1da177e4c3
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
475 lines
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475 lines
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The CIFS VFS support for Linux supports many advanced network filesystem
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features such as heirarchical 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.
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For questions or bug reports please contact:
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sfrench@samba.org (sfrench@us.ibm.com)
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Build instructions:
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==================
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For Linux 2.4:
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1) Get the kernel source (e.g.from http://www.kernel.org)
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and download the cifs vfs source (see the project page
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at http://us1.samba.org/samba/Linux_CIFS_client.html)
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and change directory into the top of the kernel directory
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then patch the kernel (e.g. "patch -p1 < cifs_24.patch")
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to add the cifs vfs to your kernel configure options if
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it has not already been added (e.g. current SuSE and UL
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users do not need to apply the cifs_24.patch since the cifs vfs is
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already in the kernel configure menu) and then
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mkdir linux/fs/cifs and then copy the current cifs vfs files from
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the cifs download to your kernel build directory e.g.
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cp <cifs_download_dir>/fs/cifs/* to <kernel_download_dir>/fs/cifs
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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 dep
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6) make modules (or "make" if CIFS VFS not to be built as a module)
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For Linux 2.6:
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1) Download the kernel (e.g. from http://www.kernel.org or from bitkeeper
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at bk://linux.bkbits.net/linux-2.5) and change directory into the top
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of the kernel directory tree (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/2.4.10-4GB/kernel/fs/cifs/cifs.o).
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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 3.0 source tree and on
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the CIFS VFS web site) copy it to the same directory in which mount.smbfs and
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similar files reside (usually /sbin). Although the helper software is not
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required, mount.cifs is recommended. Eventually the Samba 3.0 utility program
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"net" may also be helpful since it may someday provide easier mount syntax for
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users who are used to Windows e.g. net use <mount point> <UNC name or cifs URL>
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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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trivially built from Samba 3.0 or later source e.g. by executing:
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gcc samba/source/client/mount.cifs.c -o mount.cifs
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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 kernel/fs/cifs/cifs.ko
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on kernel/fs/cifs/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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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:
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gcc samba/source/client/mount.cifs.c -DCIFS_ALLOW_USR_SUID -o mount.cifs
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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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Samba Considerations
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====================
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To get the maximum benefit from the CIFS VFS, we recommend using a server that
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supports the SNIA CIFS Unix Extensions standard (e.g. Samba 2.2.5 or later or
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Samba 3.0) 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 invisbile 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.o), you can use mount syntax like the following to access Samba or Windows
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servers:
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mount -t cifs //9.53.216.11/e$ /mnt -o user=myname,pass=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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user=<username>
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pass=<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 the NTLM SMB dialect (which is the most recent, supported
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by Samba and Windows NT version 4, 2000 and XP and many other SMB/CIFS servers)
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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." Neither of these is likely to be a
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problem as most servers support this. IPv6 support is planned for the future,
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and is almost complete.
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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).
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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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user The user name to use when trying to establish
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the CIFS session.
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password 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 it is not supplied.
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ip The ip address of the target server
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unc The target server Universal Network Name (export) to
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mount.
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domain Set the SMB/CIFS workgroup name prepended to the
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username during CIFS session establishment
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uid If CIFS Unix extensions are not supported by the server
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this overrides the default uid for inodes. For mounts to
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servers which do support the CIFS Unix extensions, such
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as a properly configured Samba server, the server provides
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the uid, gid and mode. For servers which do not support
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the Unix extensions, the default uid (and gid) returned on
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lookup of existing files is 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. For the uid (gid) of newly
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created files and directories, ie files created since
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the last mount of the server share, the expected uid
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(gid) is cached as as long as the inode remains in
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memory on the client. 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
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gid If CIFS Unix extensions are not supported by the server
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this overrides the default gid for inodes.
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file_mode 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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dir_mode 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 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 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 default read size
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wsize default write size
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rw 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 mount network share read-only
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version used to distinguish different versions of the
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mount helper utility (not typically needed)
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sep if first mount option (after the -o), overrides
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the comma as the separator between the mount
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parms. 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 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 Permit execution of binaries on the mount.
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noexec Do not permit execution of binaries on the mount.
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dev Recognize block devices on the remote mount.
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nodev Do not recognize devices on the remote mount.
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suid 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 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 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 Client does permission checks (vfs_permission check of uid
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and gid of the file against the mode and desired operation),
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Note that this is in addition to the normal ACL check on the
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target machine done by the server software.
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Client permission checking is enabled by default.
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noperm Client does not do permission checks. This can expose
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files on this mount to access by other users on the local
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client system. It is typically only needed when the server
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supports the CIFS Unix Extensions but the UIDs/GIDs on the
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client and server system do not match closely enough to allow
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access by the user doing the mount.
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Note that this does not affect the normal ACL check on the
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target machine done by the server software (of the server
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ACL against the user name provided at mount time).
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serverino Use servers inode numbers instead of generating automatically
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incrementing inode numbers on the client. Although this will
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make it easier to spot hardlinked files (as they will have
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the same inode numbers) and inode numbers may be persistent,
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note that the server does not guarantee that the inode numbers
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are unique if multiple server side mounts are exported under a
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single share (since inode numbers on the servers might not
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be unique if multiple filesystems are mounted under the same
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shared higher level directory). Note that this requires that
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the server support the CIFS Unix Extensions as other servers
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do not return a unique IndexNumber on SMB FindFirst (most
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servers return zero as the IndexNumber). Parameter has no
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effect to Windows servers and others which do not support the
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CIFS Unix Extensions.
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noserverino Client generates inode numbers (rather than using the actual one
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from the server) by default.
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setuids If the CIFS Unix extensions are negotiated with the server
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the client will attempt to set the effective uid and gid of
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the local process on newly created files, directories, and
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devices (create, mkdir, mknod).
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nosetuids The client will not attempt to set the uid and gid on
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on newly created files, directories, and devices (create,
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mkdir, mknod) which will result in the server setting the
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uid and gid to the default (usually the server uid of the
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usern who mounted the share). Letting the server (rather than
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the client) set the uid and gid is the default. This
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parameter has no effect if the CIFS Unix Extensions are not
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negotiated.
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netbiosname When mounting to servers via port 139, specifies the RFC1001
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source name to use to represent the client netbios machine
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name when doing the RFC1001 netbios session initialize.
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direct Do not do inode data caching on files opened on this mount.
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This precludes mmaping files on this mount. In some cases
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with fast networks and little or no caching benefits on the
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client (e.g. when the application is doing large sequential
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reads bigger than page size without rereading the same data)
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this can provide better performance than the default
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behavior which caches reads (reaadahead) and writes
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(writebehind) through the local Linux client pagecache
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if oplock (caching token) is granted and held. Note that
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direct allows write operations larger than page size
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to be sent to the server.
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acl Allow setfacl and getfacl to manage posix ACLs if server
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supports them. (default)
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noacl Do not allow setfacl and getfacl calls on this mount
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user_xattr Allow getting and setting user xattrs as OS/2 EAs (extended
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attributes) to the server (default) e.g. via setfattr
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and getfattr utilities.
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nouser_xattr Do not allow getfattr/setfattr to get/set xattrs
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The mount.cifs mount helper also accepts a few mount options before -o
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including:
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-S take password from stdin (equivalent to setting the environment
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variable "PASSWD_FD=0"
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-V print mount.cifs version
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-? display simple usage information
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With recent 2.6 kernel versions of modutils, the version of the cifs kernel
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module can be displayed via modinfo.
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Misc /proc/fs/cifs Flags and Debug Info
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=======================================
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Informational pseudo-files:
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DebugData Displays information about active CIFS sessions
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and shares.
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Stats Lists summary resource usage information as well as per
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share statistics, if CONFIG_CIFS_STATS in enabled
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in the kernel configuration.
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Configuration pseudo-files:
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MultiuserMount If set to one, more than one CIFS session to
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the same server ip address can be established
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if more than one uid accesses the same mount
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point and if the uids user/password mapping
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information is available. (default is 0)
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PacketSigningEnabled If set to one, cifs packet signing is enabled
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and will be used if the server requires
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it. If set to two, cifs packet signing is
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required even if the server considers packet
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signing optional. (default 1)
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cifsFYI If set to one, additional debug information is
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logged to the system error log. (default 0)
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ExtendedSecurity If set to one, SPNEGO session establishment
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is allowed which enables more advanced
|
|
secure CIFS session establishment (default 0)
|
|
NTLMV2Enabled If set to one, more secure password hashes
|
|
are used when the server supports them and
|
|
when kerberos is not negotiated (default 0)
|
|
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)
|
|
OplockEnabled If set to one, safe distributed caching enabled.
|
|
(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)
|
|
|
|
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 1 > /proc/fs/cifs/cifsFYI
|
|
|
|
and for more extensive tracing including the start of smb requests and responses
|
|
|
|
echo 1 > /proc/fs/cifs/traceSMB
|
|
|
|
Two other experimental features are under development and to test
|
|
require enabling CONFIG_CIFS_EXPERIMENTAL
|
|
|
|
More efficient write operations and SMB buffer handling
|
|
|
|
DNOTIFY fcntl: needed for support of directory change
|
|
notification and perhaps later for file leases)
|
|
|
|
Per share (per client mount) statistics are available in /proc/fs/cifs/Stats
|
|
if the kernel was configured with cifs statistics enabled. The statistics
|
|
represent the number of successful (ie non-zero return code from the server)
|
|
SMB responses to some of the more common commands (open, delete, mkdir 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.
|
|
The statistics for the number of total SMBs and oplock breaks are different in
|
|
that they represent all for that share, not just those for which the server
|
|
returned success.
|
|
|
|
Also note that "cat /proc/fs/cifs/DebugData" will display information about
|
|
the active sessions and the shares that are mounted. Note: NTLMv2 enablement
|
|
will not work since they its implementation is not quite complete yet.
|
|
Do not alter these configuration values unless you are doing specific testing.
|
|
Enabling extended security works to Windows 2000 Workstations and XP but not to
|
|
Windows 2000 server or Samba since it does not usually send "raw NTLMSSP"
|
|
(instead it sends NTLMSSP encapsulated in SPNEGO/GSSAPI, which support is not
|
|
complete in the CIFS VFS yet).
|