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
101 Some administrators also change the "map archive" and the "create mask"
102 parameters from their default values. Creating special devices (mknod) remotely
103 may require specifying a mkdev function to Samba. For more information on these
104 see the manual pages ("man smb.conf") on the Samba server system. Note that the
105 cifs vfs, unlike the smbfs vfs, does not read the smb.conf on the client system
106 (the few optional settings are passed in on mount via -o parameters instead).
107 Note that Samba 2.2.7 or later includes a fix that allows the CIFS VFS to delete
108 open files (required for strict POSIX compliance). Windows Servers already
109 supported this feature.
113 Once the CIFS VFS support is built into the kernel or installed as a module
114 (cifs.o), you can use mount syntax like the following to access Samba or Windows
117 mount -t cifs //9.53.216.11/e$ /mnt -o user=myname,pass=mypassword
119 Before -o the option -v may be specified to make the mount.cifs
120 mount helper display the mount steps more verbosely.
121 After -o the following commonly used cifs vfs specific options
128 Other cifs mount options are described below. Use of TCP names (in addition to
129 ip addresses) is available if the mount helper (mount.cifs) is installed. If
130 you do not trust the server to which are mounted, or if you do not have
131 cifs signing enabled (and the physical network is insecure), consider use
132 of the standard mount options "noexec" and "nosuid" to reduce the risk of
133 running an altered binary on your local system (downloaded from a hostile server
134 or altered by a hostile router).
136 When using the mount helper mount.cifs, passwords may be specified via alternate
137 mechanisms, instead of specifying it after -o using the normal "pass=" syntax
139 1) By including it in a credential file. Specify credentials=filename as one
140 of the mount options. Credential files contain two lines
142 password=your_password
143 2) By specifying the password in the PASSWD environment variable (similarly
144 the user name can be taken from the USER environment variable).
146 If no password is provided, mount.cifs will prompt for password entry
150 Servers must support the NTLM SMB dialect (which is the most recent, supported
151 by Samba and Windows NT version 4, 2000 and XP and many other SMB/CIFS servers)
152 Servers must support either "pure-TCP" (port 445 TCP/IP CIFS connections) or RFC
153 1001/1002 support for "Netbios-Over-TCP/IP." Neither of these is likely to be a
154 problem as most servers support this. IPv6 support is planned for the future.
156 CIFS VFS Mount Options
157 ======================
158 A partial list of the supported mount options follows:
159 user The user name to use when trying to establish
161 password The user password. If the mount helper is
162 installed, the user will be prompted for password
163 if it is not supplied.
164 ip The ip address of the target server
165 unc The target server Universal Network Name (export) to
167 domain Set the SMB/CIFS workgroup name prepended to the
168 username during CIFS session establishment
169 uid If CIFS Unix extensions are not supported by the server
170 this overrides the default uid for inodes.
171 gid If CIFS Unix extensions are not supported by the server
172 this overrides the default gid for inodes.
173 file_mode If CIFS Unix extensions are not supported by the server
174 this overrides the default mode for file inodes.
175 dir_mode If CIFS Unix extensions are not supported by the server
176 this overrides the default mode for directory inodes.
177 port attempt to contact the server on this tcp port, before
178 trying the usual ports (port 445, then 139).
179 iocharset Codepage used to convert local path names to and from
180 Unicode. Unicode is used by default for network path
181 names if the server supports it. If iocharset is
182 not specified then the nls_default specified
183 during the local client kernel build will be used.
184 If server does not support Unicode, this parameter is
186 rsize default read size
187 wsize default write size
188 rw mount the network share read-write (note that the
189 server may still consider the share read-only)
190 ro mount network share read-only
191 version used to distinguish different versions of the
192 mount helper utility (not typically needed)
193 sep if first mount option (after the -o), overrides
194 the comma as the separator between the mount
196 -o user=myname,password=mypassword,domain=mydom
197 could be passed instead with period as the separator by
198 -o sep=.user=myname.password=mypassword.domain=mydom
199 this might be useful when comma is contained within username
200 or password or domain. This option is less important
201 when the cifs mount helper cifs.mount (version 1.1 or later)
203 nosuid Do not allow remote executables with the suid bit
204 program to be executed. This is only meaningful for mounts
205 to servers such as Samba which support the CIFS Unix Extensions.
206 If you do not trust the servers in your network (your mount
207 targets) it is recommended that you specify this option for
209 suid Allow remote files on this mountpoint with suid enabled to
210 be executed (default for mounts when executed as root,
211 nosuid is default for user mounts).
212 credentials Although ignored by the cifs kernel component, it is used by
213 the mount helper, mount.cifs. When mount.cifs is installed it
214 opens and reads the credential file specified in order
215 to obtain the userid and password arguments which are passed to
217 guest Although ignored by the kernel component, the mount.cifs
218 mount helper will not prompt the user for a password
219 if guest is specified on the mount options. If no
220 password is specified a null password will be used.
222 Misc /proc/fs/cifs Flags and Debug Info
223 =======================================
224 Informational pseudo-files:
225 DebugData Displays information about active CIFS sessions
226 SimultaneousOps Counter which holds maximum number of
227 simultaneous outstanding SMB/CIFS requests.
228 Stats Lists summary resource usage information
230 Configuration pseudo-files:
231 MultiuserMount If set to one, more than one CIFS session to
232 the same server ip address can be established
233 if more than one uid accesses the same mount
234 point and if the uids user/password mapping
235 information is available. (default is 0)
236 PacketSigningEnabled If set to one, cifs packet signing is enabled
237 and will be used if the server requires
238 it. If set to two, cifs packet signing is
239 required even if the server considers packet
240 signing optional. (default 1)
241 cifsFYI If set to one, additional debug information is
242 logged to the system error log. (default 0)
243 ExtendedSecurity If set to one, SPNEGO session establishment
244 is allowed which enables more advanced
245 secure CIFS session establishment (default 0)
246 NTLMV2Enabled If set to one, more secure password hashes
247 are used when the server supports them and
248 when kerberos is not negotiated (default 0)
249 traceSMB If set to one, debug information is logged to the
250 system error log with the start of smb requests
251 and responses (default 0)
252 LookupCacheEnable If set to one, inode information is kept cached
253 for one second improving performance of lookups
255 OplockEnabled If set to one, safe distributed caching enabled.
257 LinuxExtensionsEnabled If set to one then the client will attempt to
258 use the CIFS "UNIX" extensions which are optional
259 protocol enhancements that allow CIFS servers
260 to return accurate UID/GID information as well
261 as support symbolic links. If you use servers
262 such as Samba that support the CIFS Unix
263 extensions but do not want to use symbolic link
264 support and want to map the uid and gid fields
265 to values supplied at mount (rather than the
266 actual values, then set this to zero. (default 1)
268 These experimental features and tracing can be enabled by changing flags in
269 /proc/fs/cifs (after the cifs module has been installed or built into the
270 kernel, e.g. insmod cifs). To enable a feature set it to 1 e.g. to enable
271 tracing to the kernel message log type:
273 echo 1 > /proc/fs/cifs/cifsFYI
275 and for more extensive tracing including the start of smb requests and responses
277 echo 1 > /proc/fs/cifs/traceSMB
279 Three other experimental features are under development and to test
280 require enabling an ifdef (e.g. by adding "#define CIFS_FCNTL" in cifsglob.h)
286 CIFS_FCNTL (fcntl needed for support of directory change notification)
288 Also note that "cat /proc/fs/cifs/DebugData" will display some information about
289 the active sessions and the shares that are mounted. Note: NTLMv2 enablement
290 will not work since they its implementation is not quite complete yet.
291 Do not alter these configuration values unless you are doing specific testing.
292 Enabling extended security works to Windows 2000 Workstations and XP but not to
293 Windows 2000 server or Samba since it does not usually send "raw NTLMSSP"
294 (instead it sends NTLMSSP encapsulated in SPNEGO/GSSAPI, which support is not
295 complete in the CIFS VFS yet).