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一份很好的linux入门资料

underscore)&nbsp;characters&nbsp;are&nbsp;not&nbsp;legal.&nbsp;Note&nbsp;that&nbsp;hostnames&nbsp;include&nbsp;the&nbsp;owners&nbsp;of&nbsp;A&nbsp;and&nbsp;MX&nbsp;records&nbsp;and&nbsp;.in-addr.arpa&nbsp;<BR>
PTR&nbsp;records,&nbsp;and&nbsp;the&nbsp;data&nbsp;fields&nbsp;of&nbsp;MX&nbsp;and&nbsp;.in-addr.arpa&nbsp;PTR&nbsp;records:&nbsp;in&nbsp;other&nbsp;words,&nbsp;almost&nbsp;all&nbsp;currently&nbsp;used&nbsp;DNS&nbsp;<BR>
entries!&nbsp;The&nbsp;current&nbsp;releases&nbsp;of&nbsp;the&nbsp;BIND&nbsp;name&nbsp;server&nbsp;software&nbsp;enforce&nbsp;these&nbsp;restrictions.&nbsp;20-Nov-1997,&nbsp;10-Apr-1996&nbsp;&nbsp;<BR>
&nbsp;<BR>
Checking&nbsp;if&nbsp;a&nbsp;domain&nbsp;is&nbsp;registered&nbsp;already&nbsp;<BR>
&nbsp;<BR>
Based&nbsp;on&nbsp;a&nbsp;question&nbsp;by&nbsp;Plato&nbsp;&lt;<A HREF="mailto:[e-mail]>">[e-mail]></A>&nbsp;&nbsp;<BR>
&nbsp;<BR>
To&nbsp;check&nbsp;if&nbsp;a&nbsp;domain&nbsp;has&nbsp;been&nbsp;registered,&nbsp;there&nbsp;are&nbsp;a&nbsp;couple&nbsp;of&nbsp;approaches.&nbsp;&nbsp;<BR>
&nbsp;<BR>
Brute&nbsp;force&nbsp;search&nbsp;of&nbsp;DNS&nbsp;zone&nbsp;file&nbsp;&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If&nbsp;the&nbsp;relevant&nbsp;zone&nbsp;file&nbsp;corresponding&nbsp;to&nbsp;the&nbsp;domain&nbsp;can&nbsp;be&nbsp;obtained,&nbsp;standard&nbsp;text&nbsp;searching&nbsp;tools&nbsp;can&nbsp;be&nbsp;used&nbsp;to&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;check&nbsp;the&nbsp;file&nbsp;for&nbsp;the&nbsp;domain&nbsp;or&nbsp;variants.&nbsp;This&nbsp;procedure&nbsp;is&nbsp;flexible&nbsp;and&nbsp;quick&nbsp;once&nbsp;the&nbsp;file&nbsp;has&nbsp;been&nbsp;obtained&nbsp;since&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;it&nbsp;is&nbsp;performed&nbsp;off&nbsp;line.&nbsp;The&nbsp;zones&nbsp;ARPA,&nbsp;COM,&nbsp;EDU,&nbsp;GOV,&nbsp;INADDR.ARPA,&nbsp;MIL,&nbsp;NET,&nbsp;and&nbsp;ORG&nbsp;are&nbsp;available&nbsp;at&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;the&nbsp;InterNIC.&nbsp;Other&nbsp;zones&nbsp;may&nbsp;be&nbsp;available&nbsp;via&nbsp;ftp,&nbsp;but&nbsp;will&nbsp;usually&nbsp;need&nbsp;to&nbsp;be&nbsp;downloaded&nbsp;using&nbsp;the&nbsp;zone&nbsp;transfer&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;mechanism&nbsp;of&nbsp;DNS.&nbsp;If&nbsp;a&nbsp;server&nbsp;is&nbsp;configured&nbsp;to&nbsp;disallow&nbsp;zone&nbsp;transfers,&nbsp;it&nbsp;may&nbsp;not&nbsp;be&nbsp;possible&nbsp;to&nbsp;easily&nbsp;obtain&nbsp;a&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;copy&nbsp;of&nbsp;the&nbsp;zone&nbsp;file.&nbsp;&nbsp;<BR>
WHOIS&nbsp;lookups&nbsp;&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;If&nbsp;the&nbsp;domain&nbsp;being&nbsp;sought&nbsp;is&nbsp;in&nbsp;one&nbsp;of&nbsp;the&nbsp;InterNIC&nbsp;maintained&nbsp;zones,&nbsp;information&nbsp;about&nbsp;the&nbsp;domain&nbsp;will&nbsp;be&nbsp;stored&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;in&nbsp;the&nbsp;InterNIC&nbsp;WHOIS&nbsp;database.&nbsp;A&nbsp;standard&nbsp;whois&nbsp;client&nbsp;can&nbsp;be&nbsp;used&nbsp;to&nbsp;query&nbsp;this&nbsp;database,&nbsp;currently&nbsp;located&nbsp;at&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;rs.internic.net.&nbsp;In&nbsp;the&nbsp;absence&nbsp;of&nbsp;a&nbsp;client,&nbsp;rs.internic.net&nbsp;also&nbsp;offers&nbsp;telnet&nbsp;access&nbsp;to&nbsp;the&nbsp;database.&nbsp;For&nbsp;some&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;domains,&nbsp;information&nbsp;is&nbsp;kept&nbsp;in&nbsp;WHOIS-like&nbsp;services&nbsp;like&nbsp;RWHOIS&nbsp;or&nbsp;in&nbsp;domain-specific&nbsp;WHOIS&nbsp;registries.&nbsp;&nbsp;<BR>
Checking&nbsp;the&nbsp;DNS&nbsp;&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Using&nbsp;DNS&nbsp;query&nbsp;tools&nbsp;like&nbsp;dig&nbsp;or&nbsp;nslookup&nbsp;with&nbsp;query&nbsp;types&nbsp;NS,&nbsp;MX&nbsp;or&nbsp;A,&nbsp;information&nbsp;about&nbsp;the&nbsp;existence&nbsp;of&nbsp;a&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;domain&nbsp;name&nbsp;can&nbsp;be&nbsp;obtained.&nbsp;This&nbsp;is&nbsp;the&nbsp;most&nbsp;general&nbsp;method,&nbsp;although&nbsp;it&nbsp;requires&nbsp;an&nbsp;exact&nbsp;guess&nbsp;to&nbsp;be&nbsp;made&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;both&nbsp;of&nbsp;the&nbsp;type&nbsp;of&nbsp;records&nbsp;associated&nbsp;with&nbsp;the&nbsp;domain&nbsp;name&nbsp;and&nbsp;the&nbsp;name&nbsp;itself.&nbsp;Using&nbsp;a&nbsp;query&nbsp;type&nbsp;ANY&nbsp;can&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;sometimes&nbsp;be&nbsp;effective,&nbsp;but&nbsp;can&nbsp;also&nbsp;result&nbsp;in&nbsp;misleading&nbsp;answers.&nbsp;&nbsp;<BR>
&nbsp;<BR>
Setting&nbsp;up&nbsp;a&nbsp;resolver&nbsp;<BR>
&nbsp;<BR>
Based&nbsp;on&nbsp;a&nbsp;question&nbsp;by&nbsp;Aidan&nbsp;N.R.&nbsp;Low&nbsp;&lt;<A HREF="mailto:[e-mail]>">[e-mail]></A>&nbsp;&nbsp;<BR>
&nbsp;<BR>
Setting&nbsp;up&nbsp;the&nbsp;client&nbsp;side&nbsp;of&nbsp;DNS&nbsp;depends&nbsp;on&nbsp;the&nbsp;operating&nbsp;environment&nbsp;of&nbsp;the&nbsp;client.&nbsp;For&nbsp;a&nbsp;Unix&nbsp;machine,&nbsp;the&nbsp;resolver&nbsp;is&nbsp;<BR>
configured&nbsp;through&nbsp;a&nbsp;text&nbsp;file,&nbsp;usually&nbsp;/etc/resolv.conf&nbsp;which&nbsp;commonly&nbsp;contains&nbsp;the&nbsp;IP&nbsp;address&nbsp;of&nbsp;the&nbsp;name&nbsp;server&nbsp;or&nbsp;<BR>
servers&nbsp;which&nbsp;will&nbsp;be&nbsp;used&nbsp;to&nbsp;do&nbsp;the&nbsp;actual&nbsp;work.&nbsp;An&nbsp;adequate&nbsp;resolv.conf&nbsp;file&nbsp;contains&nbsp;just&nbsp;the&nbsp;one&nbsp;line&nbsp;&nbsp;<BR>
&nbsp;<BR>
nameserver&nbsp;x.y.z.w&nbsp;<BR>
&nbsp;<BR>
where&nbsp;x.y.z.w&nbsp;is&nbsp;the&nbsp;IP&nbsp;address&nbsp;of&nbsp;a&nbsp;suitable&nbsp;name&nbsp;server.&nbsp;Often&nbsp;this&nbsp;will&nbsp;be&nbsp;a&nbsp;server&nbsp;provided&nbsp;by&nbsp;the&nbsp;Internet&nbsp;service&nbsp;<BR>
provider.&nbsp;It&nbsp;is&nbsp;a&nbsp;bad&nbsp;idea&nbsp;to&nbsp;point&nbsp;resolvers&nbsp;to&nbsp;name&nbsp;servers&nbsp;controlled&nbsp;by&nbsp;organisations&nbsp;with&nbsp;which&nbsp;there&nbsp;is&nbsp;no&nbsp;<BR>
organisational&nbsp;relationship:&nbsp;the&nbsp;name&nbsp;server&nbsp;could&nbsp;be&nbsp;configured&nbsp;to&nbsp;return&nbsp;bogus&nbsp;information,&nbsp;especially&nbsp;if&nbsp;permission&nbsp;was&nbsp;<BR>
not&nbsp;sought&nbsp;first&nbsp;for&nbsp;using&nbsp;the&nbsp;server.&nbsp;&nbsp;<BR>
&nbsp;<BR>
For&nbsp;PC&nbsp;type&nbsp;resolvers&nbsp;there&nbsp;is&nbsp;usually&nbsp;a&nbsp;network&nbsp;configuration&nbsp;option&nbsp;which&nbsp;specifies&nbsp;the&nbsp;same&nbsp;information&nbsp;as&nbsp;resolv.conf.&nbsp;<BR>
Each&nbsp;network&nbsp;stack&nbsp;tends&nbsp;to&nbsp;have&nbsp;its&nbsp;own&nbsp;set&nbsp;of&nbsp;configuration&nbsp;information.&nbsp;However,&nbsp;on&nbsp;MacOS,&nbsp;there&nbsp;are&nbsp;moves&nbsp;towards&nbsp;<BR>
central&nbsp;network&nbsp;configuration.&nbsp;&nbsp;<BR>
&nbsp;<BR>
For&nbsp;SunOS&nbsp;4.x,&nbsp;the&nbsp;resolver&nbsp;is&nbsp;by&nbsp;default&nbsp;not&nbsp;set&nbsp;up&nbsp;to&nbsp;use&nbsp;DNS.&nbsp;The&nbsp;standard&nbsp;operating&nbsp;procedure&nbsp;to&nbsp;get&nbsp;SunOS&nbsp;to&nbsp;use&nbsp;<BR>
DNS&nbsp;is&nbsp;in&nbsp;the&nbsp;comp.sys.sun&nbsp;FAQ,&nbsp;last&nbsp;I&nbsp;looked&nbsp;these&nbsp;were&nbsp;questions&nbsp;1&nbsp;and&nbsp;2.&nbsp;In&nbsp;short,&nbsp;&nbsp;<BR>
&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;add&nbsp;the&nbsp;DNS&nbsp;trapdoor&nbsp;to&nbsp;NIS,&nbsp;or&nbsp;&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;rebuild&nbsp;libc.a&nbsp;using&nbsp;resolv+&nbsp;or&nbsp;the&nbsp;BIND&nbsp;4.9.3&nbsp;resolver&nbsp;routines.&nbsp;&nbsp;<BR>
&nbsp;<BR>
Of&nbsp;these,&nbsp;the&nbsp;BIND&nbsp;4.9.3&nbsp;option&nbsp;is&nbsp;recommended.&nbsp;&nbsp;<BR>
&nbsp;<BR>
Solaris&nbsp;2.x&nbsp;is&nbsp;also&nbsp;not&nbsp;set&nbsp;up&nbsp;to&nbsp;use&nbsp;DNS&nbsp;by&nbsp;default.&nbsp;In&nbsp;the&nbsp;file&nbsp;/etc/nsswitch.conf&nbsp;there&nbsp;is&nbsp;a&nbsp;line&nbsp;&nbsp;<BR>
&nbsp;<BR>
hosts:&nbsp;files&nbsp;<BR>
&nbsp;<BR>
which&nbsp;needs&nbsp;to&nbsp;be&nbsp;changed&nbsp;to&nbsp;&nbsp;<BR>
&nbsp;<BR>
hosts:&nbsp;files&nbsp;dns&nbsp;<BR>
&nbsp;<BR>
for&nbsp;the&nbsp;machine&nbsp;to&nbsp;use&nbsp;DNS.&nbsp;&nbsp;<BR>
&nbsp;<BR>
Given&nbsp;a&nbsp;choice&nbsp;of&nbsp;servers,&nbsp;which&nbsp;one&nbsp;is&nbsp;queried?&nbsp;<BR>
&nbsp;<BR>
Based&nbsp;on&nbsp;a&nbsp;question&nbsp;by&nbsp;Mark&nbsp;A.&nbsp;Dohm&nbsp;&lt;<A HREF="mailto:[e-mail]>">[e-mail]></A>&nbsp;and&nbsp;answer&nbsp;by&nbsp;Paul&nbsp;A&nbsp;Vixie&nbsp;&lt;<A HREF="mailto:[e-mail]>">[e-mail]></A>&nbsp;&nbsp;<BR>
&nbsp;<BR>
Every&nbsp;recursive&nbsp;BIND&nbsp;name&nbsp;server&nbsp;(that&nbsp;is,&nbsp;one&nbsp;which&nbsp;is&nbsp;willing&nbsp;to&nbsp;go&nbsp;out&nbsp;and&nbsp;find&nbsp;something&nbsp;if&nbsp;asked&nbsp;something&nbsp;it&nbsp;doesn't&nbsp;<BR>
know)&nbsp;will&nbsp;remember&nbsp;the&nbsp;measured&nbsp;round&nbsp;trip&nbsp;time&nbsp;(RTT)&nbsp;to&nbsp;each&nbsp;server&nbsp;it&nbsp;sends&nbsp;queries&nbsp;to.&nbsp;If&nbsp;it&nbsp;has&nbsp;a&nbsp;choice&nbsp;of&nbsp;several&nbsp;<BR>
servers&nbsp;for&nbsp;some&nbsp;domain&nbsp;(like&nbsp;&quot;.&quot;&nbsp;for&nbsp;example)&nbsp;it&nbsp;will&nbsp;use&nbsp;the&nbsp;one&nbsp;whose&nbsp;measured&nbsp;RTT&nbsp;is&nbsp;lowest.&nbsp;&nbsp;<BR>
&nbsp;<BR>
Since&nbsp;the&nbsp;measured&nbsp;RTT&nbsp;of&nbsp;all&nbsp;NS&nbsp;RRs&nbsp;starts&nbsp;at&nbsp;zero&nbsp;(0),&nbsp;every&nbsp;one&nbsp;is&nbsp;tried&nbsp;once.&nbsp;Once&nbsp;all&nbsp;have&nbsp;responded,&nbsp;all&nbsp;RTT's&nbsp;will&nbsp;<BR>
be&nbsp;nonzero,&nbsp;and&nbsp;the&nbsp;&quot;fastest&nbsp;server&quot;&nbsp;will&nbsp;get&nbsp;all&nbsp;queries&nbsp;henceforth,&nbsp;until&nbsp;it&nbsp;slows&nbsp;down&nbsp;for&nbsp;some&nbsp;reason.&nbsp;&nbsp;<BR>
&nbsp;<BR>
To&nbsp;promote&nbsp;dispersion&nbsp;and&nbsp;good&nbsp;recordkeeping,&nbsp;BIND&nbsp;will&nbsp;penalize&nbsp;the&nbsp;RTT&nbsp;by&nbsp;a&nbsp;little&nbsp;bit&nbsp;each&nbsp;time&nbsp;a&nbsp;server&nbsp;is&nbsp;reused,&nbsp;<BR>
and&nbsp;it&nbsp;will&nbsp;penalize&nbsp;the&nbsp;RTT&nbsp;a&nbsp;_lot_&nbsp;if&nbsp;it&nbsp;ever&nbsp;has&nbsp;to&nbsp;retransmit&nbsp;a&nbsp;query.&nbsp;For&nbsp;a&nbsp;server&nbsp;to&nbsp;stay&nbsp;&quot;#1&quot;,&nbsp;it&nbsp;has&nbsp;to&nbsp;keep&nbsp;on&nbsp;<BR>
answering&nbsp;quickly&nbsp;and&nbsp;consistently.&nbsp;&nbsp;<BR>
&nbsp;<BR>
Note&nbsp;that&nbsp;this&nbsp;is&nbsp;something&nbsp;BIND&nbsp;does&nbsp;that&nbsp;the&nbsp;DNS&nbsp;Specification&nbsp;does&nbsp;not&nbsp;mention&nbsp;at&nbsp;all.&nbsp;So&nbsp;other&nbsp;servers,&nbsp;those&nbsp;not&nbsp;<BR>
based&nbsp;on&nbsp;BIND,&nbsp;might&nbsp;behave&nbsp;very&nbsp;differently.&nbsp;&nbsp;<BR>
&nbsp;<BR>
Transferring&nbsp;zones&nbsp;from&nbsp;a&nbsp;server&nbsp;running&nbsp;Microsoft&nbsp;NT&nbsp;Server&nbsp;4.0&nbsp;<BR>
&nbsp;<BR>
Based&nbsp;on&nbsp;an&nbsp;answer&nbsp;by&nbsp;Stuart&nbsp;Kwan&nbsp;&lt;<A HREF="mailto:[e-mail]>">[e-mail]></A>&nbsp;&nbsp;<BR>
&nbsp;<BR>
If&nbsp;Microsoft's&nbsp;DNS&nbsp;server&nbsp;is&nbsp;integrated&nbsp;with&nbsp;WINS,&nbsp;it&nbsp;needs&nbsp;to&nbsp;be&nbsp;explicitly&nbsp;configured&nbsp;to&nbsp;interoperate&nbsp;with&nbsp;non-Microsoft&nbsp;<BR>
name&nbsp;servers.&nbsp;Microsoft&nbsp;represents&nbsp;WINS&nbsp;information&nbsp;in&nbsp;the&nbsp;DNS&nbsp;using&nbsp;a&nbsp;nonstandard&nbsp;resource&nbsp;record&nbsp;type.&nbsp;This&nbsp;can&nbsp;<BR>
cause&nbsp;a&nbsp;name&nbsp;server&nbsp;to&nbsp;fail&nbsp;when&nbsp;attempting&nbsp;a&nbsp;zone&nbsp;transfer&nbsp;from&nbsp;a&nbsp;Microsoft&nbsp;server.&nbsp;Older&nbsp;BIND&nbsp;servers&nbsp;may&nbsp;actually&nbsp;<BR>
terminate&nbsp;when&nbsp;receiving&nbsp;such&nbsp;resource&nbsp;records&nbsp;in&nbsp;a&nbsp;zone&nbsp;transfer.&nbsp;&nbsp;<BR>
&nbsp;<BR>
To&nbsp;correct&nbsp;the&nbsp;problem,&nbsp;ensure&nbsp;that&nbsp;the&nbsp;option&nbsp;&quot;Zone&nbsp;Properties&nbsp;-&gt;&nbsp;WINS&nbsp;Lookup&nbsp;-&gt;&nbsp;Settings&nbsp;only&nbsp;affect&nbsp;local&nbsp;server&quot;&nbsp;is&nbsp;<BR>
set&nbsp;for&nbsp;each&nbsp;such&nbsp;zone&nbsp;on&nbsp;the&nbsp;Microsoft&nbsp;server.&nbsp;&nbsp;<BR>
&nbsp;<BR>
&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<BR>
&nbsp;<BR>
<A HREF="mailto:[e-mail]">[e-mail]</A>&nbsp;/&nbsp;The&nbsp;Internet&nbsp;Solution&nbsp;&nbsp;<BR>
&nbsp;<BR>
--&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;白马带著她一步步的回到中原。白马已经老了，只能慢慢的走，&nbsp;<BR>
但终是能回到中原的。江南有杨柳、桃花，有燕子、金鱼……&nbsp;<BR>
汉人中有的是英俊勇武的少年，倜傥潇洒的少年……但这个美&nbsp;<BR>
丽的姑娘就像古高昌国人那样固执:&nbsp;<BR>
&nbsp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;「那都是很好很好的，可是我偏不喜欢。」&nbsp;&nbsp;<BR>
&nbsp;<BR>
※&nbsp;来源:·BBS&nbsp;水木清华站&nbsp;bbs.net.tsinghua.edu.cn·[FROM:&nbsp;159.226.21.172]&nbsp;<BR>


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