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