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
69 To permit users to mount and unmount over directories they own is possible
70 with the cifs vfs. A way to enable such mounting is to mark the mount.cifs
71 utility as suid (e.g. "chmod +s /sbin/mount/cifs). To enable users to
72 umount shares they mount requires
73 1) mount.cifs version 1.4 or later
74 2) an entry for the share in /etc/fstab indicating that a user may
76 //server/usersharename /mnt/username cifs user 0 0
78 Note that when the mount.cifs utility is run suid (allowing user mounts),
79 in order to reduce risks, the "nosuid" mount flag is passed in on mount to
80 disallow execution of an suid program mounted on the remote target.
81 When mount is executed as root, nosuid is not passed in by default,
82 and execution of suid programs on the remote target would be enabled
83 by default. This can be changed, as with nfs and other filesystems,
84 by simply specifying "nosuid" among the mount options. For user mounts
85 though to be able to pass the suid flag to mount requires rebuilding
86 mount.cifs with the following flag:
88 gcc samba/source/client/mount.cifs.c -DCIFS_ALLOW_USR_SUID -o mount.cifs
90 There is a corresponding manual page for cifs mounting in the Samba 3.0 and
91 later source tree in docs/manpages/mount.cifs.8
95 To get the maximum benefit from the CIFS VFS, we recommend using a server that
96 supports the SNIA CIFS Unix Extensions standard (e.g. Samba 2.2.5 or later or
97 Samba 3.0) but the CIFS vfs works fine with a wide variety of CIFS servers.
98 Note that uid, gid and file permissions will display default values if you do
99 not have a server that supports the Unix extensions for CIFS (such as Samba
100 2.2.5 or later). To enable the Unix CIFS Extensions in the Samba server, add
103 unix extensions = yes
105 to your smb.conf file on the server. Note that the following smb.conf settings
106 are also useful (on the Samba server) when the majority of clients are Unix or
110 delete readonly = yes
113 Note that server ea support is required for supporting xattrs from the Linux
114 cifs client, and that EA support is present in later versions of Samba (e.g.
115 3.0.6 and later (also EA support works in all versions of Windows, at least to
116 shares on NTFS filesystems). Extended Attribute (xattr) support is an optional
117 feature of most Linux filesystems which may require enabling via
120 Some administrators may want to change Samba's smb.conf "map archive" and
121 "create mask" parameters from the default. Creating special devices (mknod)
122 remotely may require specifying a mkdev function to Samba if you are not using
123 Samba 3.0.6 or later. For more information on these see the manual pages
124 ("man smb.conf") on the Samba server system. Note that the cifs vfs,
125 unlike the smbfs vfs, does not read the smb.conf on the client system
126 (the few optional settings are passed in on mount via -o parameters instead).
127 Note that Samba 2.2.7 or later includes a fix that allows the CIFS VFS to delete
128 open files (required for strict POSIX compliance). Windows Servers already
129 supported this feature. Samba server does not allow symlinks that refer to files
130 outside of the share, so in Samba versions prior to 3.0.6, most symlinks to
131 files with absolute paths (ie beginning with slash) such as:
133 would be forbidden. Samba 3.0.6 server or later includes the ability to create
134 such symlinks safely by converting unsafe symlinks (ie symlinks to server
135 files that are outside of the share) to a samba specific format on the server
136 that is ignored by local server applications and non-cifs clients and that will
137 not be traversed by the Samba server). This is opaque to the Linux client
138 application using the cifs vfs. Absolute symlinks will work to Samba 3.0.5 or
139 later, but only for remote clients using the CIFS Unix extensions, and will
140 be invisbile to Windows clients and typically will not affect local
141 applications running on the same server as Samba.
145 Once the CIFS VFS support is built into the kernel or installed as a module
146 (cifs.o), you can use mount syntax like the following to access Samba or Windows
149 mount -t cifs //9.53.216.11/e$ /mnt -o user=myname,pass=mypassword
151 Before -o the option -v may be specified to make the mount.cifs
152 mount helper display the mount steps more verbosely.
153 After -o the following commonly used cifs vfs specific options
160 Other cifs mount options are described below. Use of TCP names (in addition to
161 ip addresses) is available if the mount helper (mount.cifs) is installed. If
162 you do not trust the server to which are mounted, or if you do not have
163 cifs signing enabled (and the physical network is insecure), consider use
164 of the standard mount options "noexec" and "nosuid" to reduce the risk of
165 running an altered binary on your local system (downloaded from a hostile server
166 or altered by a hostile router).
168 Although mounting using format corresponding to the CIFS URL specification is
169 not possible in mount.cifs yet, it is possible to use an alternate format
170 for the server and sharename (which is somewhat similar to NFS style mount
171 syntax) instead of the more widely used UNC format (i.e. \\server\share):
172 mount -t cifs tcp_name_of_server:share_name /mnt -o user=myname,pass=mypasswd
174 When using the mount helper mount.cifs, passwords may be specified via alternate
175 mechanisms, instead of specifying it after -o using the normal "pass=" syntax
177 1) By including it in a credential file. Specify credentials=filename as one
178 of the mount options. Credential files contain two lines
180 password=your_password
181 2) By specifying the password in the PASSWD environment variable (similarly
182 the user name can be taken from the USER environment variable).
183 3) By specifying the password in a file by name via PASSWD_FILE
184 4) By specifying the password in a file by file descriptor via PASSWD_FD
186 If no password is provided, mount.cifs will prompt for password entry
190 Servers must support the NTLM SMB dialect (which is the most recent, supported
191 by Samba and Windows NT version 4, 2000 and XP and many other SMB/CIFS servers)
192 Servers must support either "pure-TCP" (port 445 TCP/IP CIFS connections) or RFC
193 1001/1002 support for "Netbios-Over-TCP/IP." Neither of these is likely to be a
194 problem as most servers support this. IPv6 support is planned for the future.
196 CIFS VFS Mount Options
197 ======================
198 A partial list of the supported mount options follows:
199 user The user name to use when trying to establish
201 password The user password. If the mount helper is
202 installed, the user will be prompted for password
203 if it is not supplied.
204 ip The ip address of the target server
205 unc The target server Universal Network Name (export) to
207 domain Set the SMB/CIFS workgroup name prepended to the
208 username during CIFS session establishment
209 uid If CIFS Unix extensions are not supported by the server
210 this overrides the default uid for inodes. For mounts to
211 servers which do support the CIFS Unix extensions, such
212 as a properly configured Samba server, the server provides
213 the uid, gid and mode. For servers which do not support
214 the Unix extensions, the default uid (and gid) returned on
215 lookup of existing files is the uid (gid) of the person
216 who executed the mount (root, except when mount.cifs
217 is configured setuid for user mounts) unless the "uid="
218 (gid) mount option is specified. For the uid (gid) of newly
219 created files and directories, ie files created since
220 the last mount of the server share, the expected uid
221 (gid) is cached as as long as the inode remains in
222 memory on the client. Also note that permission
223 checks (authorization checks) on accesses to a file occur
224 at the server, but there are cases in which an administrator
225 may want to restrict at the client as well. For those
226 servers which do not report a uid/gid owner
227 (such as Windows), permissions can also be checked at the
228 client, and a crude form of client side permission checking
229 can be enabled by specifying file_mode and dir_mode on
231 gid If CIFS Unix extensions are not supported by the server
232 this overrides the default gid for inodes.
233 file_mode If CIFS Unix extensions are not supported by the server
234 this overrides the default mode for file inodes.
235 dir_mode If CIFS Unix extensions are not supported by the server
236 this overrides the default mode for directory inodes.
237 port attempt to contact the server on this tcp port, before
238 trying the usual ports (port 445, then 139).
239 iocharset Codepage used to convert local path names to and from
240 Unicode. Unicode is used by default for network path
241 names if the server supports it. If iocharset is
242 not specified then the nls_default specified
243 during the local client kernel build will be used.
244 If server does not support Unicode, this parameter is
246 rsize default read size
247 wsize default write size
248 rw mount the network share read-write (note that the
249 server may still consider the share read-only)
250 ro mount network share read-only
251 version used to distinguish different versions of the
252 mount helper utility (not typically needed)
253 sep if first mount option (after the -o), overrides
254 the comma as the separator between the mount
256 -o user=myname,password=mypassword,domain=mydom
257 could be passed instead with period as the separator by
258 -o sep=.user=myname.password=mypassword.domain=mydom
259 this might be useful when comma is contained within username
260 or password or domain. This option is less important
261 when the cifs mount helper cifs.mount (version 1.1 or later)
263 nosuid Do not allow remote executables with the suid bit
264 program to be executed. This is only meaningful for mounts
265 to servers such as Samba which support the CIFS Unix Extensions.
266 If you do not trust the servers in your network (your mount
267 targets) it is recommended that you specify this option for
269 suid Allow remote files on this mountpoint with suid enabled to
270 be executed (default for mounts when executed as root,
271 nosuid is default for user mounts).
272 credentials Although ignored by the cifs kernel component, it is used by
273 the mount helper, mount.cifs. When mount.cifs is installed it
274 opens and reads the credential file specified in order
275 to obtain the userid and password arguments which are passed to
277 guest Although ignored by the kernel component, the mount.cifs
278 mount helper will not prompt the user for a password
279 if guest is specified on the mount options. If no
280 password is specified a null password will be used.
281 perm Client does permission checks (vfs_permission check of uid
282 and gid of the file against the mode and desired operation),
283 Note that this is in addition to the normal ACL check on the
284 target machine done by the server software.
285 Client permission checking is enabled by default.
286 noperm Client does not do permission checks. This can expose
287 files on this mount to access by other users on the local
288 client system. It is typically only needed when the server
289 supports the CIFS Unix Extensions but the UIDs/GIDs on the
290 client and server system do not match closely enough to allow
291 access by the user doing the mount.
292 Note that this does not affect the normal ACL check on the
293 target machine done by the server software (of the server
294 ACL against the user name provided at mount time).
295 setuids If the CIFS Unix extensions are negotiated with the server
296 the client will attempt to set the effective uid and gid of
297 the local process on newly created files, directories, and
298 devices (create, mkdir, mknod).
299 nosetuids The client will not attempt to set the uid and gid on
300 on newly created files, directories, and devices (create,
301 mkdir, mknod) which will result in the server setting the
302 uid and gid to the default (usually the server uid of the
303 usern who mounted the share). Letting the server (rather than
304 the client) set the uid and gid is the default. This
305 parameter has no effect if the CIFS Unix Extensions are not
308 The mount.cifs mount helper also accepts a few mount options before -o
311 -S take password from stdin (equivalent to setting the environment
312 variable "PASSWD_FD=0"
313 -V print mount.cifs version
314 -? display simple usage information
316 With recent 2.6 kernel versions of modutils, the version of the cifs kernel
317 module can be displayed via modinfo.
319 Misc /proc/fs/cifs Flags and Debug Info
320 =======================================
321 Informational pseudo-files:
322 DebugData Displays information about active CIFS sessions
324 Stats Lists summary resource usage information as well as per
325 share statistics, if CONFIG_CIFS_STATS in enabled
326 in the kernel configuration.
328 Configuration pseudo-files:
329 MultiuserMount If set to one, more than one CIFS session to
330 the same server ip address can be established
331 if more than one uid accesses the same mount
332 point and if the uids user/password mapping
333 information is available. (default is 0)
334 PacketSigningEnabled If set to one, cifs packet signing is enabled
335 and will be used if the server requires
336 it. If set to two, cifs packet signing is
337 required even if the server considers packet
338 signing optional. (default 1)
339 cifsFYI If set to one, additional debug information is
340 logged to the system error log. (default 0)
341 ExtendedSecurity If set to one, SPNEGO session establishment
342 is allowed which enables more advanced
343 secure CIFS session establishment (default 0)
344 NTLMV2Enabled If set to one, more secure password hashes
345 are used when the server supports them and
346 when kerberos is not negotiated (default 0)
347 traceSMB If set to one, debug information is logged to the
348 system error log with the start of smb requests
349 and responses (default 0)
350 LookupCacheEnable If set to one, inode information is kept cached
351 for one second improving performance of lookups
353 OplockEnabled If set to one, safe distributed caching enabled.
355 LinuxExtensionsEnabled If set to one then the client will attempt to
356 use the CIFS "UNIX" extensions which are optional
357 protocol enhancements that allow CIFS servers
358 to return accurate UID/GID information as well
359 as support symbolic links. If you use servers
360 such as Samba that support the CIFS Unix
361 extensions but do not want to use symbolic link
362 support and want to map the uid and gid fields
363 to values supplied at mount (rather than the
364 actual values, then set this to zero. (default 1)
366 These experimental features and tracing can be enabled by changing flags in
367 /proc/fs/cifs (after the cifs module has been installed or built into the
368 kernel, e.g. insmod cifs). To enable a feature set it to 1 e.g. to enable
369 tracing to the kernel message log type:
371 echo 1 > /proc/fs/cifs/cifsFYI
373 and for more extensive tracing including the start of smb requests and responses
375 echo 1 > /proc/fs/cifs/traceSMB
377 Two other experimental features are under development and to test
378 require enabling an ifdef (e.g. by adding "#define CIFS_FCNTL" in cifsglob.h)
382 CONFIG_CIFS_FCNTL (fcntl needed for support of directory change
383 notification and perhaps later for file leases)
385 Per share (per client mount) statistics are available in /proc/fs/cifs/DebugData
386 if the kernel was configured with cifs statistics enabled. The statistics
387 represent the number of successful (ie non-zero return code from the server)
388 SMB responses to some of the more common commands (open, delete, mkdir etc.).
389 Also recorded is the total bytes read and bytes written to the server for
390 that share. Note that due to client caching effects this can be less than the
391 number of bytes read and written by the application running on the client.
392 The statistics for the number of total SMBs and oplock breaks are different in
393 that they represent all for that share, not just those for which the server
396 Also note that "cat /proc/fs/cifs/DebugData" will display information about
397 the active sessions and the shares that are mounted. Note: NTLMv2 enablement
398 will not work since they its implementation is not quite complete yet.
399 Do not alter these configuration values unless you are doing specific testing.
400 Enabling extended security works to Windows 2000 Workstations and XP but not to
401 Windows 2000 server or Samba since it does not usually send "raw NTLMSSP"
402 (instead it sends NTLMSSP encapsulated in SPNEGO/GSSAPI, which support is not
403 complete in the CIFS VFS yet).