1 The CIFS VFS support for Linux supports many advanced network filesystem
2 features such as hierarchical dfs like namespace, hardlinks, locking and more.
3 It was designed to comply with the SNIA CIFS Technical Reference (which
4 supersedes the 1992 X/Open SMB Standard) as well as to perform best practice
5 practical interoperability with Windows 2000, Windows XP, Samba and equivalent
6 servers. This code was developed in participation with the Protocol Freedom
7 Information Foundation.
10 http://protocolfreedom.org/ and
11 http://samba.org/samba/PFIF/
15 For questions or bug reports please contact:
16 sfrench@samba.org (sfrench@us.ibm.com)
21 1) Get the kernel source (e.g.from http://www.kernel.org)
22 and download the cifs vfs source (see the project page
23 at http://us1.samba.org/samba/Linux_CIFS_client.html)
24 and change directory into the top of the kernel directory
25 then patch the kernel (e.g. "patch -p1 < cifs_24.patch")
26 to add the cifs vfs to your kernel configure options if
27 it has not already been added (e.g. current SuSE and UL
28 users do not need to apply the cifs_24.patch since the cifs vfs is
29 already in the kernel configure menu) and then
30 mkdir linux/fs/cifs and then copy the current cifs vfs files from
31 the cifs download to your kernel build directory e.g.
33 cp <cifs_download_dir>/fs/cifs/* to <kernel_download_dir>/fs/cifs
35 2) make menuconfig (or make xconfig)
36 3) select cifs from within the network filesystem choices
39 6) make modules (or "make" if CIFS VFS not to be built as a module)
42 1) Download the kernel (e.g. from http://www.kernel.org)
43 and change directory into the top of the kernel directory tree
44 (e.g. /usr/src/linux-2.5.73)
45 2) make menuconfig (or make xconfig)
46 3) select cifs from within the network filesystem choices
51 Installation instructions:
52 =========================
53 If you have built the CIFS vfs as module (successfully) simply
54 type "make modules_install" (or if you prefer, manually copy the file to
55 the modules directory e.g. /lib/modules/2.4.10-4GB/kernel/fs/cifs/cifs.o).
57 If you have built the CIFS vfs into the kernel itself, follow the instructions
58 for your distribution on how to install a new kernel (usually you
59 would simply type "make install").
61 If you do not have the utility mount.cifs (in the Samba 3.0 source tree and on
62 the CIFS VFS web site) copy it to the same directory in which mount.smbfs and
63 similar files reside (usually /sbin). Although the helper software is not
64 required, mount.cifs is recommended. Eventually the Samba 3.0 utility program
65 "net" may also be helpful since it may someday provide easier mount syntax for
66 users who are used to Windows e.g.
67 net use <mount point> <UNC name or cifs URL>
68 Note that running the Winbind pam/nss module (logon service) on all of your
69 Linux clients is useful in mapping Uids and Gids consistently across the
70 domain to the proper network user. The mount.cifs mount helper can be
71 trivially built from Samba 3.0 or later source e.g. by executing:
73 gcc samba/source/client/mount.cifs.c -o mount.cifs
75 If cifs is built as a module, then the size and number of network buffers
76 and maximum number of simultaneous requests to one server can be configured.
77 Changing these from their defaults is not recommended. By executing modinfo
78 modinfo kernel/fs/cifs/cifs.ko
79 on kernel/fs/cifs/cifs.ko the list of configuration changes that can be made
80 at module initialization time (by running insmod cifs.ko) can be seen.
84 To permit users to mount and unmount over directories they own is possible
85 with the cifs vfs. A way to enable such mounting is to mark the mount.cifs
86 utility as suid (e.g. "chmod +s /sbin/mount.cifs). To enable users to
87 umount shares they mount requires
88 1) mount.cifs version 1.4 or later
89 2) an entry for the share in /etc/fstab indicating that a user may
91 //server/usersharename /mnt/username cifs user 0 0
93 Note that when the mount.cifs utility is run suid (allowing user mounts),
94 in order to reduce risks, the "nosuid" mount flag is passed in on mount to
95 disallow execution of an suid program mounted on the remote target.
96 When mount is executed as root, nosuid is not passed in by default,
97 and execution of suid programs on the remote target would be enabled
98 by default. This can be changed, as with nfs and other filesystems,
99 by simply specifying "nosuid" among the mount options. For user mounts
100 though to be able to pass the suid flag to mount requires rebuilding
101 mount.cifs with the following flag:
103 gcc samba/source/client/mount.cifs.c -DCIFS_ALLOW_USR_SUID -o mount.cifs
105 There is a corresponding manual page for cifs mounting in the Samba 3.0 and
106 later source tree in docs/manpages/mount.cifs.8
108 Allowing User Unmounts
109 ======================
110 To permit users to ummount directories that they have user mounted (see above),
111 the utility umount.cifs may be used. It may be invoked directly, or if
112 umount.cifs is placed in /sbin, umount can invoke the cifs umount helper
113 (at least for most versions of the umount utility) for umount of cifs
114 mounts, unless umount is invoked with -i (which will avoid invoking a umount
115 helper). As with mount.cifs, to enable user unmounts umount.cifs must be marked
116 as suid (e.g. "chmod +s /sbin/umount.cifs") or equivalent (some distributions
117 allow adding entries to a file to the /etc/permissions file to achieve the
118 equivalent suid effect). For this utility to succeed the target path
119 must be a cifs mount, and the uid of the current user must match the uid
120 of the user who mounted the resource.
122 Also note that the customary way of allowing user mounts and unmounts is
123 (instead of using mount.cifs and unmount.cifs as suid) to add a line
124 to the file /etc/fstab for each //server/share you wish to mount, but
125 this can become unwieldy when potential mount targets include many
126 or unpredictable UNC names.
130 To get the maximum benefit from the CIFS VFS, we recommend using a server that
131 supports the SNIA CIFS Unix Extensions standard (e.g. Samba 2.2.5 or later or
132 Samba 3.0) but the CIFS vfs works fine with a wide variety of CIFS servers.
133 Note that uid, gid and file permissions will display default values if you do
134 not have a server that supports the Unix extensions for CIFS (such as Samba
135 2.2.5 or later). To enable the Unix CIFS Extensions in the Samba server, add
138 unix extensions = yes
140 to your smb.conf file on the server. Note that the following smb.conf settings
141 are also useful (on the Samba server) when the majority of clients are Unix or
145 delete readonly = yes
148 Note that server ea support is required for supporting xattrs from the Linux
149 cifs client, and that EA support is present in later versions of Samba (e.g.
150 3.0.6 and later (also EA support works in all versions of Windows, at least to
151 shares on NTFS filesystems). Extended Attribute (xattr) support is an optional
152 feature of most Linux filesystems which may require enabling via
153 make menuconfig. Client support for extended attributes (user xattr) can be
154 disabled on a per-mount basis by specifying "nouser_xattr" on mount.
156 The CIFS client can get and set POSIX ACLs (getfacl, setfacl) to Samba servers
157 version 3.10 and later. Setting POSIX ACLs requires enabling both XATTR and
158 then POSIX support in the CIFS configuration options when building the cifs
159 module. POSIX ACL support can be disabled on a per mount basic by specifying
162 Some administrators may want to change Samba's smb.conf "map archive" and
163 "create mask" parameters from the default. Unless the create mask is changed
164 newly created files can end up with an unnecessarily restrictive default mode,
165 which may not be what you want, although if the CIFS Unix extensions are
166 enabled on the server and client, subsequent setattr calls (e.g. chmod) can
167 fix the mode. Note that creating special devices (mknod) remotely
168 may require specifying a mkdev function to Samba if you are not using
169 Samba 3.0.6 or later. For more information on these see the manual pages
170 ("man smb.conf") on the Samba server system. Note that the cifs vfs,
171 unlike the smbfs vfs, does not read the smb.conf on the client system
172 (the few optional settings are passed in on mount via -o parameters instead).
173 Note that Samba 2.2.7 or later includes a fix that allows the CIFS VFS to delete
174 open files (required for strict POSIX compliance). Windows Servers already
175 supported this feature. Samba server does not allow symlinks that refer to files
176 outside of the share, so in Samba versions prior to 3.0.6, most symlinks to
177 files with absolute paths (ie beginning with slash) such as:
179 would be forbidden. Samba 3.0.6 server or later includes the ability to create
180 such symlinks safely by converting unsafe symlinks (ie symlinks to server
181 files that are outside of the share) to a samba specific format on the server
182 that is ignored by local server applications and non-cifs clients and that will
183 not be traversed by the Samba server). This is opaque to the Linux client
184 application using the cifs vfs. Absolute symlinks will work to Samba 3.0.5 or
185 later, but only for remote clients using the CIFS Unix extensions, and will
186 be invisbile to Windows clients and typically will not affect local
187 applications running on the same server as Samba.
191 Once the CIFS VFS support is built into the kernel or installed as a module
192 (cifs.o), you can use mount syntax like the following to access Samba or Windows
195 mount -t cifs //9.53.216.11/e$ /mnt -o user=myname,pass=mypassword
197 Before -o the option -v may be specified to make the mount.cifs
198 mount helper display the mount steps more verbosely.
199 After -o the following commonly used cifs vfs specific options
206 Other cifs mount options are described below. Use of TCP names (in addition to
207 ip addresses) is available if the mount helper (mount.cifs) is installed. If
208 you do not trust the server to which are mounted, or if you do not have
209 cifs signing enabled (and the physical network is insecure), consider use
210 of the standard mount options "noexec" and "nosuid" to reduce the risk of
211 running an altered binary on your local system (downloaded from a hostile server
212 or altered by a hostile router).
214 Although mounting using format corresponding to the CIFS URL specification is
215 not possible in mount.cifs yet, it is possible to use an alternate format
216 for the server and sharename (which is somewhat similar to NFS style mount
217 syntax) instead of the more widely used UNC format (i.e. \\server\share):
218 mount -t cifs tcp_name_of_server:share_name /mnt -o user=myname,pass=mypasswd
220 When using the mount helper mount.cifs, passwords may be specified via alternate
221 mechanisms, instead of specifying it after -o using the normal "pass=" syntax
223 1) By including it in a credential file. Specify credentials=filename as one
224 of the mount options. Credential files contain two lines
226 password=your_password
227 2) By specifying the password in the PASSWD environment variable (similarly
228 the user name can be taken from the USER environment variable).
229 3) By specifying the password in a file by name via PASSWD_FILE
230 4) By specifying the password in a file by file descriptor via PASSWD_FD
232 If no password is provided, mount.cifs will prompt for password entry
236 Servers must support either "pure-TCP" (port 445 TCP/IP CIFS connections) or RFC
237 1001/1002 support for "Netbios-Over-TCP/IP." This is not likely to be a
238 problem as most servers support this.
240 Valid filenames differ between Windows and Linux. Windows typically restricts
241 filenames which contain certain reserved characters (e.g.the character :
242 which is used to delimit the beginning of a stream name by Windows), while
243 Linux allows a slightly wider set of valid characters in filenames. Windows
244 servers can remap such characters when an explicit mapping is specified in
245 the Server's registry. Samba starting with version 3.10 will allow such
246 filenames (ie those which contain valid Linux characters, which normally
247 would be forbidden for Windows/CIFS semantics) as long as the server is
248 configured for Unix Extensions (and the client has not disabled
249 /proc/fs/cifs/LinuxExtensionsEnabled).
252 CIFS VFS Mount Options
253 ======================
254 A partial list of the supported mount options follows:
255 user The user name to use when trying to establish
257 password The user password. If the mount helper is
258 installed, the user will be prompted for password
260 ip The ip address of the target server
261 unc The target server Universal Network Name (export) to
263 domain Set the SMB/CIFS workgroup name prepended to the
264 username during CIFS session establishment
265 forceuid Set the default uid for inodes to the uid
266 passed in on mount. For mounts to servers
267 which do support the CIFS Unix extensions, such as a
268 properly configured Samba server, the server provides
269 the uid, gid and mode so this parameter should not be
270 specified unless the server and clients uid and gid
271 numbering differ. If the server and client are in the
272 same domain (e.g. running winbind or nss_ldap) and
273 the server supports the Unix Extensions then the uid
274 and gid can be retrieved from the server (and uid
275 and gid would not have to be specifed on the mount.
276 For servers which do not support the CIFS Unix
277 extensions, the default uid (and gid) returned on lookup
278 of existing files will be the uid (gid) of the person
279 who executed the mount (root, except when mount.cifs
280 is configured setuid for user mounts) unless the "uid="
281 (gid) mount option is specified. Also note that permission
282 checks (authorization checks) on accesses to a file occur
283 at the server, but there are cases in which an administrator
284 may want to restrict at the client as well. For those
285 servers which do not report a uid/gid owner
286 (such as Windows), permissions can also be checked at the
287 client, and a crude form of client side permission checking
288 can be enabled by specifying file_mode and dir_mode on
289 the client. (default)
290 forcegid (similar to above but for the groupid instead of uid) (default)
291 noforceuid Fill in file owner information (uid) by requesting it from
292 the server if possible. With this option, the value given in
293 the uid= option (on mount) will only be used if the server
294 can not support returning uids on inodes.
295 noforcegid (similar to above but for the group owner, gid, instead of uid)
296 uid Set the default uid for inodes, and indicate to the
297 cifs kernel driver which local user mounted. If the server
298 supports the unix extensions the default uid is
299 not used to fill in the owner fields of inodes (files)
300 unless the "forceuid" parameter is specified.
301 gid Set the default gid for inodes (similar to above).
302 file_mode If CIFS Unix extensions are not supported by the server
303 this overrides the default mode for file inodes.
304 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
315 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
330 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
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)
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
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
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
377 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)
381 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).
384 serverino Use server's inode numbers instead of generating automatically
385 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
392 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.
397 This is now the default if server supports the
398 required network operation.
399 noserverino Client generates inode numbers (rather than using the actual one
400 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
404 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
407 devices (create, mkdir, mknod). If the CIFS Unix Extensions
408 are not negotiated, for newly created files and directories
409 instead of using the default uid and gid specified on
410 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).
413 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
417 user who mounted the share). Letting the server (rather than
418 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.
422 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
431 behavior which caches reads (readahead) and writes
432 (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
439 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)
443 nouser_xattr Do not allow getfattr/setfattr to get/set/list xattrs
444 mapchars Translate six of the seven reserved characters (not backslash)
446 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
454 nomapchars Do not translate any of these seven characters (default).
455 nocase Request case insensitive path name matching (case
456 sensitive is the default if the server suports it).
457 (mount option "ignorecase" is identical to "nocase")
458 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).
465 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
472 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
477 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
486 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
499 nodfs Disable DFS (global name space support) even if the
500 server claims to support it. This can help work around
501 a problem with parsing of DFS paths with Samba server
502 versions 3.0.24 and 3.0.25.
503 remount remount the share (often used to change from ro to rw mounts
505 cifsacl Report mode bits (e.g. on stat) based on the Windows ACL for
506 the file. (EXPERIMENTAL)
507 servern Specify the server 's netbios name (RFC1001 name) to use
508 when attempting to setup a session to the server.
509 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.
513 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
517 SFU does). In the future the bottom 9 bits of the
518 mode also will be emulated using queries of the security
520 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.
523 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.
528 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)
541 sec Security mode. Allowed values are:
542 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
551 lanman (if configured in kernel config) use older
553 hard Retry file operations if server is not responding
554 soft Limit retries to unresponsive servers (usually only
555 one retry) before returning an error. (default)
557 The mount.cifs mount helper also accepts a few mount options before -o
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
565 With most 2.6 kernel versions of modutils, the version of the cifs kernel
566 module can be displayed via modinfo.
568 Misc /proc/fs/cifs Flags and Debug Info
569 =======================================
570 Informational pseudo-files:
571 DebugData Displays information about active CIFS sessions
572 and shares, as well as the cifs.ko version.
573 Stats Lists summary resource usage information as well as per
574 share statistics, if CONFIG_CIFS_STATS in enabled
575 in the kernel configuration.
577 Configuration pseudo-files:
578 MultiuserMount 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)
583 PacketSigningEnabled 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)
588 SecurityFlags 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
595 (NTLM, NTLMv2 and packet signing allowed). The maximum
596 allowable flags if you want to allow mounts to servers
597 using weaker password hashes is 0x37037 (lanman,
598 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
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
616 may use Kerberos security 0x00008
617 must use Kerberos 0x08008
618 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
624 cifsFYI 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):
634 log cifs informational messages 0x01
635 log return codes from cifs entry points 0x02
636 log slow responses (ie which take longer than 1 second)
637 CONFIG_CIFS_STATS2 must be enabled in .config 0x04
640 traceSMB 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)
643 LookupCacheEnable If set to one, inode information is kept cached
644 for one second improving performance of lookups
646 OplockEnabled If set to one, safe distributed caching enabled.
648 LinuxExtensionsEnabled 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)
658 Experimental 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
664 be used to use the new experimental directory change
665 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.
675 These 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
677 kernel, e.g. insmod cifs). To enable a feature set it to 1 e.g. to enable
678 tracing to the kernel message log type:
680 echo 7 > /proc/fs/cifs/cifsFYI
682 cifsFYI functions as a bit mask. Setting it to 1 enables additional kernel
683 logging of various informational messages. 2 enables logging of non-zero
684 SMB return codes while 4 enables logging of requests that take longer
685 than one second to complete (except for byte range lock requests).
686 Setting it to 4 requires defining CONFIG_CIFS_STATS2 manually in the
687 source code (typically by setting it in the beginning of cifsglob.h),
688 and setting it to seven enables all three. Finally, tracing
689 the start of smb requests and responses can be enabled via:
691 echo 1 > /proc/fs/cifs/traceSMB
693 Two other experimental features are under development. To test these
694 requires enabling CONFIG_CIFS_EXPERIMENTAL
696 cifsacl support needed to retrieve approximated mode bits based on
697 the contents on the CIFS ACL.
699 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.
702 DNOTIFY fcntl: needed for support of directory change
703 notification and perhaps later for file leases)
705 Per share (per client mount) statistics are available in /proc/fs/cifs/Stats
706 if the kernel was configured with cifs statistics enabled. The statistics
707 represent the number of successful (ie non-zero return code from the server)
708 SMB responses to some of the more common commands (open, delete, mkdir etc.).
709 Also recorded is the total bytes read and bytes written to the server for
710 that share. Note that due to client caching effects this can be less than the
711 number of bytes read and written by the application running on the client.
712 The statistics for the number of total SMBs and oplock breaks are different in
713 that they represent all for that share, not just those for which the server
716 Also note that "cat /proc/fs/cifs/DebugData" will display information about
717 the active sessions and the shares that are mounted.
719 Enabling Kerberos (extended security) works but requires version 1.2 or later
720 of 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
722 project(http://www.samba.org). NTLM and NTLMv2 and LANMAN support do not
723 require this helper. Note that NTLMv2 security (which does not require the
724 cifs.upcall helper program), instead of using Kerberos, is sufficient for
727 DFS support allows transparent redirection to shares in an MS-DFS name space.
728 In addition, DFS support for target shares which are specified as UNC
729 names which begin with host names (rather than IP addresses) requires
730 a user space helper (such as cifs.upcall) to be present in order to
731 translate host names to ip address, and the user space helper must also
732 be configured in the file /etc/request-key.conf. Samba, Windows servers and
733 many NAS appliances support DFS as a way of constructing a global name
734 space to ease network configuration and improve reliability.
736 To use cifs Kerberos and DFS support, the Linux keyutils package should be
737 installed and something like the following lines should be added to the
738 /etc/request-key.conf file:
740 create cifs.spnego * * /usr/local/sbin/cifs.upcall %k
741 create dns_resolver * * /usr/local/sbin/cifs.upcall %k
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