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Commit | Line | Data |
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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 |