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/etc/network/interfaces 中的 dns-search 选项含义是什么？

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/etc/network/interfaces 中的 dns-search 选项含义是什么？

有人能向我解释一下文件dns-search中的指令吗：/etc/network/interfaces

iface eth0 inet static
    address 192.168.3.3
    netmask 255.255.255.0
    gateway 192.168.3.1
    dns-search example.com
    dns-nameservers 192.168.3.45 192.168.8.10

这是强制性的吗？我该如何配置它？

答案1

dns-search确定为 DNS 查找附加哪个域。

通常您将在这里指定与 返回的相同的域hostname -f。

有关详细信息，请参阅以下引文man resolv.conf：

search Search list for host-name lookup.
    The  search  list  is  normally  determined from the local domain name; by
    default, it contains only the local domain name.  This may be changed by listing
    the desired domain search path following the search keyword with spaces or tabs
    separating  the  names.  Resolver queries having fewer than ndots dots (default
    is 1) in them will be attempted using each component of the search path in turn
    until a match is found.  For environments with multiple  subdomains  please read
    options ndots:n below to avoid man-in-the-middle attacks and unnecessary traffic
    for the root-dns-servers.  Note that this process may be slow and will generate
    a lot of network traffic if the servers for the  listed  domains  are not local,
    and that queries will time out if no server is available for one of the domains.

    The search list is currently limited to six domains with a total of 256 characters.

答案2

我还在 Ubuntu 14.04 上的 /usr/share/doc/resolvconf 中的 README.gz 中找到了这一点。它提供了更清晰的信息。

注意由服务 resolvconf 管理的 resolv.conf 文件。

dns-search 似乎是逻辑接口节中必需的一行。

  3.4 ifupdown
    * Remove any "up" or "down" commands from /etc/network/interfaces
      that futz with /etc/resolv.conf and remove any scripts from
      /etc/network/if-*.d/ that futz with /etc/resolv.conf.
    * For each inet static logical interface through which a nameserver is
      accessible, add lines like the following to /etc/network/interfaces .

          dns-nameservers 11.22.33.44 55.66.77.88
          dns-search foo.org bar.com

      Other recognized option words are 'dns-domain' and 'dns-sortlist'.
      These option names correspond to the option names used in the
      resolv.conf file with one exception: whereas one lists several
      nameserver addresses in /etc/resolv.conf on several "nameserver"
      lines, here one should list them all on a single "dns-nameservers"
      line.  See resolv.conf(5) for more information.  The lines entered
      in /etc/network/interfaces will be added to the resolver
      configuration file (without the "dns-" prefix, of course) when a
      physical interface is brought up as that logical interface.
      Note that the resolver configuration is updated AFTER all the "up"
      commands have been run; therefore "up" commands cannot make use of
      nameservers listed on "dns-nameservers" lines in the same logical
      interface stanza.  Changing this will require modifying ifupdown
      so that it talks to resolvconf; currently resolvconf hooks into
      ifupdown using the script /etc/network/if-up.d/000resolvconf. Note
      too that scripts in /etc/network/if-up.d/ CAN make use of the
      added nameservers because those scripts run after 000resolvconf.

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