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      1 Domain Name System
      2 -------------------------------------------
      3 
      4 The Domain Name System (DNS) is a hierarchical naming system for computers,
      5 services, or any resource participating in the Internet. It associates various
      6 information with domain names assigned to each of the participants. Most
      7 importantly, it translates domain names meaningful to humans into the numerical
      8 (binary) identifiers associated with networking equipment for the purpose of
      9 locating and addressing these devices world-wide. An often used analogy to
     10 explain the Domain Name System is that it serves as the "phone book" for the
     11 Internet by translating human-friendly computer hostnames into IP addresses.
     12 For example, www.example.com translates to 208.77.188.166.
     13 
     14 For more information on DNS - http://en.wikipedia.org/wiki/Domain_Name_System
     15 
     16 U-Boot and DNS
     17 ------------------------------------------
     18 
     19 CONFIG_CMD_DNS - controls if the 'dns' command is compiled in. If it is, it
     20 		 will send name lookups to the dns server (env var 'dnsip')
     21 		 Turning this option on will about abou 1k to U-Boot's size.
     22 
     23 		 Example:
     24 
     25 bfin> print dnsip
     26 dnsip=192.168.0.1
     27 
     28 bfin> dns www.google.com
     29 66.102.1.104
     30 
     31 		 By default, dns does nothing except print the IP number on
     32 		 the default console - which by itself, would be pretty
     33 		 useless. Adding a third argument to the dns command will
     34 		 use that as the environment variable to be set.
     35 
     36 		 Example:
     37 
     38 bfin> print googleip
     39 ## Error: "googleip" not defined
     40 bfin> dns www.google.com googleip
     41 64.233.161.104
     42 bfin> print googleip
     43 googleip=64.233.161.104
     44 bfin> ping ${googleip}
     45 Using Blackfin EMAC device
     46 host 64.233.161.104 is alive
     47 
     48 		 In this way, you can lookup, and set many more meaningful
     49 		 things.
     50 
     51 bfin> sntp
     52 ntpserverip not set
     53 bfin> dns pool.ntp.org ntpserverip
     54 72.18.205.156
     55 bfin> sntp
     56 Date: 2009-07-18 Time:	4:06:57
     57 
     58 		 For some helpful things that can be related to DNS in U-Boot,
     59 		 look at the top level README for these config options:
     60 		    CONFIG_CMD_DHCP
     61 		    CONFIG_BOOTP_DNS
     62 		    CONFIG_BOOTP_DNS2
     63