README.dns 2.0 KB

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