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