197 lines
9.0 KiB
Diff
197 lines
9.0 KiB
Diff
From 0b3c633002a10419080312ce72cf1a971fd383d0 Mon Sep 17 00:00:00 2001
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From: Steve French <stfrench@microsoft.com>
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Date: Wed, 3 Apr 2019 23:46:34 -0500
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Subject: [PATCH 21/36] Update man page for mount.cifs to add new options
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Add description of "snapshot" and "handletimeout" mount
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options and a security section noting that the use of
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cifs is discouraged, and various minor updates.
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Signed-off-by: Steve French <stfrench@microsoft.com>
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Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
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Reviewed-by: Paulo Alcantara <palcantara@suse.de>
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(cherry picked from commit cbdd6552bc5978476e344a253941e714d983c27b)
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Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
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---
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mount.cifs.rst | 98 +++++++++++++++++++++++++++++++++++-----------------------
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1 file changed, 60 insertions(+), 38 deletions(-)
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diff --git a/mount.cifs.rst b/mount.cifs.rst
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index f64d1f1..8ba6e7b 100644
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--- a/mount.cifs.rst
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+++ b/mount.cifs.rst
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@@ -15,13 +15,13 @@ SYNOPSIS
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This tool is part of the cifs-utils suite.
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-``mount.cifs`` mounts a Linux CIFS filesystem. It is usually invoked
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-indirectly by the mount(8) command when using the "-t cifs"
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+``mount.cifs`` mounts a CIFS or SMB3 filesystem from Linux. It is
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+usually invoked indirectly by the mount(8) command when using the "-t cifs"
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option. This command only works in Linux, and the kernel must support
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-the cifs filesystem. The CIFS protocol is the successor to the SMB
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-protocol and is supported by most Windows servers and many other
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-commercial servers and Network Attached Storage appliances as well as
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-by the popular Open Source server Samba.
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+the cifs filesystem. The SMB3 protocol is the successor to the CIFS (SMB)
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+protocol and is supported by most Windows servers, Azure (cloud storage),
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+Macs and many other commercial servers and Network Attached Storage
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+appliances as well as by the popular Open Source server Samba.
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The mount.cifs utility attaches the UNC name (exported network
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resource) specified as service (using ``//server/share`` syntax, where
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@@ -266,6 +266,13 @@ handlecache
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nohandlecache
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Disable caching of the share root directory handle.
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+handletimeout=arg
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+ The time (in milliseconds) for which the server should reserve the handle after
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+ a failover waiting for the client to reconnect. When mounting with
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+ resilienthandles or persistenthandles mount option, or when their use is
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+ requested by the server (continuous availability shares) then this parameter
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+ overrides the server default handle timeout (which for most servers is 120 seconds).
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+
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rwpidforward
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Forward pid of a process who opened a file to any read or write
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operation on that file. This prevent applications like wine(1) from
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@@ -387,6 +394,12 @@ persistenthandles
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nopersistenthandles
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(default) Disable persistent handles.
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+snapshot=time
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+ Mount a specific snapshot of the remote share. ``time`` must be a
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+ positive integer identifying the snapshot requested (in 100-nanosecond
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+ units that have elapsed since January 1, 1601, or alternatively it can
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+ be specified in GMT format e.g. @GMT-2019.03.27-20.52.19)
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+
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nobrl
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Do not send byte range lock requests to the server. This is necessary
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for certain applications that break with cifs style mandatory byte
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@@ -401,7 +414,7 @@ locallease
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Check cached leases locally instead of querying the server.
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sfu
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- When the CIFS Unix Extensions are not negotiated, attempt to create
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+ When the CIFS or SMB3 Unix Extensions are not negotiated, attempt to create
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device files and fifos in a format compatible with Services for Unix
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(SFU). In addition retrieve bits 10-12 of the mode via the
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``SETFILEBITS`` extended attribute (as SFU does). In the future the
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@@ -450,11 +463,11 @@ noserverino
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See section `INODE NUMBERS`_ for more information.
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-unix|linux
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+posix|unix|linux
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(default) Enable Unix Extensions for this mount. Requires CIFS
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(vers=1.0) or SMB3.1.1 (vers=3.1.1) and a server supporting them.
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-nounix|nolinux
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+noposix|nounix|nolinux
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Disable the Unix Extensions for this mount. This can be useful in
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order to turn off multiple settings at once. This includes POSIX acls,
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POSIX locks, POSIX paths, symlink support and retrieving
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@@ -479,38 +492,35 @@ nosharesock
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Do not try to reuse sockets if the system is already connected to
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the server via an existing mount point. This will make the client
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always make a new connection to the server no matter what he is
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- already connected to.
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+ already connected to. This can be useful in simulating multiple
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+ clients connecting to the same server, as each mount point
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+ will use a different TCP socket.
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noblocksend
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Send data on the socket using non blocking operations (MSG_DONTWAIT flag).
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rsize=bytes
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Maximum amount of data that the kernel will request in a read request
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- in bytes. Prior to kernel 3.2.0, the default was 16k, and the maximum
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- size was limited by the ``CIFSMaxBufSize`` module parameter. As of
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- kernel 3.2.0, the behavior varies according to whether POSIX
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- extensions are enabled on the mount and the server supports large
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- POSIX reads. If they are, then the default is 1M, and the maximum is
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- 16M. If they are not supported by the server, then the default is 60k
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- and the maximum is around 127k. The reason for the 60k is because it's
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- the maximum size read that windows servers can fill. Note that this
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- value is a maximum, and the client may settle on a smaller size to
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- accommodate what the server supports. In kernels prior to 3.2.0, no
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- negotiation is performed.
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+ in bytes. Maximum size that servers will accept is typically 8MB for SMB3
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+ or later dialects. Default requested during mount is 4MB. Prior to the 4.20
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+ kernel the default requested was 1MB. Prior to the SMB2.1 dialect the
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+ maximum was usually 64K.
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wsize=bytes
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Maximum amount of data that the kernel will send in a write request in
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- bytes. Prior to kernel 3.0.0, the default and maximum was 57344 (14 \*
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- 4096 pages). As of 3.0.0, the default depends on whether the client
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- and server negotiate large writes via POSIX extensions. If they do,
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- then the default is 1M, and the maximum allowed is 16M. If they do
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- not, then the default is 65536 and the maximum allowed is 131007. Note
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- that this value is just a starting point for negotiation in 3.0.0 and
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- up. The client and server may negotiate this size downward according
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- to the server's capabilities. In kernels prior to 3.0.0, no
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- negotiation is performed. It can end up with an existing superblock if
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- this value isn't specified or it's greater or equal than the existing
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- one.
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+ bytes. Maximum size that servers will accept is typically 8MB for SMB3
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+ or later dialects. Default requested during mount is 4MB. Prior to the 4.20
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+ kernel the default requested was 1MB. Prior to the SMB2.1 dialect the
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+ maximum was usually 64K.
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+
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+bsize=bytes
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+ Override the default blocksize (1MB) reported on SMB3 files (requires
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+ kernel version of 5.1 or later). Prior to kernel version 5.1, the
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+ blocksize was always reported as 16K instead of 1MB (and was not
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+ configurable) which can hurt the performance of tools like cp and scp
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+ (especially for uncached I/O) which decide on the read and write size
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+ to use for file copies based on the inode blocksize. bsize may not be
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+ less than 16K or greater than 16M.
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max_credits=n
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Maximum credits the SMB2 client can have. Default is 32000. Must be
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@@ -885,14 +895,26 @@ CONFIGURATION
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The primary mechanism for making configuration changes and for reading
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debug information for the cifs vfs is via the Linux /proc
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filesystem. In the directory */proc/fs/cifs* are various
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-configuration files and pseudo files which can display debug
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-information. There are additional startup options such as maximum
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-buffer size and number of buffers which only may be set when the
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+configuration files and pseudo files which can display debug information
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+and performance statistics. There are additional startup options such as
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+maximum buffer size and number of buffers which only may be set when the
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kernel cifs vfs (cifs.ko module) is loaded. These can be seen by
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running the ``modinfo`` utility against the file cifs.ko which will
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list the options that may be passed to cifs during module installation
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(device driver load). For more information see the kernel file
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-*fs/cifs/README*.
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+*fs/cifs/README*. When configuring dynamic tracing (trace-cmd)
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+note that the list of SMB3 events which can be enabled can be seen at:
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+*/sys/kernel/debug/tracing/events/cifs/*.
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+
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+********
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+SECURITY
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+********
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+
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+The use of SMB2.1 or later (including the latest dialect SMB3.1.1)
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+is recommended for improved security and SMB1 is no longer requested
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+by default at mount time. Old dialects such as CIFS (SMB1, ie vers=1.0)
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+have much weaker security. Use of CIFS (SMB1) can be disabled by
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+modprobe cifs disable_legacy_dialects=y.
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****
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BUGS
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@@ -913,8 +935,8 @@ bugs (minimum: mount.cifs (try ``mount.cifs -V``), kernel (see
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VERSION
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*******
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-This man page is correct for version 1.74 of the cifs vfs filesystem
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-(roughly Linux kernel 3.0).
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+This man page is correct for version 2.18 of the cifs vfs filesystem
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+(roughly Linux kernel 5.0).
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********
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SEE ALSO
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--
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1.8.3.1
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