MOUNT.CIFS(8) System Administration tools MOUNT.CIFS(8)NAMEmount.cifs - mount using the Common Internet File System (CIFS)
SYNOPSISmount.cifs {service} {mount-point} [-o options]
DESCRIPTION
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).
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. The
format of the file is:
username=value
password=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 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.
gid=arg
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.
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).
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.
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 3.10 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.
nocase
Request case insensitive path name matching (case sensitive is the
default if the server suports it).
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 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]
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.
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.
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.
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.
Samba 3.0 11/20/2008 MOUNT.CIFS(8)
