Linux From Scratch HOWTO: Setting up Email sub system

13. Setting up Email sub system

13.1 Preparing system for Email sub system

Creating extra groups and user

We need to add a few groups and a user which will be used by the email utilities.

Create the bin group by running groupadd -g 1 bin
Create the kmem group by running groupadd -g 2 kmem
Create the mail group by running groupadd -g 3 mail
Create the bin user by running useradd -u 1 -g bin -d /bin -s /bin/sh bin

Creating directories

There are two directories used by the email sub system, thus we need to create them and give them the proper permissions.

Create the /var/spool directory
Create the /var/spool/mqueue directory
Create the /var/spool/mail directory
Set permissions on /tmp by running chmod 777 /tmp
Set permissions on /var/spool/mqueue by running chmod 700 /var/spool/mqueue
Set permissions on /var/spool/mail by running chmod 775 /var/spool/mail
Put /var/spool/mail in the mail group by running chgrp mail /var/spool/mail

13.2 Installing Procmail

Unpack the Procmail archive
Compile the package by running make
Install the package by running make install
Set the proper permissions on the Procmail utilities by running make install-suid

13.3 Installing Sendmail

Installing Sendmail

Unpack the Sendmail archive
Go to the src directory
Compile the package by running Build
Install the package by running Build install

Configuring Sendmail

Configuring Sendmail isn't as easily said as done. There are a lot of things you need to consider while configuring Sendmail and I can't take everything into account. That's why at this time we'll create a very basic and standard setup. If you want to tweak Sendmail to your own liking, go right ahead, but this is not the right article. You could always use your existing /etc/sendmail.cf (or /etc/mail/sendmail.cf) file if you need to use certain features.

Go to the cf directory
Create a new file cf/lfs.mc containing the following:

OSTYPE(LFS)
FEATURE(nouucp)
define(`LOCAL_MAILER_PATH', /usr/bin/procmail)
MAILER(local)
MAILER(smtp)

Create an empty file ostype/lfs.m4 by running touch ostype/lfs.m4
Compile the lfs.mc file by running m4 m4/cf.m4 cf/lfs.cf > cf/lfs.cf
Copy the cf/lfs.cf to /etc/sendmail.cf
Create an empty /etc/aliases file by running touch /etc/aliases
Initialize this (empty) alias database by running sendmail -v -bi

13.4 Installing Mailx

Unpack the Mailx archive
Compile the package by running gcc *.c -o mail

Ignore possible 'comparison between pointer and integer' and 'assignments makes integer from pointer without a cast' warnings. You'll probably get quite a few of these. Though, the program seems to work just fine nevertheless.

Copy the following binary to /usr/bin: mail
Place the /usr/bin/mail program in the mail group by running chgrp mail /usr/bin/mail
Let the /usr/bin/mail program be executed sgid by running chmod 2755 /usr/bin/mail

13.5 Creating /etc/init.d/sendmail bootscript

Create a new file /etc/init.d/sendmail containing the following:

#!/bin/sh
# Begin /etc/init.d/sendmail
 
check_status()
{
  if [ $? = 0 ]
  then
    echo "OK"
  else
    echo "FAILED"
  fi
}
 
case "$1" in
  start)
    echo -n "Starting Sendmail..."
    start-stop-daemon -S -q -p /var/run/sendmail.pid \
        -x /usr/sbin/sendmail -- -bd
    check_status
    ;;
 
  stop)
    echo -n "Stopping Sendmail..."
    start-stop-daemon -K -q -p /var/run/sendmail.pid
    check_status
    ;;
 
  reload)
    echo -n "Reloading Sendmail configuration file..."
    start-stop-daemon -K -q -s 1 -p /var/run/sendmail.pid
    check_status
    ;;
 
  restart)
    echo -n "Stopping Sendmail..."
    start-stop-daemon -K -q -p /var/run/sendmail.pid
    check_status
 
    sleep 1
 
    echo -n "Starting Sendmail..."
    start-stop-daemon -S -q -p /var/run/sendmail.pid \
        -x /usr/sbin/sendmail -- -bd
    check_status
    ;;
 
  *)
    echo "Usage: $0 {start|stop|reload|restart}"
    exit 1
    ;;
 
esac
 
# End /etc/init.d/sendmail

13.6 Setting up permissions and symlinks

Set the proper permissions by running chmod 755 /etc/init.d/sendmail
Create the proper symlinks by running:

cd /etc/init.d/rc2.d; ln -s ../init.d/sendmail S20sendmail
cd ../rc0.d; ln -s ../init.d/sendmail K20sendmail
cd ../rc6.d; ln -s ../init.d/sendmail K20sendmail

13.7 Installing Mutt

My favorite email client is Mutt, so that's why we're installing this one. Feel free to skip the installation of Mutt and install your own favorite client. After all, this is going to be your system. Not mine.

If your favorite client is an X Window client (such as Netscape Mail) then you'll have to sit tight a little while till we've installed X.

Unpack the Mutt archive
Configure the package by running configure
Compile the package by running make
Install the package by running make install

13.8 Installing Fetchmail

Unpack the Fetchmail archive
Configure the package by running configure
Compile the package by running make
Install the package by running make install

13.9 Testing the Email sub system

It's time to test the email system now.

Start Sendmail by running /usr/sbin/sendmail -bd (you need to start sendmail using the full path. If you don't, you can't let sendmail reload the sendmail.cf by with kill -1 <sendmail pid>).
Send yourself an email by running echo "this is an email test" | mail -s test root
Start the mail program and you should see your email there.
Create a new user by running useradd -m testuser
Send an email to testuser by running echo "test mail to testuser" | mail -s test testuser
Login as testuser, try to obtain that email (using the mail program) and send an email to root in the same way as you send an email to testuser.

If this all worked just fine, you have a working email system for local email. It's not necessarily ready for Internet yet. You can remove the testuser by running userdel -r testuser

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