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Text File | 1995-12-14 | 15.6 KB | 357 lines

# Copyright (c) 1994,1995 Jason L. Haar # Copyright (c) 1994,1995 Lazerjem Ltd. # All rights reserved. # # THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND # ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE # ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE # FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS # OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) # HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY # OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF # SUCH DAMAGE. # # @(#)00README.linux 1.0 (Lazerjem) 17/Jul/94 # 23/Feb/95 # 2/Apr/95 # 14/Dec/95 This is a binary release of sendmail-8.7.3 for Linux. I think this package should give you a _total_ MTA environment - from sendmail down to local delivery agents mail.local and (by popular demand!) procmail (v3.11pre3) [thanks to Stephen R. van den Berg for the package, and allowing me to include the binaries here]. This was compiled under Linux 1.2.13; gcc-2.5.8/libc-4.5.26. Sendmail can be compiled for use on a NIS network - but I didn't need that so it isn't here :-) Also, I used the New Berkeley DB database instead of the older 'dbm' format 'cause it's better. I've also included mail.local and my procmail binary distribution - a bigger package overall, but procmail is soooo good, I feel it should be shared by all :-) I have put together an install script 'install_sendmail' which isn't intended to be run blindly. Edit it to match your situation (BUT KEEP READING THIS FILE FIRST!). Below is an introductory article to sendmail I've written that may be of help to those just getting into the area. Don't forget - for any real detail - Read The Manual! I've included a copy of the Sendmail Operation Manual in this distribution (PostScript and Text form [the latter looks OK to me in an xterm and console - anything else I can't guarantee]). It's a bit of a jumble of information - some only appropriate for those wanting to compile the package themselves - and some which everyone should read/know. Something else I wrote (file Internet-Mail) may be of help to real beginners. It covers the DNS (you can't run mail on the Internet without knowledge of this) as well as Internet mail itself. Any comments to me at: Jason Haar <j.haar@lazerjem.demon.co.uk> Sendmail V8 ----------- Sendmail-V8 (latest release 8.7.3) is written by Eric Allman, and is considered the official release of sendmail. Most vendors base their own sendmail on this release, but they usually screw up somewhere ;-). If you are managing a network of Unix boxes of differing vendors, I'd STRONGLY suggest that you throw out all the vendor-specific sendmail and install sendmail-V8 instead. Configuration format for sendmail is specific to each vendor, thus you will save yourself a lot of work by learning one sendmail really well instead of several poorly. Usenet News is the best place to get help from about sendmail. The newsgroups comp.mail.sendmail (and friends) are read by the authors of the major Email packages, and provide good advice, as well as announcements of bug fixes and security holes. ** NOTE ** Unless you have a problem compiling sendmail, NONE of the Linux newsgroups/mailing-lists are appropriate for such questions - let's try to lower the amount of traffic on those groups by ensuring our enquiries go to the right places. There's nothing special about Linux now - it's just another Un*x :-) IDA vs Sendmail V8 ------------------- Which is best? Sendmail V8 :-) The current version of 8.7.3 contains support for more new features than IDA, such as MIME support and 8-bit traffic. These are standards-based, unlike similar features in the current version of IDA. Also, the mere fact that it is newer means that there are more bug fixes, including several security bugs that still affect most other versions. If you are interested in compiling your own version from scratch, the official anonymous ftp site for sendmail-8.7.3 is: <URL:ftp://ftp.cs.berkeley.edu:/ucb/src/sendmail/sendmail.8.7.3.tar.gz> The latest release (as at 2nd Oct 1995) is 8.7.3. This package amounts to over 900Kbytes (tar.gz), and includes full documentation on sendmail. By that I mean FULL. O'Reilly & Associates have recently published a Nutshell Handbook on sendmail (covers both V8 and IDA - really good), but the docs in this distribution would be more than enough for anyone to really get into the nitty-gritty of sendmail. Anyway, if you decide on sendmail-V8, get the latest version. 8.7.3 compiles and runs fine under Linux - you could just type "makesendmail". BTW, I also grabbed the db-1.85 package so that I could use the reverse-alias features of sendmail (my binaries use db instead of dbm for this too). [NOTE to sendmail-8.6 users: FLOCK is still broken under Linux - but under 8.7 that is known - you don't need to set HASFLOCK to 0 anymore - it already is :-) ] Don't forget to ALWAYS copy out of the way any existing files you have, just in case you want to go back to an older release. The 'install_sendmail' script contains information on file-protections that I use - they're about as scrict as you can put them. The "getloadav" feature of sendmail normally needs sendmail to be setgid to kmem, but Linux's /proc file system removes the need for that :-) Sendmail can be used in one of two ways. 1) Started from /etc/rc.* (default). This means sendmail is running continually. Invoked as: /usr/lib/sendmail -bd -q1h The "-bd" option tells sendmail it is running as a permanent daemon, and the "-q1h" tells it that Email messages that weren't deliverable the first time are to be re-tried at 1 hour intervals. If you are on a SLIP/PPP link, even 1 hour may be too often - you could take it out altogether and manaully run the queue during the first moments of bringing up your PPP/SLIP link (via 'sendmail -q'). 2) Started from /etc/inetd.conf. This means sendmail is only running when there is an incoming SMTP connection, but this actually is heavier on the system due to the overheads at initial startup. The advantage of this method is that you can use tcp_wrapper on it, so that you can configure just who can make SMTP connections to you. Invoked as: /usr/lib/sendmail -bs The "-bs" means run as a SMTP connection, that exits after it finishes. You can't use the "-q" option here, so this must be done manually by creating a cron job to run at regular intervals (doesn't need to be as root unless you're using the "restrictqrun" option). Sendmail reads the file /etc/sendmail.cf at startup, and logs everything via syslog. If you have problems with sendmail, see what /var/log/syslog tells you (assuming that's where your syslog messages for mail goes to). Sendmail is very difficult to configure. The secret to success with sendmail is to configure it as little as possible. You should take some time (days to weeks) to decide just what you want sendmail to do for you. A lot of sites end up with extremely ugly- looking sendmail configurations because they didn't plan in advance, and then are forced to "patch it up" as time goes by. Both sendmail-8.7.3 and sendmail-IDA use the m4 preprocessor to manipulate their config files. My own config file for sendmail is 14 lines long, yet m4 produces a 600+ line file out of that which sendmail actually uses. This preprocessor design greatly simplifies the creation and management of sendmail config files. Not only are they more human-readable, but global configuration bugs and re-writes can be corrected very quickly and seamlessly with patches. Sendmail-8.7.3 comes with several example configurations that you can look over for help (in cf/cf). My own config is called lazerjem.mc. You simply run m4 on these ".mc" files to create ".cf" files that sendmail would actually use. E.g m4 lazerjem.mc > sendmail.cf *** PLEASE!!!! Don't use any of these without editing!!! *** Some Configuration Options -------------------------- I won't go into too much detail here as they are all covered in the documentation and README file in the "cf" directory. However, I will comment on a few that I think are important/interesting. *** FEATURE(always_add_domain) I _always_ configure mailers to _always_ write the fully qualified domain name after every address - even local ones (e.g. "jason@lazerjem.demon.co.uk" instead of "jason@lazerjem" or even "jason"). My reason for this is to ensure that the people using Email always know what their "true" Email address is - not just a limited part of it. There have been so many times I've talked to people who didn't know what their own Email address was, because their site hadn't configured their MTAs to fully expand all addresses. *** define(`confUSERDB_SPEC', `/etc/userdb.db')dnl This allows you to perform "reverse aliasing" on outgoing messages. The "/etc/aliases" file allows you to define strings which map to usercodes; well the reverse-alias file allows you to map usercodes onto strings! That way you can have all your Email going out as "j.haar@lazerjem.demon.co.uk" instead of "jason@lazerjem.demon.co.uk" (where "jason" is the usercode). This requires the New Berkeley DB format - none of the others will do. I'd suggest compiling sendmail with this database format as it supposedly operates faster/more efficiently than any of the others anyway - as well as allowing you to share the database files over different architectures - something no other database format can do. You can get this database package from: <URL:ftp://ftp.cs.berkeley.edu:/ucb/4bsd/db.1.85.tar.Z> *** FEATURE(local_procmail) This tells sendmail to configure itself to use procmail as it's local mailer instead of <whatever>. However, I like using the "-t" option to procmail which says that if procmail fails to deal with a message (say, due to diskspace problems, or a bad .procmailrc file), then it will tell sendmail to REQUEUE to message instead of BOUNCING it. So in lazerjem.mc you will see I override the default values of PROCMAIL_MAILER_ARGS and LOCAL_MAILER_ARGS - adding "-t". *** define(`LUSER_RELAY', procmail:/etc/procmailrcs/lusers)dnl This is a feature much asked after for dialup sites. LUSER is the action to do when a message comes in for a local address that doesn't exist. Normally such messages are bounced "No such user" - this option allows such messages to instead be accepted and delivered to the routine mentioned. In the cf/cf directory, you will find my /etc/procmailrcs/lusers file - very sophisticated ;-) *** define(`SMART_HOST', smtp:host.domain) This is to be used if you are allowed to redirect all your non-local mailer to a smarter mail hub. Good for PPP/SLIP sites. Check with your Network Provider to see if they'd mind you doing that - it saves you having to hang around waiting for connections to succeed/fail. NOTE: That reminds me. Don't forget that EVERY SMTP site/machine *must always* accept Email for "postmaster@machine_name". This alias usually points to the person who is responsible for Email on that system - probably you! So *make sure* there is an entry for postmaster in your /etc/aliases file; mine looks like this: #/etc/aliases #----- BEGIN FILE ------- postmaster: jason mailer-daemon: postmaster root: postmaster j.haar: jason jason.haar: jason Don't forget that aliases aren't case-sensitive - "PostMASter" is the same as "postmaster". For reverse-aliases, your file appears as follows: #/etc/userdb #--- BEGIN FILE --- jason:mailname J.Haar@lazerjem.demon.co.uk #--- END FILE --- Then you run makemap on it to produce the DB file sendmail actually uses. makemap btree /etc/userdb.db < /etc/userdb I actually wrote a wee script to replace 'newaliases' so that both aliases and reverse-aliases files were updated simultaneously when it's run. What options do I need? ----------------------- This is why sendmail is so difficult to configure. A site may need a gateway into UUCP, fax software, X400, as well as SMTP. All these require their own special calls/rewrites, and it all adds up into one big mess. The m4 preprocessor goes some way towards simplifying all this by allowing mail managers to produce macros which "plug into" their existing sendmail configurations. Two such examples are the Usenet and Fax gateways (the hooks, not the software ;-) that are included in the base sendmail distribution - I personally use the fax gateway with FlexFAX (a freely available fax package). If you decide to use them, you just have to add one or two lines to your sendmail ".mc" file, and re-create your config. I personally like the new sendmail as it is possible to remove all UUCP-related code with one line ("FEATURE(nouucp)") - I have no need for any of that. I will just cover what I feel are the three most likely configurations for sendmail hosts. Anything more complicated than this will require more options than I can possibly cover - so Read The Fine Manual! :-) 1) These days a lot of networked machines having some form of direct Internet access, so it is relatively easy to come up with sendmail configurations for these. Most will probably just want local mail to be handled by the local mailer, and all the rest to be dealt with by the DNS/SMTP pair. The file tcpproto.mc does this job for you. Actually, my file lazerjem.mc will also do the trick - the only change being that you don't need the SMART_HOST option (that's basically the only difference between a SLIP/PPP site and a fully-connected site). 2) You may have a nice cluster of Linux workstations which NFS mount their /var/spool/mail partition from a central hub. As you don't want these workstations to handle incoming mail themselves, you can put a minimal config file on them that simply directs all mail that they send to the hub to deal with. Don't forget that these machines won't need a sendmail daemon running on them (only needed for incoming - not outgoing), so save a little memory and remove it from the appropriate /etc/rc* file (although you may need a queuing run [sendmail -q] to run on occasion from cron for the case when the hub is down). For this setup, just use clientproto.mc NOTE: Running mail over NFS is potentially pretty rotten - you have to be VERY careful about file locking. Ensure you're running lockd or statd on the server, and YOU REALLY SHOULD use procmail as you're local delivery agent - it is very good at handling file locking - even over NFS. 3) Dial-up Internet connections. That means SLIP or PPP. I just use the 'nodns' option. Under 8.7.3, that actually stops sendmail bothering to ask the DNS for anything. So if you send a mail message to yourself, or to anything mentioned in your /etc/hosts file, then sendmail will do it without bothering to ask the DNS (in the past it would always do a DNS lookup - even for local deliveries.). I use dial-on-demand PPP, and with sendmail-8.7.3 everything is perfect. If mail is sent locally - it just gets delivered, but if a message is sent to an unknown host, then sendmail tries to connect to the SMART_HOST - which starts the dial-on-demand PPP link. I also have ppp configured to force a sendmail queue run (sendmail -q) whenever the link goes up (via /etc/ppp/ip-up). Packages mentioned: ------------------ sendmail ftp://ftp.cs.berkeley.edu/ucb/src/sendmail/sendmail.8.7.3.tar.gz procmail ftp://ftp.informatik.rwth-aachen.de/pub/packages/procmail/procmail.tar.gz db ftp://ftp.cs.berkeley.edu/ucb/4bsd/db.tar.gz As usual - _please_ use archie to find a closer site to you than these.