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July 1999

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RE: [wlug] RH6.0 & DNS?
by Daniel Lawson 26 Jul '99

26 Jul '99

>Yeah - I realised I hadn't mentioned that when I sent the message :) no problem >I've got it config'd as a dialin server and want to be able to use virtual >hosts etc for remote callers. I've already got them to put entries in their >c:\windows\hosts files but it's messy. Hmm, okay. >Okay - so how do I find out what IHUG's are? I can look it up on their web >site but there must be an easier way - either using W95/98 or RH6.0. Oh, i assumed your isp was clear because of your email address :) 203.29.160.4 203.29.160.2 :) >Yeah, I'd appreciate that - please do. Start with "You add entries to your >DNS by ...." <sigh>. :) this will be a LONG post i feel... Its probably worth sending to the mailing list however, so that anyone else who is curious about setting up DNS can have a look... First of all, redhat 6.0 ships with bind-8.2-6 do 'rpm -qa | grep bind' as root to see what bind rpms you have installed, if any you should have bind-8.2-6 bind-devel-8.2-6 bind-utils-8.2-6 or something very similar (ie, the revision number might have changed for your release of rh6.0) if you dont have these then install them.. (either use an X-based package management tool like gnorpm, or use rpm from the command line..) put your rh6.0 cd in the cdrom drive mount /mnt/cdrom rpm -Uvh /mnt/cdrom/Redhat/RPMS/bind* and you should be away :) right... now for the config files at this point i VERY strongly recommend you go away and read the docs for bind at www.isc.org here's some pointers Some config hints for bind 8.2.1 (slightly newwer version that the rh6.0 one, but still applies) http://www.isc.org/view.cgi?/products/BIND/misc/config_hints.phtml Bind 8.2 configuration guide http://www.isc.org/view.cgi?/products/BIND/docs/config/index.phtml bind 8.2 master file format http://www.isc.org/view.cgi?/products/BIND/docs/bind8.2_master-file.phtml The BOG (BIND Operations Guide) was a very useful resource for bind-4.9.7, but this version of bind is oldish and you should probably use 8.2 series. the configuration guide tells you what to do, more or less, but we can have a look at them here too... i'll add comments, these are indicated by // preceeding ------ /etc/named.conf ------ // make sure you get all the {'s and ;'s in the right place here options { directory "/var/named"; // this tells named where to set its base dir to. }; logging { category lame-servers { null; }; / these send all the boring errors that you dont category cname { null; }; // care about to null, rather than actually logging them }; zone "." in { type hint; // the 'hint' file is a set of root servers. these are important if you file "named.cache"; // want your dns server to work on address outside your zones }; // i'll show how to get a named.cache file later zone "0.0.127.in-addr.arpa" in { // the 0.0.127 zone is the reverse zone for your localhost type master; // its a master file notify no; // dont notify file "slave/127.0.0.in-addr.arpa"; // the file name }; zone "foo.org" in { // forward lookup for your 'domain' on your local network type master; //master file file "slave/foo.org"; //filename }; zone "0.168.192.in-addr.arpa" in { //reverse lookup for your domain, on 192.168.0.xxx type master; // note the reverse order of ip addresses file "slave/0.168.192.in-addr.arpa"; }; ---- eof----- right, now in /var/named you should have some files... /var/named/named.cache there is possibly already a named.cache file, but we should update it anyway.. anonymous ftp to ftp.internic.net cd domain get named.cache cp named.cache /var/named/named.cache -f okay, thats your cache file set up. now to set up some zone files first of all, make a directory in /var/named to hold the zone files.. mkdir /var/named/zone cd /var/named/zone now.. there are two types of zone files.. forward lookup (which contain mappings from hostnames to ip addresses) and reverse lookup (which contain mappings from ip addresses to hostnames) first we'll look at the forward zone files. /var/named/zone/foo.org (or whatever you call it, make sure the entry in the named.conf file points to the right place tho) ; denotes a comment in these files ------------------- ; ; /var/named/zone/foo.org ; zone file for foo.org ; 27/7/1999 @ IN SOA server. root.server. ( 1999072701 ; Serial 8H ; Refresh 2H ; Retry 1W ; Expire 1D) ; minimum ; first of all, lets look at these. ; the @ inserts the domain information by default. so, it expands out to foo.org ; the rest of that line says that the Start Of Authority (SOA) for the domain is server ; and the admin email is root(a)server ; the serial number is important. when you change a zone file, change its serial number, ; otherwise bind will not reload it. ; also, bind will only load /higher/ serial numbers. you can number any way you like, for ; example starting at 1, but it is sometimes handy to put them in the format yyyymmdd ; where yyyy == year, dd = day of month, mm = month, rr = revision number. ; the refresh, retry, expire and minimum values are all required by named, it tells it how ; often to do the related action. ; ie, Refresh this zone every 8 hours. rertry an ip on this zone every 2 ; NS server.foo.org. ;specifies that the NameServer for the domain is server.foo.org. MX 10 server.foo.org. ; Mail eXchange for the domain is server.foo.org. the number is the priority, 10 is a good ; number to leave there. NOTE both of these have a trailing '.' - if you DONT include this it ; will expand out with your domain name after it (ie, to server.foo.org.foo.org ) !!! localhost A 127.0.0.1 ; A records point from the hostname to its ip. this is the ip of the localhost (the server) server A 192.168.0.2 ; this is the A record for the server, assuming its ip addresss is 192.168.0.2 HINFO "Pentium" "Linux 2.2" TXT "Gateway / Server" ; these lines aren't needed, but add extra information. There are a lot of extra lines like this ; dont worry about them if you like - not including them is perhaps a /good/ thing. mail CNAME server www CNAME server ftp CNAME server proxy CNAME server dns CNAME server ; CNAMES are records that point to an A record. Not needed really, but sometimes is nicer ; (and more obvious) to use 'proxy' for your proxy settings, and 'mail' in your mailclient setup. ; Various DNS experts discourage the usage of CNAME, because it can lead to trouble if ; you do things like point your MX record to a CNAME. ; You could use multiple A records (eg, 'ftp A 192.168.0.2' but that gets messy, ; and you only have one reverse lookup anyway windows A 192.168.0.1 ; A record for your windows computer dialin1 A 192.168.0.10 dialin2 A 192.168.0.11 ; A records for your dialin ip addresses. ; I forget how dialing into a linux server works, particularly with regards to ip allocation, ; you may only be able to specify 1 ip address for each dialin device. ------ EOF ----- thats the end of it! there are a lot of things you COULD include in there, but thats all you need. now, onto the reverse lookup zone files /var/named/zone/0.0.127.in-addr.arpa --------------- ; ; /var/named/zone/0.0.127.in-addr.arpa ; zone file for 0.0.127.in-addr.arpa ; 27/7/1999 @ IN SOA localhost. root.localhost ( 1999072701 8H 2H 1W 1S ) ; note, we condensed everything down here. the whitespace in the previous example ; is for clarity, you dont need it or the comments at all. NS server.foo.org. ; nameserver entry. note the trailing '.' 1 PTR localhost. ; PTR record. this is a reverse lookup for 1.0.0.127.in-addr.arpa (ie, if you do 'nslookup ; 127.0.0.1' - it'll look in this file, find the PTR entry for '1', and reply with the given value. ; again note the trailing '.' - if you forgot that it would expand to localhost.0.0.127.in-addr.arpa ------ EOF ---- /var/named/zone/0.168.192.in-addr.arpa ---------------- ; ; /var/named/zone/0.168.192.in-addr.arpa ; zone file for 0.168.192.in-addr.arpa ; 27/7/1999 @ IN SOA server. root.server. ( 1999072701 8H 2H 1W 1D) IN NS server.foo.org. ; NS for zone is server.foo.org - again, note the trailing '.' 1 IN PTR windows.foo.org. 2 IN PTR server.foo.org. 10 IN PTR dialin1.foo.org. 11 IN PTR dialin2.foo.org. -------- EOF ----------- once you have created all these files, try starting named by going /etc/rc.d/init.d/named start if you check the output of /var/log/messages , it should display some information about whats happening (tail -f /var/log/messages on another console to look at it, ctrl-c to break out of 'tail' ) it should give you some output along the lines of... Jul 27 02:22:40 server named[12344]: starting. named 8.1.2 Thu Sep 24 02:47:08 EDT 1998 ^Iroot(a)porky.redhat.com:/usr/src/bs/BUILD/src/bin/named Jul 27 02:22:40 server named[12344]: cache zone "" (IN) loaded (serial 0) Jul 27 02:22:40 server named[12344]: master zone "0.0.127.in-addr.arpa" (IN) loaded (serial 1997072701) Jul 27 02:22:40 server named[12344]: master zone "0.168.192.in-addr.arpa" (IN) loaded (serial 1997072701) Jul 27 02:22:41 server named[12344]: master zone "foo.org" (IN) loaded (serial 1997072701) Jul 27 02:22:41 server named[12344]: listening on [127.0.0.1].53 (lo) Jul 27 02:22:41 server named[12344]: listening on [192.168.0.2].53 (eth0) Jul 27 02:22:41 server named[12344]: listening on [203.109.198.21].53 (ppp0) Jul 27 02:22:41 server named[12344]: Ready to answer queries. okay.. now, make sure your /etc/resolv.conf has the line 'nameserver 192.168.0.2' at the TOP of the nameserver lists. then do.. nslookup server.foo.org you should get the response -- Server: server.foo.org Address: 192.168.0.2 Name: server.foo.org Address: 192.168.0.2 -- now do nslookup localhost -- Server: server.foo.org Address: 192.168.0.2 Name: localhost Address: 127.0.0.1 --- (or something similar) nslookup 192.168.0.1 you should get -- Server: server.foo.org Address: 192.168.0.2 Name windows.foo.org Address: 192.168.0.1 -- if thats all go, then forward DNS works. now try reverse.. nslookup 192.168.0.1 -- Server: server.foo.org Address: 192.168.0.2 Name windows.foo.org Address: 192.168.0.1 -- as you can see, it looks the same :) So, all you have to do now is set up your dialin clients to use your dns server - i'm not sure if this can be forced upon them when they dial in, or if they should set it manually, but that's for you to work out :) I've led you through this entirely - thats because I was very bored tonight, and had nothing else to do :). I do urge you to go and read the documentation on www.isc.org, and the docs that come with the bind rpms. UNDERSTAND them... no point in doing things like this if you dont understand them.. Good luck. you shouldn't have many problems (unless i included some typos there), but if you do, read the docs, work it out, and then report back to the list telling us what went wrong and how you fixed it :) Daniel Lawson

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