source: branches/samba-3.5.x/docs-xml/smbdotconf/security/rootdirectory.xml

<samba:parameter name="root directory"
        context="G"
        type="string"
                 advanced="1" developer="1"
                 xmlns:samba="http://www.samba.org/samba/DTD/samba-doc">
<synonym>root</synonym>
<synonym>root dir</synonym>
<description>
    <para>The server will <command moreinfo="none">chroot()</command> (i.e. 
    Change its root directory) to this directory on startup. This is 
    not strictly necessary for secure operation. Even without it the 
    server will deny access to files not in one of the service entries. 
    It may also check for, and deny access to, soft links to other 
    parts of the filesystem, or attempts to use &quot;..&quot; in file names 
    to access other directories (depending on the setting of the
        <smbconfoption name="wide smbconfoptions"/> parameter).
    </para>

    <para>Adding a <parameter moreinfo="none">root directory</parameter> entry other 
    than &quot;/&quot; adds an extra level of security, but at a price. It 
    absolutely ensures that no access is given to files not in the 
    sub-tree specified in the <parameter moreinfo="none">root directory</parameter> 
    option, <emphasis>including</emphasis> some files needed for 
    complete operation of the server. To maintain full operability 
    of the server you will need to mirror some system files 
    into the <parameter moreinfo="none">root directory</parameter> tree. In particular 
    you will need to mirror <filename moreinfo="none">/etc/passwd</filename> (or a 
    subset of it), and any binaries or configuration files needed for 
    printing (if required). The set of files that must be mirrored is
    operating system dependent.</para>
</description>

<value type="default">/</value>
<value type="example">/homes/smb</value>
</samba:parameter>