present, even if it holds no options. Every other section
defines one export; the names of these sections are not
important, except that you should take care to make sure that
- each section name is unique (future versions of
- <command>nbd-server</command> may use the section name to refer
- to an export)
+ each section name is unique. The section name is used as the name
+ for the export in case the client connects with a name rather than
+ a port to specify an export, and must therefore be unique.
</para>
<para>
A comment line is a line that starts with optional whitespace,
followed by an equals sign ("="), followed by the option
value. An option can be of type string, of type integer, or of
type boolean. The value of a boolean option can be denoted with
- either true or false (so not yes, no, on, off, 1, or 0); all
- booleans default to false unless specified otherwise; no value
- may be quoted (always enter it directly); for a string option,
+ either true or false (so not yes, no, on, off, 1, or 0). All
+ booleans default to false unless specified otherwise. No value
+ may be quoted; always enter it directly. For a string option,
leading whitespace is stripped (but trailing whitespace is not).
</para>
</para>
</listitem>
</varlistentry>
+ <varlistentry>
+ <term><option>oldstyle</option></term>
+ <listitem>
+ <para>
+ Optional; boolean
+ </para>
+ <para>
+ If this option is set to true, nbd-server will export all
+ exports on a separate port with the old (pre-2.9.17)
+ handshake protocol. In that case, the 'port' option for
+ individual exports is mandatory.
+ </para>
+ <para>
+ If the option is set to false, the 'port' option for
+ individual exports is optional (and will be ignored if
+ specified). The server will only export devices on the
+ standard port.
+ </para>
+ <para>
+ For upgrades from pre-2.9.17 versions of nbd, it may be
+ appropriate to enable the oldstyle parameter until all
+ clients have been converted to using name-based exports.
+ </para>
+ <para>
+ Note that exports specified on the command line will
+ always use the old handshake protocol and will not allow
+ name-based exports.
+ </para>
+ <para>
+ Also note that even if this parameter is set to true, all
+ exports will also be made available using the new handshake
+ protocol; it is not possible to switch that off. The reason
+ for this is that the old style protocol will eventually be
+ deprecated, and this option is only available to allow for
+ smooth upgrades.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><option>listenaddr</option></term>
+ <listitem>
+ <para>
+ Optional; string
+ </para>
+ <para>If this option is set, it should contain the local IP
+ address on which we should listen to
+ <command>nbd-client</command>(8) connections. If it is not
+ set, <command>nbd-server</command> will listen to all
+ local IPv4 and IPv6 addresses. To limit to IPv6, specify the
+ address as "::". To limit to IPv4, specify as "0.0.0.0". It
+ is not possible to specify more than one IP address
+ here.</para>
+ </listitem>
+ </varlistentry
</variablelist>
</refsect1>
<refsect1>
</listitem>
</varlistentry>
<varlistentry>
- <term><option>autoreadonly</option></term>
- <listitem>
- <para>Optional; boolean.</para>
- <para>
- If this option is set to true, then
- <command>nbd-server</command> will automatically switch to
- readonly if it cannot write to the file.
- </para>
- <para>Does not have a corresponding command-line
- argument</para>
- <para>TODO: verify whether this option actually works as
- documented. I have a feeling I've been terribly
- stupid.
- </para>
- </listitem>
- </varlistentry>
- <varlistentry>
<term><option>copyonwrite</option></term>
<listitem>
<para>
writes to this export will not be written to the master
file, but to a separate file which will be removed upon
disconnect. The result of using this option is that
- nbd-server will be slower, and that any writes will be
- lost upon disconnect.
+ nbd-server will be somewhat slower, and that any writes will
+ be lost upon disconnect.
</para>
<para>Corresponds to the <option>-c</option> option on the
command line</para>
<listitem>
<para>Required; string.</para>
<para>
- The name of the file that will be exported. This must be a
- fully-qualified path and filename; relative paths are not
- allowed.
+ The name of the file (or block device) that will be
+ exported. This must be a fully-qualified path and filename;
+ relative paths are not allowed.
</para>
<para>
Note that <command>nbd-server</command> will only try to
<varlistentry>
<term>listenaddr</term>
<listitem>
- <para>Optional; string</para>
- <para>If this option is set, it should contain the local IP
- address (in "dotted-quad" notation) on which we should
- listen to <command>nbd-client</command>(8) connections. If
- it is not set, 0.0.0.0 is used (i.e., "listen on all local
- IP addresses")</para>
+ <para>
+ Optional; string
+ </para>
+ <para>
+ If the 'oldstyle' global parameter is specified, works
+ similarly to the global listenaddr parameter, but for the
+ individual port of this particular export. If the 'oldstyle'
+ parameter is not set, this parameter is ignored.
+ </para>
</listitem>
</varlistentry>
<varlistentry>
form
<replaceable>exportname</replaceable>.<replaceable>integer</replaceable>,
with <replaceable>exportname</replaceable> being the
- filename that would otherwise have been used (after
- name transformation for virtualization, if any, has been
+ filename that would otherwise have been used (after name
+ transformation for virtualization, if any, has been
performed) and <replaceable>integer</replaceable> an
integer number, starting with 0 and ending when no more
files can be found.
<para>
The size of the individual files will be autodetected,
<emphasis>even</emphasis> if the <option>filesize</option>
- option has been specified. See the documentation for the
- <option>multifile</option> for details.
+ option has been specified.
</para>
<para>
Corresponds to the <option>-m</option> option on the
<varlistentry>
<term><option>port</option></term>
<listitem>
- <para>Required; integer.</para>
+ <para>Required if 'oldstyle' global parameter is set; integer.</para>
+ <para>
+ The port on which this export is to be served using the
+ old-style handshake protocol.
+ </para>
+ <para>
+ This parameter only makes sense when the 'oldstyle'
+ parameter is set to true in the 'generic' section. If that
+ parameter is not set, but this parameter is found in an
+ export section, then nbd-server will issue a warning upon
+ startup but should otherwise continue to function correctly.
+ </para>
<para>
- The port on which this export is to be served. Currently
- it is not possible to export multiple block devices on the
- same port unless virtualization is used; future versions
- of <command>nbd-server</command> may add this
- functionality.
+ It is not possible to combine multiple exports on the same
+ port using the old style handshake. Please use the new style
+ handshake for that purpose.
</para>
<para>
When specified on the command line, this should be the
</listitem>
</varlistentry>
<varlistentry>
- <term><option>sdp</option></term>
+ <term><option>sdp</option></term>
<listitem>
<para>Optional; boolean.</para>
<para>
then <command>nbd-server</command> will exit with an error
message.
</para>
- </listitem
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><option>sync</option></term>
+ <listitem>
+ <para>Optional; boolean.</para>
+ <para>When this option is enabled,
+ <command>nbd-server</command> will call an fsync() after every
+ write to the backend storage. Calling fsync() increases
+ reliability in case of an unclean shutdown of nbd-server; but,
+ depending on the file system used on the nbd-server side, may
+ degrade performance. The use of this option isn't always
+ necessary; e.g., on ext3 filesystems, it is recommended that
+ it is <emphasis>not</emphasis> enabled, since it seriously
+ reduces performance on ext3 filesystems while not
+ importantly impacting reliability.
+ </para>
+ </listitem>
</varlistentry>
<varlistentry>
<term><option>sparse_cow</option></term>
Defines the style of virtualization. Virtualization allows
one to create one export that will serve a different file
depending on the IP address that is connecting. When
- virtualization is There are three types of virtualization
- that <command>nbd-server</command> supports:
+ virtualization is active, the
+ <replaceable>exportname</replaceable> parameter needs to
+ contain the string '%s'; this will then be replaced by the
+ IP address of the client connecting, in accordance with the
+ option selected here. The result of this transformation is
+ then used as the filename to be opened.
+ </para>
+ <para>
+ There are four types of virtualization that
+ <command>nbd-server</command> supports:
</para>
<variablelist>
<varlistentry>
<term><option>ipliteral</option></term>
<listitem>
<para>
- <command>nbd-server</command> will look for the
- literal string '%s' in the
- <option>exportname</option>, and replace it by the
- IP address of the connecting host in dotted-quad
- notation. The string that results from this
- transformation will be used as an absolute pathname
- that <command>nbd-server</command> will attempt to
- open. As an example, if a client connects from
- 192.168.1.100 and <option>exportname</option> is
- specified as <filename>/export/%s</filename>, then
- nbd-server will attempt to serve
- <filename>/export/192.168.1.100</filename>
+ The %s is replaced by the IP address of the connecting
+ host is used as-is. For IPv4, this is done in
+ dotted-quad notation; for IPv6, in hexadecimal form
+ with leading zeros omitted.
+ </para>
+ <para>
+ As an example, if a client connects from 192.168.1.100
+ and <option>exportname</option> is specified as
+ <filename>/export/%s</filename>, then nbd-server will
+ attempt to serve
+ <filename>/export/192.168.1.100</filename>. For IPv6,
+ with a client connecting from 2001:6f8:32f::39, the
+ filename would be
+ <filename>/export/2001:6f8:32f:0:0:0:0:39</filename>
</para>
</listitem>
</varlistentry>
open <filename>/export/192/168/1/100</filename>
instead.
</para>
+ <para>
+ Since there are no dots in most IPv6 addresses, the
+ effect of using this option when IPv6 is in use is
+ indistinguishable from the ipliteral option. It was
+ thought that having to create an eight-deep directory
+ structure would not be as useful.
+ </para>
</listitem>
</varlistentry>
<varlistentry>
<command>nbd-server</command> will try to open
<filename>/export/192.168.1.64/192.168.1.100</filename>.
</para>
+ <para>For IPv6, in the above example, with
+ <constant>cidrhash 42</constant>, the filename would
+ be
+ <filename>/export/2001:32f:6c0:0:0:0:0:0/2001:32f:6f8:0:0:0:0:39</filename>.</para>
</listitem>
</varlistentry>
</variablelist>
projects / nbd.git / blobdiff