mount.cifs(8)
MOUNT.CIFS(8) MAINTENANCE COMMANDS 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 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 popu-
lar Open Source server Samba.
The mount.cifs utility attaches the UNC name (exported net-
work 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. Unrecog-
nized 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
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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 charac-
ter (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 pass-
word. 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. This parameter is ignored when the target
server supports the CIFS Unix extensions.
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. This parameter is ignored when the target
server supports the CIFS Unix extensions.
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.
netbiosname=arg
When mounting to servers via port 139, specifies the
RFC1001 source name to use to represent the client net-
bios 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.
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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 host or IP address.
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 sup-
port 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
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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 opera-
tions 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
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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, set-
facl) 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 sensi-
tive 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 sign-
ing
[NB This [sec parameter] is under development and
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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 generat-
ing 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 direc-
tory). 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
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wsize=arg
default network write size
--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
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 (dev-
ice 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 sugges-
tion to try the latest version first. So please try doing
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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 1.39 of the cifs vfs
filesystem (roughly Linux kernel 2.6.15).
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 Ver-
nooij.
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 pro-
grams.
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