MOUNT.CIFS(8)

NAME

mount.cifs - mount using the Common Internet File System (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
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 specified.
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.
credentials=filename
specifies a file that contains a username and/or password and
optionally the name of the workgroup. The format of the file is:

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.
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 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.
servern=arg
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.
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
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.
perm
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
default.
noperm
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.
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
mapchars mount option may not be accessible if the share is mounted without that option.
nomapchars
Do not translate any of these seven characters (default)
intr
currently unimplemented
nointr
(default) currently unimplemented
hard
The program accessing a file on the cifs mounted file system will
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 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 basis by specifying "noacl" on mount.
nocase
Request case insensitive path name matching (case sensitive is the default if the server suports it).
sec=
Security mode. Allowed values are:
o none attempt to connection as a null user (no name)
o krb5 Use Kerberos version 5 authentication
o krb5i Use Kerberos authentication and packet signing
o ntlm Use NTLM password hashing (default)
o ntlmi Use NTLM password hashing with signing (if
/proc/fs/cifs/PacketSigningEnabled on or if server requires
signing also can be the default)
o ntlmv2 Use NTLMv2 password hashing
o 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]
nobrl
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).
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.
noserverino
Client generates inode numbers (rather than using the actual one
from the server) by default.
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
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)
wsize=arg
default network write size (default 57344) maximum wsize currently allowed by CIFS is 57344 (fourteen 4096 byte pages)
--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.

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
correspond to the credentials used to mount the share, and not
necessarily to the user who is accessing the share.

ENVIRONMENT VARIABLES

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 client.

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.

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 1.52 of the cifs vfs filesystem
(roughly Linux kernel 2.6.24).

SEE ALSO

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

umount.cifs(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 ask questions regarding these programs.
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