en_US.ISO8859-1/errata/article.xml

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<article xmlns="http://docbook.org/ns/docbook"
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  <info>
    <title>&os; &release.current; Errata </title>

    <author><orgname>The &os; Project</orgname></author>

    <pubdate>$FreeBSD: releng/10.1/release/doc/en_US.ISO8859-1/errata/article.xml 273620 2014-10-25 01:17:29Z gjb $</pubdate>

    <copyright>
      <year>2014</year>

      <holder role="mailto:doc@FreeBSD.org">The &os; Documentation
	Project</holder>
    </copyright>

    <legalnotice xml:id="trademarks" role="trademarks">
      &tm-attrib.freebsd;
      &tm-attrib.intel;
      &tm-attrib.sparc;
      &tm-attrib.general;
    </legalnotice>

    <abstract>
      <para>This document lists errata items for &os; &release.current;,
	containing significant information discovered after the
	release or too late in the release cycle to be otherwise
	included in the release documentation.  This information
	includes security advisories, as well as news relating to the
	software or documentation that could affect its operation or
	usability.  An up-to-date version of this document should
	always be consulted before installing this version of
	&os;.</para>

      <para>This errata document for &os; &release.current; will be
	maintained until the release of &os; &release.next;.</para>
    </abstract>
  </info>

  <sect1 xml:id="intro">
    <title>Introduction</title>

    <para>This errata document contains <quote>late-breaking
	news</quote> about &os; &release.current; before installing this
      version, it is important to consult this document to learn about
      any post-release discoveries or problems that may already have
      been found and fixed.</para>

    <para>Any version of this errata document actually distributed
      with the release (for example, on a CDROM distribution) will be
      out of date by definition, but other copies are kept updated on
      the Internet and should be consulted as the <quote>current
	errata</quote> for this release.  These other copies of the
      errata are located at <link
	xlink:href="http://www.FreeBSD.org/releases/" />, plus any
      sites which keep up-to-date mirrors of this location.</para>

    <para>Source and binary snapshots of &os; &release.branch; also
      contain up-to-date copies of this document (as of the time of
      the snapshot).</para>

    <para>For a list of all &os; CERT security advisories, see <link
	xlink:href="http://www.FreeBSD.org/security/"/> or <link
      xlink:href="ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/"/>.</para>
  </sect1>

  <sect1 xml:id="security">
    <title>Security Advisories</title>

    <informaltable frame="none" pgwide="0">
      <tgroup cols="3">
	<colspec colwidth="1*" />
	<colspec colwidth="1*" />
	<colspec colwidth="3*" />
	<thead>
	  <row>
	    <entry>Advisory</entry>
	    <entry>Date</entry>
	    <entry>Topic</entry>
	  </row>
	</thead>

	<tbody>
	  <row>
	    <entry>No advisories.</entry>
	    <entry>&nbsp;</entry>
	    <entry>&nbsp;</entry>
	  </row>
	</tbody>
      </tgroup>
    </informaltable>
  </sect1>

  <sect1 xml:id="open-issues">
    <title>Open Issues</title>

    <itemizedlist>
      <listitem>
	<para>&os;/&arch.i386; &release.current; running as a guest
	  operating system on <application>VirtualBox</application>
	  can have a problem with disk I/O access.  It depends on some
	  specific hardware configuration and does not depend on a
	  specific version of <application>VirtualBox</application> or
	  host operating system.</para>

	<para>It causes various errors and makes &os; quite unstable.
	  Although the cause is still unclear, disabling unmapped I/O
	  works as a workaround.  To disable it, choose
	  <literal>Escape to loader prompt</literal> in the boot menu
	  and enter the following lines from &man.loader.8; prompt,
	  after an <literal>OK</literal>:</para>

	<screen>set vfs.unmapped_buf_allowed=0
boot</screen>

	<para>Note that the following line has to be added to
	  <filename>/boot/loader.conf</filename> after a boot.  It
	  disables unmapped I/O at every boot:</para>

	<programlisting>vfs.unmapped_buf_allowed=0</programlisting>

	<para>[2014-04-03 update]  It has been reported that
	  instability may be present on virtual machines running
	  on other hypervisors, such as Xen or KVM.</para>
      </listitem>

      <listitem>
	<para>&os;/&arch.i386;&nbsp;&release.current; configured with
	  a multi-disk ZFS dataset (mirror, raidz1, raidz2, raidz3)
	  may crash during boot when the ZFS pool mount is attempted
	  while booting an unmodified <literal>GENERIC</literal>
	  kernel.</para>

	<para>As described in <filename>/usr/src/UPDATING</filename>
	  entry <literal>20121223</literal>, rebuilding the kernel
	  with <literal>options KSTACK_PAGES=4</literal> has been
	  observed to resolve the boot-time crash.  This, however, is
	  not an ideal solution for inclusion in the
	  <literal>GENERIC</literal> kernel configuration, as
	  increasing <literal>KSTACK_PAGES</literal> implicitly
	  decreases available usermode threads in an environment that
	  is already resource-starved.</para>

	<para>Taking into account the heavy resource requirements of
	  ZFS, in addition to the &arch.i386;-specific tuning
	  requirements for general workloads, using ZFS with the
	  &os;/&arch.i386;&nbsp;<literal>GENERIC</literal> kernel
	  is strongly discouraged.</para>

	<warning>
	  <para>It is extremely important to take note that, by
	    default, &man.freebsd-update.8; will install the
	    <literal>GENERIC</literal> kernel configuration, and
	    as such, &man.freebsd-update.8; consumers are strongly
	    encouraged to avoid &os;-provided kernel binary upgrades
	    with such configurations.</para>
	</warning>

	<note>
	  <para>Although there is slight change in how the crash
	    manifests on &os;/&arch.i386; between &release.prev; and
	    &release.current;, and given the date of the
	    <filename>/usr/src/UPDATING</filename> entry, there is no
	    evidence suggesting this is a regression between
	    &os;&nbsp;&release.prev; and &os;&nbsp;&release.current;
	    directly.</para>
	</note>
      </listitem>
    </itemizedlist>
  </sect1>

  <sect1 xml:id="late-news">
    <title>Late-Breaking News</title>

    <para>No news.</para>
  </sect1>
</article>