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README.dns

README.dns 2.0 KB
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  1. Domain Name System
    2. 

  2. -------------------------------------------
    3. 

  3. 

  4. The Domain Name System (DNS) is a hierarchical naming system for computers,
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  5. services, or any resource participating in the Internet. It associates various
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  6. information with domain names assigned to each of the participants. Most
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  7. importantly, it translates domain names meaningful to humans into the numerical
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  8. (binary) identifiers associated with networking equipment for the purpose of
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  9. locating and addressing these devices world-wide. An often used analogy to
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  10. explain the Domain Name System is that it serves as the "phone book" for the
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  11. Internet by translating human-friendly computer hostnames into IP addresses.
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  12. For example, www.example.com translates to 208.77.188.166.
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  13. 

  14. For more information on DNS - http://en.wikipedia.org/wiki/Domain_Name_System
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  15. 

  16. U-Boot and DNS
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  17. ------------------------------------------
    18. 

  18. 

  19. CONFIG_CMD_DNS - controls if the 'dns' command is compiled in. If it is, it
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  20. 		 will send name lookups to the dns server (env var 'dnsip')
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  21. 		 Turning this option on will about abou 1k to U-Boot's size.
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  22. 

  23. 		 Example:
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  24. 

  25. bfin> print dnsip
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  26. dnsip=192.168.0.1
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  27. 

  28. bfin> dns www.google.com
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  29. 66.102.1.104
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  30. 

  31. 		 By default, dns does nothing except print the IP number on
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  32. 		 the default console - which by itself, would be pretty
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  33. 		 useless. Adding a third argument to the dns command will
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  34. 		 use that as the environment variable to be set.
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  35. 

  36. 		 Example:
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  37. 

  38. bfin> print googleip
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  39. ## Error: "googleip" not defined
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  40. bfin> dns www.google.com googleip
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  41. 64.233.161.104
    42. 

  42. bfin> print googleip
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  43. googleip=64.233.161.104
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  44. bfin> ping ${googleip}
    45. 

  45. Using Blackfin EMAC device
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  46. host 64.233.161.104 is alive
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  47. 

  48. 		 In this way, you can lookup, and set many more meaningful
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  49. 		 things.
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  50. 

  51. bfin> sntp
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  52. ntpserverip not set
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  53. bfin> dns pool.ntp.org ntpserverip
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  54. 72.18.205.156
    55. 

  55. bfin> sntp
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  56. Date: 2009-07-18 Time:	4:06:57
    57. 

  57. 

  58. 		 For some helpful things that can be related to DNS in U-Boot,
    59. 

  59. 		 look at the top level README for these config options:
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  60. 		    CONFIG_CMD_DHCP
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  61. 		    CONFIG_BOOTP_DNS
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  62. 		    CONFIG_BOOTP_DNS2
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