1MOUNT.CIFS(8) System Administration tools MOUNT.CIFS(8)
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6 mount.cifs - mount using the Common Internet File System (CIFS)
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9 mount.cifs {service} {mount-point} [-o options]
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12 This tool is part of the cifs-utils suite.
13 mount.cifs mounts a Linux CIFS filesystem. It is usually invoked
15 indirectly by the mount(8) command when using the "-t cifs" option.
16 This command only works in Linux, and the kernel must support the cifs
17 filesystem. The CIFS protocol is the successor to the SMB protocol and
18 is supported by most Windows servers and many other commercial servers
19 and Network Attached Storage appliances as well as by the popular Open
20 Source server Samba.
21 The mount.cifs utility attaches the UNC name (exported network
23 resource) specified as service (using //server/share syntax, where
24 "server" is the server name or IP address and "share" is the name of
25 the share) to the local directory mount-point.
26 Options to mount.cifs are specified as a comma-separated list of
28 key=value pairs. It is possible to send options other than those listed
29 here, assuming that the cifs filesystem kernel module (cifs.ko)
30 supports them. Unrecognized cifs mount options passed to the cifs vfs
31 kernel code will be logged to the kernel log.
32 mount.cifs causes the cifs vfs to launch a thread named cifsd. After
34 mounting it keeps running until the mounted resource is unmounted
35 (usually via the umount utility).
36 mount.cifs -V command displays the version of cifs mount helper.
38 modinfo cifs command displays the version of cifs module.
40
42 user=arg
43 specifies the username to connect as. If this is not given, then
44 the environment variable USER is used. This option can also take
45 the form "user%password" or "workgroup/user" or
46 "workgroup/user%password" to allow the password and workgroup to be
47 specified as part of the username.
48 Note
50 The cifs vfs accepts the parameter user=, or for users familiar
51 with smbfs it accepts the longer form of the parameter
52 username=. Similarly the longer smbfs style parameter names may
53 be accepted as synonyms for the shorter cifs parameters
54 pass=,dom= and cred=.
55 password=arg
57 specifies the CIFS password. If this option is not given then the
58 environment variable PASSWD is used. If the password is not
59 specified directly or indirectly via an argument to mount,
60 mount.cifs will prompt for a password, unless the guest option is
61 specified.
62 Note that a password which contains the delimiter character (i.e. a
64 comma ´,´) will fail to be parsed correctly on the command line.
65 However, the same password defined in the PASSWD environment
66 variable or via a credentials file (see below) or entered at the
67 password prompt will be read correctly.
68 credentials=filename
70 specifies a file that contains a username and/or password and
71 optionally the name of the workgroup. The format of the file is:
72 username=value
74 password=value
75 domain=value
76 This is preferred over having passwords in plaintext in a shared
78 file, such as /etc/fstab. Be sure to protect any credentials file
79 properly.
80 uid=arg
82 sets the uid that will own all files or directories on the mounted
83 filesystem when the server does not provide ownership information.
84 It may be specified as either a username or a numeric uid. When not
85 specified, the default is uid 0. The mount.cifs helper must be at
86 version 1.10 or higher to support specifying the uid in non-numeric
87 form. See the section on FILE AND DIRECTORY OWNERSHIP AND
88 PERMISSIONS below for more information.
89 forceuid
91 instructs the client to ignore any uid provided by the server for
92 files and directories and to always assign the owner to be the
93 value of the uid= option. See the section on FILE AND DIRECTORY
94 OWNERSHIP AND PERMISSIONS below for more information.
95 cruid=arg
97 sets the uid of the owner of the credentials cache. This is
98 primarily useful with sec=krb5. The default is the real uid of the
99 process performing the mount. Setting this parameter directs the
100 upcall to look for a credentials cache owned by that user.
101 gid=arg
103 sets the gid that will own all files or directories on the mounted
104 filesystem when the server does not provide ownership information.
105 It may be specified as either a groupname or a numeric gid. When
106 not specified, the default is gid 0. The mount.cifs helper must be
107 at version 1.10 or higher to support specifying the gid in
108 non-numeric form. See the section on FILE AND DIRECTORY OWNERSHIP
109 AND PERMISSIONS below for more information.
110 forcegid
112 instructs the client to ignore any gid provided by the server for
113 files and directories and to always assign the owner to be the
114 value of the gid= option. See the section on FILE AND DIRECTORY
115 OWNERSHIP AND PERMISSIONS below for more information.
116 port=arg
118 sets the port number on which the client will attempt to contact
119 the CIFS server. If this value is specified, look for an existing
120 connection with this port, and use that if one exists. If one
121 doesn't exist, try to create a new connection on that port. If that
122 connection fails, return an error. If this value isn't specified,
123 look for an existing connection on port 445 or 139. If no such
124 connection exists, try to connect on port 445 first and then port
125 139 if that fails. Return an error if both fail.
126 servern=arg
128 Specify the server netbios name (RFC1001 name) to use when
129 attempting to setup a session to the server. Although rarely needed
130 for mounting to newer servers, this option is needed for mounting
131 to some older servers (such as OS/2 or Windows 98 and Windows ME)
132 since when connecting over port 139 they, unlike most newer
133 servers, do not support a default server name. A server name can be
134 up to 15 characters long and is usually uppercased.
135 netbiosname=arg
137 When mounting to servers via port 139, specifies the RFC1001 source
138 name to use to represent the client netbios machine name when doing
139 the RFC1001 netbios session initialize.
140 file_mode=arg
142 If the server does not support the CIFS Unix extensions this
143 overrides the default file mode.
144 dir_mode=arg
146 If the server does not support the CIFS Unix extensions this
147 overrides the default mode for directories.
148 ip=arg
150 sets the destination IP address. This option is set automatically
151 if the server name portion of the requested UNC name can be
152 resolved so rarely needs to be specified by the user.
153 domain=arg
155 sets the domain (workgroup) of the user
156 guest
158 don´t prompt for a password
159 iocharset
161 Charset used to convert local path names to and from Unicode.
162 Unicode is used by default for network path names if the server
163 supports it. If iocharset is not specified then the nls_default
164 specified during the local client kernel build will be used. If
165 server does not support Unicode, this parameter is unused.
166 ro
168 mount read-only
169 rw
171 mount read-write
172 setuids
174 If the CIFS Unix extensions are negotiated with the server the
175 client will attempt to set the effective uid and gid of the local
176 process on newly created files, directories, and devices (create,
177 mkdir, mknod). If the CIFS Unix Extensions are not negotiated, for
178 newly created files and directories instead of using the default
179 uid and gid specified on the the mount, cache the new file´s uid
180 and gid locally which means that the uid for the file can change
181 when the inode is reloaded (or the user remounts the share).
182 nosetuids
184 The client will not attempt to set the uid and gid on on newly
185 created files, directories, and devices (create, mkdir, mknod)
186 which will result in the server setting the uid and gid to the
187 default (usually the server uid of the user who mounted the share).
188 Letting the server (rather than the client) set the uid and gid is
189 the default.If the CIFS Unix Extensions are not negotiated then the
190 uid and gid for new files will appear to be the uid (gid) of the
191 mounter or the uid (gid) parameter specified on the mount.
192 perm
194 Client does permission checks (vfs_permission check of uid and gid
195 of the file against the mode and desired operation), Note that this
196 is in addition to the normal ACL check on the target machine done
197 by the server software. Client permission checking is enabled by
198 default.
199 noperm
201 Client does not do permission checks. This can expose files on this
202 mount to access by other users on the local client system. It is
203 typically only needed when the server supports the CIFS Unix
204 Extensions but the UIDs/GIDs on the client and server system do not
205 match closely enough to allow access by the user doing the mount.
206 Note that this does not affect the normal ACL check on the target
207 machine done by the server software (of the server ACL against the
208 user name provided at mount time).
209 dynperm
211 Instructs the server to maintain ownership and permissions in
212 memory that can´t be stored on the server. This information can
213 disappear at any time (whenever the inode is flushed from the
214 cache), so while this may help make some applications work, it´s
215 behavior is somewhat unreliable. See the section below on FILE AND
216 DIRECTORY OWNERSHIP AND PERMISSIONS for more information.
217 directio
219 Do not do inode data caching on files opened on this mount. This
220 precludes mmaping files on this mount. In some cases with fast
221 networks and little or no caching benefits on the client (e.g. when
222 the application is doing large sequential reads bigger than page
223 size without rereading the same data) this can provide better
224 performance than the default behavior which caches reads
225 (readahead) and writes (writebehind) through the local Linux client
226 pagecache if oplock (caching token) is granted and held. Note that
227 direct allows write operations larger than page size to be sent to
228 the server. On some kernels this requires the cifs.ko module to be
229 built with the CIFS_EXPERIMENTAL configure option.
230 mapchars
232 Translate six of the seven reserved characters (not backslash, but
233 including the colon, question mark, pipe, asterik, greater than and
234 less than characters) to the remap range (above 0xF000), which also
235 allows the CIFS client to recognize files created with such
236 characters by Windows´s POSIX emulation. This can also be useful
237 when mounting to most versions of Samba (which also forbids
238 creating and opening files whose names contain any of these seven
239 characters). This has no effect if the server does not support
240 Unicode on the wire. Please note that the files created with
241 mapchars mount option may not be accessible if the share is mounted
242 without that option.
243 nomapchars
245 Do not translate any of these seven characters (default)
246 intr
248 currently unimplemented
249 nointr
251 (default) currently unimplemented
252 hard
254 The program accessing a file on the cifs mounted file system will
255 hang when the server crashes.
256 soft
258 (default) The program accessing a file on the cifs mounted file
259 system will not hang when the server crashes and will return errors
260 to the user application.
261 noacl
263 Do not allow POSIX ACL operations even if server would support
264 them.
265 The CIFS client can get and set POSIX ACLs (getfacl, setfacl) to
267 Samba servers version 3.0.10 and later. Setting POSIX ACLs requires
268 enabling both XATTR and then POSIX support in the CIFS
269 configuration options when building the cifs module. POSIX ACL
270 support can be disabled on a per mount basis by specifying "noacl"
271 on mount.
272 nocase
274 Request case insensitive path name matching (case sensitive is the
275 default if the server suports it).
276 sec=
278 Security mode. Allowed values are:
279 · none attempt to connection as a null user (no name)
281 · krb5 Use Kerberos version 5 authentication
283 · krb5i Use Kerberos authentication and packet signing
285 · ntlm Use NTLM password hashing (default)
287 · ntlmi Use NTLM password hashing with signing (if
289 /proc/fs/cifs/PacketSigningEnabled on or if server requires
290 signing also can be the default)
291 · ntlmv2 Use NTLMv2 password hashing
293 · ntlmv2i Use NTLMv2 password hashing with packet signing
295 [NB This [sec parameter] is under development and expected to be
297 available in cifs kernel module 1.40 and later]
298 nobrl
300 Do not send byte range lock requests to the server. This is
301 necessary for certain applications that break with cifs style
302 mandatory byte range locks (and most cifs servers do not yet
303 support requesting advisory byte range locks).
304 sfu
306 When the CIFS Unix Extensions are not negotiated, attempt to create
307 device files and fifos in a format compatible with Services for
308 Unix (SFU). In addition retrieve bits 10-12 of the mode via the
309 SETFILEBITS extended attribute (as SFU does). In the future the
310 bottom 9 bits of the mode mode also will be emulated using queries
311 of the security descriptor (ACL). [NB: requires version 1.39 or
312 later of the CIFS VFS. To recognize symlinks and be able to create
313 symlinks in an SFU interoperable form requires version 1.40 or
314 later of the CIFS VFS kernel module.
315 serverino
317 Use inode numbers (unique persistent file identifiers) returned by
318 the server instead of automatically generating temporary inode
319 numbers on the client. Although server inode numbers make it easier
320 to spot hardlinked files (as they will have the same inode numbers)
321 and inode numbers may be persistent (which is userful for some
322 sofware), the server does not guarantee that the inode numbers are
323 unique if multiple server side mounts are exported under a single
324 share (since inode numbers on the servers might not be unique if
325 multiple filesystems are mounted under the same shared higher level
326 directory). Note that not all servers support returning server
327 inode numbers, although those that support the CIFS Unix
328 Extensions, and Windows 2000 and later servers typically do support
329 this (although not necessarily on every local server filesystem).
330 Parameter has no effect if the server lacks support for returning
331 inode numbers or equivalent.
332 noserverino
334 Client generates inode numbers (rather than using the actual one
335 from the server) by default.
336 See section INODE NUMBERS for more information.
338 nounix
340 Disable the CIFS Unix Extensions for this mount. This can be useful
341 in order to turn off multiple settings at once. This includes POSIX
342 acls, POSIX locks, POSIX paths, symlink support and retrieving
343 uids/gids/mode from the server. This can also be useful to work
344 around a bug in a server that supports Unix Extensions.
345 See section INODE NUMBERS for more information.
347 nouser_xattr
349 (default) Do not allow getfattr/setfattr to get/set xattrs, even if
350 server would support it otherwise.
351 rsize=arg
353 default network read size (usually 16K). The client currently can
354 not use rsize larger than CIFSMaxBufSize. CIFSMaxBufSize defaults
355 to 16K and may be changed (from 8K to the maximum kmalloc size
356 allowed by your kernel) at module install time for cifs.ko. Setting
357 CIFSMaxBufSize to a very large value will cause cifs to use more
358 memory and may reduce performance in some cases. To use rsize
359 greater than 127K (the original cifs protocol maximum) also
360 requires that the server support a new Unix Capability flag (for
361 very large read) which some newer servers (e.g. Samba 3.0.26 or
362 later) do. rsize can be set from a minimum of 2048 to a maximum of
363 130048 (127K or CIFSMaxBufSize, whichever is smaller)
364 wsize=arg
366 default network write size (default 57344) maximum wsize currently
367 allowed by CIFS is 57344 (fourteen 4096 byte pages)
368 fsc
370 Enable local disk caching using FS-Cache for CIFS. This option
371 could be useful to improve performance on a slow link, heavily
372 loaded server and/or network where reading from the disk is faster
373 than reading from the server (over the network). This could also
374 impact the scalability positively as the number of calls to the
375 server are reduced. But, be warned that local caching is not
376 suitable for all workloads, for e.g., read-once type workloads. So,
377 you need to consider carefully the situation/workload before using
378 this option. Currently, local disk caching is enabled for CIFS
379 files opened as read-only.
380 NOTE: This feature is available only in the recent kernels that
382 have been built with the kernel config option CONFIG_CIFS_FSCACHE.
383 You also need to have cachefilesd daemon installed and running to
384 make the cache operational.
385 multiuser
387 Map user accesses to individual credentials when accessing the
388 server. By default, CIFS mounts only use a single set of user
389 credentials (the mount credentials) when accessing a share. With
390 this option, the client instead creates a new session with the
391 server using the user's credentials whenever a new user accesses
392 the mount. Further accesses by that user will also use those
393 credentials. Because the kernel cannot prompt for passwords,
394 multiuser mounts are limited to mounts using sec= options that
395 don't require passwords.
396 With this change, it's feasible for the server to handle
398 permissions enforcement, so this option also implies "noperm".
399 Furthermore, when unix extensions aren't in use and the
400 administrator has not overriden ownership using the uid= or gid=
401 options, ownership of files is presented as the current user
402 accessing the share.
403 actimeo=arg
405 The time (in seconds) that the CIFS client caches attributes of a
406 file or directory before it requests attribute information from a
407 server. During this period the changes that occur on the server
408 remain undetected until the client checks the server again.
409 By default, the attribute cache timeout is set to 1 second. This
411 means more frequent on-the-wire calls to the server to check
412 whether attributes have changed which could impact performance.
413 With this option users can make a tradeoff between performance and
414 cache metadata correctness, depending on workload needs. Shorter
415 timeouts mean better cache coherency, but frequent increased number
416 of calls to the server. Longer timeouts mean a reduced number of
417 calls to the server but looser cache coherency. The actimeo value
418 is a positive integer that can hold values between 0 and a maximum
419 value of 2^30 * HZ (frequency of timer interrupt) setting.
420 --verbose
422 Print additional debugging information for the mount. Note that
423 this parameter must be specified before the -o. For example:
424 mount -t cifs //server/share /mnt --verbose -o user=username
426
428 It´s generally preferred to use forward slashes (/) as a delimiter in
429 service names. They are considered to be the "universal delimiter"
430 since they are generally not allowed to be embedded within path
431 components on Windows machines and the client can convert them to
432 blackslashes (\) unconditionally. Conversely, backslash characters are
433 allowed by POSIX to be part of a path component, and can´t be
434 automatically converted in the same way.
435 mount.cifs will attempt to convert backslashes to forward slashes where
437 it´s able to do so, but it cannot do so in any path component following
438 the sharename.
439
441 When Unix Extensions are enabled, we use the actual inode number
442 provided by the server in response to the POSIX calls as an inode
443 number.
444 When Unix Extensions are disabled and "serverino" mount option is
446 enabled there is no way to get the server inode number. The client
447 typically maps the server-assigned "UniqueID" onto an inode number.
448 Note that the UniqueID is a different value from the server inode
450 number. The UniqueID value is unique over the scope of the entire
451 server and is often greater than 2 power 32. This value often makes
452 programs that are not compiled with LFS (Large File Support), to
453 trigger a glibc EOVERFLOW error as this won´t fit in the target
454 structure field. It is strongly recommended to compile your programs
455 with LFS support (i.e. with -D_FILE_OFFSET_BITS=64) to prevent this
456 problem. You can also use "noserverino" mount option to generate inode
457 numbers smaller than 2 power 32 on the client. But you may not be able
458 to detect hardlinks properly.
459
461 The core CIFS protocol does not provide unix ownership information or
462 mode for files and directories. Because of this, files and directories
463 will generally appear to be owned by whatever values the uid= or gid=
464 options are set, and will have permissions set to the default file_mode
465 and dir_mode for the mount. Attempting to change these values via
466 chmod/chown will return success but have no effect.
467 When the client and server negotiate unix extensions, files and
469 directories will be assigned the uid, gid, and mode provided by the
470 server. Because CIFS mounts are generally single-user, and the same
471 credentials are used no matter what user accesses the mount, newly
472 created files and directories will generally be given ownership
473 corresponding to whatever credentials were used to mount the share.
474 If the uid´s and gid´s being used do not match on the client and
476 server, the forceuid and forcegid options may be helpful. Note however,
477 that there is no corresponding option to override the mode. Permissions
478 assigned to a file when forceuid or forcegid are in effect may not
479 reflect the the real permissions.
480 When unix extensions are not negotiated, it´s also possible to emulate
482 them locally on the server using the "dynperm" mount option. When this
483 mount option is in effect, newly created files and directories will
484 receive what appear to be proper permissions. These permissions are not
485 stored on the server however and can disappear at any time in the
486 future (subject to the whims of the kernel flushing out the inode
487 cache). In general, this mount option is discouraged.
488 It´s also possible to override permission checking on the client
490 altogether via the noperm option. Server-side permission checks cannot
491 be overriden. The permission checks done by the server will always
492 correspond to the credentials used to mount the share, and not
493 necessarily to the user who is accessing the share.
494
496 The variable USER may contain the username of the person to be used to
497 authenticate to the server. The variable can be used to set both
498 username and password by using the format username%password.
499 The variable PASSWD may contain the password of the person using the
501 client.
502 The variable PASSWD_FILE may contain the pathname of a file to read the
504 password from. A single line of input is read and used as the password.
505
507 This command may be used only by root, unless installed setuid, in
508 which case the noeexec and nosuid mount flags are enabled. When
509 installed as a setuid program, the program follows the conventions set
510 forth by the mount program for user mounts.
511 Some samba client tools like smbclient(8) honour client-side
513 configuration parameters present in smb.conf. Unlike those client
514 tools, mount.cifs ignores smb.conf completely.
515
517 The primary mechanism for making configuration changes and for reading
518 debug information for the cifs vfs is via the Linux /proc filesystem.
519 In the directory /proc/fs/cifs are various configuration files and
520 pseudo files which can display debug information. There are additional
521 startup options such as maximum buffer size and number of buffers which
522 only may be set when the kernel cifs vfs (cifs.ko module) is loaded.
523 These can be seen by running the modinfo utility against the file
524 cifs.ko which will list the options that may be passed to cifs during
525 module installation (device driver load). For more information see the
526 kernel file fs/cifs/README.
527
529 Mounting using the CIFS URL specification is currently not supported.
530 The credentials file does not handle usernames or passwords with
532 leading space.
533 Note that the typical response to a bug report is a suggestion to try
535 the latest version first. So please try doing that first, and always
536 include which versions you use of relevant software when reporting bugs
537 (minimum: mount.cifs (try mount.cifs -V), kernel (see /proc/version)
538 and server type you are trying to contact.
539
541 This man page is correct for version 1.52 of the cifs vfs filesystem
542 (roughly Linux kernel 2.6.24).
543
545 Documentation/filesystems/cifs.txt and fs/cifs/README in the linux
546 kernel source tree may contain additional options and information.
547 cifs.upcall(8)
549
551 Steve French
552 The syntax and manpage were loosely based on that of smbmount. It was
554 converted to Docbook/XML by Jelmer Vernooij.
555 The maintainer of the Linux cifs vfs and the userspace tool mount.cifs
557 is Steve French. The Linux CIFS Mailing list is the preferred place to
558 ask questions regarding these programs.
559cifs-utils 4.0 02/07/2010 MOUNT.CIFS(8)