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    Command:

    mount.cifs

    
    
    

    SYNOPSIS

           mount.cifs {service} {mount-point} [-o options]
    
    
    

    DESCRIPTION

           This tool is part of the cifs-utils suite.
    
           mount.cifs mounts a Linux CIFS filesystem. It is usually invoked
           indirectly by the mount(8) command when using the "-t cifs" option.
           This command only works in Linux, and the kernel must support the cifs
           filesystem. The CIFS protocol is the successor to the SMB protocol and
           is supported by most Windows servers and many other commercial servers
           and Network Attached Storage appliances as well as by the popular Open
           Source server Samba.
    
           The mount.cifs utility attaches the UNC name (exported network
           resource) specified as service (using //server/share syntax, where
           "server" is the server name or IP address and "share" is the name of
           the share) to the local directory mount-point.
    
           Options to mount.cifs are specified as a comma-separated list of
           key=value pairs. It is possible to send options other than those listed
           here, assuming that the cifs filesystem kernel module (cifs.ko)
           supports them. Unrecognized cifs mount options passed to the cifs vfs
           kernel code will be logged to the kernel log.
    
           mount.cifs causes the cifs vfs to launch a thread named cifsd. After
           mounting it keeps running until the mounted resource is unmounted
           (usually via the umount utility).
    
           mount.cifs -V command displays the version of cifs mount helper.
    
           modinfo cifs command displays the version of cifs module.
    
    
    

    OPTIONS

           user=arg
               specifies the username to connect as. If this is not given, then
               the environment variable USER is used. This option can also take
               the form "user%password" or "workgroup/user" or
               "workgroup/user%password" to allow the password and workgroup to be
               specified as part of the username.
    
                   Note
                   The cifs vfs accepts the parameter user=, or for users familiar
                   with smbfs it accepts the longer form of the parameter
                   username=. Similarly the longer smbfs style parameter names may
                   be accepted as synonyms for the shorter cifs parameters
                   pass=,dom= and cred=.
    
           password=arg
               specifies the CIFS password. If this option is not given then the
    
                             username=value
                             password=value
                             domain=value
    
               This is preferred over having passwords in plaintext in a shared
               file, such as /etc/fstab. Be sure to protect any credentials file
               properly.
    
           uid=arg
               sets the uid that will own all files or directories on the mounted
               filesystem when the server does not provide ownership information.
               It may be specified as either a username or a numeric uid. When not
               specified, the default is uid 0. The mount.cifs helper must be at
               version 1.10 or higher to support specifying the uid in non-numeric
               form. See the section on FILE AND DIRECTORY OWNERSHIP AND
               PERMISSIONS below for more information.
    
           forceuid
               instructs the client to ignore any uid provided by the server for
               files and directories and to always assign the owner to be the
               value of the uid= option. See the section on FILE AND DIRECTORY
               OWNERSHIP AND PERMISSIONS below for more information.
    
           cruid=arg
               sets the uid of the owner of the credentials cache. This is
               primarily useful with sec=krb5. The default is the real uid of the
               process performing the mount. Setting this parameter directs the
               upcall to look for a credentials cache owned by that user.
    
           gid=arg
               sets the gid that will own all files or directories on the mounted
               filesystem when the server does not provide ownership information.
               It may be specified as either a groupname or a numeric gid. When
               not specified, the default is gid 0. The mount.cifs helper must be
               at version 1.10 or higher to support specifying the gid in
               non-numeric form. See the section on FILE AND DIRECTORY OWNERSHIP
               AND PERMISSIONS below for more information.
    
           forcegid
               instructs the client to ignore any gid provided by the server for
               files and directories and to always assign the owner to be the
               value of the gid= option. See the section on FILE AND DIRECTORY
               OWNERSHIP AND PERMISSIONS below for more information.
    
           port=arg
               sets the port number on which the client will attempt to contact
               the CIFS server. If this value is specified, look for an existing
               connection with this port, and use that if one exists. If one
               doesn't exist, try to create a new connection on that port. If that
               connection fails, return an error. If this value isn't specified,
               look for an existing connection on port 445 or 139. If no such
    
           netbiosname=arg
               When mounting to servers via port 139, specifies the RFC1001 source
               name to use to represent the client netbios machine name when doing
               the RFC1001 netbios session initialize.
    
           file_mode=arg
               If the server does not support the CIFS Unix extensions this
               overrides the default file mode.
    
           dir_mode=arg
               If the server does not support the CIFS Unix extensions this
               overrides the default mode for directories.
    
           ip=arg
               sets the destination IP address. This option is set automatically
               if the server name portion of the requested UNC name can be
               resolved so rarely needs to be specified by the user.
    
           domain=arg
               sets the domain (workgroup) of the user
    
           guest
               don?t prompt for a password
    
           iocharset
               Charset used to convert local path names to and from Unicode.
               Unicode is used by default for network path names if the server
               supports it. If iocharset is not specified then the nls_default
               specified during the local client kernel build will be used. If
               server does not support Unicode, this parameter is unused.
    
           ro
               mount read-only
    
           rw
               mount read-write
    
           setuids
               If the CIFS Unix extensions are negotiated with the server the
               client will attempt to set the effective uid and gid of the local
               process on newly created files, directories, and devices (create,
               mkdir, mknod). If the CIFS Unix Extensions are not negotiated, for
               newly created files and directories instead of using the default
               uid and gid specified on the the mount, cache the new file?s uid
               and gid locally which means that the uid for the file can change
               when the inode is reloaded (or the user remounts the share).
    
           nosetuids
               The client will not attempt to set the uid and gid on on newly
               created files, directories, and devices (create, mkdir, mknod)
               which will result in the server setting the uid and gid to the
               Client does not do permission checks. This can expose files on this
               mount to access by other users on the local client system. It is
               typically only needed when the server supports the CIFS Unix
               Extensions but the UIDs/GIDs on the client and server system do not
               match closely enough to allow access by the user doing the mount.
               Note that this does not affect the normal ACL check on the target
               machine done by the server software (of the server ACL against the
               user name provided at mount time).
    
           dynperm
               Instructs the server to maintain ownership and permissions in
               memory that can?t be stored on the server. This information can
               disappear at any time (whenever the inode is flushed from the
               cache), so while this may help make some applications work, it?s
               behavior is somewhat unreliable. See the section below on FILE AND
               DIRECTORY OWNERSHIP AND PERMISSIONS for more information.
    
           directio
               Do not do inode data caching on files opened on this mount. This
               precludes mmaping files on this mount. In some cases with fast
               networks and little or no caching benefits on the client (e.g. when
               the application is doing large sequential reads bigger than page
               size without rereading the same data) this can provide better
               performance than the default behavior which caches reads
               (readahead) and writes (writebehind) through the local Linux client
               pagecache if oplock (caching token) is granted and held. Note that
               direct allows write operations larger than page size to be sent to
               the server. On some kernels this requires the cifs.ko module to be
               built with the CIFS_EXPERIMENTAL configure option.
    
           strictcache
               Use for switching on strict cache mode. In this mode the client
               reads from the cache all the time it has Oplock Level II, otherwise
               - read from the server. As for write - the client stores a data in
               the cache in Exclusive Oplock case, otherwise - write directly to
               the server.
    
           rwpidforward
               Forward pid of a process who opened a file to any read or write
               operation on that file. This prevent applications like WINE from
               failing on read and write if we use mandatory brlock style.
    
           mapchars
               Translate six of the seven reserved characters (not backslash, but
               including the colon, question mark, pipe, asterik, greater than and
               less than characters) to the remap range (above 0xF000), which also
               allows the CIFS client to recognize files created with such
               characters by Windows?s POSIX emulation. This can also be useful
               when mounting to most versions of Samba (which also forbids
               creating and opening files whose names contain any of these seven
               characters). This has no effect if the server does not support
               Unicode on the wire. Please note that the files created with
               hang when the server crashes.
    
           soft
               (default) The program accessing a file on the cifs mounted file
               system will not hang when the server crashes and will return errors
               to the user application.
    
           noacl
               Do not allow POSIX ACL operations even if server would support
               them.
    
               The CIFS client can get and set POSIX ACLs (getfacl, setfacl) to
               Samba servers version 3.0.10 and later. Setting POSIX ACLs requires
               enabling both CIFS_XATTR and then CIFS_POSIX support in the CIFS
               configuration options when building the cifs module. POSIX ACL
               support can be disabled on a per mount basis by specifying "noacl"
               on mount.
    
           cifsacl
               This option is used to map CIFS/NTFS ACLs to/from Linux permission
               bits, map SIDs to/from UIDs and GIDs, and get and set Security
               Descriptors.
    
               See sections on CIFS/NTFS ACL, SID/UID/GID MAPPING, SECURITY
               DESCRIPTORS for more information.
    
           nocase
               Request case insensitive path name matching (case sensitive is the
               default if the server suports it).
    
           ignorecase
               Synonym for nocase.
    
           sec=
               Security mode. Allowed values are:
    
               ?   none attempt to connection as a null user (no name)
    
               ?   krb5 Use Kerberos version 5 authentication
    
               ?   krb5i Use Kerberos authentication and forcibly enable packet
                   signing
    
               ?   ntlm Use NTLM password hashing (default)
    
               ?   ntlmi Use NTLM password hashing and force packet signing
    
               ?   ntlmv2 Use NTLMv2 password hashing
    
               ?   ntlmv2i Use NTLMv2 password hashing and force packet signing
    
               ?   ntlmssp Use NTLMv2 password hashing encapsulated in Raw NTLMSSP
    
           sfu
               When the CIFS Unix Extensions are not negotiated, attempt to create
               device files and fifos in a format compatible with Services for
               Unix (SFU). In addition retrieve bits 10-12 of the mode via the
               SETFILEBITS extended attribute (as SFU does). In the future the
               bottom 9 bits of the mode mode also will be emulated using queries
               of the security descriptor (ACL). [NB: requires version 1.39 or
               later of the CIFS VFS. To recognize symlinks and be able to create
               symlinks in an SFU interoperable form requires version 1.40 or
               later of the CIFS VFS kernel module.
    
           serverino
               Use inode numbers (unique persistent file identifiers) returned by
               the server instead of automatically generating temporary inode
               numbers on the client. Although server inode numbers make it easier
               to spot hardlinked files (as they will have the same inode numbers)
               and inode numbers may be persistent (which is userful for some
               sofware), the server does not guarantee that the inode numbers are
               unique if multiple server side mounts are exported under a single
               share (since inode numbers on the servers might not be unique if
               multiple filesystems are mounted under the same shared higher level
               directory). Note that not all servers support returning server
               inode numbers, although those that support the CIFS Unix
               Extensions, and Windows 2000 and later servers typically do support
               this (although not necessarily on every local server filesystem).
               Parameter has no effect if the server lacks support for returning
               inode numbers or equivalent. This behavior is enabled by default.
    
           noserverino
               Client generates inode numbers itself rather than using the actual
               ones from the server.
    
               See section INODE NUMBERS for more information.
    
           nounix
               Disable the CIFS Unix Extensions for this mount. This can be useful
               in order to turn off multiple settings at once. This includes POSIX
               acls, POSIX locks, POSIX paths, symlink support and retrieving
               uids/gids/mode from the server. This can also be useful to work
               around a bug in a server that supports Unix Extensions.
    
               See section INODE NUMBERS for more information.
    
           nouser_xattr
               (default) Do not allow getfattr/setfattr to get/set xattrs, even if
               server would support it otherwise.
    
           rsize=arg
               default network read size (usually 16K). The client currently can
               not use rsize larger than CIFSMaxBufSize. CIFSMaxBufSize defaults
               to 16K and may be changed (from 8K to the maximum kmalloc size
               negotiation in 3.0.0 and up. The client and server may negotiate
               this size downward according to the server's capabilities. In
               kernels prior to 3.0.0, no negotiation is performed. It can end up
               with an existing superblock if this value isn't specified or it's
               greater or equal than the existing one.
    
           fsc
               Enable local disk caching using FS-Cache for CIFS. This option
               could be useful to improve performance on a slow link, heavily
               loaded server and/or network where reading from the disk is faster
               than reading from the server (over the network). This could also
               impact the scalability positively as the number of calls to the
               server are reduced. But, be warned that local caching is not
               suitable for all workloads, for e.g., read-once type workloads. So,
               you need to consider carefully the situation/workload before using
               this option. Currently, local disk caching is enabled for CIFS
               files opened as read-only.
    
               NOTE: This feature is available only in the recent kernels that
               have been built with the kernel config option CONFIG_CIFS_FSCACHE.
               You also need to have cachefilesd daemon installed and running to
               make the cache operational.
    
           multiuser
               Map user accesses to individual credentials when accessing the
               server. By default, CIFS mounts only use a single set of user
               credentials (the mount credentials) when accessing a share. With
               this option, the client instead creates a new session with the
               server using the user's credentials whenever a new user accesses
               the mount. Further accesses by that user will also use those
               credentials. Because the kernel cannot prompt for passwords,
               multiuser mounts are limited to mounts using sec= options that
               don't require passwords.
    
               With this change, it's feasible for the server to handle
               permissions enforcement, so this option also implies "noperm".
               Furthermore, when unix extensions aren't in use and the
               administrator has not overriden ownership using the uid= or gid=
               options, ownership of files is presented as the current user
               accessing the share.
    
           actimeo=arg
               The time (in seconds) that the CIFS client caches attributes of a
               file or directory before it requests attribute information from a
               server. During this period the changes that occur on the server
               remain undetected until the client checks the server again.
    
               By default, the attribute cache timeout is set to 1 second. This
               means more frequent on-the-wire calls to the server to check
               whether attributes have changed which could impact performance.
               With this option users can make a tradeoff between performance and
               cache metadata correctness, depending on workload needs. Shorter
               Inverse of noposixpaths.
    
           --verbose
               Print additional debugging information for the mount. Note that
               this parameter must be specified before the -o. For example:
    
               mount -t cifs //server/share /mnt --verbose -o user=username
    
    
    

    SERVICE FORMATTING AND DELIMITERS

           It?s generally preferred to use forward slashes (/) as a delimiter in
           service names. They are considered to be the "universal delimiter"
           since they are generally not allowed to be embedded within path
           components on Windows machines and the client can convert them to
           blackslashes (\) unconditionally. Conversely, backslash characters are
           allowed by POSIX to be part of a path component, and can?t be
           automatically converted in the same way.
    
           mount.cifs will attempt to convert backslashes to forward slashes where
           it?s able to do so, but it cannot do so in any path component following
           the sharename.
    
    
    

    INODE NUMBERS

           When Unix Extensions are enabled, we use the actual inode number
           provided by the server in response to the POSIX calls as an inode
           number.
    
           When Unix Extensions are disabled and "serverino" mount option is
           enabled there is no way to get the server inode number. The client
           typically maps the server-assigned "UniqueID" onto an inode number.
    
           Note that the UniqueID is a different value from the server inode
           number. The UniqueID value is unique over the scope of the entire
           server and is often greater than 2 power 32. This value often makes
           programs that are not compiled with LFS (Large File Support), to
           trigger a glibc EOVERFLOW error as this won?t fit in the target
           structure field. It is strongly recommended to compile your programs
           with LFS support (i.e. with -D_FILE_OFFSET_BITS=64) to prevent this
           problem. You can also use "noserverino" mount option to generate inode
           numbers smaller than 2 power 32 on the client. But you may not be able
           to detect hardlinks properly.
    
    
    

    CIFS/NTFS ACL, SID/UID/GID MAPPING, SECURITY DESCRIPTORS

           This option is used to work with file objects which posses Security
           Descriptors and CIFS/NTFS ACL instead of UID, GID, file permission
           bits, and POSIX ACL as user authentication model. This is the most
           common authentication model for CIFS servers and is the one used by
           Windows.
    
           Support for this requires both CIFS_XATTR and CIFS_ACL support in the
           CIFS configuration options when building the cifs module.
    
           A CIFS/NTFS ACL is mapped to file permission bits using an algorithm
           Security descriptors for a file object can be retrieved and set
           directly using extended attribute named system.cifs_acl. The security
           descriptors presented via this interface are "raw" blobs of data and
           need a userspace utility to either parse and format or to assemble it
           such as getcifsacl(8) and setcifsacl(8) respectively.
    
           Some of the things to consider while using this mount option:
    
           ?   There may be an increased latency when handling metadata due to
               additional requests to get and set security descriptors.
    
           ?   The mapping between a CIFS/NTFS ACL and POSIX file permission bits
               is imperfect and some ACL information may be lost in the
               translation.
    
           ?   If either upcall to cifs.idmap is not setup correctly or winbind is
               not configured and running, ID mapping will fail. In that case uid
               and gid will default to either to those values of the share or to
               the values of uid and/or gid mount options if specified.
    
    
    

    FILE AND DIRECTORY OWNERSHIP AND PERMISSIONS

           The core CIFS protocol does not provide unix ownership information or
           mode for files and directories. Because of this, files and directories
           will generally appear to be owned by whatever values the uid= or gid=
           options are set, and will have permissions set to the default file_mode
           and dir_mode for the mount. Attempting to change these values via
           chmod/chown will return success but have no effect.
    
           When the client and server negotiate unix extensions, files and
           directories will be assigned the uid, gid, and mode provided by the
           server. Because CIFS mounts are generally single-user, and the same
           credentials are used no matter what user accesses the mount, newly
           created files and directories will generally be given ownership
           corresponding to whatever credentials were used to mount the share.
    
           If the uid?s and gid?s being used do not match on the client and
           server, the forceuid and forcegid options may be helpful. Note however,
           that there is no corresponding option to override the mode. Permissions
           assigned to a file when forceuid or forcegid are in effect may not
           reflect the the real permissions.
    
           When unix extensions are not negotiated, it?s also possible to emulate
           them locally on the server using the "dynperm" mount option. When this
           mount option is in effect, newly created files and directories will
           receive what appear to be proper permissions. These permissions are not
           stored on the server however and can disappear at any time in the
           future (subject to the whims of the kernel flushing out the inode
           cache). In general, this mount option is discouraged.
    
           It?s also possible to override permission checking on the client
           altogether via the noperm option. Server-side permission checks cannot
           be overriden. The permission checks done by the server will always
    
    
    

    NOTES

           This command may be used only by root, unless installed setuid, in
           which case the noeexec and nosuid mount flags are enabled. When
           installed as a setuid program, the program follows the conventions set
           forth by the mount program for user mounts.
    
           Some samba client tools like smbclient(8) honour client-side
           configuration parameters present in smb.conf. Unlike those client
           tools, mount.cifs ignores smb.conf completely.
    
    
    

    CONFIGURATION

           The primary mechanism for making configuration changes and for reading
           debug information for the cifs vfs is via the Linux /proc filesystem.
           In the directory /proc/fs/cifs are various configuration files and
           pseudo files which can display debug information. There are additional
           startup options such as maximum buffer size and number of buffers which
           only may be set when the kernel cifs vfs (cifs.ko module) is loaded.
           These can be seen by running the modinfo utility against the file
           cifs.ko which will list the options that may be passed to cifs during
           module installation (device driver load). For more information see the
           kernel file fs/cifs/README.
    
    
    

    BUGS

           Mounting using the CIFS URL specification is currently not supported.
    
           The credentials file does not handle usernames or passwords with
           leading space.
    
           Note that the typical response to a bug report is a suggestion to try
           the latest version first. So please try doing that first, and always
           include which versions you use of relevant software when reporting bugs
           (minimum: mount.cifs (try mount.cifs -V), kernel (see /proc/version)
           and server type you are trying to contact.
    
    
    

    VERSION

           This man page is correct for version 1.74 of the cifs vfs filesystem
           (roughly Linux kernel 3.0).
    
    
    

    SEE ALSO

           Documentation/filesystems/cifs.txt and fs/cifs/README in the linux
           kernel source tree may contain additional options and information.
    
           cifs.upcall(8)
    
    
    

    AUTHOR

           Steve French
    
           The syntax and manpage were loosely based on that of smbmount. It was
           converted to Docbook/XML by Jelmer Vernooij.
    
           The maintainer of the Linux cifs vfs and the userspace tool mount.cifs
           is Steve French. The Linux CIFS Mailing list is the preferred place to
    
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