1 The CIFS VFS support for Linux supports many advanced network filesystem
2 features such as heirarchical 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
8 For questions or bug reports please contact:
9 sfrench@samba.org (sfrench@us.ibm.com)
14 1) Get the kernel source (e.g.from http://www.kernel.org)
15 and download the cifs vfs source (see the project page
16 at http://us1.samba.org/samba/Linux_CIFS_client.html)
17 and change directory into the top of the kernel directory
18 then patch the kernel (e.g. "patch -p1 < cifs_24.patch")
19 to add the cifs vfs to your kernel configure options if
20 it has not already been added (e.g. current SuSE and UL
21 users do not need to apply the cifs_24.patch since the cifs vfs is
22 already in the kernel configure menu) and then
23 mkdir linux/fs/cifs and then copy the current cifs vfs files from
24 the cifs download to your kernel build directory e.g.
26 cp <cifs_download_dir>/fs/cifs/* to <kernel_download_dir>/fs/cifs
28 2) make menuconfig (or make xconfig)
29 3) select cifs from within the network filesystem choices
32 6) make modules (or "make" if CIFS VFS not to be built as a module)
35 1) Download the kernel (e.g. from http://www.kernel.org or from bitkeeper
36 at bk://linux.bkbits.net/linux-2.5) and change directory into the top
37 of the kernel directory tree (e.g. /usr/src/linux-2.5.73)
38 2) make menuconfig (or make xconfig)
39 3) select cifs from within the network filesystem choices
44 Installation instructions:
45 =========================
46 If you have built the CIFS vfs as module (successfully) simply
47 type "make modules_install" (or if you prefer, manually copy the file to
48 the modules directory e.g. /lib/modules/2.4.10-4GB/kernel/fs/cifs/cifs.o).
50 If you have built the CIFS vfs into the kernel itself, follow the instructions
51 for your distribution on how to install a new kernel (usually you
52 would simply type "make install").
54 If you do not have the utility mount.cifs (in the Samba 3.0 source tree and on
55 the CIFS VFS web site) copy it to the same directory in which mount.smbfs and
56 similar files reside (usually /sbin). Although the helper software is not
57 required, mount.cifs is recommended. Eventually the Samba 3.0 utility program
58 "net" may also be helpful since it may someday provide easier mount syntax for
59 users who are used to Windows e.g. net use <mount point> <UNC name or cifs URL>
60 Note that running the Winbind pam/nss module (logon service) on all of your
61 Linux clients is useful in mapping Uids and Gids consistently across the
62 domain to the proper network user. The mount.cifs mount helper can be
63 trivially built from Samba 3.0 or later source e.g. by executing:
65 gcc samba/source/client/mount.cifs.c -o mount.cifs
67 If cifs is built as a module, then the size and number of network buffers
68 and maximum number of simultaneous requests to one server can be configured.
69 Changing these from their defaults is not recommended. By executing modinfo
70 modinfo kernel/fs/cifs/cifs.ko
71 on kernel/fs/cifs/cifs.ko the list of configuration changes that can be made
72 at module initialization time (by running insmod cifs.ko) can be seen.
76 To permit users to mount and unmount over directories they own is possible
77 with the cifs vfs. A way to enable such mounting is to mark the mount.cifs
78 utility as suid (e.g. "chmod +s /sbin/mount/cifs). To enable users to
79 umount shares they mount requires
80 1) mount.cifs version 1.4 or later
81 2) an entry for the share in /etc/fstab indicating that a user may
83 //server/usersharename /mnt/username cifs user 0 0
85 Note that when the mount.cifs utility is run suid (allowing user mounts),
86 in order to reduce risks, the "nosuid" mount flag is passed in on mount to
87 disallow execution of an suid program mounted on the remote target.
88 When mount is executed as root, nosuid is not passed in by default,
89 and execution of suid programs on the remote target would be enabled
90 by default. This can be changed, as with nfs and other filesystems,
91 by simply specifying "nosuid" among the mount options. For user mounts
92 though to be able to pass the suid flag to mount requires rebuilding
93 mount.cifs with the following flag:
95 gcc samba/source/client/mount.cifs.c -DCIFS_ALLOW_USR_SUID -o mount.cifs
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
102 To get the maximum benefit from the CIFS VFS, we recommend using a server that
103 supports the SNIA CIFS Unix Extensions standard (e.g. Samba 2.2.5 or later or
104 Samba 3.0) but the CIFS vfs works fine with a wide variety of CIFS servers.
105 Note that uid, gid and file permissions will display default values if you do
106 not have a server that supports the Unix extensions for CIFS (such as Samba
107 2.2.5 or later). To enable the Unix CIFS Extensions in the Samba server, add
110 unix extensions = yes
112 to your smb.conf file on the server. Note that the following smb.conf settings
113 are also useful (on the Samba server) when the majority of clients are Unix or
117 delete readonly = yes
120 Note that server ea support is required for supporting xattrs from the Linux
121 cifs client, and that EA support is present in later versions of Samba (e.g.
122 3.0.6 and later (also EA support works in all versions of Windows, at least to
123 shares on NTFS filesystems). Extended Attribute (xattr) support is an optional
124 feature of most Linux filesystems which may require enabling via
127 The CIFS client can get and set POSIX ACLs (getfacl, setfacl) to Samba servers
128 version 3.10 and later. Setting POSIX ACLs requires enabling both XATTR and
129 then POSIX support in the CIFS configuration options when building the cifs
132 Some administrators may want to change Samba's smb.conf "map archive" and
133 "create mask" parameters from the default. Unless the create mask is changed
134 newly created files can end up with an unnecessarily restrictive default mode,
135 which may not be what you want, although if the CIFS Unix extensions are
136 enabled on the server and client, subsequent setattr calls (e.g. chmod) can
137 fix the mode. Note that creating special devices (mknod) remotely
138 may require specifying a mkdev function to Samba if you are not using
139 Samba 3.0.6 or later. For more information on these see the manual pages
140 ("man smb.conf") on the Samba server system. Note that the cifs vfs,
141 unlike the smbfs vfs, does not read the smb.conf on the client system
142 (the few optional settings are passed in on mount via -o parameters instead).
143 Note that Samba 2.2.7 or later includes a fix that allows the CIFS VFS to delete
144 open files (required for strict POSIX compliance). Windows Servers already
145 supported this feature. Samba server does not allow symlinks that refer to files
146 outside of the share, so in Samba versions prior to 3.0.6, most symlinks to
147 files with absolute paths (ie beginning with slash) such as:
149 would be forbidden. Samba 3.0.6 server or later includes the ability to create
150 such symlinks safely by converting unsafe symlinks (ie symlinks to server
151 files that are outside of the share) to a samba specific format on the server
152 that is ignored by local server applications and non-cifs clients and that will
153 not be traversed by the Samba server). This is opaque to the Linux client
154 application using the cifs vfs. Absolute symlinks will work to Samba 3.0.5 or
155 later, but only for remote clients using the CIFS Unix extensions, and will
156 be invisbile to Windows clients and typically will not affect local
157 applications running on the same server as Samba.
161 Once the CIFS VFS support is built into the kernel or installed as a module
162 (cifs.o), you can use mount syntax like the following to access Samba or Windows
165 mount -t cifs //9.53.216.11/e$ /mnt -o user=myname,pass=mypassword
167 Before -o the option -v may be specified to make the mount.cifs
168 mount helper display the mount steps more verbosely.
169 After -o the following commonly used cifs vfs specific options
176 Other cifs mount options are described below. Use of TCP names (in addition to
177 ip addresses) is available if the mount helper (mount.cifs) is installed. If
178 you do not trust the server to which are mounted, or if you do not have
179 cifs signing enabled (and the physical network is insecure), consider use
180 of the standard mount options "noexec" and "nosuid" to reduce the risk of
181 running an altered binary on your local system (downloaded from a hostile server
182 or altered by a hostile router).
184 Although mounting using format corresponding to the CIFS URL specification is
185 not possible in mount.cifs yet, it is possible to use an alternate format
186 for the server and sharename (which is somewhat similar to NFS style mount
187 syntax) instead of the more widely used UNC format (i.e. \\server\share):
188 mount -t cifs tcp_name_of_server:share_name /mnt -o user=myname,pass=mypasswd
190 When using the mount helper mount.cifs, passwords may be specified via alternate
191 mechanisms, instead of specifying it after -o using the normal "pass=" syntax
193 1) By including it in a credential file. Specify credentials=filename as one
194 of the mount options. Credential files contain two lines
196 password=your_password
197 2) By specifying the password in the PASSWD environment variable (similarly
198 the user name can be taken from the USER environment variable).
199 3) By specifying the password in a file by name via PASSWD_FILE
200 4) By specifying the password in a file by file descriptor via PASSWD_FD
202 If no password is provided, mount.cifs will prompt for password entry
206 Servers must support the NTLM SMB dialect (which is the most recent, supported
207 by Samba and Windows NT version 4, 2000 and XP and many other SMB/CIFS servers)
208 Servers must support either "pure-TCP" (port 445 TCP/IP CIFS connections) or RFC
209 1001/1002 support for "Netbios-Over-TCP/IP." Neither of these is likely to be a
210 problem as most servers support this. IPv6 support is planned for the future,
211 and is almost complete.
213 Valid filenames differ between Windows and Linux. Windows typically restricts
214 filenames which contain certain reserved characters (e.g.the character :
215 which is used to delimit the beginning of a stream name by Windows), while
216 Linux allows a slightly wider set of valid characters in filenames. Windows
217 servers can remap such characters when an explicit mapping is specified in
218 the Server's registry. Samba starting with version 3.10 will allow such
219 filenames (ie those which contain valid Linux characters, which normally
220 would be forbidden for Windows/CIFS semantics) as long as the server is
221 configured for Unix Extensions (and the client has not disabled
222 /proc/fs/cifs/LinuxExtensionsEnabled).
225 CIFS VFS Mount Options
226 ======================
227 A partial list of the supported mount options follows:
228 user The user name to use when trying to establish
230 password The user password. If the mount helper is
231 installed, the user will be prompted for password
232 if it is not supplied.
233 ip The ip address of the target server
234 unc The target server Universal Network Name (export) to
236 domain Set the SMB/CIFS workgroup name prepended to the
237 username during CIFS session establishment
238 uid If CIFS Unix extensions are not supported by the server
239 this overrides the default uid for inodes. For mounts to
240 servers which do support the CIFS Unix extensions, such
241 as a properly configured Samba server, the server provides
242 the uid, gid and mode. For servers which do not support
243 the Unix extensions, the default uid (and gid) returned on
244 lookup of existing files is the uid (gid) of the person
245 who executed the mount (root, except when mount.cifs
246 is configured setuid for user mounts) unless the "uid="
247 (gid) mount option is specified. For the uid (gid) of newly
248 created files and directories, ie files created since
249 the last mount of the server share, the expected uid
250 (gid) is cached as as long as the inode remains in
251 memory on the client. Also note that permission
252 checks (authorization checks) on accesses to a file occur
253 at the server, but there are cases in which an administrator
254 may want to restrict at the client as well. For those
255 servers which do not report a uid/gid owner
256 (such as Windows), permissions can also be checked at the
257 client, and a crude form of client side permission checking
258 can be enabled by specifying file_mode and dir_mode on
260 gid If CIFS Unix extensions are not supported by the server
261 this overrides the default gid for inodes.
262 file_mode If CIFS Unix extensions are not supported by the server
263 this overrides the default mode for file inodes.
264 dir_mode If CIFS Unix extensions are not supported by the server
265 this overrides the default mode for directory inodes.
266 port attempt to contact the server on this tcp port, before
267 trying the usual ports (port 445, then 139).
268 iocharset Codepage used to convert local path names to and from
269 Unicode. Unicode is used by default for network path
270 names if the server supports it. If iocharset is
271 not specified then the nls_default specified
272 during the local client kernel build will be used.
273 If server does not support Unicode, this parameter is
275 rsize default read size
276 wsize default write size
277 rw mount the network share read-write (note that the
278 server may still consider the share read-only)
279 ro mount network share read-only
280 version used to distinguish different versions of the
281 mount helper utility (not typically needed)
282 sep if first mount option (after the -o), overrides
283 the comma as the separator between the mount
285 -o user=myname,password=mypassword,domain=mydom
286 could be passed instead with period as the separator by
287 -o sep=.user=myname.password=mypassword.domain=mydom
288 this might be useful when comma is contained within username
289 or password or domain. This option is less important
290 when the cifs mount helper cifs.mount (version 1.1 or later)
292 nosuid Do not allow remote executables with the suid bit
293 program to be executed. This is only meaningful for mounts
294 to servers such as Samba which support the CIFS Unix Extensions.
295 If you do not trust the servers in your network (your mount
296 targets) it is recommended that you specify this option for
298 exec Permit execution of binaries on the mount.
299 noexec Do not permit execution of binaries on the mount.
300 dev Recognize block devices on the remote mount.
301 nodev Do not recognize devices on the remote mount.
302 suid Allow remote files on this mountpoint with suid enabled to
303 be executed (default for mounts when executed as root,
304 nosuid is default for user mounts).
305 credentials Although ignored by the cifs kernel component, it is used by
306 the mount helper, mount.cifs. When mount.cifs is installed it
307 opens and reads the credential file specified in order
308 to obtain the userid and password arguments which are passed to
310 guest Although ignored by the kernel component, the mount.cifs
311 mount helper will not prompt the user for a password
312 if guest is specified on the mount options. If no
313 password is specified a null password will be used.
314 perm Client does permission checks (vfs_permission check of uid
315 and gid of the file against the mode and desired operation),
316 Note that this is in addition to the normal ACL check on the
317 target machine done by the server software.
318 Client permission checking is enabled by default.
319 noperm Client does not do permission checks. This can expose
320 files on this mount to access by other users on the local
321 client system. It is typically only needed when the server
322 supports the CIFS Unix Extensions but the UIDs/GIDs on the
323 client and server system do not match closely enough to allow
324 access by the user doing the mount.
325 Note that this does not affect the normal ACL check on the
326 target machine done by the server software (of the server
327 ACL against the user name provided at mount time).
328 serverino Use servers inode numbers instead of generating automatically
329 incrementing inode numbers on the client. Although this will
330 make it easier to spot hardlinked files (as they will have
331 the same inode numbers) and inode numbers may be persistent,
332 note that the server does not guarantee that the inode numbers
333 are unique if multiple server side mounts are exported under a
334 single share (since inode numbers on the servers might not
335 be unique if multiple filesystems are mounted under the same
336 shared higher level directory). Note that this requires that
337 the server support the CIFS Unix Extensions as other servers
338 do not return a unique IndexNumber on SMB FindFirst (most
339 servers return zero as the IndexNumber). Parameter has no
340 effect to Windows servers and others which do not support the
341 CIFS Unix Extensions.
342 noserverino Client generates inode numbers (rather than using the actual one
343 from the server) by default.
344 setuids If the CIFS Unix extensions are negotiated with the server
345 the client will attempt to set the effective uid and gid of
346 the local process on newly created files, directories, and
347 devices (create, mkdir, mknod).
348 nosetuids The client will not attempt to set the uid and gid on
349 on newly created files, directories, and devices (create,
350 mkdir, mknod) which will result in the server setting the
351 uid and gid to the default (usually the server uid of the
352 usern who mounted the share). Letting the server (rather than
353 the client) set the uid and gid is the default. This
354 parameter has no effect if the CIFS Unix Extensions are not
356 netbiosname When mounting to servers via port 139, specifies the RFC1001
357 source name to use to represent the client netbios machine
358 name when doing the RFC1001 netbios session initialize.
359 direct Do not do inode data caching on files opened on this mount.
360 This precludes mmaping files on this mount. In some cases
361 with fast networks and little or no caching benefits on the
362 client (e.g. when the application is doing large sequential
363 reads bigger than page size without rereading the same data)
364 this can provide better performance than the default
365 behavior which caches reads (reaadahead) and writes
366 (writebehind) through the local Linux client pagecache
367 if oplock (caching token) is granted and held. Note that
368 direct allows write operations larger than page size
369 to be sent to the server.
370 acl Allow setfacl and getfacl to manage posix ACLs if server
371 supports them. (default)
372 noacl Do not allow setfacl and getfacl calls on this mount
374 The mount.cifs mount helper also accepts a few mount options before -o
377 -S take password from stdin (equivalent to setting the environment
378 variable "PASSWD_FD=0"
379 -V print mount.cifs version
380 -? display simple usage information
382 With recent 2.6 kernel versions of modutils, the version of the cifs kernel
383 module can be displayed via modinfo.
385 Misc /proc/fs/cifs Flags and Debug Info
386 =======================================
387 Informational pseudo-files:
388 DebugData Displays information about active CIFS sessions
390 Stats Lists summary resource usage information as well as per
391 share statistics, if CONFIG_CIFS_STATS in enabled
392 in the kernel configuration.
394 Configuration pseudo-files:
395 MultiuserMount If set to one, more than one CIFS session to
396 the same server ip address can be established
397 if more than one uid accesses the same mount
398 point and if the uids user/password mapping
399 information is available. (default is 0)
400 PacketSigningEnabled If set to one, cifs packet signing is enabled
401 and will be used if the server requires
402 it. If set to two, cifs packet signing is
403 required even if the server considers packet
404 signing optional. (default 1)
405 cifsFYI If set to one, additional debug information is
406 logged to the system error log. (default 0)
407 ExtendedSecurity If set to one, SPNEGO session establishment
408 is allowed which enables more advanced
409 secure CIFS session establishment (default 0)
410 NTLMV2Enabled If set to one, more secure password hashes
411 are used when the server supports them and
412 when kerberos is not negotiated (default 0)
413 traceSMB If set to one, debug information is logged to the
414 system error log with the start of smb requests
415 and responses (default 0)
416 LookupCacheEnable If set to one, inode information is kept cached
417 for one second improving performance of lookups
419 OplockEnabled If set to one, safe distributed caching enabled.
421 LinuxExtensionsEnabled If set to one then the client will attempt to
422 use the CIFS "UNIX" extensions which are optional
423 protocol enhancements that allow CIFS servers
424 to return accurate UID/GID information as well
425 as support symbolic links. If you use servers
426 such as Samba that support the CIFS Unix
427 extensions but do not want to use symbolic link
428 support and want to map the uid and gid fields
429 to values supplied at mount (rather than the
430 actual values, then set this to zero. (default 1)
432 These experimental features and tracing can be enabled by changing flags in
433 /proc/fs/cifs (after the cifs module has been installed or built into the
434 kernel, e.g. insmod cifs). To enable a feature set it to 1 e.g. to enable
435 tracing to the kernel message log type:
437 echo 1 > /proc/fs/cifs/cifsFYI
439 and for more extensive tracing including the start of smb requests and responses
441 echo 1 > /proc/fs/cifs/traceSMB
443 Two other experimental features are under development and to test
444 require enabling CONFIG_CIFS_EXPERIMENTAL
446 More efficient write operations and SMB buffer handling
448 DNOTIFY fcntl: needed for support of directory change
449 notification and perhaps later for file leases)
451 Per share (per client mount) statistics are available in /proc/fs/cifs/Stats
452 if the kernel was configured with cifs statistics enabled. The statistics
453 represent the number of successful (ie non-zero return code from the server)
454 SMB responses to some of the more common commands (open, delete, mkdir etc.).
455 Also recorded is the total bytes read and bytes written to the server for
456 that share. Note that due to client caching effects this can be less than the
457 number of bytes read and written by the application running on the client.
458 The statistics for the number of total SMBs and oplock breaks are different in
459 that they represent all for that share, not just those for which the server
462 Also note that "cat /proc/fs/cifs/DebugData" will display information about
463 the active sessions and the shares that are mounted. Note: NTLMv2 enablement
464 will not work since they its implementation is not quite complete yet.
465 Do not alter these configuration values unless you are doing specific testing.
466 Enabling extended security works to Windows 2000 Workstations and XP but not to
467 Windows 2000 server or Samba since it does not usually send "raw NTLMSSP"
468 (instead it sends NTLMSSP encapsulated in SPNEGO/GSSAPI, which support is not
469 complete in the CIFS VFS yet).
git://git.onelab.eu / linux-2.6.git / blob