863 lines
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ReStructuredText
863 lines
39 KiB
ReStructuredText
=====
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Usage
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=====
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This module supports the SMB3 family of advanced network protocols (as well
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as older dialects, originally called "CIFS" or SMB1).
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The CIFS VFS module for Linux supports many advanced network filesystem
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features such as hierarchical DFS like namespace, hardlinks, locking and more.
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It was designed to comply with the SNIA CIFS Technical Reference (which
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supersedes the 1992 X/Open SMB Standard) as well as to perform best practice
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practical interoperability with Windows 2000, Windows XP, Samba and equivalent
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servers. This code was developed in participation with the Protocol Freedom
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Information Foundation. CIFS and now SMB3 has now become a defacto
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standard for interoperating between Macs and Windows and major NAS appliances.
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Please see
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MS-SMB2 (for detailed SMB2/SMB3/SMB3.1.1 protocol specification)
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or https://samba.org/samba/PFIF/
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for more details.
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For questions or bug reports please contact:
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smfrench@gmail.com
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See the project page at: https://wiki.samba.org/index.php/LinuxCIFS_utils
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Build instructions
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==================
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For Linux:
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1) Download the kernel (e.g. from https://www.kernel.org)
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and change directory into the top of the kernel directory tree
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(e.g. /usr/src/linux-2.5.73)
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2) make menuconfig (or make xconfig)
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3) select cifs from within the network filesystem choices
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4) save and exit
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5) make
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Installation instructions
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=========================
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If you have built the CIFS vfs as module (successfully) simply
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type ``make modules_install`` (or if you prefer, manually copy the file to
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the modules directory e.g. /lib/modules/6.3.0-060300-generic/kernel/fs/smb/client/cifs.ko).
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If you have built the CIFS vfs into the kernel itself, follow the instructions
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for your distribution on how to install a new kernel (usually you
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would simply type ``make install``).
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If you do not have the utility mount.cifs (in the Samba 4.x source tree and on
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the CIFS VFS web site) copy it to the same directory in which mount helpers
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reside (usually /sbin). Although the helper software is not
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required, mount.cifs is recommended. Most distros include a ``cifs-utils``
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package that includes this utility so it is recommended to install this.
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Note that running the Winbind pam/nss module (logon service) on all of your
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Linux clients is useful in mapping Uids and Gids consistently across the
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domain to the proper network user. The mount.cifs mount helper can be
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found at cifs-utils.git on git.samba.org
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If cifs is built as a module, then the size and number of network buffers
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and maximum number of simultaneous requests to one server can be configured.
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Changing these from their defaults is not recommended. By executing modinfo::
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modinfo <path to cifs.ko>
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on kernel/fs/smb/client/cifs.ko the list of configuration changes that can be made
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at module initialization time (by running insmod cifs.ko) can be seen.
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Recommendations
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===============
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To improve security the SMB2.1 dialect or later (usually will get SMB3.1.1) is now
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the new default. To use old dialects (e.g. to mount Windows XP) use "vers=1.0"
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on mount (or vers=2.0 for Windows Vista). Note that the CIFS (vers=1.0) is
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much older and less secure than the default dialect SMB3 which includes
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many advanced security features such as downgrade attack detection
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and encrypted shares and stronger signing and authentication algorithms.
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There are additional mount options that may be helpful for SMB3 to get
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improved POSIX behavior (NB: can use vers=3 to force SMB3 or later, never 2.1):
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``mfsymlinks`` and either ``cifsacl`` or ``modefromsid`` (usually with ``idsfromsid``)
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Allowing User Mounts
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====================
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To permit users to mount and unmount over directories they own is possible
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with the cifs vfs. A way to enable such mounting is to mark the mount.cifs
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utility as suid (e.g. ``chmod +s /sbin/mount.cifs``). To enable users to
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umount shares they mount requires
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1) mount.cifs version 1.4 or later
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2) an entry for the share in /etc/fstab indicating that a user may
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unmount it e.g.::
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//server/usersharename /mnt/username cifs user 0 0
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Note that when the mount.cifs utility is run suid (allowing user mounts),
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in order to reduce risks, the ``nosuid`` mount flag is passed in on mount to
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disallow execution of an suid program mounted on the remote target.
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When mount is executed as root, nosuid is not passed in by default,
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and execution of suid programs on the remote target would be enabled
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by default. This can be changed, as with nfs and other filesystems,
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by simply specifying ``nosuid`` among the mount options. For user mounts
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though to be able to pass the suid flag to mount requires rebuilding
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mount.cifs with the following flag: CIFS_ALLOW_USR_SUID
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There is a corresponding manual page for cifs mounting in the Samba 3.0 and
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later source tree in docs/manpages/mount.cifs.8
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Allowing User Unmounts
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======================
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To permit users to unmount directories that they have user mounted (see above),
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the utility umount.cifs may be used. It may be invoked directly, or if
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umount.cifs is placed in /sbin, umount can invoke the cifs umount helper
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(at least for most versions of the umount utility) for umount of cifs
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mounts, unless umount is invoked with -i (which will avoid invoking a umount
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helper). As with mount.cifs, to enable user unmounts umount.cifs must be marked
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as suid (e.g. ``chmod +s /sbin/umount.cifs``) or equivalent (some distributions
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allow adding entries to a file to the /etc/permissions file to achieve the
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equivalent suid effect). For this utility to succeed the target path
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must be a cifs mount, and the uid of the current user must match the uid
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of the user who mounted the resource.
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Also note that the customary way of allowing user mounts and unmounts is
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(instead of using mount.cifs and unmount.cifs as suid) to add a line
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to the file /etc/fstab for each //server/share you wish to mount, but
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this can become unwieldy when potential mount targets include many
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or unpredictable UNC names.
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Samba Considerations
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====================
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Most current servers support SMB2.1 and SMB3 which are more secure,
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but there are useful protocol extensions for the older less secure CIFS
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dialect, so to get the maximum benefit if mounting using the older dialect
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(CIFS/SMB1), we recommend using a server that supports the SNIA CIFS
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Unix Extensions standard (e.g. almost any version of Samba ie version
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2.2.5 or later) but the CIFS vfs works fine with a wide variety of CIFS servers.
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Note that uid, gid and file permissions will display default values if you do
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not have a server that supports the Unix extensions for CIFS (such as Samba
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2.2.5 or later). To enable the Unix CIFS Extensions in the Samba server, add
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the line::
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unix extensions = yes
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to your smb.conf file on the server. Note that the following smb.conf settings
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are also useful (on the Samba server) when the majority of clients are Unix or
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Linux::
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case sensitive = yes
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delete readonly = yes
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ea support = yes
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Note that server ea support is required for supporting xattrs from the Linux
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cifs client, and that EA support is present in later versions of Samba (e.g.
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3.0.6 and later (also EA support works in all versions of Windows, at least to
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shares on NTFS filesystems). Extended Attribute (xattr) support is an optional
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feature of most Linux filesystems which may require enabling via
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make menuconfig. Client support for extended attributes (user xattr) can be
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disabled on a per-mount basis by specifying ``nouser_xattr`` on mount.
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The CIFS client can get and set POSIX ACLs (getfacl, setfacl) to Samba servers
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version 3.10 and later. Setting POSIX ACLs requires enabling both XATTR and
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then POSIX support in the CIFS configuration options when building the cifs
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module. POSIX ACL support can be disabled on a per mount basic by specifying
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``noacl`` on mount.
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Some administrators may want to change Samba's smb.conf ``map archive`` and
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``create mask`` parameters from the default. Unless the create mask is changed
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newly created files can end up with an unnecessarily restrictive default mode,
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which may not be what you want, although if the CIFS Unix extensions are
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enabled on the server and client, subsequent setattr calls (e.g. chmod) can
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fix the mode. Note that creating special devices (mknod) remotely
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may require specifying a mkdev function to Samba if you are not using
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Samba 3.0.6 or later. For more information on these see the manual pages
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(``man smb.conf``) on the Samba server system. Note that the cifs vfs,
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unlike the smbfs vfs, does not read the smb.conf on the client system
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(the few optional settings are passed in on mount via -o parameters instead).
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Note that Samba 2.2.7 or later includes a fix that allows the CIFS VFS to delete
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open files (required for strict POSIX compliance). Windows Servers already
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supported this feature. Samba server does not allow symlinks that refer to files
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outside of the share, so in Samba versions prior to 3.0.6, most symlinks to
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files with absolute paths (ie beginning with slash) such as::
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ln -s /mnt/foo bar
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would be forbidden. Samba 3.0.6 server or later includes the ability to create
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such symlinks safely by converting unsafe symlinks (ie symlinks to server
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files that are outside of the share) to a samba specific format on the server
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that is ignored by local server applications and non-cifs clients and that will
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not be traversed by the Samba server). This is opaque to the Linux client
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application using the cifs vfs. Absolute symlinks will work to Samba 3.0.5 or
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later, but only for remote clients using the CIFS Unix extensions, and will
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be invisible to Windows clients and typically will not affect local
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applications running on the same server as Samba.
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Use instructions
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================
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Once the CIFS VFS support is built into the kernel or installed as a module
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(cifs.ko), you can use mount syntax like the following to access Samba or
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Mac or Windows servers::
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mount -t cifs //9.53.216.11/e$ /mnt -o username=myname,password=mypassword
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Before -o the option -v may be specified to make the mount.cifs
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mount helper display the mount steps more verbosely.
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After -o the following commonly used cifs vfs specific options
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are supported::
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username=<username>
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password=<password>
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domain=<domain name>
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Other cifs mount options are described below. Use of TCP names (in addition to
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ip addresses) is available if the mount helper (mount.cifs) is installed. If
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you do not trust the server to which are mounted, or if you do not have
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cifs signing enabled (and the physical network is insecure), consider use
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of the standard mount options ``noexec`` and ``nosuid`` to reduce the risk of
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running an altered binary on your local system (downloaded from a hostile server
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or altered by a hostile router).
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Although mounting using format corresponding to the CIFS URL specification is
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not possible in mount.cifs yet, it is possible to use an alternate format
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for the server and sharename (which is somewhat similar to NFS style mount
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syntax) instead of the more widely used UNC format (i.e. \\server\share)::
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mount -t cifs tcp_name_of_server:share_name /mnt -o user=myname,pass=mypasswd
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When using the mount helper mount.cifs, passwords may be specified via alternate
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mechanisms, instead of specifying it after -o using the normal ``pass=`` syntax
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on the command line:
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1) By including it in a credential file. Specify credentials=filename as one
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of the mount options. Credential files contain two lines::
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username=someuser
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password=your_password
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2) By specifying the password in the PASSWD environment variable (similarly
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the user name can be taken from the USER environment variable).
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3) By specifying the password in a file by name via PASSWD_FILE
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4) By specifying the password in a file by file descriptor via PASSWD_FD
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If no password is provided, mount.cifs will prompt for password entry
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Restrictions
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============
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Servers must support either "pure-TCP" (port 445 TCP/IP CIFS connections) or RFC
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1001/1002 support for "Netbios-Over-TCP/IP." This is not likely to be a
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problem as most servers support this.
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Valid filenames differ between Windows and Linux. Windows typically restricts
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filenames which contain certain reserved characters (e.g.the character :
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which is used to delimit the beginning of a stream name by Windows), while
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Linux allows a slightly wider set of valid characters in filenames. Windows
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servers can remap such characters when an explicit mapping is specified in
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the Server's registry. Samba starting with version 3.10 will allow such
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filenames (ie those which contain valid Linux characters, which normally
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would be forbidden for Windows/CIFS semantics) as long as the server is
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configured for Unix Extensions (and the client has not disabled
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/proc/fs/cifs/LinuxExtensionsEnabled). In addition the mount option
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``mapposix`` can be used on CIFS (vers=1.0) to force the mapping of
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illegal Windows/NTFS/SMB characters to a remap range (this mount parameter
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is the default for SMB3). This remap (``mapposix``) range is also
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compatible with Mac (and "Services for Mac" on some older Windows).
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CIFS VFS Mount Options
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======================
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A partial list of the supported mount options follows:
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username
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The user name to use when trying to establish
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the CIFS session.
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password
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The user password. If the mount helper is
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installed, the user will be prompted for password
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if not supplied.
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ip
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The ip address of the target server
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unc
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The target server Universal Network Name (export) to
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mount.
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domain
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Set the SMB/CIFS workgroup name prepended to the
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username during CIFS session establishment
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forceuid
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Set the default uid for inodes to the uid
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passed in on mount. For mounts to servers
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which do support the CIFS Unix extensions, such as a
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properly configured Samba server, the server provides
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the uid, gid and mode so this parameter should not be
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specified unless the server and clients uid and gid
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numbering differ. If the server and client are in the
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same domain (e.g. running winbind or nss_ldap) and
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the server supports the Unix Extensions then the uid
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and gid can be retrieved from the server (and uid
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and gid would not have to be specified on the mount.
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For servers which do not support the CIFS Unix
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extensions, the default uid (and gid) returned on lookup
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of existing files will be the uid (gid) of the person
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who executed the mount (root, except when mount.cifs
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is configured setuid for user mounts) unless the ``uid=``
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(gid) mount option is specified. Also note that permission
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checks (authorization checks) on accesses to a file occur
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at the server, but there are cases in which an administrator
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may want to restrict at the client as well. For those
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servers which do not report a uid/gid owner
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(such as Windows), permissions can also be checked at the
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client, and a crude form of client side permission checking
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can be enabled by specifying file_mode and dir_mode on
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the client. (default)
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forcegid
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(similar to above but for the groupid instead of uid) (default)
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noforceuid
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Fill in file owner information (uid) by requesting it from
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the server if possible. With this option, the value given in
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the uid= option (on mount) will only be used if the server
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can not support returning uids on inodes.
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noforcegid
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(similar to above but for the group owner, gid, instead of uid)
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uid
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Set the default uid for inodes, and indicate to the
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cifs kernel driver which local user mounted. If the server
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supports the unix extensions the default uid is
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not used to fill in the owner fields of inodes (files)
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unless the ``forceuid`` parameter is specified.
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gid
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Set the default gid for inodes (similar to above).
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file_mode
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If CIFS Unix extensions are not supported by the server
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this overrides the default mode for file inodes.
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fsc
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Enable local disk caching using FS-Cache (off by default). This
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option could be useful to improve performance on a slow link,
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heavily loaded server and/or network where reading from the
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disk is faster than reading from the server (over the network).
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This could also impact scalability positively as the
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number of calls to the server are reduced. However, local
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caching is not suitable for all workloads for e.g. read-once
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type workloads. So, you need to consider carefully your
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workload/scenario before using this option. Currently, local
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disk caching is functional for CIFS files opened as read-only.
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dir_mode
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If CIFS Unix extensions are not supported by the server
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this overrides the default mode for directory inodes.
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port
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attempt to contact the server on this tcp port, before
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trying the usual ports (port 445, then 139).
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iocharset
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Codepage used to convert local path names to and from
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Unicode. Unicode is used by default for network path
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names if the server supports it. If iocharset is
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not specified then the nls_default specified
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during the local client kernel build will be used.
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If server does not support Unicode, this parameter is
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unused.
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rsize
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default read size (usually 16K). The client currently
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can not use rsize larger than CIFSMaxBufSize. CIFSMaxBufSize
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defaults to 16K and may be changed (from 8K to the maximum
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kmalloc size allowed by your kernel) at module install time
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for cifs.ko. Setting CIFSMaxBufSize to a very large value
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will cause cifs to use more memory and may reduce performance
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in some cases. To use rsize greater than 127K (the original
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cifs protocol maximum) also requires that the server support
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a new Unix Capability flag (for very large read) which some
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newer servers (e.g. Samba 3.0.26 or later) do. rsize can be
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set from a minimum of 2048 to a maximum of 130048 (127K or
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CIFSMaxBufSize, whichever is smaller)
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wsize
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default write size (default 57344)
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maximum wsize currently allowed by CIFS is 57344 (fourteen
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4096 byte pages)
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actimeo=n
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attribute cache timeout in seconds (default 1 second).
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After this timeout, the cifs client requests fresh attribute
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information from the server. This option allows to tune the
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attribute cache timeout to suit the workload needs. Shorter
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timeouts mean better the cache coherency, but increased number
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of calls to the server. Longer timeouts mean reduced number
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of calls to the server at the expense of less stricter cache
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coherency checks (i.e. incorrect attribute cache for a short
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period of time).
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rw
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mount the network share read-write (note that the
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server may still consider the share read-only)
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ro
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mount network share read-only
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version
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used to distinguish different versions of the
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mount helper utility (not typically needed)
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sep
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if first mount option (after the -o), overrides
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the comma as the separator between the mount
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parameters. e.g.::
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-o user=myname,password=mypassword,domain=mydom
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could be passed instead with period as the separator by::
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-o sep=.user=myname.password=mypassword.domain=mydom
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this might be useful when comma is contained within username
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or password or domain. This option is less important
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when the cifs mount helper cifs.mount (version 1.1 or later)
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is used.
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nosuid
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Do not allow remote executables with the suid bit
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program to be executed. This is only meaningful for mounts
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to servers such as Samba which support the CIFS Unix Extensions.
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If you do not trust the servers in your network (your mount
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targets) it is recommended that you specify this option for
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greater security.
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exec
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Permit execution of binaries on the mount.
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noexec
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Do not permit execution of binaries on the mount.
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dev
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Recognize block devices on the remote mount.
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nodev
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Do not recognize devices on the remote mount.
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suid
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Allow remote files on this mountpoint with suid enabled to
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be executed (default for mounts when executed as root,
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nosuid is default for user mounts).
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credentials
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Although ignored by the cifs kernel component, it is used by
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the mount helper, mount.cifs. When mount.cifs is installed it
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opens and reads the credential file specified in order
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to obtain the userid and password arguments which are passed to
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the cifs vfs.
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guest
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Although ignored by the kernel component, the mount.cifs
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mount helper will not prompt the user for a password
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if guest is specified on the mount options. If no
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password is specified a null password will be used.
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perm
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|
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, but it may be useful with
|
|
non CIFS Unix Extension mounts for cases in which the default
|
|
mode is specified on the mount but is not to be enforced on the
|
|
client (e.g. perhaps when MultiUserMount is enabled)
|
|
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).
|
|
serverino
|
|
Use server's inode numbers instead of generating automatically
|
|
incrementing inode numbers on the client. Although this will
|
|
make it easier to spot hardlinked files (as they will have
|
|
the same inode numbers) and inode numbers may be persistent,
|
|
note that 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 some older
|
|
(e.g. pre-Windows 2000) do not support returning UniqueIDs
|
|
or the CIFS Unix Extensions equivalent and for those
|
|
this mount option will have no effect. Exporting cifs mounts
|
|
under nfsd requires this mount option on the cifs mount.
|
|
This is now the default if server supports the
|
|
required network operation.
|
|
noserverino
|
|
Client generates inode numbers (rather than using the actual one
|
|
from the server). These inode numbers will vary after
|
|
unmount or reboot which can confuse some applications,
|
|
but not all server filesystems support unique inode
|
|
numbers.
|
|
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 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.
|
|
netbiosname
|
|
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.
|
|
direct
|
|
Do not do inode data caching on files opened on this mount.
|
|
This precludes mmapping 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.
|
|
strictcache
|
|
Use for switching on strict cache mode. In this mode the
|
|
client read from the cache all the time it has Oplock Level II,
|
|
otherwise - read from the server. All written data are stored
|
|
in the cache, but if the client doesn't have Exclusive Oplock,
|
|
it writes the data 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.
|
|
acl
|
|
Allow setfacl and getfacl to manage posix ACLs if server
|
|
supports them. (default)
|
|
noacl
|
|
Do not allow setfacl and getfacl calls on this mount
|
|
user_xattr
|
|
Allow getting and setting user xattrs (those attributes whose
|
|
name begins with ``user.`` or ``os2.``) as OS/2 EAs (extended
|
|
attributes) to the server. This allows support of the
|
|
setfattr and getfattr utilities. (default)
|
|
nouser_xattr
|
|
Do not allow getfattr/setfattr to get/set/list xattrs
|
|
mapchars
|
|
Translate six of the seven reserved characters (not backslash)::
|
|
|
|
*?<>|:
|
|
|
|
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).
|
|
nocase
|
|
Request case insensitive path name matching (case
|
|
sensitive is the default if the server supports it).
|
|
(mount option ``ignorecase`` is identical to ``nocase``)
|
|
posixpaths
|
|
If CIFS Unix extensions are supported, attempt to
|
|
negotiate posix path name support which allows certain
|
|
characters forbidden in typical CIFS filenames, without
|
|
requiring remapping. (default)
|
|
noposixpaths
|
|
If CIFS Unix extensions are supported, do not request
|
|
posix path name support (this may cause servers to
|
|
reject creatingfile with certain reserved characters).
|
|
nounix
|
|
Disable the CIFS Unix Extensions for this mount (tree
|
|
connection). This is rarely needed, but it may be useful
|
|
in order to turn off multiple settings all at once (ie
|
|
posix acls, posix locks, posix paths, symlink support
|
|
and retrieving uids/gids/mode from the server) or to
|
|
work around a bug in server which implement the Unix
|
|
Extensions.
|
|
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).
|
|
forcemandatorylock
|
|
Even if the server supports posix (advisory) byte range
|
|
locking, send only mandatory lock requests. For some
|
|
(presumably rare) applications, originally coded for
|
|
DOS/Windows, which require Windows style mandatory byte range
|
|
locking, they may be able to take advantage of this option,
|
|
forcing the cifs client to only send mandatory locks
|
|
even if the cifs server would support posix advisory locks.
|
|
``forcemand`` is accepted as a shorter form of this mount
|
|
option.
|
|
nostrictsync
|
|
If this mount option is set, when an application does an
|
|
fsync call then the cifs client does not send an SMB Flush
|
|
to the server (to force the server to write all dirty data
|
|
for this file immediately to disk), although cifs still sends
|
|
all dirty (cached) file data to the server and waits for the
|
|
server to respond to the write. Since SMB Flush can be
|
|
very slow, and some servers may be reliable enough (to risk
|
|
delaying slightly flushing the data to disk on the server),
|
|
turning on this option may be useful to improve performance for
|
|
applications that fsync too much, at a small risk of server
|
|
crash. If this mount option is not set, by default cifs will
|
|
send an SMB flush request (and wait for a response) on every
|
|
fsync call.
|
|
nodfs
|
|
Disable DFS (global name space support) even if the
|
|
server claims to support it. This can help work around
|
|
a problem with parsing of DFS paths with Samba server
|
|
versions 3.0.24 and 3.0.25.
|
|
remount
|
|
remount the share (often used to change from ro to rw mounts
|
|
or vice versa)
|
|
cifsacl
|
|
Report mode bits (e.g. on stat) based on the Windows ACL for
|
|
the file. (EXPERIMENTAL)
|
|
servern
|
|
Specify the server 's netbios name (RFC1001 name) to use
|
|
when attempting to setup a session to the server.
|
|
This is needed for mounting to some older servers (such
|
|
as OS/2 or Windows 98 and Windows ME) since they do not
|
|
support a default server name. A server name can be up
|
|
to 15 characters long and is usually uppercased.
|
|
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 also will be emulated using queries of the security
|
|
descriptor (ACL).
|
|
mfsymlinks
|
|
Enable support for Minshall+French symlinks
|
|
(see http://wiki.samba.org/index.php/UNIX_Extensions#Minshall.2BFrench_symlinks)
|
|
This option is ignored when specified together with the
|
|
'sfu' option. Minshall+French symlinks are used even if
|
|
the server supports the CIFS Unix Extensions.
|
|
sign
|
|
Must use packet signing (helps avoid unwanted data modification
|
|
by intermediate systems in the route). Note that signing
|
|
does not work with lanman or plaintext authentication.
|
|
seal
|
|
Must seal (encrypt) all data on this mounted share before
|
|
sending on the network. Requires support for Unix Extensions.
|
|
Note that this differs from the sign mount option in that it
|
|
causes encryption of data sent over this mounted share but other
|
|
shares mounted to the same server are unaffected.
|
|
locallease
|
|
This option is rarely needed. Fcntl F_SETLEASE is
|
|
used by some applications such as Samba and NFSv4 server to
|
|
check to see whether a file is cacheable. CIFS has no way
|
|
to explicitly request a lease, but can check whether a file
|
|
is cacheable (oplocked). Unfortunately, even if a file
|
|
is not oplocked, it could still be cacheable (ie cifs client
|
|
could grant fcntl leases if no other local processes are using
|
|
the file) for cases for example such as when the server does not
|
|
support oplocks and the user is sure that the only updates to
|
|
the file will be from this client. Specifying this mount option
|
|
will allow the cifs client to check for leases (only) locally
|
|
for files which are not oplocked instead of denying leases
|
|
in that case. (EXPERIMENTAL)
|
|
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
|
|
lanman
|
|
(if configured in kernel config) use older
|
|
lanman hash
|
|
hard
|
|
Retry file operations if server is not responding
|
|
soft
|
|
Limit retries to unresponsive servers (usually only
|
|
one retry) before returning an error. (default)
|
|
|
|
The mount.cifs mount helper also accepts a few mount options before -o
|
|
including:
|
|
|
|
=============== ===============================================================
|
|
-S take password from stdin (equivalent to setting the environment
|
|
variable ``PASSWD_FD=0``
|
|
-V print mount.cifs version
|
|
-? display simple usage information
|
|
=============== ===============================================================
|
|
|
|
With most 2.6 kernel versions of modutils, the version of the cifs kernel
|
|
module can be displayed via modinfo.
|
|
|
|
Misc /proc/fs/cifs Flags and Debug Info
|
|
=======================================
|
|
|
|
Informational pseudo-files:
|
|
|
|
======================= =======================================================
|
|
DebugData Displays information about active CIFS sessions and
|
|
shares, features enabled as well as the cifs.ko
|
|
version.
|
|
Stats Lists summary resource usage information as well as per
|
|
share statistics.
|
|
open_files List all the open file handles on all active SMB sessions.
|
|
mount_params List of all mount parameters available for the module
|
|
======================= =======================================================
|
|
|
|
Configuration pseudo-files:
|
|
|
|
======================= =======================================================
|
|
SecurityFlags Flags which control security negotiation and
|
|
also packet signing. Authentication (may/must)
|
|
flags (e.g. for NTLMv2) may be combined with
|
|
the signing flags. Specifying two different password
|
|
hashing mechanisms (as "must use") on the other hand
|
|
does not make much sense. Default flags are::
|
|
|
|
0x00C5
|
|
|
|
(NTLMv2 and packet signing allowed). Some SecurityFlags
|
|
may require enabling a corresponding menuconfig option.
|
|
|
|
may use packet signing 0x00001
|
|
must use packet signing 0x01001
|
|
may use NTLMv2 0x00004
|
|
must use NTLMv2 0x04004
|
|
may use Kerberos security (krb5) 0x00008
|
|
must use Kerberos 0x08008
|
|
may use NTLMSSP 0x00080
|
|
must use NTLMSSP 0x80080
|
|
seal (packet encryption) 0x00040
|
|
must seal 0x40040
|
|
|
|
cifsFYI If set to non-zero value, additional debug information
|
|
will be logged to the system error log. This field
|
|
contains three flags controlling different classes of
|
|
debugging entries. The maximum value it can be set
|
|
to is 7 which enables all debugging points (default 0).
|
|
Some debugging statements are not compiled into the
|
|
cifs kernel unless CONFIG_CIFS_DEBUG2 is enabled in the
|
|
kernel configuration. cifsFYI may be set to one or
|
|
more of the following flags (7 sets them all)::
|
|
|
|
+-----------------------------------------------+------+
|
|
| log cifs informational messages | 0x01 |
|
|
+-----------------------------------------------+------+
|
|
| log return codes from cifs entry points | 0x02 |
|
|
+-----------------------------------------------+------+
|
|
| log slow responses | 0x04 |
|
|
| (ie which take longer than 1 second) | |
|
|
| | |
|
|
| CONFIG_CIFS_STATS2 must be enabled in .config | |
|
|
+-----------------------------------------------+------+
|
|
|
|
traceSMB If set to one, debug information is logged to the
|
|
system error log with the start of smb requests
|
|
and responses (default 0)
|
|
LookupCacheEnable If set to one, inode information is kept cached
|
|
for one second improving performance of lookups
|
|
(default 1)
|
|
LinuxExtensionsEnabled If set to one then the client will attempt to
|
|
use the CIFS "UNIX" extensions which are optional
|
|
protocol enhancements that allow CIFS servers
|
|
to return accurate UID/GID information as well
|
|
as support symbolic links. If you use servers
|
|
such as Samba that support the CIFS Unix
|
|
extensions but do not want to use symbolic link
|
|
support and want to map the uid and gid fields
|
|
to values supplied at mount (rather than the
|
|
actual values, then set this to zero. (default 1)
|
|
dfscache List the content of the DFS cache.
|
|
If set to 0, the client will clear the cache.
|
|
======================= =======================================================
|
|
|
|
These experimental features and tracing can be enabled by changing flags in
|
|
/proc/fs/cifs (after the cifs module has been installed or built into the
|
|
kernel, e.g. insmod cifs). To enable a feature set it to 1 e.g. to enable
|
|
tracing to the kernel message log type::
|
|
|
|
echo 7 > /proc/fs/cifs/cifsFYI
|
|
|
|
cifsFYI functions as a bit mask. Setting it to 1 enables additional kernel
|
|
logging of various informational messages. 2 enables logging of non-zero
|
|
SMB return codes while 4 enables logging of requests that take longer
|
|
than one second to complete (except for byte range lock requests).
|
|
Setting it to 4 requires CONFIG_CIFS_STATS2 to be set in kernel configuration
|
|
(.config). Setting it to seven enables all three. Finally, tracing
|
|
the start of smb requests and responses can be enabled via::
|
|
|
|
echo 1 > /proc/fs/cifs/traceSMB
|
|
|
|
Per share (per client mount) statistics are available in /proc/fs/cifs/Stats.
|
|
Additional information is available if CONFIG_CIFS_STATS2 is enabled in the
|
|
kernel configuration (.config). The statistics returned include counters which
|
|
represent the number of attempted and failed (ie non-zero return code from the
|
|
server) SMB3 (or cifs) requests grouped by request type (read, write, close etc.).
|
|
Also recorded is the total bytes read and bytes written to the server for
|
|
that share. Note that due to client caching effects this can be less than the
|
|
number of bytes read and written by the application running on the client.
|
|
Statistics can be reset to zero by ``echo 0 > /proc/fs/cifs/Stats`` which may be
|
|
useful if comparing performance of two different scenarios.
|
|
|
|
Also note that ``cat /proc/fs/cifs/DebugData`` will display information about
|
|
the active sessions and the shares that are mounted.
|
|
|
|
Enabling Kerberos (extended security) works but requires version 1.2 or later
|
|
of the helper program cifs.upcall to be present and to be configured in the
|
|
/etc/request-key.conf file. The cifs.upcall helper program is from the Samba
|
|
project(https://www.samba.org). NTLM and NTLMv2 and LANMAN support do not
|
|
require this helper. Note that NTLMv2 security (which does not require the
|
|
cifs.upcall helper program), instead of using Kerberos, is sufficient for
|
|
some use cases.
|
|
|
|
DFS support allows transparent redirection to shares in an MS-DFS name space.
|
|
In addition, DFS support for target shares which are specified as UNC
|
|
names which begin with host names (rather than IP addresses) requires
|
|
a user space helper (such as cifs.upcall) to be present in order to
|
|
translate host names to ip address, and the user space helper must also
|
|
be configured in the file /etc/request-key.conf. Samba, Windows servers and
|
|
many NAS appliances support DFS as a way of constructing a global name
|
|
space to ease network configuration and improve reliability.
|
|
|
|
To use cifs Kerberos and DFS support, the Linux keyutils package should be
|
|
installed and something like the following lines should be added to the
|
|
/etc/request-key.conf file::
|
|
|
|
create cifs.spnego * * /usr/local/sbin/cifs.upcall %k
|
|
create dns_resolver * * /usr/local/sbin/cifs.upcall %k
|
|
|
|
CIFS kernel module parameters
|
|
=============================
|
|
These module parameters can be specified or modified either during the time of
|
|
module loading or during the runtime by using the interface::
|
|
|
|
/sys/module/cifs/parameters/<param>
|
|
|
|
i.e.::
|
|
|
|
echo "value" > /sys/module/cifs/parameters/<param>
|
|
|
|
More detailed descriptions of the available module parameters and their values
|
|
can be seen by doing:
|
|
|
|
modinfo cifs (or modinfo smb3)
|
|
|
|
================= ==========================================================
|
|
1. enable_oplocks Enable or disable oplocks. Oplocks are enabled by default.
|
|
[Y/y/1]. To disable use any of [N/n/0].
|
|
================= ==========================================================
|