1The CIFS VFS support for Linux supports many advanced network filesystem 2features such as hierarchical dfs like namespace, hardlinks, locking and more. 3It was designed to comply with the SNIA CIFS Technical Reference (which 4supersedes the 1992 X/Open SMB Standard) as well as to perform best practice 5practical interoperability with Windows 2000, Windows XP, Samba and equivalent 6servers. 7 8For questions or bug reports please contact: 9 sfrench@samba.org (sfrench@us.ibm.com) 10 11Build instructions: 12================== 13For Linux 2.4: 141) Get the kernel source (e.g.from http://www.kernel.org) 15and download the cifs vfs source (see the project page 16at http://us1.samba.org/samba/Linux_CIFS_client.html) 17and change directory into the top of the kernel directory 18then patch the kernel (e.g. "patch -p1 < cifs_24.patch") 19to add the cifs vfs to your kernel configure options if 20it has not already been added (e.g. current SuSE and UL 21users do not need to apply the cifs_24.patch since the cifs vfs is 22already in the kernel configure menu) and then 23mkdir linux/fs/cifs and then copy the current cifs vfs files from 24the cifs download to your kernel build directory e.g. 25 26 cp <cifs_download_dir>/fs/cifs/* to <kernel_download_dir>/fs/cifs 27 282) make menuconfig (or make xconfig) 293) select cifs from within the network filesystem choices 304) save and exit 315) make dep 326) make modules (or "make" if CIFS VFS not to be built as a module) 33 34For Linux 2.6: 351) Download the kernel (e.g. from http://www.kernel.org) 36and change directory into the top of the kernel directory tree 37(e.g. /usr/src/linux-2.5.73) 382) make menuconfig (or make xconfig) 393) select cifs from within the network filesystem choices 404) save and exit 415) make 42 43 44Installation instructions: 45========================= 46If you have built the CIFS vfs as module (successfully) simply 47type "make modules_install" (or if you prefer, manually copy the file to 48the modules directory e.g. /lib/modules/2.4.10-4GB/kernel/fs/cifs/cifs.o). 49 50If you have built the CIFS vfs into the kernel itself, follow the instructions 51for your distribution on how to install a new kernel (usually you 52would simply type "make install"). 53 54If you do not have the utility mount.cifs (in the Samba 3.0 source tree and on 55the CIFS VFS web site) copy it to the same directory in which mount.smbfs and 56similar files reside (usually /sbin). Although the helper software is not 57required, 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 59users who are used to Windows e.g. net use <mount point> <UNC name or cifs URL> 60Note that running the Winbind pam/nss module (logon service) on all of your 61Linux clients is useful in mapping Uids and Gids consistently across the 62domain to the proper network user. The mount.cifs mount helper can be 63trivially built from Samba 3.0 or later source e.g. by executing: 64 65 gcc samba/source/client/mount.cifs.c -o mount.cifs 66 67If cifs is built as a module, then the size and number of network buffers 68and maximum number of simultaneous requests to one server can be configured. 69Changing these from their defaults is not recommended. By executing modinfo 70 modinfo kernel/fs/cifs/cifs.ko 71on kernel/fs/cifs/cifs.ko the list of configuration changes that can be made 72at module initialization time (by running insmod cifs.ko) can be seen. 73 74Allowing User Mounts 75==================== 76To permit users to mount and unmount over directories they own is possible 77with the cifs vfs. A way to enable such mounting is to mark the mount.cifs 78utility as suid (e.g. "chmod +s /sbin/mount.cifs). To enable users to 79umount shares they mount requires 801) mount.cifs version 1.4 or later 812) an entry for the share in /etc/fstab indicating that a user may 82unmount it e.g. 83//server/usersharename /mnt/username cifs user 0 0 84 85Note that when the mount.cifs utility is run suid (allowing user mounts), 86in order to reduce risks, the "nosuid" mount flag is passed in on mount to 87disallow execution of an suid program mounted on the remote target. 88When mount is executed as root, nosuid is not passed in by default, 89and execution of suid programs on the remote target would be enabled 90by default. This can be changed, as with nfs and other filesystems, 91by simply specifying "nosuid" among the mount options. For user mounts 92though to be able to pass the suid flag to mount requires rebuilding 93mount.cifs with the following flag: 94 95 gcc samba/source/client/mount.cifs.c -DCIFS_ALLOW_USR_SUID -o mount.cifs 96 97There is a corresponding manual page for cifs mounting in the Samba 3.0 and 98later source tree in docs/manpages/mount.cifs.8 99 100Allowing User Unmounts 101====================== 102To permit users to ummount directories that they have user mounted (see above), 103the utility umount.cifs may be used. It may be invoked directly, or if 104umount.cifs is placed in /sbin, umount can invoke the cifs umount helper 105(at least for most versions of the umount utility) for umount of cifs 106mounts, unless umount is invoked with -i (which will avoid invoking a umount 107helper). As with mount.cifs, to enable user unmounts umount.cifs must be marked 108as suid (e.g. "chmod +s /sbin/umount.cifs") or equivalent (some distributions 109allow adding entries to a file to the /etc/permissions file to achieve the 110equivalent suid effect). For this utility to succeed the target path 111must be a cifs mount, and the uid of the current user must match the uid 112of the user who mounted the resource. 113 114Also note that the customary way of allowing user mounts and unmounts is 115(instead of using mount.cifs and unmount.cifs as suid) to add a line 116to the file /etc/fstab for each //server/share you wish to mount, but 117this can become unwieldy when potential mount targets include many 118or unpredictable UNC names. 119 120Samba Considerations 121==================== 122To get the maximum benefit from the CIFS VFS, we recommend using a server that 123supports the SNIA CIFS Unix Extensions standard (e.g. Samba 2.2.5 or later or 124Samba 3.0) but the CIFS vfs works fine with a wide variety of CIFS servers. 125Note that uid, gid and file permissions will display default values if you do 126not have a server that supports the Unix extensions for CIFS (such as Samba 1272.2.5 or later). To enable the Unix CIFS Extensions in the Samba server, add 128the line: 129 130 unix extensions = yes 131 132to your smb.conf file on the server. Note that the following smb.conf settings 133are also useful (on the Samba server) when the majority of clients are Unix or 134Linux: 135 136 case sensitive = yes 137 delete readonly = yes 138 ea support = yes 139 140Note that server ea support is required for supporting xattrs from the Linux 141cifs client, and that EA support is present in later versions of Samba (e.g. 1423.0.6 and later (also EA support works in all versions of Windows, at least to 143shares on NTFS filesystems). Extended Attribute (xattr) support is an optional 144feature of most Linux filesystems which may require enabling via 145make menuconfig. Client support for extended attributes (user xattr) can be 146disabled on a per-mount basis by specifying "nouser_xattr" on mount. 147 148The CIFS client can get and set POSIX ACLs (getfacl, setfacl) to Samba servers 149version 3.10 and later. Setting POSIX ACLs requires enabling both XATTR and 150then POSIX support in the CIFS configuration options when building the cifs 151module. POSIX ACL support can be disabled on a per mount basic by specifying 152"noacl" on mount. 153 154Some administrators may want to change Samba's smb.conf "map archive" and 155"create mask" parameters from the default. Unless the create mask is changed 156newly created files can end up with an unnecessarily restrictive default mode, 157which may not be what you want, although if the CIFS Unix extensions are 158enabled on the server and client, subsequent setattr calls (e.g. chmod) can 159fix the mode. Note that creating special devices (mknod) remotely 160may require specifying a mkdev function to Samba if you are not using 161Samba 3.0.6 or later. For more information on these see the manual pages 162("man smb.conf") on the Samba server system. Note that the cifs vfs, 163unlike the smbfs vfs, does not read the smb.conf on the client system 164(the few optional settings are passed in on mount via -o parameters instead). 165Note that Samba 2.2.7 or later includes a fix that allows the CIFS VFS to delete 166open files (required for strict POSIX compliance). Windows Servers already 167supported this feature. Samba server does not allow symlinks that refer to files 168outside of the share, so in Samba versions prior to 3.0.6, most symlinks to 169files with absolute paths (ie beginning with slash) such as: 170 ln -s /mnt/foo bar 171would be forbidden. Samba 3.0.6 server or later includes the ability to create 172such symlinks safely by converting unsafe symlinks (ie symlinks to server 173files that are outside of the share) to a samba specific format on the server 174that is ignored by local server applications and non-cifs clients and that will 175not be traversed by the Samba server). This is opaque to the Linux client 176application using the cifs vfs. Absolute symlinks will work to Samba 3.0.5 or 177later, but only for remote clients using the CIFS Unix extensions, and will 178be invisbile to Windows clients and typically will not affect local 179applications running on the same server as Samba. 180 181Use instructions: 182================ 183Once the CIFS VFS support is built into the kernel or installed as a module 184(cifs.o), you can use mount syntax like the following to access Samba or Windows 185servers: 186 187 mount -t cifs //9.53.216.11/e$ /mnt -o user=myname,pass=mypassword 188 189Before -o the option -v may be specified to make the mount.cifs 190mount helper display the mount steps more verbosely. 191After -o the following commonly used cifs vfs specific options 192are supported: 193 194 user=<username> 195 pass=<password> 196 domain=<domain name> 197 198Other cifs mount options are described below. Use of TCP names (in addition to 199ip addresses) is available if the mount helper (mount.cifs) is installed. If 200you do not trust the server to which are mounted, or if you do not have 201cifs signing enabled (and the physical network is insecure), consider use 202of the standard mount options "noexec" and "nosuid" to reduce the risk of 203running an altered binary on your local system (downloaded from a hostile server 204or altered by a hostile router). 205 206Although mounting using format corresponding to the CIFS URL specification is 207not possible in mount.cifs yet, it is possible to use an alternate format 208for the server and sharename (which is somewhat similar to NFS style mount 209syntax) instead of the more widely used UNC format (i.e. \\server\share): 210 mount -t cifs tcp_name_of_server:share_name /mnt -o user=myname,pass=mypasswd 211 212When using the mount helper mount.cifs, passwords may be specified via alternate 213mechanisms, instead of specifying it after -o using the normal "pass=" syntax 214on the command line: 2151) By including it in a credential file. Specify credentials=filename as one 216of the mount options. Credential files contain two lines 217 username=someuser 218 password=your_password 2192) By specifying the password in the PASSWD environment variable (similarly 220the user name can be taken from the USER environment variable). 2213) By specifying the password in a file by name via PASSWD_FILE 2224) By specifying the password in a file by file descriptor via PASSWD_FD 223 224If no password is provided, mount.cifs will prompt for password entry 225 226Restrictions 227============ 228Servers must support the NTLM SMB dialect (which is the most recent, supported 229by Samba and Windows NT version 4, 2000 and XP and many other SMB/CIFS servers) 230Servers must support either "pure-TCP" (port 445 TCP/IP CIFS connections) or RFC 2311001/1002 support for "Netbios-Over-TCP/IP." Neither of these is likely to be a 232problem as most servers support this. IPv6 support is planned for the future, 233and is almost complete. 234 235Valid filenames differ between Windows and Linux. Windows typically restricts 236filenames which contain certain reserved characters (e.g.the character : 237which is used to delimit the beginning of a stream name by Windows), while 238Linux allows a slightly wider set of valid characters in filenames. Windows 239servers can remap such characters when an explicit mapping is specified in 240the Server's registry. Samba starting with version 3.10 will allow such 241filenames (ie those which contain valid Linux characters, which normally 242would be forbidden for Windows/CIFS semantics) as long as the server is 243configured for Unix Extensions (and the client has not disabled 244/proc/fs/cifs/LinuxExtensionsEnabled). 245 246 247CIFS VFS Mount Options 248====================== 249A partial list of the supported mount options follows: 250 user The user name to use when trying to establish 251 the CIFS session. 252 password The user password. If the mount helper is 253 installed, the user will be prompted for password 254 if it is not supplied. 255 ip The ip address of the target server 256 unc The target server Universal Network Name (export) to 257 mount. 258 domain Set the SMB/CIFS workgroup name prepended to the 259 username during CIFS session establishment 260 uid Set the default uid for inodes. For mounts to servers 261 which do support the CIFS Unix extensions, such as a 262 properly configured Samba server, the server provides 263 the uid, gid and mode so this parameter should not be 264 specified unless the server and clients uid and gid 265 numbering differ. If the server and client are in the 266 same domain (e.g. running winbind or nss_ldap) and 267 the server supports the Unix Extensions then the uid 268 and gid can be retrieved from the server (and uid 269 and gid would not have to be specifed on the mount. 270 For servers which do not support the CIFS Unix 271 extensions, the default uid (and gid) returned on lookup 272 of existing files will be the uid (gid) of the person 273 who executed the mount (root, except when mount.cifs 274 is configured setuid for user mounts) unless the "uid=" 275 (gid) mount option is specified. For the uid (gid) of newly 276 created files and directories, ie files created since 277 the last mount of the server share, the expected uid 278 (gid) is cached as long as the inode remains in 279 memory on the client. Also note that permission 280 checks (authorization checks) on accesses to a file occur 281 at the server, but there are cases in which an administrator 282 may want to restrict at the client as well. For those 283 servers which do not report a uid/gid owner 284 (such as Windows), permissions can also be checked at the 285 client, and a crude form of client side permission checking 286 can be enabled by specifying file_mode and dir_mode on 287 the client. Note that the mount.cifs helper must be 288 at version 1.10 or higher to support specifying the uid 289 (or gid) in non-numberic form. 290 gid Set the default gid for inodes (similar to above). 291 file_mode If CIFS Unix extensions are not supported by the server 292 this overrides the default mode for file inodes. 293 dir_mode If CIFS Unix extensions are not supported by the server 294 this overrides the default mode for directory inodes. 295 port attempt to contact the server on this tcp port, before 296 trying the usual ports (port 445, then 139). 297 iocharset Codepage used to convert local path names to and from 298 Unicode. Unicode is used by default for network path 299 names if the server supports it. If iocharset is 300 not specified then the nls_default specified 301 during the local client kernel build will be used. 302 If server does not support Unicode, this parameter is 303 unused. 304 rsize default read size (usually 16K) 305 wsize default write size (usually 16K, 32K is often better over GigE) 306 maximum wsize currently allowed by CIFS is 57344 (14 4096 byte 307 pages) 308 rw mount the network share read-write (note that the 309 server may still consider the share read-only) 310 ro mount network share read-only 311 version used to distinguish different versions of the 312 mount helper utility (not typically needed) 313 sep if first mount option (after the -o), overrides 314 the comma as the separator between the mount 315 parms. e.g. 316 -o user=myname,password=mypassword,domain=mydom 317 could be passed instead with period as the separator by 318 -o sep=.user=myname.password=mypassword.domain=mydom 319 this might be useful when comma is contained within username 320 or password or domain. This option is less important 321 when the cifs mount helper cifs.mount (version 1.1 or later) 322 is used. 323 nosuid Do not allow remote executables with the suid bit 324 program to be executed. This is only meaningful for mounts 325 to servers such as Samba which support the CIFS Unix Extensions. 326 If you do not trust the servers in your network (your mount 327 targets) it is recommended that you specify this option for 328 greater security. 329 exec Permit execution of binaries on the mount. 330 noexec Do not permit execution of binaries on the mount. 331 dev Recognize block devices on the remote mount. 332 nodev Do not recognize devices on the remote mount. 333 suid Allow remote files on this mountpoint with suid enabled to 334 be executed (default for mounts when executed as root, 335 nosuid is default for user mounts). 336 credentials Although ignored by the cifs kernel component, it is used by 337 the mount helper, mount.cifs. When mount.cifs is installed it 338 opens and reads the credential file specified in order 339 to obtain the userid and password arguments which are passed to 340 the cifs vfs. 341 guest Although ignored by the kernel component, the mount.cifs 342 mount helper will not prompt the user for a password 343 if guest is specified on the mount options. If no 344 password is specified a null password will be used. 345 perm Client does permission checks (vfs_permission check of uid 346 and gid of the file against the mode and desired operation), 347 Note that this is in addition to the normal ACL check on the 348 target machine done by the server software. 349 Client permission checking is enabled by default. 350 noperm Client does not do permission checks. This can expose 351 files on this mount to access by other users on the local 352 client system. It is typically only needed when the server 353 supports the CIFS Unix Extensions but the UIDs/GIDs on the 354 client and server system do not match closely enough to allow 355 access by the user doing the mount, but it may be useful with 356 non CIFS Unix Extension mounts for cases in which the default 357 mode is specified on the mount but is not to be enforced on the 358 client (e.g. perhaps when MultiUserMount is enabled) 359 Note that this does not affect the normal ACL check on the 360 target machine done by the server software (of the server 361 ACL against the user name provided at mount time). 362 serverino Use servers inode numbers instead of generating automatically 363 incrementing inode numbers on the client. Although this will 364 make it easier to spot hardlinked files (as they will have 365 the same inode numbers) and inode numbers may be persistent, 366 note that the server does not guarantee that the inode numbers 367 are unique if multiple server side mounts are exported under a 368 single share (since inode numbers on the servers might not 369 be unique if multiple filesystems are mounted under the same 370 shared higher level directory). Note that this requires that 371 the server support the CIFS Unix Extensions as other servers 372 do not return a unique IndexNumber on SMB FindFirst (most 373 servers return zero as the IndexNumber). Parameter has no 374 effect to Windows servers and others which do not support the 375 CIFS Unix Extensions. 376 noserverino Client generates inode numbers (rather than using the actual one 377 from the server) by default. 378 setuids If the CIFS Unix extensions are negotiated with the server 379 the client will attempt to set the effective uid and gid of 380 the local process on newly created files, directories, and 381 devices (create, mkdir, mknod). If the CIFS Unix Extensions 382 are not negotiated, for newly created files and directories 383 instead of using the default uid and gid specified on 384 the mount, cache the new file's uid and gid locally which means 385 that the uid for the file can change when the inode is 386 reloaded (or the user remounts the share). 387 nosetuids The client will not attempt to set the uid and gid on 388 on newly created files, directories, and devices (create, 389 mkdir, mknod) which will result in the server setting the 390 uid and gid to the default (usually the server uid of the 391 user who mounted the share). Letting the server (rather than 392 the client) set the uid and gid is the default. If the CIFS 393 Unix Extensions are not negotiated then the uid and gid for 394 new files will appear to be the uid (gid) of the mounter or the 395 uid (gid) parameter specified on the mount. 396 netbiosname When mounting to servers via port 139, specifies the RFC1001 397 source name to use to represent the client netbios machine 398 name when doing the RFC1001 netbios session initialize. 399 direct Do not do inode data caching on files opened on this mount. 400 This precludes mmaping files on this mount. In some cases 401 with fast networks and little or no caching benefits on the 402 client (e.g. when the application is doing large sequential 403 reads bigger than page size without rereading the same data) 404 this can provide better performance than the default 405 behavior which caches reads (readahead) and writes 406 (writebehind) through the local Linux client pagecache 407 if oplock (caching token) is granted and held. Note that 408 direct allows write operations larger than page size 409 to be sent to the server. 410 acl Allow setfacl and getfacl to manage posix ACLs if server 411 supports them. (default) 412 noacl Do not allow setfacl and getfacl calls on this mount 413 user_xattr Allow getting and setting user xattrs as OS/2 EAs (extended 414 attributes) to the server (default) e.g. via setfattr 415 and getfattr utilities. 416 nouser_xattr Do not allow getfattr/setfattr to get/set/list xattrs 417 mapchars Translate six of the seven reserved characters (not backslash) 418 *?<>|: 419 to the remap range (above 0xF000), which also 420 allows the CIFS client to recognize files created with 421 such characters by Windows's POSIX emulation. This can 422 also be useful when mounting to most versions of Samba 423 (which also forbids creating and opening files 424 whose names contain any of these seven characters). 425 This has no effect if the server does not support 426 Unicode on the wire. 427 nomapchars Do not translate any of these seven characters (default). 428 nocase Request case insensitive path name matching (case 429 sensitive is the default if the server suports it). 430 posixpaths If CIFS Unix extensions are supported, attempt to 431 negotiate posix path name support which allows certain 432 characters forbidden in typical CIFS filenames, without 433 requiring remapping. (default) 434 noposixpaths If CIFS Unix extensions are supported, do not request 435 posix path name support (this may cause servers to 436 reject creatingfile with certain reserved characters). 437 nobrl Do not send byte range lock requests to the server. 438 This is necessary for certain applications that break 439 with cifs style mandatory byte range locks (and most 440 cifs servers do not yet support requesting advisory 441 byte range locks). 442 remount remount the share (often used to change from ro to rw mounts 443 or vice versa) 444 sfu When the CIFS Unix Extensions are not negotiated, attempt to 445 create device files and fifos in a format compatible with 446 Services for Unix (SFU). In addition retrieve bits 10-12 447 of the mode via the SETFILEBITS extended attribute (as 448 SFU does). In the future the bottom 9 bits of the 449 mode also will be emulated using queries of the security 450 descriptor (ACL). 451 sign Must use packet signing (helps avoid unwanted data modification 452 by intermediate systems in the route). Note that signing 453 does not work with lanman or plaintext authentication. 454 sec Security mode. Allowed values are: 455 none attempt to connection as a null user (no name) 456 krb5 Use Kerberos version 5 authentication 457 krb5i Use Kerberos authentication and packet signing 458 ntlm Use NTLM password hashing (default) 459 ntlmi Use NTLM password hashing with signing (if 460 /proc/fs/cifs/PacketSigningEnabled on or if 461 server requires signing also can be the default) 462 ntlmv2 Use NTLMv2 password hashing 463 ntlmv2i Use NTLMv2 password hashing with packet signing 464 lanman (if configured in kernel config) use older 465 lanman hash 466 467The mount.cifs mount helper also accepts a few mount options before -o 468including: 469 470 -S take password from stdin (equivalent to setting the environment 471 variable "PASSWD_FD=0" 472 -V print mount.cifs version 473 -? display simple usage information 474 475With most 2.6 kernel versions of modutils, the version of the cifs kernel 476module can be displayed via modinfo. 477 478Misc /proc/fs/cifs Flags and Debug Info 479======================================= 480Informational pseudo-files: 481DebugData Displays information about active CIFS sessions 482 and shares, as well as the cifs.ko version. 483Stats Lists summary resource usage information as well as per 484 share statistics, if CONFIG_CIFS_STATS in enabled 485 in the kernel configuration. 486 487Configuration pseudo-files: 488MultiuserMount If set to one, more than one CIFS session to 489 the same server ip address can be established 490 if more than one uid accesses the same mount 491 point and if the uids user/password mapping 492 information is available. (default is 0) 493PacketSigningEnabled If set to one, cifs packet signing is enabled 494 and will be used if the server requires 495 it. If set to two, cifs packet signing is 496 required even if the server considers packet 497 signing optional. (default 1) 498SecurityFlags Flags which control security negotiation and 499 also packet signing. Authentication (may/must) 500 flags (e.g. for NTLM and/or NTLMv2) may be combined with 501 the signing flags. Specifying two different password 502 hashing mechanisms (as "must use") on the other hand 503 does not make much sense. Default flags are 504 0x07007 505 (NTLM, NTLMv2 and packet signing allowed). Maximum 506 allowable flags if you want to allow mounts to servers 507 using weaker password hashes is 0x37037 (lanman, 508 plaintext, ntlm, ntlmv2, signing allowed): 509 510 may use packet signing 0x00001 511 must use packet signing 0x01001 512 may use NTLM (most common password hash) 0x00002 513 must use NTLM 0x02002 514 may use NTLMv2 0x00004 515 must use NTLMv2 0x04004 516 may use Kerberos security (not implemented yet) 0x00008 517 must use Kerberos (not implemented yet) 0x08008 518 may use lanman (weak) password hash 0x00010 519 must use lanman password hash 0x10010 520 may use plaintext passwords 0x00020 521 must use plaintext passwords 0x20020 522 (reserved for future packet encryption) 0x00040 523 524cifsFYI If set to non-zero value, additional debug information 525 will be logged to the system error log. This field 526 contains three flags controlling different classes of 527 debugging entries. The maximum value it can be set 528 to is 7 which enables all debugging points (default 0). 529 Some debugging statements are not compiled into the 530 cifs kernel unless CONFIG_CIFS_DEBUG2 is enabled in the 531 kernel configuration. cifsFYI may be set to one or 532 nore of the following flags (7 sets them all): 533 534 log cifs informational messages 0x01 535 log return codes from cifs entry points 0x02 536 log slow responses (ie which take longer than 1 second) 537 CONFIG_CIFS_STATS2 must be enabled in .config 0x04 538 539 540traceSMB If set to one, debug information is logged to the 541 system error log with the start of smb requests 542 and responses (default 0) 543LookupCacheEnable If set to one, inode information is kept cached 544 for one second improving performance of lookups 545 (default 1) 546OplockEnabled If set to one, safe distributed caching enabled. 547 (default 1) 548LinuxExtensionsEnabled If set to one then the client will attempt to 549 use the CIFS "UNIX" extensions which are optional 550 protocol enhancements that allow CIFS servers 551 to return accurate UID/GID information as well 552 as support symbolic links. If you use servers 553 such as Samba that support the CIFS Unix 554 extensions but do not want to use symbolic link 555 support and want to map the uid and gid fields 556 to values supplied at mount (rather than the 557 actual values, then set this to zero. (default 1) 558Experimental When set to 1 used to enable certain experimental 559 features (currently enables multipage writes 560 when signing is enabled, the multipage write 561 performance enhancement was disabled when 562 signing turned on in case buffer was modified 563 just before it was sent, also this flag will 564 be used to use the new experimental sessionsetup 565 code). 566 567These experimental features and tracing can be enabled by changing flags in 568/proc/fs/cifs (after the cifs module has been installed or built into the 569kernel, e.g. insmod cifs). To enable a feature set it to 1 e.g. to enable 570tracing to the kernel message log type: 571 572 echo 7 > /proc/fs/cifs/cifsFYI 573 574cifsFYI functions as a bit mask. Setting it to 1 enables additional kernel 575logging of various informational messages. 2 enables logging of non-zero 576SMB return codes while 4 enables logging of requests that take longer 577than one second to complete (except for byte range lock requests). 578Setting it to 4 requires defining CONFIG_CIFS_STATS2 manually in the 579source code (typically by setting it in the beginning of cifsglob.h), 580and setting it to seven enables all three. Finally, tracing 581the start of smb requests and responses can be enabled via: 582 583 echo 1 > /proc/fs/cifs/traceSMB 584 585Two other experimental features are under development and to test 586require enabling CONFIG_CIFS_EXPERIMENTAL 587 588 More efficient write operations 589 590 DNOTIFY fcntl: needed for support of directory change 591 notification and perhaps later for file leases) 592 593Per share (per client mount) statistics are available in /proc/fs/cifs/Stats 594if the kernel was configured with cifs statistics enabled. The statistics 595represent the number of successful (ie non-zero return code from the server) 596SMB responses to some of the more common commands (open, delete, mkdir etc.). 597Also recorded is the total bytes read and bytes written to the server for 598that share. Note that due to client caching effects this can be less than the 599number of bytes read and written by the application running on the client. 600The statistics for the number of total SMBs and oplock breaks are different in 601that they represent all for that share, not just those for which the server 602returned success. 603 604Also note that "cat /proc/fs/cifs/DebugData" will display information about 605the active sessions and the shares that are mounted. Note: NTLMv2 enablement 606will not work since its implementation is not quite complete yet. Do not alter 607the ExtendedSecurity configuration value unless you are doing specific testing. 608Enabling extended security works to Windows 2000 Workstations and XP but not to 609Windows 2000 server or Samba since it does not usually send "raw NTLMSSP" 610(instead it sends NTLMSSP encapsulated in SPNEGO/GSSAPI, which support is not 611complete in the CIFS VFS yet). 612