1 This module supports the SMB3 family of advanced network protocols (as well
2 as older dialects, originally called "CIFS" or SMB1).
4 The CIFS VFS module for Linux supports many advanced network filesystem
5 features such as hierarchical DFS like namespace, hardlinks, locking and more.
6 It was designed to comply with the SNIA CIFS Technical Reference (which
7 supersedes the 1992 X/Open SMB Standard) as well as to perform best practice
8 practical interoperability with Windows 2000, Windows XP, Samba and equivalent
9 servers. This code was developed in participation with the Protocol Freedom
10 Information Foundation. CIFS and now SMB3 has now become a defacto
11 standard for interoperating between Macs and Windows and major NAS appliances.
14 http://protocolfreedom.org/ and
15 http://samba.org/samba/PFIF/
19 For questions or bug reports please contact:
20 sfrench@samba.org (sfrench@us.ibm.com)
22 See the project page at: https://wiki.samba.org/index.php/LinuxCIFS_utils
27 1) Download the kernel (e.g. from http://www.kernel.org)
28 and change directory into the top of the kernel directory tree
29 (e.g. /usr/src/linux-2.5.73)
30 2) make menuconfig (or make xconfig)
31 3) select cifs from within the network filesystem choices
36 Installation instructions:
37 =========================
38 If you have built the CIFS vfs as module (successfully) simply
39 type "make modules_install" (or if you prefer, manually copy the file to
40 the modules directory e.g. /lib/modules/2.4.10-4GB/kernel/fs/cifs/cifs.o).
42 If you have built the CIFS vfs into the kernel itself, follow the instructions
43 for your distribution on how to install a new kernel (usually you
44 would simply type "make install").
46 If you do not have the utility mount.cifs (in the Samba 3.0 source tree and on
47 the CIFS VFS web site) copy it to the same directory in which mount.smbfs and
48 similar files reside (usually /sbin). Although the helper software is not
49 required, mount.cifs is recommended. Most distros include a "cifs-utils"
50 package that includes this utility so it is recommended to install this.
52 Note that running the Winbind pam/nss module (logon service) on all of your
53 Linux clients is useful in mapping Uids and Gids consistently across the
54 domain to the proper network user. The mount.cifs mount helper can be
55 found at cifs-utils.git on git.samba.org
57 If cifs is built as a module, then the size and number of network buffers
58 and maximum number of simultaneous requests to one server can be configured.
59 Changing these from their defaults is not recommended. By executing modinfo
60 modinfo kernel/fs/cifs/cifs.ko
61 on kernel/fs/cifs/cifs.ko the list of configuration changes that can be made
62 at module initialization time (by running insmod cifs.ko) can be seen.
66 To improve security the SMB2.1 dialect or later (usually will get SMB3) is now
67 the new default. To use old dialects (e.g. to mount Windows XP) use "vers=1.0"
68 on mount (or vers=2.0 for Windows Vista). Note that the CIFS (vers=1.0) is
69 much older and less secure than the default dialect SMB3 which includes
70 many advanced security features such as downgrade attack detection
71 and encrypted shares and stronger signing and authentication algorithms.
72 There are additional mount options that may be helpful for SMB3 to get
73 improved POSIX behavior (NB: can use vers=3.0 to force only SMB3, never 2.1):
74 "mfsymlinks" and "cifsacl" and "idsfromsid"
78 To permit users to mount and unmount over directories they own is possible
79 with the cifs vfs. A way to enable such mounting is to mark the mount.cifs
80 utility as suid (e.g. "chmod +s /sbin/mount.cifs). To enable users to
81 umount shares they mount requires
82 1) mount.cifs version 1.4 or later
83 2) an entry for the share in /etc/fstab indicating that a user may
85 //server/usersharename /mnt/username cifs user 0 0
87 Note that when the mount.cifs utility is run suid (allowing user mounts),
88 in order to reduce risks, the "nosuid" mount flag is passed in on mount to
89 disallow execution of an suid program mounted on the remote target.
90 When mount is executed as root, nosuid is not passed in by default,
91 and execution of suid programs on the remote target would be enabled
92 by default. This can be changed, as with nfs and other filesystems,
93 by simply specifying "nosuid" among the mount options. For user mounts
94 though to be able to pass the suid flag to mount requires rebuilding
95 mount.cifs with the following flag: CIFS_ALLOW_USR_SUID
97 There is a corresponding manual page for cifs mounting in the Samba 3.0 and
98 later source tree in docs/manpages/mount.cifs.8
100 Allowing User Unmounts
101 ======================
102 To permit users to ummount directories that they have user mounted (see above),
103 the utility umount.cifs may be used. It may be invoked directly, or if
104 umount.cifs is placed in /sbin, umount can invoke the cifs umount helper
105 (at least for most versions of the umount utility) for umount of cifs
106 mounts, unless umount is invoked with -i (which will avoid invoking a umount
107 helper). As with mount.cifs, to enable user unmounts umount.cifs must be marked
108 as suid (e.g. "chmod +s /sbin/umount.cifs") or equivalent (some distributions
109 allow adding entries to a file to the /etc/permissions file to achieve the
110 equivalent suid effect). For this utility to succeed the target path
111 must be a cifs mount, and the uid of the current user must match the uid
112 of the user who mounted the resource.
114 Also note that the customary way of allowing user mounts and unmounts is
115 (instead of using mount.cifs and unmount.cifs as suid) to add a line
116 to the file /etc/fstab for each //server/share you wish to mount, but
117 this can become unwieldy when potential mount targets include many
118 or unpredictable UNC names.
122 To get the maximum benefit from the CIFS VFS, we recommend using a server that
123 supports the SNIA CIFS Unix Extensions standard (e.g. Samba 2.2.5 or later or
124 Samba 3.0) but the CIFS vfs works fine with a wide variety of CIFS servers.
125 Note that uid, gid and file permissions will display default values if you do
126 not have a server that supports the Unix extensions for CIFS (such as Samba
127 2.2.5 or later). To enable the Unix CIFS Extensions in the Samba server, add
130 unix extensions = yes
132 to your smb.conf file on the server. Note that the following smb.conf settings
133 are also useful (on the Samba server) when the majority of clients are Unix or
137 delete readonly = yes
140 Note that server ea support is required for supporting xattrs from the Linux
141 cifs client, and that EA support is present in later versions of Samba (e.g.
142 3.0.6 and later (also EA support works in all versions of Windows, at least to
143 shares on NTFS filesystems). Extended Attribute (xattr) support is an optional
144 feature of most Linux filesystems which may require enabling via
145 make menuconfig. Client support for extended attributes (user xattr) can be
146 disabled on a per-mount basis by specifying "nouser_xattr" on mount.
148 The CIFS client can get and set POSIX ACLs (getfacl, setfacl) to Samba servers
149 version 3.10 and later. Setting POSIX ACLs requires enabling both XATTR and
150 then POSIX support in the CIFS configuration options when building the cifs
151 module. POSIX ACL support can be disabled on a per mount basic by specifying
154 Some administrators may want to change Samba's smb.conf "map archive" and
155 "create mask" parameters from the default. Unless the create mask is changed
156 newly created files can end up with an unnecessarily restrictive default mode,
157 which may not be what you want, although if the CIFS Unix extensions are
158 enabled on the server and client, subsequent setattr calls (e.g. chmod) can
159 fix the mode. Note that creating special devices (mknod) remotely
160 may require specifying a mkdev function to Samba if you are not using
161 Samba 3.0.6 or later. For more information on these see the manual pages
162 ("man smb.conf") on the Samba server system. Note that the cifs vfs,
163 unlike the smbfs vfs, does not read the smb.conf on the client system
164 (the few optional settings are passed in on mount via -o parameters instead).
165 Note that Samba 2.2.7 or later includes a fix that allows the CIFS VFS to delete
166 open files (required for strict POSIX compliance). Windows Servers already
167 supported this feature. Samba server does not allow symlinks that refer to files
168 outside of the share, so in Samba versions prior to 3.0.6, most symlinks to
169 files with absolute paths (ie beginning with slash) such as:
171 would be forbidden. Samba 3.0.6 server or later includes the ability to create
172 such symlinks safely by converting unsafe symlinks (ie symlinks to server
173 files that are outside of the share) to a samba specific format on the server
174 that is ignored by local server applications and non-cifs clients and that will
175 not be traversed by the Samba server). This is opaque to the Linux client
176 application using the cifs vfs. Absolute symlinks will work to Samba 3.0.5 or
177 later, but only for remote clients using the CIFS Unix extensions, and will
178 be invisbile to Windows clients and typically will not affect local
179 applications running on the same server as Samba.
183 Once the CIFS VFS support is built into the kernel or installed as a module
184 (cifs.ko), you can use mount syntax like the following to access Samba or
185 Mac or Windows servers:
187 mount -t cifs //9.53.216.11/e$ /mnt -o username=myname,password=mypassword
189 Before -o the option -v may be specified to make the mount.cifs
190 mount helper display the mount steps more verbosely.
191 After -o the following commonly used cifs vfs specific options
198 Other cifs mount options are described below. Use of TCP names (in addition to
199 ip addresses) is available if the mount helper (mount.cifs) is installed. If
200 you do not trust the server to which are mounted, or if you do not have
201 cifs signing enabled (and the physical network is insecure), consider use
202 of the standard mount options "noexec" and "nosuid" to reduce the risk of
203 running an altered binary on your local system (downloaded from a hostile server
204 or altered by a hostile router).
206 Although mounting using format corresponding to the CIFS URL specification is
207 not possible in mount.cifs yet, it is possible to use an alternate format
208 for the server and sharename (which is somewhat similar to NFS style mount
209 syntax) instead of the more widely used UNC format (i.e. \\server\share):
210 mount -t cifs tcp_name_of_server:share_name /mnt -o user=myname,pass=mypasswd
212 When using the mount helper mount.cifs, passwords may be specified via alternate
213 mechanisms, instead of specifying it after -o using the normal "pass=" syntax
215 1) By including it in a credential file. Specify credentials=filename as one
216 of the mount options. Credential files contain two lines
218 password=your_password
219 2) By specifying the password in the PASSWD environment variable (similarly
220 the user name can be taken from the USER environment variable).
221 3) By specifying the password in a file by name via PASSWD_FILE
222 4) By specifying the password in a file by file descriptor via PASSWD_FD
224 If no password is provided, mount.cifs will prompt for password entry
228 Servers must support either "pure-TCP" (port 445 TCP/IP CIFS connections) or RFC
229 1001/1002 support for "Netbios-Over-TCP/IP." This is not likely to be a
230 problem as most servers support this.
232 Valid filenames differ between Windows and Linux. Windows typically restricts
233 filenames which contain certain reserved characters (e.g.the character :
234 which is used to delimit the beginning of a stream name by Windows), while
235 Linux allows a slightly wider set of valid characters in filenames. Windows
236 servers can remap such characters when an explicit mapping is specified in
237 the Server's registry. Samba starting with version 3.10 will allow such
238 filenames (ie those which contain valid Linux characters, which normally
239 would be forbidden for Windows/CIFS semantics) as long as the server is
240 configured for Unix Extensions (and the client has not disabled
241 /proc/fs/cifs/LinuxExtensionsEnabled). In addition the mount option
242 "mapposix" can be used on CIFS (vers=1.0) to force the mapping of
243 illegal Windows/NTFS/SMB characters to a remap range (this mount parm
244 is the default for SMB3). This remap ("mapposix") range is also
245 compatible with Mac (and "Services for Mac" on some older Windows).
247 CIFS VFS Mount Options
248 ======================
249 A partial list of the supported mount options follows:
250 username The user name to use when trying to establish
252 password The user password. If the mount helper is
253 installed, the user will be prompted for password
255 ip The ip address of the target server
256 unc The target server Universal Network Name (export) to
258 domain Set the SMB/CIFS workgroup name prepended to the
259 username during CIFS session establishment
260 forceuid Set the default uid for inodes to the uid
261 passed in on mount. For mounts to servers
262 which do support the CIFS Unix extensions, such as a
263 properly configured Samba server, the server provides
264 the uid, gid and mode so this parameter should not be
265 specified unless the server and clients uid and gid
266 numbering differ. If the server and client are in the
267 same domain (e.g. running winbind or nss_ldap) and
268 the server supports the Unix Extensions then the uid
269 and gid can be retrieved from the server (and uid
270 and gid would not have to be specified on the mount.
271 For servers which do not support the CIFS Unix
272 extensions, the default uid (and gid) returned on lookup
273 of existing files will be the uid (gid) of the person
274 who executed the mount (root, except when mount.cifs
275 is configured setuid for user mounts) unless the "uid="
276 (gid) mount option is specified. Also note that permission
277 checks (authorization checks) on accesses to a file occur
278 at the server, but there are cases in which an administrator
279 may want to restrict at the client as well. For those
280 servers which do not report a uid/gid owner
281 (such as Windows), permissions can also be checked at the
282 client, and a crude form of client side permission checking
283 can be enabled by specifying file_mode and dir_mode on
284 the client. (default)
285 forcegid (similar to above but for the groupid instead of uid) (default)
286 noforceuid Fill in file owner information (uid) by requesting it from
287 the server if possible. With this option, the value given in
288 the uid= option (on mount) will only be used if the server
289 can not support returning uids on inodes.
290 noforcegid (similar to above but for the group owner, gid, instead of uid)
291 uid Set the default uid for inodes, and indicate to the
292 cifs kernel driver which local user mounted. If the server
293 supports the unix extensions the default uid is
294 not used to fill in the owner fields of inodes (files)
295 unless the "forceuid" parameter is specified.
296 gid Set the default gid for inodes (similar to above).
297 file_mode If CIFS Unix extensions are not supported by the server
298 this overrides the default mode for file inodes.
299 fsc Enable local disk caching using FS-Cache (off by default). This
300 option could be useful to improve performance on a slow link,
301 heavily loaded server and/or network where reading from the
302 disk is faster than reading from the server (over the network).
303 This could also impact scalability positively as the
304 number of calls to the server are reduced. However, local
305 caching is not suitable for all workloads for e.g. read-once
306 type workloads. So, you need to consider carefully your
307 workload/scenario before using this option. Currently, local
308 disk caching is functional for CIFS files opened as read-only.
309 dir_mode If CIFS Unix extensions are not supported by the server
310 this overrides the default mode for directory inodes.
311 port attempt to contact the server on this tcp port, before
312 trying the usual ports (port 445, then 139).
313 iocharset Codepage used to convert local path names to and from
314 Unicode. Unicode is used by default for network path
315 names if the server supports it. If iocharset is
316 not specified then the nls_default specified
317 during the local client kernel build will be used.
318 If server does not support Unicode, this parameter is
320 rsize default read size (usually 16K). The client currently
321 can not use rsize larger than CIFSMaxBufSize. CIFSMaxBufSize
322 defaults to 16K and may be changed (from 8K to the maximum
323 kmalloc size allowed by your kernel) at module install time
324 for cifs.ko. Setting CIFSMaxBufSize to a very large value
325 will cause cifs to use more memory and may reduce performance
326 in some cases. To use rsize greater than 127K (the original
327 cifs protocol maximum) also requires that the server support
328 a new Unix Capability flag (for very large read) which some
329 newer servers (e.g. Samba 3.0.26 or later) do. rsize can be
330 set from a minimum of 2048 to a maximum of 130048 (127K or
331 CIFSMaxBufSize, whichever is smaller)
332 wsize default write size (default 57344)
333 maximum wsize currently allowed by CIFS is 57344 (fourteen
335 actimeo=n attribute cache timeout in seconds (default 1 second).
336 After this timeout, the cifs client requests fresh attribute
337 information from the server. This option allows to tune the
338 attribute cache timeout to suit the workload needs. Shorter
339 timeouts mean better the cache coherency, but increased number
340 of calls to the server. Longer timeouts mean reduced number
341 of calls to the server at the expense of less stricter cache
342 coherency checks (i.e. incorrect attribute cache for a short
344 rw mount the network share read-write (note that the
345 server may still consider the share read-only)
346 ro mount network share read-only
347 version used to distinguish different versions of the
348 mount helper utility (not typically needed)
349 sep if first mount option (after the -o), overrides
350 the comma as the separator between the mount
352 -o user=myname,password=mypassword,domain=mydom
353 could be passed instead with period as the separator by
354 -o sep=.user=myname.password=mypassword.domain=mydom
355 this might be useful when comma is contained within username
356 or password or domain. This option is less important
357 when the cifs mount helper cifs.mount (version 1.1 or later)
359 nosuid Do not allow remote executables with the suid bit
360 program to be executed. This is only meaningful for mounts
361 to servers such as Samba which support the CIFS Unix Extensions.
362 If you do not trust the servers in your network (your mount
363 targets) it is recommended that you specify this option for
365 exec Permit execution of binaries on the mount.
366 noexec Do not permit execution of binaries on the mount.
367 dev Recognize block devices on the remote mount.
368 nodev Do not recognize devices on the remote mount.
369 suid Allow remote files on this mountpoint with suid enabled to
370 be executed (default for mounts when executed as root,
371 nosuid is default for user mounts).
372 credentials Although ignored by the cifs kernel component, it is used by
373 the mount helper, mount.cifs. When mount.cifs is installed it
374 opens and reads the credential file specified in order
375 to obtain the userid and password arguments which are passed to
377 guest Although ignored by the kernel component, the mount.cifs
378 mount helper will not prompt the user for a password
379 if guest is specified on the mount options. If no
380 password is specified a null password will be used.
381 perm Client does permission checks (vfs_permission check of uid
382 and gid of the file against the mode and desired operation),
383 Note that this is in addition to the normal ACL check on the
384 target machine done by the server software.
385 Client permission checking is enabled by default.
386 noperm Client does not do permission checks. This can expose
387 files on this mount to access by other users on the local
388 client system. It is typically only needed when the server
389 supports the CIFS Unix Extensions but the UIDs/GIDs on the
390 client and server system do not match closely enough to allow
391 access by the user doing the mount, but it may be useful with
392 non CIFS Unix Extension mounts for cases in which the default
393 mode is specified on the mount but is not to be enforced on the
394 client (e.g. perhaps when MultiUserMount is enabled)
395 Note that this does not affect the normal ACL check on the
396 target machine done by the server software (of the server
397 ACL against the user name provided at mount time).
398 serverino Use server's inode numbers instead of generating automatically
399 incrementing inode numbers on the client. Although this will
400 make it easier to spot hardlinked files (as they will have
401 the same inode numbers) and inode numbers may be persistent,
402 note that the server does not guarantee that the inode numbers
403 are unique if multiple server side mounts are exported under a
404 single share (since inode numbers on the servers might not
405 be unique if multiple filesystems are mounted under the same
406 shared higher level directory). Note that some older
407 (e.g. pre-Windows 2000) do not support returning UniqueIDs
408 or the CIFS Unix Extensions equivalent and for those
409 this mount option will have no effect. Exporting cifs mounts
410 under nfsd requires this mount option on the cifs mount.
411 This is now the default if server supports the
412 required network operation.
413 noserverino Client generates inode numbers (rather than using the actual one
414 from the server). These inode numbers will vary after
415 unmount or reboot which can confuse some applications,
416 but not all server filesystems support unique inode
418 setuids If the CIFS Unix extensions are negotiated with the server
419 the client will attempt to set the effective uid and gid of
420 the local process on newly created files, directories, and
421 devices (create, mkdir, mknod). If the CIFS Unix Extensions
422 are not negotiated, for newly created files and directories
423 instead of using the default uid and gid specified on
424 the mount, cache the new file's uid and gid locally which means
425 that the uid for the file can change when the inode is
426 reloaded (or the user remounts the share).
427 nosetuids The client will not attempt to set the uid and gid on
428 on newly created files, directories, and devices (create,
429 mkdir, mknod) which will result in the server setting the
430 uid and gid to the default (usually the server uid of the
431 user who mounted the share). Letting the server (rather than
432 the client) set the uid and gid is the default. If the CIFS
433 Unix Extensions are not negotiated then the uid and gid for
434 new files will appear to be the uid (gid) of the mounter or the
435 uid (gid) parameter specified on the mount.
436 netbiosname When mounting to servers via port 139, specifies the RFC1001
437 source name to use to represent the client netbios machine
438 name when doing the RFC1001 netbios session initialize.
439 direct Do not do inode data caching on files opened on this mount.
440 This precludes mmapping files on this mount. In some cases
441 with fast networks and little or no caching benefits on the
442 client (e.g. when the application is doing large sequential
443 reads bigger than page size without rereading the same data)
444 this can provide better performance than the default
445 behavior which caches reads (readahead) and writes
446 (writebehind) through the local Linux client pagecache
447 if oplock (caching token) is granted and held. Note that
448 direct allows write operations larger than page size
449 to be sent to the server.
450 strictcache Use for switching on strict cache mode. In this mode the
451 client read from the cache all the time it has Oplock Level II,
452 otherwise - read from the server. All written data are stored
453 in the cache, but if the client doesn't have Exclusive Oplock,
454 it writes the data to the server.
455 rwpidforward Forward pid of a process who opened a file to any read or write
456 operation on that file. This prevent applications like WINE
457 from failing on read and write if we use mandatory brlock style.
458 acl Allow setfacl and getfacl to manage posix ACLs if server
459 supports them. (default)
460 noacl Do not allow setfacl and getfacl calls on this mount
461 user_xattr Allow getting and setting user xattrs (those attributes whose
462 name begins with "user." or "os2.") as OS/2 EAs (extended
463 attributes) to the server. This allows support of the
464 setfattr and getfattr utilities. (default)
465 nouser_xattr Do not allow getfattr/setfattr to get/set/list xattrs
466 mapchars Translate six of the seven reserved characters (not backslash)
468 to the remap range (above 0xF000), which also
469 allows the CIFS client to recognize files created with
470 such characters by Windows's POSIX emulation. This can
471 also be useful when mounting to most versions of Samba
472 (which also forbids creating and opening files
473 whose names contain any of these seven characters).
474 This has no effect if the server does not support
476 nomapchars Do not translate any of these seven characters (default).
477 nocase Request case insensitive path name matching (case
478 sensitive is the default if the server supports it).
479 (mount option "ignorecase" is identical to "nocase")
480 posixpaths If CIFS Unix extensions are supported, attempt to
481 negotiate posix path name support which allows certain
482 characters forbidden in typical CIFS filenames, without
483 requiring remapping. (default)
484 noposixpaths If CIFS Unix extensions are supported, do not request
485 posix path name support (this may cause servers to
486 reject creatingfile with certain reserved characters).
487 nounix Disable the CIFS Unix Extensions for this mount (tree
488 connection). This is rarely needed, but it may be useful
489 in order to turn off multiple settings all at once (ie
490 posix acls, posix locks, posix paths, symlink support
491 and retrieving uids/gids/mode from the server) or to
492 work around a bug in server which implement the Unix
494 nobrl Do not send byte range lock requests to the server.
495 This is necessary for certain applications that break
496 with cifs style mandatory byte range locks (and most
497 cifs servers do not yet support requesting advisory
499 forcemandatorylock Even if the server supports posix (advisory) byte range
500 locking, send only mandatory lock requests. For some
501 (presumably rare) applications, originally coded for
502 DOS/Windows, which require Windows style mandatory byte range
503 locking, they may be able to take advantage of this option,
504 forcing the cifs client to only send mandatory locks
505 even if the cifs server would support posix advisory locks.
506 "forcemand" is accepted as a shorter form of this mount
508 nostrictsync If this mount option is set, when an application does an
509 fsync call then the cifs client does not send an SMB Flush
510 to the server (to force the server to write all dirty data
511 for this file immediately to disk), although cifs still sends
512 all dirty (cached) file data to the server and waits for the
513 server to respond to the write. Since SMB Flush can be
514 very slow, and some servers may be reliable enough (to risk
515 delaying slightly flushing the data to disk on the server),
516 turning on this option may be useful to improve performance for
517 applications that fsync too much, at a small risk of server
518 crash. If this mount option is not set, by default cifs will
519 send an SMB flush request (and wait for a response) on every
521 nodfs Disable DFS (global name space support) even if the
522 server claims to support it. This can help work around
523 a problem with parsing of DFS paths with Samba server
524 versions 3.0.24 and 3.0.25.
525 remount remount the share (often used to change from ro to rw mounts
527 cifsacl Report mode bits (e.g. on stat) based on the Windows ACL for
528 the file. (EXPERIMENTAL)
529 servern Specify the server 's netbios name (RFC1001 name) to use
530 when attempting to setup a session to the server.
531 This is needed for mounting to some older servers (such
532 as OS/2 or Windows 98 and Windows ME) since they do not
533 support a default server name. A server name can be up
534 to 15 characters long and is usually uppercased.
535 sfu When the CIFS Unix Extensions are not negotiated, attempt to
536 create device files and fifos in a format compatible with
537 Services for Unix (SFU). In addition retrieve bits 10-12
538 of the mode via the SETFILEBITS extended attribute (as
539 SFU does). In the future the bottom 9 bits of the
540 mode also will be emulated using queries of the security
542 mfsymlinks Enable support for Minshall+French symlinks
543 (see http://wiki.samba.org/index.php/UNIX_Extensions#Minshall.2BFrench_symlinks)
544 This option is ignored when specified together with the
545 'sfu' option. Minshall+French symlinks are used even if
546 the server supports the CIFS Unix Extensions.
547 sign Must use packet signing (helps avoid unwanted data modification
548 by intermediate systems in the route). Note that signing
549 does not work with lanman or plaintext authentication.
550 seal Must seal (encrypt) all data on this mounted share before
551 sending on the network. Requires support for Unix Extensions.
552 Note that this differs from the sign mount option in that it
553 causes encryption of data sent over this mounted share but other
554 shares mounted to the same server are unaffected.
555 locallease This option is rarely needed. Fcntl F_SETLEASE is
556 used by some applications such as Samba and NFSv4 server to
557 check to see whether a file is cacheable. CIFS has no way
558 to explicitly request a lease, but can check whether a file
559 is cacheable (oplocked). Unfortunately, even if a file
560 is not oplocked, it could still be cacheable (ie cifs client
561 could grant fcntl leases if no other local processes are using
562 the file) for cases for example such as when the server does not
563 support oplocks and the user is sure that the only updates to
564 the file will be from this client. Specifying this mount option
565 will allow the cifs client to check for leases (only) locally
566 for files which are not oplocked instead of denying leases
567 in that case. (EXPERIMENTAL)
568 sec Security mode. Allowed values are:
569 none attempt to connection as a null user (no name)
570 krb5 Use Kerberos version 5 authentication
571 krb5i Use Kerberos authentication and packet signing
572 ntlm Use NTLM password hashing (default)
573 ntlmi Use NTLM password hashing with signing (if
574 /proc/fs/cifs/PacketSigningEnabled on or if
575 server requires signing also can be the default)
576 ntlmv2 Use NTLMv2 password hashing
577 ntlmv2i Use NTLMv2 password hashing with packet signing
578 lanman (if configured in kernel config) use older
580 hard Retry file operations if server is not responding
581 soft Limit retries to unresponsive servers (usually only
582 one retry) before returning an error. (default)
584 The mount.cifs mount helper also accepts a few mount options before -o
587 -S take password from stdin (equivalent to setting the environment
588 variable "PASSWD_FD=0"
589 -V print mount.cifs version
590 -? display simple usage information
592 With most 2.6 kernel versions of modutils, the version of the cifs kernel
593 module can be displayed via modinfo.
595 Misc /proc/fs/cifs Flags and Debug Info
596 =======================================
597 Informational pseudo-files:
598 DebugData Displays information about active CIFS sessions and
599 shares, features enabled as well as the cifs.ko
601 Stats Lists summary resource usage information as well as per
602 share statistics, if CONFIG_CIFS_STATS in enabled
603 in the kernel configuration.
605 Configuration pseudo-files:
606 PacketSigningEnabled If set to one, cifs packet signing is enabled
607 and will be used if the server requires
608 it. If set to two, cifs packet signing is
609 required even if the server considers packet
610 signing optional. (default 1)
611 SecurityFlags Flags which control security negotiation and
612 also packet signing. Authentication (may/must)
613 flags (e.g. for NTLM and/or NTLMv2) may be combined with
614 the signing flags. Specifying two different password
615 hashing mechanisms (as "must use") on the other hand
616 does not make much sense. Default flags are
618 (NTLM, NTLMv2 and packet signing allowed). The maximum
619 allowable flags if you want to allow mounts to servers
620 using weaker password hashes is 0x37037 (lanman,
621 plaintext, ntlm, ntlmv2, signing allowed). Some
622 SecurityFlags require the corresponding menuconfig
623 options to be enabled (lanman and plaintext require
624 CONFIG_CIFS_WEAK_PW_HASH for example). Enabling
625 plaintext authentication currently requires also
626 enabling lanman authentication in the security flags
627 because the cifs module only supports sending
628 laintext passwords using the older lanman dialect
629 form of the session setup SMB. (e.g. for authentication
630 using plain text passwords, set the SecurityFlags
633 may use packet signing 0x00001
634 must use packet signing 0x01001
635 may use NTLM (most common password hash) 0x00002
636 must use NTLM 0x02002
637 may use NTLMv2 0x00004
638 must use NTLMv2 0x04004
639 may use Kerberos security 0x00008
640 must use Kerberos 0x08008
641 may use lanman (weak) password hash 0x00010
642 must use lanman password hash 0x10010
643 may use plaintext passwords 0x00020
644 must use plaintext passwords 0x20020
645 (reserved for future packet encryption) 0x00040
647 cifsFYI If set to non-zero value, additional debug information
648 will be logged to the system error log. This field
649 contains three flags controlling different classes of
650 debugging entries. The maximum value it can be set
651 to is 7 which enables all debugging points (default 0).
652 Some debugging statements are not compiled into the
653 cifs kernel unless CONFIG_CIFS_DEBUG2 is enabled in the
654 kernel configuration. cifsFYI may be set to one or
655 nore of the following flags (7 sets them all):
657 log cifs informational messages 0x01
658 log return codes from cifs entry points 0x02
659 log slow responses (ie which take longer than 1 second)
660 CONFIG_CIFS_STATS2 must be enabled in .config 0x04
663 traceSMB If set to one, debug information is logged to the
664 system error log with the start of smb requests
665 and responses (default 0)
666 LookupCacheEnable If set to one, inode information is kept cached
667 for one second improving performance of lookups
669 OplockEnabled If set to one, safe distributed caching enabled.
671 LinuxExtensionsEnabled If set to one then the client will attempt to
672 use the CIFS "UNIX" extensions which are optional
673 protocol enhancements that allow CIFS servers
674 to return accurate UID/GID information as well
675 as support symbolic links. If you use servers
676 such as Samba that support the CIFS Unix
677 extensions but do not want to use symbolic link
678 support and want to map the uid and gid fields
679 to values supplied at mount (rather than the
680 actual values, then set this to zero. (default 1)
682 These experimental features and tracing can be enabled by changing flags in
683 /proc/fs/cifs (after the cifs module has been installed or built into the
684 kernel, e.g. insmod cifs). To enable a feature set it to 1 e.g. to enable
685 tracing to the kernel message log type:
687 echo 7 > /proc/fs/cifs/cifsFYI
689 cifsFYI functions as a bit mask. Setting it to 1 enables additional kernel
690 logging of various informational messages. 2 enables logging of non-zero
691 SMB return codes while 4 enables logging of requests that take longer
692 than one second to complete (except for byte range lock requests).
693 Setting it to 4 requires defining CONFIG_CIFS_STATS2 manually in the
694 source code (typically by setting it in the beginning of cifsglob.h),
695 and setting it to seven enables all three. Finally, tracing
696 the start of smb requests and responses can be enabled via:
698 echo 1 > /proc/fs/cifs/traceSMB
700 Per share (per client mount) statistics are available in /proc/fs/cifs/Stats
701 if the kernel was configured with cifs statistics enabled. The statistics
702 represent the number of successful (ie non-zero return code from the server)
703 SMB responses to some of the more common commands (open, delete, mkdir etc.).
704 Also recorded is the total bytes read and bytes written to the server for
705 that share. Note that due to client caching effects this can be less than the
706 number of bytes read and written by the application running on the client.
707 The statistics for the number of total SMBs and oplock breaks are different in
708 that they represent all for that share, not just those for which the server
711 Also note that "cat /proc/fs/cifs/DebugData" will display information about
712 the active sessions and the shares that are mounted.
714 Enabling Kerberos (extended security) works but requires version 1.2 or later
715 of the helper program cifs.upcall to be present and to be configured in the
716 /etc/request-key.conf file. The cifs.upcall helper program is from the Samba
717 project(http://www.samba.org). NTLM and NTLMv2 and LANMAN support do not
718 require this helper. Note that NTLMv2 security (which does not require the
719 cifs.upcall helper program), instead of using Kerberos, is sufficient for
722 DFS support allows transparent redirection to shares in an MS-DFS name space.
723 In addition, DFS support for target shares which are specified as UNC
724 names which begin with host names (rather than IP addresses) requires
725 a user space helper (such as cifs.upcall) to be present in order to
726 translate host names to ip address, and the user space helper must also
727 be configured in the file /etc/request-key.conf. Samba, Windows servers and
728 many NAS appliances support DFS as a way of constructing a global name
729 space to ease network configuration and improve reliability.
731 To use cifs Kerberos and DFS support, the Linux keyutils package should be
732 installed and something like the following lines should be added to the
733 /etc/request-key.conf file:
735 create cifs.spnego * * /usr/local/sbin/cifs.upcall %k
736 create dns_resolver * * /usr/local/sbin/cifs.upcall %k
738 CIFS kernel module parameters
739 =============================
740 These module parameters can be specified or modified either during the time of
741 module loading or during the runtime by using the interface
742 /proc/module/cifs/parameters/<param>
744 i.e. echo "value" > /sys/module/cifs/parameters/<param>
746 1. enable_oplocks - Enable or disable oplocks. Oplocks are enabled by default.
747 [Y/y/1]. To disable use any of [N/n/0].
projects / mirror_ubuntu-bionic-kernel.git / blob