mount.cifs manpage

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MOUNT.CIFS(8)		  System Administration tools		 MOUNT.CIFS(8)

       mount.cifs - mount using the Common Internet File System (CIFS)

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

       This tool is part of the samba(7) 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) to the local directory mount-point. It is possible to set the
       mode for mount.cifs to setuid root to allow non-root users to mount
       shares to directories for which they have write permission.

       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).

	   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.

	   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=.

	   specifies the CIFS password. If this option is not given then the
	   environment variable PASSWD is used. If the password is not
	   specified directly or indirectly via an argument to mount,
	   mount.cifs will prompt for a password, unless the guest option is

	   Note that a password which contains the delimiter character (i.e. a
	   comma ?,?) will fail to be parsed correctly on the command line.
	   However, the same password defined in the PASSWD environment
	   variable or via a credentials file (see below) or entered at the
	   password prompt will be read correctly.

	   specifies a file that contains a username and/or password. The
	   format of the file is:

	   This is preferred over having passwords in plaintext in a shared
	   file, such as /etc/fstab. Be sure to protect any credentials file

	   sets the uid that will own all files on the mounted filesystem. It
	   may be specified as either a username or a numeric uid. For mounts
	   to servers which do support the CIFS Unix extensions, such as a
	   properly configured Samba server, the server provides the uid, gid
	   and mode so this parameter should not be specified unless the
	   server and client uid and gid numbering differ. If the server and
	   client are in the same domain (e.g. running winbind or nss_ldap)
	   and the server supports the Unix Extensions then the uid and gid
	   can be retrieved from the server (and uid and gid would not have to
	   be specifed on the mount. For servers which do not support the CIFS
	   Unix extensions, the default uid (and gid) returned on lookup of
	   existing files will be the uid (gid) of the person who executed the
	   mount (root, except when mount.cifs is configured setuid for user
	   mounts) unless the "uid=" (gid) mount option is specified. For the
	   uid (gid) of newly created files and directories, ie files created
	   since the last mount of the server share, the expected uid (gid) is
	   cached as long as the inode remains in memory on the client. Also
	   note that permission checks (authorization checks) on accesses to a
	   file occur at the server, but there are cases in which an
	   administrator may want to restrict at the client as well. For those
	   servers which do not report a uid/gid owner (such as Windows),
	   permissions can also be checked at the client, and a crude form of
	   client side permission checking can be enabled by specifying
	   file_mode and dir_mode on the client. Note that the mount.cifs
	   helper must be at version 1.10 or higher to support specifying the
	   uid (or gid) in non-numeric form.

	   sets the gid that will own all files on the mounted filesystem. It
	   may be specified as either a groupname or a numeric gid. For other
	   considerations see the description of uid above.

	   sets the port number on the server to attempt to contact to
	   negotiate CIFS support. If the CIFS server is not listening on this
	   port or if it is not specified, the default ports will be tried
	   i.e. port 445 is tried and if no response then port 139 is tried.

	   Specify the server netbios name (RFC1001 name) to use when
	   attempting to setup a session to the server. Although rarely needed
	   for mounting to newer servers, this option is needed for mounting
	   to some older servers (such as OS/2 or Windows 98 and Windows ME)
	   since when connecting over port 139 they, unlike most newer
	   servers, do not support a default server name. A server name can be
	   up to 15 characters long and is usually uppercased.

	   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.

	   If the server does not support the CIFS Unix extensions this
	   overrides the default file mode.

	   If the server does not support the CIFS Unix extensions this
	   overrides the default mode for directories.

	   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.

	   sets the domain (workgroup) of the user

	   don?t prompt for a password

	   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.

	   mount read-only

	   mount read-write

	   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).

	   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
	   default (usually the server uid of the user who mounted the share).
	   Letting the server (rather than the client) set the uid and gid is
	   the default.If the CIFS Unix Extensions are not negotiated then the
	   uid and gid for new files will appear to be the uid (gid) of the
	   mounter or the uid (gid) parameter specified on the mount.

	   Client does permission checks (vfs_permission check of uid and gid
	   of the file against the mode and desired operation), Note that this
	   is in addition to the normal ACL check on the target machine done
	   by the server software. Client permission checking is enabled by

	   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).

	   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.

	   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.

	   Do not translate any of these seven characters (default)

	   currently unimplemented

	   (default) currently unimplemented

	   The program accessing a file on the cifs mounted file system will
	   hang when the server crashes.

	   (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.

	   Do not allow POSIX ACL operations even if server would support

	   The CIFS client can get and set POSIX ACLs (getfacl, setfacl) to
	   Samba servers version 3.10 and later. Setting POSIX ACLs requires
	   enabling both XATTR and then POSIX support in the CIFS
	   configuration options when building the cifs module. POSIX ACL
	   support can be disabled on a per mount basic by specifying "noacl"
	   on mount.

	   Request case insensitive path name matching (case sensitive is the
	   default if the server suports it).

	   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 packet signing

	   ?   ntlm Use NTLM password hashing (default)

	   ?   ntlmi Use NTLM password hashing with signing (if
	       /proc/fs/cifs/PacketSigningEnabled on or if server requires
	       signing also can be the default)

	   ?   ntlmv2 Use NTLMv2 password hashing

	   ?   ntlmv2i Use NTLMv2 password hashing with packet signing

	   [NB This [sec parameter] is under development and expected to be
	   available in cifs kernel module 1.40 and later]

	   Do not send byte range lock requests to the server. This is
	   necessary for certain applications that break with cifs style
	   mandatory byte range locks (and most cifs servers do not yet
	   support requesting advisory byte range locks).

	   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.

	   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.

	   client generates inode numbers (rather than using the actual one
	   from the server) by default.

	   (default) Do not allow getfattr/setfattr to get/set xattrs, even if
	   server would support it otherwise.

	   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
	   allowed by your kernel) at module install time for cifs.ko. Setting
	   CIFSMaxBufSize to a very large value will cause cifs to use more
	   memory and may reduce performance in some cases. To use rsize
	   greater than 127K (the original cifs protocol maximum) also
	   requires that the server support a new Unix Capability flag (for
	   very large read) which some newer servers (e.g. Samba 3.0.26 or
	   later) do. rsize can be set from a minimum of 2048 to a maximum of
	   130048 (127K or CIFSMaxBufSize, whichever is smaller)

	   default network write size (default 57344) maximum wsize currently
	   allowed by CIFS is 57344 (fourteen 4096 byte pages)

	   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

       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.

       The variable USER may contain the username of the person to be used to
       authenticate to the server. The variable can be used to set both
       username and password by using the format username%password.

       The variable PASSWD may contain the password of the person using the

       The variable PASSWD_FILE may contain the pathname of a file to read the
       password from. A single line of input is read and used as the password.

       This command may be used only by root, unless installed setuid, in
       which case the noeexec and nosuid mount flags are enabled.

       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.

       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.

       This man page is correct for version 1.52 of the cifs vfs filesystem
       (roughly Linux kernel 2.6.24).

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


       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
       ask questions regarding these programs.

Samba 3.0			  11/20/2008			 MOUNT.CIFS(8)
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