to distinguish different versions of the
334 mount helper utility (not typically needed)
335 sep if first mount option (after the -o), overrides
336 the comma as the separator between the mount
337 parms. e.g.
338 -o user=myname,password=mypassword,domain=mydom
339 could be passed instead with period as the separator by
340 -o sep=.user=myname.password=mypassword.domain=mydom
341 this might be useful when comma is contained within username
342 or password or domain. This option is less important
343 when the cifs mount helper cifs.mount (version 1.1 or later)
344 is used.
345 nosuid Do not allow remote executables with the suid bit
346 program to be executed. This is only meaningful for mounts
347 to servers such as Samba which support the CIFS Unix Extensions.
348 If you do not trust the servers in your network (your mount
349 targets) it is recommended that you specify this option for
350 greater security.
351 exec Permit execution of binaries on the mount.
352 noexec Do not permit execution of binaries on the mount.
353 dev Recognize block devices on the remote mount.
354 nodev Do not recognize devices on the remote mount.
355 suid Allow remote files on this mountpoint with suid enabled to
356 be executed (default for mounts when executed as root,
357 nosuid is default for user mounts).
358 credentials Although ignored by the cifs kernel component, it is used by
359 the mount helper, mount.cifs. When mount.cifs is installed it
360 opens and reads the credential file specified in order
361 to obtain the userid and password arguments which are passed to
362 the cifs vfs.
363 guest Although ignored by the kernel component, the mount.cifs
364 mount helper will not prompt the user for a password
365 if guest is specified on the mount options. If no
366 password is specified a null password will be used.
367 perm Client does permission checks (vfs_permission check of uid
368 and gid of the file against the mode and desired operation),
369 Note that this is in addition to the normal ACL check on the
370 target machine done by the server software.
371 Client permission checking is enabled by default.
372 noperm Client does not do permission checks. This can expose
373 files on this mount to access by other users on the local
374 client system. It is typically only needed when the server
375 supports the CIFS Unix Extensions but the UIDs/GIDs on the
376 client and server system do not match closely enough to allow
Steve French6473a552005-11-29 20:20:10 -0800377 access by the user doing the mount, but it may be useful with
378 non CIFS Unix Extension mounts for cases in which the default
379 mode is specified on the mount but is not to be enforced on the
380 client (e.g. perhaps when MultiUserMount is enabled)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700381 Note that this does not affect the normal ACL check on the
382 target machine done by the server software (of the server
383 ACL against the user name provided at mount time).
Steve French7521a3c2007-07-11 18:30:34 +0000384 serverino Use server's inode numbers instead of generating automatically
Linus Torvalds1da177e2005-04-16 15:20:36 -0700385 incrementing inode numbers on the client. Although this will
386 make it easier to spot hardlinked files (as they will have
387 the same inode numbers) and inode numbers may be persistent,
388 note that the server does not guarantee that the inode numbers
389 are unique if multiple server side mounts are exported under a
390 single share (since inode numbers on the servers might not
391 be unique if multiple filesystems are mounted under the same
Steve French7521a3c2007-07-11 18:30:34 +0000392 shared higher level directory). Note that some older
393 (e.g. pre-Windows 2000) do not support returning UniqueIDs
394 or the CIFS Unix Extensions equivalent and for those
395 this mount option will have no effect. Exporting cifs mounts
396 under nfsd requires this mount option on the cifs mount.
Steve Frenchc5077ec2009-05-28 15:09:04 +0000397 This is now the default if server supports the
398 required network operation.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700399 noserverino Client generates inode numbers (rather than using the actual one
Steve Frenchc5077ec2009-05-28 15:09:04 +0000400 from the server). These inode numbers will vary after
401 unmount or reboot which can confuse some applications,
402 but not all server filesystems support unique inode
403 numbers.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700404 setuids If the CIFS Unix extensions are negotiated with the server
405 the client will attempt to set the effective uid and gid of
406 the local process on newly created files, directories, and
Steve French6473a552005-11-29 20:20:10 -0800407 devices (create, mkdir, mknod). If the CIFS Unix Extensions
408 are not negotiated, for newly created files and directories
Matt LaPlantecab00892006-10-03 22:36:44 +0200409 instead of using the default uid and gid specified on
Steve French6473a552005-11-29 20:20:10 -0800410 the mount, cache the new file's uid and gid locally which means
411 that the uid for the file can change when the inode is
412 reloaded (or the user remounts the share).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700413 nosetuids The client will not attempt to set the uid and gid on
414 on newly created files, directories, and devices (create,
415 mkdir, mknod) which will result in the server setting the
416 uid and gid to the default (usually the server uid of the
Steve French67594fe2005-05-17 13:04:49 -0500417 user who mounted the share). Letting the server (rather than
Steve French6473a552005-11-29 20:20:10 -0800418 the client) set the uid and gid is the default. If the CIFS
419 Unix Extensions are not negotiated then the uid and gid for
420 new files will appear to be the uid (gid) of the mounter or the
421 uid (gid) parameter specified on the mount.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700422 netbiosname When mounting to servers via port 139, specifies the RFC1001
423 source name to use to represent the client netbios machine
424 name when doing the RFC1001 netbios session initialize.
425 direct Do not do inode data caching on files opened on this mount.
426 This precludes mmaping files on this mount. In some cases
427 with fast networks and little or no caching benefits on the
428 client (e.g. when the application is doing large sequential
429 reads bigger than page size without rereading the same data)
430 this can provide better performance than the default
Steve French67594fe2005-05-17 13:04:49 -0500431 behavior which caches reads (readahead) and writes
Linus Torvalds1da177e2005-04-16 15:20:36 -0700432 (writebehind) through the local Linux client pagecache
433 if oplock (caching token) is granted and held. Note that
434 direct allows write operations larger than page size
435 to be sent to the server.
436 acl Allow setfacl and getfacl to manage posix ACLs if server
437 supports them. (default)
438 noacl Do not allow setfacl and getfacl calls on this mount
Steve Frenchf6d09982008-01-08 23:18:22 +0000439 user_xattr Allow getting and setting user xattrs (those attributes whose
440 name begins with "user." or "os2.") as OS/2 EAs (extended
441 attributes) to the server. This allows support of the
442 setfattr and getfattr utilities. (default)
Steve Frenchea4c07d2006-08-16 19:44:25 +0000443 nouser_xattr Do not allow getfattr/setfattr to get/set/list xattrs
Steve French737b7582005-04-28 22:41:06 -0700444 mapchars Translate six of the seven reserved characters (not backslash)
445 *?<>|:
Steve French6a0b4822005-04-28 22:41:05 -0700446 to the remap range (above 0xF000), which also
447 allows the CIFS client to recognize files created with
448 such characters by Windows's POSIX emulation. This can
449 also be useful when mounting to most versions of Samba
450 (which also forbids creating and opening files
451 whose names contain any of these seven characters).
452 This has no effect if the server does not support
453 Unicode on the wire.
454 nomapchars Do not translate any of these seven characters (default).
Steve Frenchc46fa8a2005-08-18 20:49:57 -0700455 nocase Request case insensitive path name matching (case
456 sensitive is the default if the server suports it).
Steve Frenchf6d09982008-01-08 23:18:22 +0000457 (mount option "ignorecase" is identical to "nocase")
Steve French82940a42006-03-02 03:24:57 +0000458 posixpaths If CIFS Unix extensions are supported, attempt to
459 negotiate posix path name support which allows certain
460 characters forbidden in typical CIFS filenames, without
461 requiring remapping. (default)
462 noposixpaths If CIFS Unix extensions are supported, do not request
463 posix path name support (this may cause servers to
464 reject creatingfile with certain reserved characters).
Steve Frencha403a0a2007-07-26 15:54:16 +0000465 nounix Disable the CIFS Unix Extensions for this mount (tree
466 connection). This is rarely needed, but it may be useful
467 in order to turn off multiple settings all at once (ie
468 posix acls, posix locks, posix paths, symlink support
469 and retrieving uids/gids/mode from the server) or to
470 work around a bug in server which implement the Unix
471 Extensions.
Steve Frenchc46fa8a2005-08-18 20:49:57 -0700472 nobrl Do not send byte range lock requests to the server.
473 This is necessary for certain applications that break
474 with cifs style mandatory byte range locks (and most
475 cifs servers do not yet support requesting advisory
476 byte range locks).
Steve French13a6e422008-12-02 17:24:33 +0000477 forcemandatorylock Even if the server supports posix (advisory) byte range
478 locking, send only mandatory lock requests. For some
479 (presumably rare) applications, originally coded for
480 DOS/Windows, which require Windows style mandatory byte range
481 locking, they may be able to take advantage of this option,
482 forcing the cifs client to only send mandatory locks
483 even if the cifs server would support posix advisory locks.
484 "forcemand" is accepted as a shorter form of this mount
485 option.
Steve Frenchbe652442009-02-23 15:21:59 +0000486 nostrictsync If this mount option is set, when an application does an
487 fsync call then the cifs client does not send an SMB Flush
488 to the server (to force the server to write all dirty data
489 for this file immediately to disk), although cifs still sends
490 all dirty (cached) file data to the server and waits for the
491 server to respond to the write. Since SMB Flush can be
492 very slow, and some servers may be reliable enough (to risk
493 delaying slightly flushing the data to disk on the server),
494 turning on this option may be useful to improve performance for
495 applications that fsync too much, at a small risk of server
496 crash. If this mount option is not set, by default cifs will
497 send an SMB flush request (and wait for a response) on every
498 fsync call.
Steve French2c1b8612008-10-16 18:35:21 +0000499 nodfs Disable DFS (global name space support) even if the
500 server claims to support it. This can help work around
Steve French13a6e422008-12-02 17:24:33 +0000501 a problem with parsing of DFS paths with Samba server
502 versions 3.0.24 and 3.0.25.
Steve French0cb766a2005-04-28 22:41:11 -0700503 remount remount the share (often used to change from ro to rw mounts
504 or vice versa)
Jeff Laytoncea21802007-11-20 23:19:03 +0000505 cifsacl Report mode bits (e.g. on stat) based on the Windows ACL for
506 the file. (EXPERIMENTAL)
Cyrill Gorcunov5e6e6232007-08-18 00:15:20 +0000507 servern Specify the server 's netbios name (RFC1001 name) to use
Steve Frenchad7a2922008-02-07 23:25:02 +0000508 when attempting to setup a session to the server.
Cyrill Gorcunov5e6e6232007-08-18 00:15:20 +0000509 This is needed for mounting to some older servers (such
510 as OS/2 or Windows 98 and Windows ME) since they do not
511 support a default server name. A server name can be up
512 to 15 characters long and is usually uppercased.
Steve French6473a552005-11-29 20:20:10 -0800513 sfu When the CIFS Unix Extensions are not negotiated, attempt to
514 create device files and fifos in a format compatible with
515 Services for Unix (SFU). In addition retrieve bits 10-12
516 of the mode via the SETFILEBITS extended attribute (as
Matt LaPlantecab00892006-10-03 22:36:44 +0200517 SFU does). In the future the bottom 9 bits of the
Steve French6473a552005-11-29 20:20:10 -0800518 mode also will be emulated using queries of the security
519 descriptor (ACL).
Steve French750d1152006-06-27 06:28:30 +0000520 sign Must use packet signing (helps avoid unwanted data modification
521 by intermediate systems in the route). Note that signing
522 does not work with lanman or plaintext authentication.
Steve French95b1cb92008-05-15 16:44:38 +0000523 seal Must seal (encrypt) all data on this mounted share before
524 sending on the network. Requires support for Unix Extensions.
525 Note that this differs from the sign mount option in that it
526 causes encryption of data sent over this mounted share but other
527 shares mounted to the same server are unaffected.
Steve French84210e92008-10-23 04:42:37 +0000528 locallease This option is rarely needed. Fcntl F_SETLEASE is
529 used by some applications such as Samba and NFSv4 server to
530 check to see whether a file is cacheable. CIFS has no way
531 to explicitly request a lease, but can check whether a file
532 is cacheable (oplocked). Unfortunately, even if a file
533 is not oplocked, it could still be cacheable (ie cifs client
534 could grant fcntl leases if no other local processes are using
535 the file) for cases for example such as when the server does not
536 support oplocks and the user is sure that the only updates to
537 the file will be from this client. Specifying this mount option
538 will allow the cifs client to check for leases (only) locally
539 for files which are not oplocked instead of denying leases
540 in that case. (EXPERIMENTAL)
Steve French750d1152006-06-27 06:28:30 +0000541 sec Security mode. Allowed values are:
Steve Frenchbf820672005-12-01 22:32:42 -0800542 none attempt to connection as a null user (no name)
543 krb5 Use Kerberos version 5 authentication
544 krb5i Use Kerberos authentication and packet signing
545 ntlm Use NTLM password hashing (default)
546 ntlmi Use NTLM password hashing with signing (if
547 /proc/fs/cifs/PacketSigningEnabled on or if
548 server requires signing also can be the default)
549 ntlmv2 Use NTLMv2 password hashing
550 ntlmv2i Use NTLMv2 password hashing with packet signing
Steve French189acaa2006-06-23 02:33:48 +0000551 lanman (if configured in kernel config) use older
552 lanman hash
Steve Frenchf6d09982008-01-08 23:18:22 +0000553hard Retry file operations if server is not responding
554soft Limit retries to unresponsive servers (usually only
555 one retry) before returning an error. (default)
Steve Frenchbf820672005-12-01 22:32:42 -0800556
Linus Torvalds1da177e2005-04-16 15:20:36 -0700557The mount.cifs mount helper also accepts a few mount options before -o
558including:
559
560 -S take password from stdin (equivalent to setting the environment
561 variable "PASSWD_FD=0"
562 -V print mount.cifs version
563 -? display simple usage information
564
Jeff Layton8426c392007-05-05 03:27:49 +0000565With most 2.6 kernel versions of modutils, the version of the cifs kernel
Linus Torvalds1da177e2005-04-16 15:20:36 -0700566module can be displayed via modinfo.
567
568Misc /proc/fs/cifs Flags and Debug Info
569=======================================
570Informational pseudo-files:
571DebugData Displays information about active CIFS sessions
Steve French09d1db52005-04-28 22:41:08 -0700572 and shares, as well as the cifs.ko version.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700573Stats Lists summary resource usage information as well as per
574 share statistics, if CONFIG_CIFS_STATS in enabled
575 in the kernel configuration.
576
577Configuration pseudo-files:
578MultiuserMount If set to one, more than one CIFS session to
579 the same server ip address can be established
580 if more than one uid accesses the same mount
581 point and if the uids user/password mapping
582 information is available. (default is 0)
583PacketSigningEnabled If set to one, cifs packet signing is enabled
584 and will be used if the server requires
585 it. If set to two, cifs packet signing is
586 required even if the server considers packet
587 signing optional. (default 1)
Steve French254e55e2006-06-04 05:53:15 +0000588SecurityFlags Flags which control security negotiation and
589 also packet signing. Authentication (may/must)
590 flags (e.g. for NTLM and/or NTLMv2) may be combined with
591 the signing flags. Specifying two different password
592 hashing mechanisms (as "must use") on the other hand
593 does not make much sense. Default flags are
594 0x07007
Steve French2e655022008-08-28 15:30:06 +0000595 (NTLM, NTLMv2 and packet signing allowed). The maximum
Steve French254e55e2006-06-04 05:53:15 +0000596 allowable flags if you want to allow mounts to servers
597 using weaker password hashes is 0x37037 (lanman,
Steve French2e655022008-08-28 15:30:06 +0000598 plaintext, ntlm, ntlmv2, signing allowed). Some
599 SecurityFlags require the corresponding menuconfig
600 options to be enabled (lanman and plaintext require
601 CONFIG_CIFS_WEAK_PW_HASH for example). Enabling
602 plaintext authentication currently requires also
603 enabling lanman authentication in the security flags
604 because the cifs module only supports sending
605 laintext passwords using the older lanman dialect
606 form of the session setup SMB. (e.g. for authentication
607 using plain text passwords, set the SecurityFlags
608 to 0x30030):
Steve French254e55e2006-06-04 05:53:15 +0000609
610 may use packet signing 0x00001
611 must use packet signing 0x01001
612 may use NTLM (most common password hash) 0x00002
613 must use NTLM 0x02002
614 may use NTLMv2 0x00004
615 must use NTLMv2 0x04004
Steve Frenchf6d09982008-01-08 23:18:22 +0000616 may use Kerberos security 0x00008
617 must use Kerberos 0x08008
Steve French254e55e2006-06-04 05:53:15 +0000618 may use lanman (weak) password hash 0x00010
619 must use lanman password hash 0x10010
620 may use plaintext passwords 0x00020
621 must use plaintext passwords 0x20020
622 (reserved for future packet encryption) 0x00040
623
Jeff Layton8426c392007-05-05 03:27:49 +0000624cifsFYI If set to non-zero value, additional debug information
625 will be logged to the system error log. This field
626 contains three flags controlling different classes of
627 debugging entries. The maximum value it can be set
628 to is 7 which enables all debugging points (default 0).
629 Some debugging statements are not compiled into the
630 cifs kernel unless CONFIG_CIFS_DEBUG2 is enabled in the
631 kernel configuration. cifsFYI may be set to one or
632 nore of the following flags (7 sets them all):
633
634 log cifs informational messages 0x01
635 log return codes from cifs entry points 0x02
Steve French0ec54aa2007-05-05 22:08:06 +0000636 log slow responses (ie which take longer than 1 second)
637 CONFIG_CIFS_STATS2 must be enabled in .config 0x04
Jeff Layton8426c392007-05-05 03:27:49 +0000638
639
Linus Torvalds1da177e2005-04-16 15:20:36 -0700640traceSMB If set to one, debug information is logged to the
641 system error log with the start of smb requests
642 and responses (default 0)
643LookupCacheEnable If set to one, inode information is kept cached
644 for one second improving performance of lookups
645 (default 1)
646OplockEnabled If set to one, safe distributed caching enabled.
647 (default 1)
648LinuxExtensionsEnabled If set to one then the client will attempt to
649 use the CIFS "UNIX" extensions which are optional
650 protocol enhancements that allow CIFS servers
651 to return accurate UID/GID information as well
652 as support symbolic links. If you use servers
653 such as Samba that support the CIFS Unix
654 extensions but do not want to use symbolic link
655 support and want to map the uid and gid fields
656 to values supplied at mount (rather than the
657 actual values, then set this to zero. (default 1)
Steve French60808232006-04-22 15:53:05 +0000658Experimental When set to 1 used to enable certain experimental
659 features (currently enables multipage writes
660 when signing is enabled, the multipage write
661 performance enhancement was disabled when
662 signing turned on in case buffer was modified
663 just before it was sent, also this flag will
Jeff Laytoncea21802007-11-20 23:19:03 +0000664 be used to use the new experimental directory change
Steve Frenchac683922009-05-06 04:16:04 +0000665 notification code). When set to 2 enables
666 an additional experimental feature, "raw ntlmssp"
667 session establishment support (which allows
668 specifying "sec=ntlmssp" on mount). The Linux cifs
669 module will use ntlmv2 authentication encapsulated
670 in "raw ntlmssp" (not using SPNEGO) when
671 "sec=ntlmssp" is specified on mount.
672 This support also requires building cifs with
673 the CONFIG_CIFS_EXPERIMENTAL configuration flag.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700674
675These experimental features and tracing can be enabled by changing flags in
676/proc/fs/cifs (after the cifs module has been installed or built into the
677kernel, e.g. insmod cifs). To enable a feature set it to 1 e.g. to enable
678tracing to the kernel message log type:
679
Steve French1047abc2005-10-11 19:58:06 -0700680 echo 7 > /proc/fs/cifs/cifsFYI
Linus Torvalds1da177e2005-04-16 15:20:36 -0700681
Steve French1047abc2005-10-11 19:58:06 -0700682cifsFYI functions as a bit mask. Setting it to 1 enables additional kernel
683logging of various informational messages. 2 enables logging of non-zero
684SMB return codes while 4 enables logging of requests that take longer
685than one second to complete (except for byte range lock requests).
686Setting it to 4 requires defining CONFIG_CIFS_STATS2 manually in the
687source code (typically by setting it in the beginning of cifsglob.h),
688and setting it to seven enables all three. Finally, tracing
689the start of smb requests and responses can be enabled via:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700690
691 echo 1 > /proc/fs/cifs/traceSMB
692
Steve French75865f82007-06-24 18:30:48 +0000693Two other experimental features are under development. To test these
694requires enabling CONFIG_CIFS_EXPERIMENTAL
Linus Torvalds1da177e2005-04-16 15:20:36 -0700695
Jeff Laytoncea21802007-11-20 23:19:03 +0000696 cifsacl support needed to retrieve approximated mode bits based on
697 the contents on the CIFS ACL.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700698
Steve French84210e92008-10-23 04:42:37 +0000699 lease support: cifs will check the oplock state before calling into
700 the vfs to see if we can grant a lease on a file.
701
Linus Torvalds1da177e2005-04-16 15:20:36 -0700702 DNOTIFY fcntl: needed for support of directory change
703 notification and perhaps later for file leases)
704
705Per share (per client mount) statistics are available in /proc/fs/cifs/Stats
706if the kernel was configured with cifs statistics enabled. The statistics
707represent the number of successful (ie non-zero return code from the server)
708SMB responses to some of the more common commands (open, delete, mkdir etc.).
709Also recorded is the total bytes read and bytes written to the server for
710that share. Note that due to client caching effects this can be less than the
711number of bytes read and written by the application running on the client.
712The statistics for the number of total SMBs and oplock breaks are different in
713that they represent all for that share, not just those for which the server
714returned success.
715
Steve French3d2af342008-08-19 20:51:09 +0000716Also note that "cat /proc/fs/cifs/DebugData" will display information about
Jeff Laytoncea21802007-11-20 23:19:03 +0000717the active sessions and the shares that are mounted.
Steve French3d2af342008-08-19 20:51:09 +0000718
719Enabling Kerberos (extended security) works but requires version 1.2 or later
720of the helper program cifs.upcall to be present and to be configured in the
721/etc/request-key.conf file. The cifs.upcall helper program is from the Samba
722project(http://www.samba.org). NTLM and NTLMv2 and LANMAN support do not
723require this helper. Note that NTLMv2 security (which does not require the
724cifs.upcall helper program), instead of using Kerberos, is sufficient for
725some use cases.
726
Steve Frenchbe652442009-02-23 15:21:59 +0000727DFS support allows transparent redirection to shares in an MS-DFS name space.
728In addition, DFS support for target shares which are specified as UNC
Steve French3d2af342008-08-19 20:51:09 +0000729names which begin with host names (rather than IP addresses) requires
730a user space helper (such as cifs.upcall) to be present in order to
731translate host names to ip address, and the user space helper must also
Steve Frenchbe652442009-02-23 15:21:59 +0000732be configured in the file /etc/request-key.conf. Samba, Windows servers and
733many NAS appliances support DFS as a way of constructing a global name
734space to ease network configuration and improve reliability.
Steve French3d2af342008-08-19 20:51:09 +0000735
736To use cifs Kerberos and DFS support, the Linux keyutils package should be
737installed and something like the following lines should be added to the
738/etc/request-key.conf file:
739
740create cifs.spnego * * /usr/local/sbin/cifs.upcall %k
741create dns_resolver * * /usr/local/sbin/cifs.upcall %k
742
743