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
125 make menuconfig. Client support for extended attributes (user xattr) can be
126 disabled on a per-mount basis by specifying "nouser_xattr" on mount.
128 The CIFS client can get and set POSIX ACLs (getfacl, setfacl) to Samba servers
129 version 3.10 and later. Setting POSIX ACLs requires enabling both XATTR and
130 then POSIX support in the CIFS configuration options when building the cifs
131 module. POSIX ACL support can be disabled on a per mount basic by specifying
134 Some administrators may want to change Samba's smb.conf "map archive" and
135 "create mask" parameters from the default. Unless the create mask is changed
136 newly created files can end up with an unnecessarily restrictive default mode,
137 which may not be what you want, although if the CIFS Unix extensions are
138 enabled on the server and client, subsequent setattr calls (e.g. chmod) can
139 fix the mode. Note that creating special devices (mknod) remotely
140 may require specifying a mkdev function to Samba if you are not using
141 Samba 3.0.6 or later. For more information on these see the manual pages
142 ("man smb.conf") on the Samba server system. Note that the cifs vfs,
143 unlike the smbfs vfs, does not read the smb.conf on the client system
144 (the few optional settings are passed in on mount via -o parameters instead).
145 Note that Samba 2.2.7 or later includes a fix that allows the CIFS VFS to delete
146 open files (required for strict POSIX compliance). Windows Servers already
147 supported this feature. Samba server does not allow symlinks that refer to files
148 outside of the share, so in Samba versions prior to 3.0.6, most symlinks to
149 files with absolute paths (ie beginning with slash) such as:
151 would be forbidden. Samba 3.0.6 server or later includes the ability to create
152 such symlinks safely by converting unsafe symlinks (ie symlinks to server
153 files that are outside of the share) to a samba specific format on the server
154 that is ignored by local server applications and non-cifs clients and that will
155 not be traversed by the Samba server). This is opaque to the Linux client
156 application using the cifs vfs. Absolute symlinks will work to Samba 3.0.5 or
157 later, but only for remote clients using the CIFS Unix extensions, and will
158 be invisbile to Windows clients and typically will not affect local
159 applications running on the same server as Samba.
163 Once the CIFS VFS support is built into the kernel or installed as a module
164 (cifs.o), you can use mount syntax like the following to access Samba or Windows
167 mount -t cifs //9.53.216.11/e$ /mnt -o user=myname,pass=mypassword
169 Before -o the option -v may be specified to make the mount.cifs
170 mount helper display the mount steps more verbosely.
171 After -o the following commonly used cifs vfs specific options
178 Other cifs mount options are described below. Use of TCP names (in addition to
179 ip addresses) is available if the mount helper (mount.cifs) is installed. If
180 you do not trust the server to which are mounted, or if you do not have
181 cifs signing enabled (and the physical network is insecure), consider use
182 of the standard mount options "noexec" and "nosuid" to reduce the risk of
183 running an altered binary on your local system (downloaded from a hostile server
184 or altered by a hostile router).
186 Although mounting using format corresponding to the CIFS URL specification is
187 not possible in mount.cifs yet, it is possible to use an alternate format
188 for the server and sharename (which is somewhat similar to NFS style mount
189 syntax) instead of the more widely used UNC format (i.e. \\server\share):
190 mount -t cifs tcp_name_of_server:share_name /mnt -o user=myname,pass=mypasswd
192 When using the mount helper mount.cifs, passwords may be specified via alternate
193 mechanisms, instead of specifying it after -o using the normal "pass=" syntax
195 1) By including it in a credential file. Specify credentials=filename as one
196 of the mount options. Credential files contain two lines
198 password=your_password
199 2) By specifying the password in the PASSWD environment variable (similarly
200 the user name can be taken from the USER environment variable).
201 3) By specifying the password in a file by name via PASSWD_FILE
202 4) By specifying the password in a file by file descriptor via PASSWD_FD
204 If no password is provided, mount.cifs will prompt for password entry
208 Servers must support the NTLM SMB dialect (which is the most recent, supported
209 by Samba and Windows NT version 4, 2000 and XP and many other SMB/CIFS servers)
210 Servers must support either "pure-TCP" (port 445 TCP/IP CIFS connections) or RFC
211 1001/1002 support for "Netbios-Over-TCP/IP." Neither of these is likely to be a
212 problem as most servers support this. IPv6 support is planned for the future,
213 and is almost complete.
215 Valid filenames differ between Windows and Linux. Windows typically restricts
216 filenames which contain certain reserved characters (e.g.the character :
217 which is used to delimit the beginning of a stream name by Windows), while
218 Linux allows a slightly wider set of valid characters in filenames. Windows
219 servers can remap such characters when an explicit mapping is specified in
220 the Server's registry. Samba starting with version 3.10 will allow such
221 filenames (ie those which contain valid Linux characters, which normally
222 would be forbidden for Windows/CIFS semantics) as long as the server is
223 configured for Unix Extensions (and the client has not disabled
224 /proc/fs/cifs/LinuxExtensionsEnabled).
227 CIFS VFS Mount Options
228 ======================
229 A partial list of the supported mount options follows:
230 user The user name to use when trying to establish
232 password The user password. If the mount helper is
233 installed, the user will be prompted for password
234 if it is not supplied.
235 ip The ip address of the target server
236 unc The target server Universal Network Name (export) to
238 domain Set the SMB/CIFS workgroup name prepended to the
239 username during CIFS session establishment
240 uid If CIFS Unix extensions are not supported by the server
241 this overrides the default uid for inodes. For mounts to
242 servers which do support the CIFS Unix extensions, such
243 as a properly configured Samba server, the server provides
244 the uid, gid and mode. For servers which do not support
245 the Unix extensions, the default uid (and gid) returned on
246 lookup of existing files is the uid (gid) of the person
247 who executed the mount (root, except when mount.cifs
248 is configured setuid for user mounts) unless the "uid="
249 (gid) mount option is specified. For the uid (gid) of newly
250 created files and directories, ie files created since
251 the last mount of the server share, the expected uid
252 (gid) is cached as as long as the inode remains in
253 memory on the client. Also note that permission
254 checks (authorization checks) on accesses to a file occur
255 at the server, but there are cases in which an administrator
256 may want to restrict at the client as well. For those
257 servers which do not report a uid/gid owner
258 (such as Windows), permissions can also be checked at the
259 client, and a crude form of client side permission checking
260 can be enabled by specifying file_mode and dir_mode on
262 gid If CIFS Unix extensions are not supported by the server
263 this overrides the default gid for inodes.
264 file_mode If CIFS Unix extensions are not supported by the server
265 this overrides the default mode for file inodes.
266 dir_mode If CIFS Unix extensions are not supported by the server
267 this overrides the default mode for directory inodes.
268 port attempt to contact the server on this tcp port, before
269 trying the usual ports (port 445, then 139).
270 iocharset Codepage used to convert local path names to and from
271 Unicode. Unicode is used by default for network path
272 names if the server supports it. If iocharset is
273 not specified then the nls_default specified
274 during the local client kernel build will be used.
275 If server does not support Unicode, this parameter is
277 rsize default read size
278 wsize default write size
279 rw mount the network share read-write (note that the
280 server may still consider the share read-only)
281 ro mount network share read-only
282 version used to distinguish different versions of the
283 mount helper utility (not typically needed)
284 sep if first mount option (after the -o), overrides
285 the comma as the separator between the mount
287 -o user=myname,password=mypassword,domain=mydom
288 could be passed instead with period as the separator by
289 -o sep=.user=myname.password=mypassword.domain=mydom
290 this might be useful when comma is contained within username
291 or password or domain. This option is less important
292 when the cifs mount helper cifs.mount (version 1.1 or later)
294 nosuid Do not allow remote executables with the suid bit
295 program to be executed. This is only meaningful for mounts
296 to servers such as Samba which support the CIFS Unix Extensions.
297 If you do not trust the servers in your network (your mount
298 targets) it is recommended that you specify this option for
300 exec Permit execution of binaries on the mount.
301 noexec Do not permit execution of binaries on the mount.
302 dev Recognize block devices on the remote mount.
303 nodev Do not recognize devices on the remote mount.
304 suid Allow remote files on this mountpoint with suid enabled to
305 be executed (default for mounts when executed as root,
306 nosuid is default for user mounts).
307 credentials Although ignored by the cifs kernel component, it is used by
308 the mount helper, mount.cifs. When mount.cifs is installed it
309 opens and reads the credential file specified in order
310 to obtain the userid and password arguments which are passed to
312 guest Although ignored by the kernel component, the mount.cifs
313 mount helper will not prompt the user for a password
314 if guest is specified on the mount options. If no
315 password is specified a null password will be used.
316 perm Client does permission checks (vfs_permission check of uid
317 and gid of the file against the mode and desired operation),
318 Note that this is in addition to the normal ACL check on the
319 target machine done by the server software.
320 Client permission checking is enabled by default.
321 noperm Client does not do permission checks. This can expose
322 files on this mount to access by other users on the local
323 client system. It is typically only needed when the server
324 supports the CIFS Unix Extensions but the UIDs/GIDs on the
325 client and server system do not match closely enough to allow
326 access by the user doing the mount.
327 Note that this does not affect the normal ACL check on the
328 target machine done by the server software (of the server
329 ACL against the user name provided at mount time).
330 serverino Use servers inode numbers instead of generating automatically
331 incrementing inode numbers on the client. Although this will
332 make it easier to spot hardlinked files (as they will have
333 the same inode numbers) and inode numbers may be persistent,
334 note that the server does not guarantee that the inode numbers
335 are unique if multiple server side mounts are exported under a
336 single share (since inode numbers on the servers might not
337 be unique if multiple filesystems are mounted under the same
338 shared higher level directory). Note that this requires that
339 the server support the CIFS Unix Extensions as other servers
340 do not return a unique IndexNumber on SMB FindFirst (most
341 servers return zero as the IndexNumber). Parameter has no
342 effect to Windows servers and others which do not support the
343 CIFS Unix Extensions.
344 noserverino Client generates inode numbers (rather than using the actual one
345 from the server) by default.
346 setuids If the CIFS Unix extensions are negotiated with the server
347 the client will attempt to set the effective uid and gid of
348 the local process on newly created files, directories, and
349 devices (create, mkdir, mknod).
350 nosetuids The client will not attempt to set the uid and gid on
351 on newly created files, directories, and devices (create,
352 mkdir, mknod) which will result in the server setting the
353 uid and gid to the default (usually the server uid of the
354 usern who mounted the share). Letting the server (rather than
355 the client) set the uid and gid is the default. This
356 parameter has no effect if the CIFS Unix Extensions are not
358 netbiosname When mounting to servers via port 139, specifies the RFC1001
359 source name to use to represent the client netbios machine
360 name when doing the RFC1001 netbios session initialize.
361 direct Do not do inode data caching on files opened on this mount.
362 This precludes mmaping files on this mount. In some cases
363 with fast networks and little or no caching benefits on the
364 client (e.g. when the application is doing large sequential
365 reads bigger than page size without rereading the same data)
366 this can provide better performance than the default
367 behavior which caches reads (reaadahead) and writes
368 (writebehind) through the local Linux client pagecache
369 if oplock (caching token) is granted and held. Note that
370 direct allows write operations larger than page size
371 to be sent to the server.
372 acl Allow setfacl and getfacl to manage posix ACLs if server
373 supports them. (default)
374 noacl Do not allow setfacl and getfacl calls on this mount
375 user_xattr Allow getting and setting user xattrs as OS/2 EAs (extended
376 attributes) to the server (default) e.g. via setfattr
377 and getfattr utilities.
378 nouser_xattr Do not allow getfattr/setfattr to get/set xattrs
380 The mount.cifs mount helper also accepts a few mount options before -o
383 -S take password from stdin (equivalent to setting the environment
384 variable "PASSWD_FD=0"
385 -V print mount.cifs version
386 -? display simple usage information
388 With recent 2.6 kernel versions of modutils, the version of the cifs kernel
389 module can be displayed via modinfo.
391 Misc /proc/fs/cifs Flags and Debug Info
392 =======================================
393 Informational pseudo-files:
394 DebugData Displays information about active CIFS sessions
396 Stats Lists summary resource usage information as well as per
397 share statistics, if CONFIG_CIFS_STATS in enabled
398 in the kernel configuration.
400 Configuration pseudo-files:
401 MultiuserMount If set to one, more than one CIFS session to
402 the same server ip address can be established
403 if more than one uid accesses the same mount
404 point and if the uids user/password mapping
405 information is available. (default is 0)
406 PacketSigningEnabled If set to one, cifs packet signing is enabled
407 and will be used if the server requires
408 it. If set to two, cifs packet signing is
409 required even if the server considers packet
410 signing optional. (default 1)
411 cifsFYI If set to one, additional debug information is
412 logged to the system error log. (default 0)
413 ExtendedSecurity If set to one, SPNEGO session establishment
414 is allowed which enables more advanced
415 secure CIFS session establishment (default 0)
416 NTLMV2Enabled If set to one, more secure password hashes
417 are used when the server supports them and
418 when kerberos is not negotiated (default 0)
419 traceSMB If set to one, debug information is logged to the
420 system error log with the start of smb requests
421 and responses (default 0)
422 LookupCacheEnable If set to one, inode information is kept cached
423 for one second improving performance of lookups
425 OplockEnabled If set to one, safe distributed caching enabled.
427 LinuxExtensionsEnabled If set to one then the client will attempt to
428 use the CIFS "UNIX" extensions which are optional
429 protocol enhancements that allow CIFS servers
430 to return accurate UID/GID information as well
431 as support symbolic links. If you use servers
432 such as Samba that support the CIFS Unix
433 extensions but do not want to use symbolic link
434 support and want to map the uid and gid fields
435 to values supplied at mount (rather than the
436 actual values, then set this to zero. (default 1)
438 These experimental features and tracing can be enabled by changing flags in
439 /proc/fs/cifs (after the cifs module has been installed or built into the
440 kernel, e.g. insmod cifs). To enable a feature set it to 1 e.g. to enable
441 tracing to the kernel message log type:
443 echo 1 > /proc/fs/cifs/cifsFYI
445 and for more extensive tracing including the start of smb requests and responses
447 echo 1 > /proc/fs/cifs/traceSMB
449 Two other experimental features are under development and to test
450 require enabling CONFIG_CIFS_EXPERIMENTAL
452 More efficient write operations and SMB buffer handling
454 DNOTIFY fcntl: needed for support of directory change
455 notification and perhaps later for file leases)
457 Per share (per client mount) statistics are available in /proc/fs/cifs/Stats
458 if the kernel was configured with cifs statistics enabled. The statistics
459 represent the number of successful (ie non-zero return code from the server)
460 SMB responses to some of the more common commands (open, delete, mkdir etc.).
461 Also recorded is the total bytes read and bytes written to the server for
462 that share. Note that due to client caching effects this can be less than the
463 number of bytes read and written by the application running on the client.
464 The statistics for the number of total SMBs and oplock breaks are different in
465 that they represent all for that share, not just those for which the server
468 Also note that "cat /proc/fs/cifs/DebugData" will display information about
469 the active sessions and the shares that are mounted. Note: NTLMv2 enablement
470 will not work since they its implementation is not quite complete yet.
471 Do not alter these configuration values unless you are doing specific testing.
472 Enabling extended security works to Windows 2000 Workstations and XP but not to
473 Windows 2000 server or Samba since it does not usually send "raw NTLMSSP"
474 (instead it sends NTLMSSP encapsulated in SPNEGO/GSSAPI, which support is not
475 complete in the CIFS VFS yet).
projects / linux-flexiantxendom0-3.2.10.git / blob