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 Note that when the mount.cifs utility is run suid (allowing user mounts),
68 in order to reduce risks, the "nosuid" mount flag is passed in on mount to
69 disallow execution of an suid program mounted on the remote target.
70 When mount is executed as root, nosuid is not passed in by default,
71 and execution of suid programs on the remote target would be enabled
72 by default. This can be changed, as with nfs and other filesystems,
73 by simply specifying "nosuid" among the mount options. For user mounts
74 though to be able to pass the suid flag to mount requires rebuilding
75 mount.cifs with the following flag:
77 gcc samba/source/client/mount.cifs.c -DCIFS_ALLOW_USR_SUID -o mount.cifs
79 There is a corresponding manual page for cifs mounting in the Samba 3.0 and
80 later source tree in docs/manpages/mount.cifs.8
84 To get the maximum benefit from the CIFS VFS, we recommend using a server that
85 supports the SNIA CIFS Unix Extensions standard (e.g. Samba 2.2.5 or later or
86 Samba 3.0) but the CIFS vfs works fine with a wide variety of CIFS servers.
87 Note that uid, gid and file permissions will display default values if you do
88 not have a server that supports the Unix extensions for CIFS (such as Samba
89 2.2.5 or later). To enable the Unix CIFS Extensions in the Samba server, add
94 to your smb.conf file on the server. Note that the following smb.conf settings
95 are also useful (on the Samba server) when the majority of clients are Unix or
102 Note that ea support is required for supporting Linux xattrs.
103 Some administrators also change the "map archive" and the "create mask"
104 parameters from their default values. Creating special devices (mknod) remotely
105 may require specifying a mkdev function to Samba. For more information on these
106 see the manual pages ("man smb.conf") on the Samba server system. Note that the
107 cifs vfs, unlike the smbfs vfs, does not read the smb.conf on the client system
108 (the few optional settings are passed in on mount via -o parameters instead).
109 Note that Samba 2.2.7 or later includes a fix that allows the CIFS VFS to delete
110 open files (required for strict POSIX compliance). Windows Servers already
111 supported this feature. Samba server does not allow symlinks that refer to files
112 outside of the share, so in Samba versions prior to 3.0.5, most symlinks to
113 files with absolute paths (ie beginning with slash) such as:
115 would be forbidden. Samba 3.0.5 server or later includes the ability to create
116 such symlinks safely by converting unsafe symlinks (ie symlinks to server
117 files that are outside of the share) to a samba specific format on the server
118 that is ignored by local server applications and non-cifs clients and that will
119 not be traversed by the Samba server). This is opaque to the Linux client
120 application using the cifs vfs. Absolute symlinks will work to Samba 3.0.5 or
121 later, but only for remote clients using the CIFS Unix extensions, and will
122 be invisbile to Windows clients and typically will not affect local
123 applications running on the same server as Samba.
127 Once the CIFS VFS support is built into the kernel or installed as a module
128 (cifs.o), you can use mount syntax like the following to access Samba or Windows
131 mount -t cifs //9.53.216.11/e$ /mnt -o user=myname,pass=mypassword
133 Before -o the option -v may be specified to make the mount.cifs
134 mount helper display the mount steps more verbosely.
135 After -o the following commonly used cifs vfs specific options
142 Other cifs mount options are described below. Use of TCP names (in addition to
143 ip addresses) is available if the mount helper (mount.cifs) is installed. If
144 you do not trust the server to which are mounted, or if you do not have
145 cifs signing enabled (and the physical network is insecure), consider use
146 of the standard mount options "noexec" and "nosuid" to reduce the risk of
147 running an altered binary on your local system (downloaded from a hostile server
148 or altered by a hostile router).
150 When using the mount helper mount.cifs, passwords may be specified via alternate
151 mechanisms, instead of specifying it after -o using the normal "pass=" syntax
153 1) By including it in a credential file. Specify credentials=filename as one
154 of the mount options. Credential files contain two lines
156 password=your_password
157 2) By specifying the password in the PASSWD environment variable (similarly
158 the user name can be taken from the USER environment variable).
159 3) By specifying the password in a file by name via PASSWD_FILE
160 4) By specifying the password in a file by file descriptor via PASSWD_FD
162 If no password is provided, mount.cifs will prompt for password entry
166 Servers must support the NTLM SMB dialect (which is the most recent, supported
167 by Samba and Windows NT version 4, 2000 and XP and many other SMB/CIFS servers)
168 Servers must support either "pure-TCP" (port 445 TCP/IP CIFS connections) or RFC
169 1001/1002 support for "Netbios-Over-TCP/IP." Neither of these is likely to be a
170 problem as most servers support this. IPv6 support is planned for the future.
172 CIFS VFS Mount Options
173 ======================
174 A partial list of the supported mount options follows:
175 user The user name to use when trying to establish
177 password The user password. If the mount helper is
178 installed, the user will be prompted for password
179 if it is not supplied.
180 ip The ip address of the target server
181 unc The target server Universal Network Name (export) to
183 domain Set the SMB/CIFS workgroup name prepended to the
184 username during CIFS session establishment
185 uid If CIFS Unix extensions are not supported by the server
186 this overrides the default uid for inodes. For mounts to
187 servers which do support the CIFS Unix extensions, such
188 as a properly configured Samba server, the server provides
189 the uid, gid and mode. For servers which do not support
190 the Unix extensions, the default uid (and gid) returned on
191 lookup of existing files is the uid (gid) of the person
192 who executed the mount (root, except when mount.cifs
193 is configured setuid for user mounts) unless the "uid="
194 (gid) mount option is specified. For the uid (gid) of newly
195 created files and directories, ie files created since
196 the last mount of the server share, the expected uid
197 (gid) is cached as as long as the inode remains in
198 memory on the client. Also note that permission
199 checks (authorization checks) on accesses to a file occur
200 at the server, but there are cases in which an administrator
201 may want to restrict at the client as well. For those
202 servers which do not report a uid/gid owner
203 (such as Windows), permissions can also be checked at the
204 client, and a crude form of client side permission checking
205 can be enabled by specifying file_mode and dir_mode on
207 gid If CIFS Unix extensions are not supported by the server
208 this overrides the default gid for inodes.
209 file_mode If CIFS Unix extensions are not supported by the server
210 this overrides the default mode for file inodes.
211 dir_mode If CIFS Unix extensions are not supported by the server
212 this overrides the default mode for directory inodes.
213 port attempt to contact the server on this tcp port, before
214 trying the usual ports (port 445, then 139).
215 iocharset Codepage used to convert local path names to and from
216 Unicode. Unicode is used by default for network path
217 names if the server supports it. If iocharset is
218 not specified then the nls_default specified
219 during the local client kernel build will be used.
220 If server does not support Unicode, this parameter is
222 rsize default read size
223 wsize default write size
224 rw mount the network share read-write (note that the
225 server may still consider the share read-only)
226 ro mount network share read-only
227 version used to distinguish different versions of the
228 mount helper utility (not typically needed)
229 sep if first mount option (after the -o), overrides
230 the comma as the separator between the mount
232 -o user=myname,password=mypassword,domain=mydom
233 could be passed instead with period as the separator by
234 -o sep=.user=myname.password=mypassword.domain=mydom
235 this might be useful when comma is contained within username
236 or password or domain. This option is less important
237 when the cifs mount helper cifs.mount (version 1.1 or later)
239 nosuid Do not allow remote executables with the suid bit
240 program to be executed. This is only meaningful for mounts
241 to servers such as Samba which support the CIFS Unix Extensions.
242 If you do not trust the servers in your network (your mount
243 targets) it is recommended that you specify this option for
245 suid Allow remote files on this mountpoint with suid enabled to
246 be executed (default for mounts when executed as root,
247 nosuid is default for user mounts).
248 credentials Although ignored by the cifs kernel component, it is used by
249 the mount helper, mount.cifs. When mount.cifs is installed it
250 opens and reads the credential file specified in order
251 to obtain the userid and password arguments which are passed to
253 guest Although ignored by the kernel component, the mount.cifs
254 mount helper will not prompt the user for a password
255 if guest is specified on the mount options. If no
256 password is specified a null password will be used.
258 The mount.cifs mount helper also accepts a few mount options before -o
261 -S take password from stdin (equivalent to setting the environment
262 variable "PASSWD_FD=0"
263 -V print mount.cifs version
264 -? display simple usage information
266 With recent 2.6 kernel versions of modutils, the version of the cifs kernel
267 module can be displayed via modinfo.
269 Misc /proc/fs/cifs Flags and Debug Info
270 =======================================
271 Informational pseudo-files:
272 DebugData Displays information about active CIFS sessions
274 SimultaneousOps Counter which holds maximum number of
275 simultaneous outstanding SMB/CIFS requests.
276 Stats Lists summary resource usage information as well as per
277 share statistics, if CONFIG_CIFS_STATS in enabled
278 in the kernel configuration.
280 Configuration pseudo-files:
281 MultiuserMount If set to one, more than one CIFS session to
282 the same server ip address can be established
283 if more than one uid accesses the same mount
284 point and if the uids user/password mapping
285 information is available. (default is 0)
286 PacketSigningEnabled If set to one, cifs packet signing is enabled
287 and will be used if the server requires
288 it. If set to two, cifs packet signing is
289 required even if the server considers packet
290 signing optional. (default 1)
291 cifsFYI If set to one, additional debug information is
292 logged to the system error log. (default 0)
293 ExtendedSecurity If set to one, SPNEGO session establishment
294 is allowed which enables more advanced
295 secure CIFS session establishment (default 0)
296 NTLMV2Enabled If set to one, more secure password hashes
297 are used when the server supports them and
298 when kerberos is not negotiated (default 0)
299 traceSMB If set to one, debug information is logged to the
300 system error log with the start of smb requests
301 and responses (default 0)
302 LookupCacheEnable If set to one, inode information is kept cached
303 for one second improving performance of lookups
305 OplockEnabled If set to one, safe distributed caching enabled.
307 LinuxExtensionsEnabled If set to one then the client will attempt to
308 use the CIFS "UNIX" extensions which are optional
309 protocol enhancements that allow CIFS servers
310 to return accurate UID/GID information as well
311 as support symbolic links. If you use servers
312 such as Samba that support the CIFS Unix
313 extensions but do not want to use symbolic link
314 support and want to map the uid and gid fields
315 to values supplied at mount (rather than the
316 actual values, then set this to zero. (default 1)
318 These experimental features and tracing can be enabled by changing flags in
319 /proc/fs/cifs (after the cifs module has been installed or built into the
320 kernel, e.g. insmod cifs). To enable a feature set it to 1 e.g. to enable
321 tracing to the kernel message log type:
323 echo 1 > /proc/fs/cifs/cifsFYI
325 and for more extensive tracing including the start of smb requests and responses
327 echo 1 > /proc/fs/cifs/traceSMB
329 Three other experimental features are under development and to test
330 require enabling an ifdef (e.g. by adding "#define CIFS_FCNTL" in cifsglob.h)
336 CONFIG_CIFS_FCNTL (fcntl needed for support of directory change
337 notification and perhaps later for file leases)
339 Per share (per client mount) statistics are available in /proc/fs/cifs/DebugData
340 if the kernel was configured with cifs statistics enabled. The statistics
341 represent the number of successful (ie non-zero return code from the server)
342 SMB responses to some of the more common commands (open, delete, mkdir etc.).
343 Also recorded is the total bytes read and bytes written to the server for
344 that share. Note that due to client caching effects this can be less than the
345 number of bytes read and written by the application running on the client.
346 The statistics for the number of total SMBs and oplock breaks are different in
347 that they represent all for that share, not just those for which the server
350 Also note that "cat /proc/fs/cifs/DebugData" will display information about
351 the active sessions and the shares that are mounted. Note: NTLMv2 enablement
352 will not work since they its implementation is not quite complete yet.
353 Do not alter these configuration values unless you are doing specific testing.
354 Enabling extended security works to Windows 2000 Workstations and XP but not to
355 Windows 2000 server or Samba since it does not usually send "raw NTLMSSP"
356 (instead it sends NTLMSSP encapsulated in SPNEGO/GSSAPI, which support is not
357 complete in the CIFS VFS yet).