Linux Sendmail+UUCP Mini HOWTO by Jamal Hadi Salim (jamal@glcom.com) v1.2, 15 March 1996 History: ------- Initial edition July/96: works only with non-bind edition of sendmail Update Oct 01 /96: works with the redhat supplied binary Update Oct 07 /96: added/modified a tip on how to compile non-bind sendmail Update Oct 25 /96: added/modified a tip on how to keep sendmail getHostbyAddr() happy via a dummy /etc/hosts entry update Mar 15 /97: I am amazed at the response/feedback i am receiving so i decided to refine this further. Fixed some small errors; added diagram + references. After finally settling down and properly reading TFM (the Bat Book, to be precise) i have solved the Caramilk secret! The steps below will work with the binary supplied by RedHat. Perhaps i should send this tip to the maintainer of the Sendmail FAQ too since there is absolutely no mention of it. What this Document tries to show you ------------------------------------ How to setup a single machine, reffered to as me.com in the example, with no direct access to the internet to route mail for you via sendmail and UUCP to a 'smarter host' eg your ISP. Optionally you can configure this machine to feed other machines i.e you are their 'smart' host or gateway. What this Document does not tell you ------------------------------------ I have been receiving incredible number of questions regarding the following topics. The purpose of this document is not to describe them so please try not send me any questions on the following: a) how to setup UUCP. Refer to many fine references on this, including: - UUCP HOWTO (Vince Skahan, ) - Using and managing UUCP (Ed Ravin et al -- publisher O'reilly)-- THE BEST - Linux Network Administrator Guide (Olaf Kirch) b) how to setup DNS. Refer to the many fine references on this, including: - Caching named mini howto (Nicolai Langfeldt) - The bat book (Sendmail;Costalles, Allman, Rickert;publisher O'reilly) - DNS and BIND (Publisher O'reilly) - TCP/IP Network Administration (Hunt, Craig;Publisher O'reilly) - Linux Network Administrator Guide (Olaf Kirch) - sendmail Theory and Practice (Avolio and Vixie; publisher Digital press) c) how to setup databases (other than the mailertable) to work with sendmail. Refer to the many fine references on this, including: - The bat book (Sendmail;Costalles, Allman, Rickert -- publisher O'reilly) - TCP/IP administration (Publisher O'reilly) - sendmail Theory and Practice (Avolio and Vixie; publisher Digital press) - docs bundled with sendmail d) how to write or modify rulesets or mailers. - All the above references (in c) You can also find help on the following newsgroups: - comp.mail.sendmail - comp.mail.uucp - comp.os.linux.networking IRC channels - #linux, #unix THE SETUP: --------- This is for a system whose mail is sent out only via UUCP. mysmarthost is the ISPs hostname as set up in the uucp sys file and me.com is the hostname we use. mysmarthost hooks to the internet. We really dont care how it does it, we just know it knows how to get us there. me.com, whose setup we describe in the example, feeds sites down.com and system1.org and their subnodes. me.com connects to down.com via TCP/IP and connects to system1.org via raw UUCP using a phone line. The setup description is shown below. ------------------------ | | | Internet | | | ----------------------- | | PPP/dedicated line running TCP-IP | ------------- | | |mysmarthost | Authoritative name server for | | *.me.com, *.down.com, *.system1.org | | -------------- | | UUCP via a phone line receive for | system1.org, *.system1.org,*.down.com, down.com | as well as me.com and *.me.com ------------ | * ***** * | ------------ | * me.com * | ------ | * * | | | | * ***** * | | | ------------ | |UUCP via phone line | uucp via TCP/IP | | ----------- ----------- | | | | |system1.org| | down.com |------- | | | | | ---------- ------------ | | | | | | | LAN: smtp to nodes | UUCP phone line | | ----------- ------------- | | | | |system1's| | down's | |subnodes | | LAN | | | ------------ ---------- pre-requisites ============== 1) If you are on a machine using uucp for mail then you dont really need to compile bind/resolv into sendmail; How to survive name canonicalization on a estand-alone machine with no DNS -------------------------------------------------------------------------------- PART I: ------ If you get a pre-compiled sendmail with BIND in it you can still live with it (As is the case with Redhat supplied sendmail). a) Refer to my solution for this based on the m4 file described (my favorite). Try to use this option unless you really insist on b) or c) below OR b)If you talk to me i could supply you with a non-BIND compiled version (8.8.5). Perhaps RedHat should consider supplying two sendmail binaries (like slakware) One with BIND and the other with no BIND. OR c) The quickest solution to get sendmail with no bind is to edit src/conf.h lines below to read as i have shown: conf.h:# ifndef NAMED_BIND conf.h:# define NAMED_BIND 0 /* use Berkeley Internet Domain Server */ AND PART II: ------- Sendmail would however normally insist on doing name look ups to resolve the host part using gethostbyaddr() for each email it sends (even if you tell it not to canonify names). a) use an RFC1597 IP address (10.0.0.0-10.255.255.255, 172.16.0.0-172.31.255.255, 192.168.0.0-192.168.255.255) Edit /etc/hosts and add the following as a sample for the host myhost 10.0.0.1 myhost.me.com myhost or b) If you use NIS (and NIS is compiled into sendmail as seems to be the case in Redhat. Redhat also has NIS built in) make sure the /etc/nsswitch.conf file contains: hosts: files dns and in /etc/hosts and add the following as a sample for the host myhost [again using RFC1597 IP addressing scheme] 10.0.0.1 myhost.me.com myhost NOTE: ---- In both a) and b) above it is critical that you list the long (fully qualified) in the /etc/hosts file used. i.e the line should read 10.0.0.1 myhost.me.com myhost and NOT 10.0.0.1 myhost you will also need to define the sendmail $w macro to hold myhost.me.com add the Following line to your /etc/sendmail.cf after it is generated Dwmyhost.me.com (or you can use MASQUAREADE_AS(myhost.me.com) in the .mc below) NOTE!!!!! myhost as a domain name is given as an example; you dont have to use it as is. Pick your own hostname if you dont have one already. -------------------------------------------------------------------------------- 2) Ensure that you have makemap and it is capable of supporting hash and or the more common dbm format or even btree format (The Redhat version does not support dbm). Makemap is normaly distributed with sendmail. SETUP -------------------------------------------------------------------------------- 1) create your .mc file using your favorite editor; i'll call this file my.mc ============== file my.mc ======================= include(`../m4/cf.m4') VERSIONID(`me.com's setup with uucp created by xxxx')dnl OSTYPE(linux) FEATURE(nodns)dnl FEATURE(nocanonify)dnl FEATURE(always_add_domain)dnl FEATURE(mailertable, hash /etc/mailertable)dnl MAILER(local)dnl MAILER(smtp)dnl MAILER(uucp) define(`SMART_HOST', uucp-dom:mysmarthost) =============================================== Let's dissect this: include(`../m4/cf.m4') requests for the m4 macro found in ../m4/cf.m4 to be include to resolve some things VERSIONID(`me.com's setup with uucp created by xxxx')dnl This is used to distinguish the different versions of .cf file you might end up creating. OSTYPE(linux) This is used to define/redefine linux specific stuff. It is safe to have it here. FEATURE(nodns)dnl This says we dont have a DNS server (so in effect we are using uucp only for mail. Sendmail must be compiled not to use bind) This is now obsolete. I will let it stay here just in case you use an older version of sendmail. FEATURE(nocanonify)dnl This says Don't pass addresses to $[ ... $] for canonification. Normally if you have BIND compiled in sendmail would try and expand the alias/IP address to a canonical name using DNS. You dont wanna do this if all you have are feeds which connect to you via UUCP i.e you are a stand alone. FEATURE(always_add_domain)dnl This adds the local domain host name even on locally delivered mail Not necessary i just like it; FEATURE(mailertable, hash /etc/mailertable)dnl the file /etc/mailertable is going to be a hash database where we will store routing information of certain sites. If you dont have anyone who you feed uucp to then you dont need this. More on this later. If you wanted to use the dbm format you would have FEATURE(mailertable, dbm /etc/mailertable)dnl If you wanted to use the btree format you would have FEATURE(mailertable, btree /etc/mailertable)dnl MAILER(local)dnl MAILER(smtp)dnl MAILER(uucp) These are the mailers we use. define(`SMART_HOST', uucp-dom:mysmarthost) Our smart host is our ISP who is defined in the uucp sys file as system mysmarthost. Any messages that we cant handle (i.e ones for domains or mailers we dont understand) will be passed on to our smarthost/ISP to figure out. note we use uucp-dom as the uucp mailer. This particular mailer uses smtp rewriting rules. 2) create your sendmail.cf file a) backup your old /etc/sendmail.cf file b) overwrite the sendmail.cf with the new one: m4 my.mc > /etc/sendmail.cf c) verify that the sendmail.cf file was correctly created based on your specifications. Some of the gotchas that i came across were: - missing uucp-dom mailer This was because i didnt have the smtp mailer entry. Actually, i understand it is important to have it defined before the uucp 4) create your /etc/mailertable if you dont have uucp sites feeding off you skip this step a) create/edit the file /etc/mailertable --------- sample /etc/mailertable ---------- system1.org uucp-dom:system1 .system1.org uucp-dom:system1 down.com uucp-dom:down up.down.com error: Host is unknown at me.com .down.com uucp-dom:down .me.com error: Host unknown at me.com ------ This says anything that is addressed to system1.org or to *.system1.org that we receive will be sent using the uucp-dom mailer and be delivered to system1 (defined in the the uucp sys file) in other words we are doing the mail routing for *.system1.org similarly for down.com and its subnodes except for the additional filtering; we bounce back any mail for down's subnode up.down.com using sendmail's built-in error mailer with the message "Host is unknown at me.com"; This is because we have been asked to do this by the admin at down.com. To bounce unknown subdomains to us we use the last line in the mailertable b) create the database with makemap if you use hash: makemap hash /etc/mailertable