Что означает опция dns-search в / etc / network / interfaces?

Question 1

Кто-нибудь может объяснить мне о директиве dns-search в файле /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

Это обязательно? И как мне это настроить?

Question 2

dns-search определяет, какой домен добавляется для поиска DNS.

Обычно вы указываете здесь тот же домен, который был возвращен hostname -f.

Подробную информацию см. В следующей цитате из 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.

.

Question 3

Question 4

Я также нашел это в README.gz, расположенном в / usr / share / doc / resolvconf в Ubuntu 14.04. Это дает немного больше ясности.

Остерегайтесь файла resolv.conf, управляемого службой resolvconf.

dns-search оказывается необходимой строкой в разделе логического интерфейса.

  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.

H.-Dirk Schmitt · Answer 1 · 10 May 2016 в 23:32