Linux mailserver-installation

Contents I

Table of Contents
Part I Document Overview 3

Part II Document Details 4

Part III General 5
1 Goals ................................................................................................................................... 5
2 Overview ................................................................................................................................... 5
3 Redhat Installation
................................................................................................................................... 6
4 The vi editor ................................................................................................................................... 8

Part IV Verifying Network Settings 10
1 Verify the hostname
................................................................................................................................... 10
2 Verify your ip address
................................................................................................................................... 10

Part V Configuring DNS 11
1 Verifying that DNS is installed
................................................................................................................................... 11
2 Configuring ................................................................................................................................... 12
DNS / BIND
3 Verifying DNS configuration
................................................................................................................................... 17
4 Configuring ................................................................................................................................... 18
named to start automatically after every reboot

Part VI Sendmail 20
1 Configuring ................................................................................................................................... 20
sendmail
2 Testing the sendmail configuration
................................................................................................................................... 21

Part VII POP3 and IMAP 22
1 Installing the Washington IMAP and POP3 services
................................................................................................................................... 22
2 Configuring ................................................................................................................................... 23
IMAP and POP3
3 Testing the POP3 and IMAP configuration
................................................................................................................................... 24
4 Enabling quotas to limit the mailbox size
................................................................................................................................... 25

Part VIII LDAP from OpenLDAP 28
1 Installing LDAP
................................................................................................................................... 28
2 Configuring ................................................................................................................................... 29
LDAP
3 Testing the LDAP configuration
................................................................................................................................... 32

Part IX Administration with Perl 34
1 Installing the necessary Modules
................................................................................................................................... 34
2 Installing the perl script
................................................................................................................................... 34

© <2003> ... NETIKUS.NET ltd

I

II Setting up an Email Server with RedHat Linux

Part X Setting up a simple webpage 35
1 Creating a group
................................................................................................................................... 35
2 Modifying file permissions
................................................................................................................................... 35
3 Creating a symbolic link
................................................................................................................................... 35

Index 0


Document Overview 3

1 Document Overview

Author: NETIKU
Date: S.NET
Revision: ltd
14th of
Novemb
er 2000
1.1

Setting up an Email Server with RedHat Linux

Title Setting up an Email Server with RedHat Linux
Summary Step-By-Step instructions on how to install an email server (including DNS,
LDAP, POP) using RedHat Linux 7. There should not be many differences
to RedHat 8 or RedHat 9.
Software RedHat 7
Washington IMAP
OpenLDAP
Perl Modules: Term::ReadKey, Passwd::Linux, Convert::ASN1, Net::LDAP
Hardware Not Applicable
Skill Level Beginner
Skills Required - Basic understanding of Networking (TCP/IP)
- Basic understanding of Linux
Download http://www.netikus.net/ (guides section)


4 Setting up an Email Server with RedHat Linux

2 Document Details

Overview This document describes in great detail how to install an email
server using RedHat Linux 7. We will explain how the VI text editor
and works and then setup DNS, Sendmail, POP3, IMAP and LDAP.

Even though this document is already a couple of years old most
parts should apply to RedHat 8 and RedHat 9.
Additional Notes The DNS service will be install so that email clients can resolve DNS
domains through this server.

The applications used here (sendmail, Washington IMAP) might not
be the most suitable for every environment but are generally a good
start.
Why? Because everybody needs an email server.


General 5

3 General
3.1 Goals
The goal is to set up a Linux server supporting the following internet services:

FTP only needed to transfer software updates optional
TELNET only needed for administrative access optional
SMTP needed for sending emails mandatory
DNS needed for SMTP name resolution mandatory
HTTP only needed for documentation optional
POP3 needed for picking up email (either pop3 or imap) mandatory
IMAP4 needed for picking up email (either imap or pop3) mandatory
LDAP needed for email resolution optional

Clients will be able to send and receive emails with this server. With ldap names can be automatically
resolved to email addresses, if the email client supports this feature. Imap enabled clients can use all
the functionality that imap supports, such as leaving their mails on the server and having multiple
folders.

3.2 Overview
We will create an imaginary company with the name OrganicBrownSugar that has a class C network
with the IP address 192.10.1.0.

Please note that this sample configuration is suitable only for a network not connected to the
internet. If you want to connect this server to the internet additional steps have to be taken that are
not covered in this document. This procedure however is a good basis for any further steps you
might want to take later.

The base for this Linux Server will be RedHat 7.0, the current version of the Redhat Distribution as of
this writing. I choose Redhat for several reasons:

1. Probably the most popular Linux distribution
2. a lot of literature is available for Redhat
3. an website with extensive resources is available at www.redhat.com
4. commercial support is available from Redhat
5. one of the most used distributions focused on server installations
6. The Redhat Package Manager for easy installations

Redhat 7 comes with 2 CDs, both of which are needed for the installation. This document does not
cover details about Linux or the installation process itself, it just guides you through the installation,
setup and configuration process of the various components. If you are new to Linux we recommend
reading a quick introduction at http://www.netikus.net/documents/winnt-to-linux.pdf. If you are
experiencing problems during installation and configuration of your Linux system, please refer to one
of the resources available at one of the following websites:

http://www.redhat.com/
http://www.linuxdoc.org/
http://www.expertse-xchange.com/



http://www.netikus.net/

I tried to make this guide as "safe" as possible. About 95% of the commands that have to be typed are
listed in an extra line. However, sometimes – especially towards the end –explanations are given to
perform a specific standard task.

This document is accompanied by the zipfile Linux-Mailserver-Installation.zip that is available in
the downloads section of www.netikus.net. It includes the tar.gz files and some configuration files
as well. You might want to check the distributors homepages for the most current version of their
applications. The included versions, however, where tested and used while writing this document.

3.3 Redhat Installation
After starting the installation, please choose the following installation options:

Language: English

Keyboard: your choice

Mouse configuration: your choice

Install type: Server System

Partition type: Automatically or manually partition with Disk Druid

/ (2Gb)
/boot (50Mb)
/home (Rest)

Network Configuration: IP Address: 192.10.1.10
Netmask: 255.255.255.0
Network: 192.10.1.0
Broadcast: 192.10.1.1.255
Hostname: email.organicbrownsugar.com
Gateway: your choice
Primary DNS: 192.10.1.10

Time Zone Selection: your choice

Account Configuration: Root Password: your choice
Account Name: testuser
Password: usertest
Full Name: Temporary test user

Package Group Selection: Web Server
DNS Name Server
Select individual packages
Individual Package Selection: (INCLUDE THE PACKAGES LISTED IF THEY ARE NOT SELECTED):


General 7

Applications
Archiving
zip
Development
Languages
cpp* (all those which start with cpp)
gcc* (all those which start with gcc)
kgcc
libgcj-devel
tk
System
kernel-headers
rpmdb-redhat
Tools
autoconf
automake
libtool
make
pmake
rpm-build
Documentation
man-pages
System Environment
Daemons
apache
bind
sendmail-cf
wu-ftpd
xinetd
telnet-server
Kernel
kernel-boot
Libraries
libgcj
Shells
mc
Individual Package Selection REMOVE (THOSE PACKAGES DON'T HURT, BUT ARE NOT NEEDED
HERE)



Applications
Internet
Elm
Mutt
Ncftp
Talk
Tin
Trn
System
isdn4k-utils
ucd-snmp-utils
System Environment
Daeomons
finger-server
imap
inews
rp-pppoe
rsh-server
rusers
rusers-server
talk-server
tftp-server
ucd-snmp

Hit next

Checking Dependencies: Install packages to satisfy dependencies
(Do this as often as necessary)

About to install: HIT NEXT

Bootdisk Creation: this is up to you, recommended though

3.4 The vi editor
Throughout this course we will use the text-based VI editor to manipulate our configuration files. If you
are not familiar with this editor, I will give you brief introduction so you will be able to use it without
getting a heart attack.

VI has to major modes: COMMAND MODE and INSERT MODE. Since VI doesn't have a menu and
fancy things like that, you can either type and modify text (INSERT MODE) or send commands such
as SAVE, QUIT … (COMMAND MODE). As soon as you start VI, you are in COMMAND MODE. To
change into INSERT MODE simply press I and you will see – INSERT – at the bottom. You can now
type your text, change text, use the PgUp and PgDown keys and so on. Once you are done editing,
you want to save your text file and quit again. To this, you first have to go back into COMMAND
MODE hitting the

ESC

key. You are now in COMMAND MODE. Now type

ZZ

To save the document and go back into the command line. This is all you will need to now about VI for
this guide. However, I included to most used commands to make editing a little more fun for you. But


General 9

always remember, don't forget which mode you are in – you will not be able to edit text while in
COMMAND MODE! Press i for INSERT MODE and ESC for COMMAND MODE.

Important commands:
ZZ<enter> Save and Quit
:w<enter> Save only
:qi<enter> Quit without saving (hooo)

dd Delete current line
yy Copy the current line into the default buffer
xyy Copy x lines into the default buffer
P Insert the content of the default buffer
u undo last command
:set number display line numbers on the left
:set nonumber don't display line numbers on the left

/pattern Search for pattern

Some of you might still remember, or use, the norton commander. Redhat 7 includes a nifty tool
called Midnight Commander which can be launched by typing mc wherever you are. It looks
almost 100% like the good old DOS Norton Commander – but works on Linux as well! I found it to
work quite reliable and I personally like the editor a lot.



4 Verifying Network Settings
After rebooting, log in as root and the password you assigned during the installation

4.1 Verify the hostname
more /etc/sysconfig/network

If the hostname does not like the one we want, go into vi and edit the file with

vi /etc/sysconfig/network

and change the hostname. If you don't know how vi works you didn't read the **short** introduction
above! Go right back and read it (again).

4.2 Verify your ip address
more /etc/sysconfig/network-scripts/ifcfg-eth0


Configuring DNS 11

5 Configuring DNS
5.1 Verifying that DNS is installed
If DNS was installed successfully, the following startup script should exist

more /etc/rc.d/init.d/named



5.2 Configuring DNS / BIND
The main configuration file of DNS is /etc/named.conf and should look, by default, something like
this:

// generated by named-bootconf.pl

options {
directory "/var/named";
/*
* If there is a firewall between you and nameservers you want
* to talk to, you might need to uncomment the query-source
* directive below. Previous versions of BIND always asked
* questions using port 53, but BIND 8.1 uses an unprivileged
* port by default.
*/
// query-source address * port 53;
};

//
// a caching only nameserver config
//
zone "." IN {
type hint;
file "named.ca";
};

zone "0.0.127.in-addr.arpa" IN {
type master;
file "named.local";
allow-update { none; };
};

We will now change it to support our domain organicbrownsugar.com which is NOT connected to
the internet by typing:

vi /etc/named.conf

And the file should look like this when we are done:

// generated by named-bootconf.pl

options {
directory "/var/named";
/*
* If there is a firewall between you and nameservers you want
* to talk to, you might need to uncomment the query-source
* directive below. Previous versions of BIND always asked
* questions using port 53, but BIND 8.1 uses an unprivileged
* port by default.
*/
// query-source address * port 53;
};

zone "." IN {
type master;
file "db.root";
};

zone "localhost" IN {
type master;
file "localhost.zone";
};


Configuring DNS 13

type master;
file "named.local";
};

zone "organicbrownsugar.com" IN {
type master;
file "organicbrownsugar.com.zone";
};

type master;
file "organicbrownsugar.com.zone.rev";
};

zone "us.organicbrownsugar.com" IN {
type master;
file "us.organicbrownsugar.com.zone";
};

This tells the DNS service which domains we are hosting here. The first paragraph adds our domain
while not allowing remote servers to send our server updates of any kind. The second paragraph
creates a so called Reverse Lookup Zone to later map IP addresses to hostnames.

After creating the config file, we now have to set up the two zone files we are pointing to. For this we
type

vi /var/named/organicbrownsugar.zone

and add the following lines (remember, you can save some typing by downloading this from
www.netikus.net):

$TTL 86400
@ IN SOA organicbrownsugar.com. hostmaster.organicbrownsugar.com.
2000103001 (
;serial number
;increase this number whenever
you make
;changes to this file. It's
necessary for
;secondary servers to know if
they have to update
;their zone data
10800 ;refresh every 10800 seconds
;tells a secondary server how
often to
;contact a (the) master server
1800 ;retry every 30 minutes
;if a connect fails to a primary
name server,
connect again in 1800 seconds
1209600 ;expire records received from
master server if I
;was not able to contact him for
1209600 seconds
604800 ) ;TTL tells other servers (cache)
to keep the
;records of this zone (file) for
604800 seconds,
;then "refresh"



;we need at least one of those entries to make this file valid
IN NS email.organicbrownsugar.com.

;where to find the email server for our domain
IN MX 10 email.organicbrownsugar.com
.

;the records
email IN A 192.10.1.10

;aliases for the email server
ftp IN CNAME email;
telnet IN CNAME email;
smtp IN CNAME email;
mail IN CNAME email;
mailhost IN CNAME email;
ns IN CNAME email;
ns1 IN CNAME email;
http IN CNAME email;
pop IN CNAME email;
pop3 IN CNAME email;
mailbox IN CNAME email;
imap IN CNAME email;
ldap IN CNAME email;
www IN CNAME email;

;our other computer where we are testing
netikus IN A 192.10.1.244

Now copy this file (organicbrownsugar.com.zone) to us.organicbrownsugar.com.zone with

cd /var/named
cp organicbrownsugar.com.zone us.organicbrownsugar.com.zone

and change the first line so it looks like this:
@ IN SOA us.organicbrownsugar.com. hostmaster.us.organicbrownsuga
r.com. (

What is this good for? Now we prepared ourselves if we want multiple mailservers someday. Now we
set up the reverse lookup file by typing

vi /var/named/organicbrownsugar.com.zone.rev

Add the following lines again:

$TTL 86400


Configuring DNS 15

@ IN SOA 1.10.192.in-addr.arpa. hostmaster.organicbrownsugar.com
. (
2000103001 ;serial number
;increase this number whenever
you make
;changes to this file
10800 ;refresh every 3 hours
;tells a secondary server how
often to
;contact this server
1800 ;retry every 30 minutes
;if a connect fails to another
name ;server,
connect again in 30 minutes
1209600 ;secondary name server discard
;cached records if you have not
been able ;to
contact your primary within this
time
604800 ) caching server discard records
if you ;did not
reach your primary

;we need at least one of those entries to make this file valid

;here we list the ip addresses in use
10 IN PTR email.organicbrownsugar.com.

;our client computer
244 IN PTR netikus.organicbrownsugar.com
.

Now comes the tricky part. We have to set up a root file because we are not connected to the internet.
It's not important for functianlity but makes the setup complete and avoids error messages in the
named logs. In named.conf we pointed to a file called db.root which we will create now with

vi /var/named/db.root

and this file should look this when we are done:

$TTL 86400
. IN SOA email.organicbrownsugar.com. root.email.organicbrownsu
gar.com. (
2000110801 ; Serial
28800 ; Refresh
14400 ; Retry
3600000 ; Expire
86400 ) ; Minimum

email.organicbrownsugar.com IN A 192.10.1.10
.

organicbrownsugar.com. IN NS email.organicbrownsugar.com.

us.organicbrownsugar.com. IN NS email.organicbrownsugar.com.



Watch out for the "." In the second line. The other files have a @ here, but since this is the root file
(and obviously different) there has to be . .

Please note a couple of things when typing the values above:

· I used <TAB> to separate values in lines
· Whenever you specify a FQDN, make sure that it ends with a . <DOT>, otherwise you make
yourself trouble

After entering all the information correctly, we start the DNS daemon and verify the configuration


Configuring DNS 17

5.3 Verifying DNS configuration
First we start the DNS daemon by typing

/etc/rc.d/init.d/named start

Then we type

nslookup

and we should see something like this

Default Server: email.organicbrownsugar.com
Address: 0.0.0.0

>

Now we see if our machine's hostname can be resolved to an ip address by typing

email.organicbrownsugar.com

… and we should get an output looking something like this

Server: email.organicbrownsugar.com
Address: 0.0.0.0

Name: email.organicbrownsugar.com
Address: 192.10.1.10

If this is what you see we can be almost sure our DNS server is working well. Now test some of the
other names we created before such as

imap.organicbrownsugar.com

and we see

Address: 0.0.0.0

Name: email.organicbrownsugar.com
Address: 192.10.1.10
Aliases: imap.organicbrownsugar.com

Great! You can now call yourself a BASIC-DNS-LINUX-INSTALLER. But now let's see if our reverse
lookup zones work as well by typing:

192.10.1.244

Now if you're your really lucky and didn't make any typo's you should most likely see
Address: 0.0.0.0

Name: netikus.organicbrownsugar.com
Address: 192.10.1.244

Before we make an end to our endless DNS verifications, we make sure that email servers will have
use of our DNS server by finding a mail exchanger (MX) for our domain @organicbrownsugar.com
by typing:

set query=mx



organicbrownsugar.com

This should yield

Address: 0.0.0.0

organicbrownsugar.com preference = 10, mail exchanger = email.organicbrownsugar.com
organicbrownsugar.com nameserver = email.organicbrownsugar.com
email. organicbrownsugar.com internet address = 192.10.1.10

Okay now, if all this worked our DNS server is configured correctly for stand alone operation and we
can type exit to leave nslookup. Please note that we do not have a secondary server at this time
which inevitably results in absolutely now redundancy. But since we only have one server for all our
services anyways it doesn't really matter for our scenario. You can say a little prayer to the hardware
god before you go to bed tonight.

Now the only thing that's missing to make our name resolution life wonderful is to make our DNS
daemon start automatically after every boot.

5.4 Configuring named to start automatically after every reboot
The following might look a little complicated, read it twice if you feel that you don't understand what's
going on here. Services are started by startup-scripts in the directory /etc/rc.d/init.d/. This is how we
started named just a few minutes ago (depends how fast you are typing and reading …). Now we
have to tell linux to start named automatically. You can use tools from x-windows, but since I like Linux
because I don't need a graphic interface, we will do it by hand, without any special tool. If we run ls
/etc/rc.d, we will see the following directories (among others): rc0.d, rc1.d, rc2.d, rc3.d,
rc4.d, rc5.d, rc6.d

Each of those directories refers to a runlevel, for example rc3.d refers to runlevel three. Runlevels
could be described as a state of the system. Look at the following table:

0 Halt the system
1 Enter single-user mode (no networking is enabled)
2 Multiuser mode, but without NFS
3 Full multiuser mode (normal operation)
4 Unused
5 Same as runlevel 3, except using an X Windows login rather than a text-based login
6 Reboot the system

To tell our linux system when to start which service, we would have to place a startup script in the
corresponding directory. However, to make things not more complicated than they already are we will
use symbolic links rather than a separate script file everytime. But just adding named to the rc3.d
directory (standard runlevel our server should be in most of the time) is not enough. We have to tell
linux in which order to start or stop the services.

Let's take a look at result of ls /etc/rc.d/rc3.d/:


Configuring DNS 19

K20nfs K20rwalld K20rwhod K34yppasswdd
K45arpwatch K45named K84ypserv S05kudzu
S08ipchains S10network S12syslog S13portmap
S14nfslock S16apmd S20random S25netfs
S35identd S40atd S45pcmcia S50xinetd
S55sshd S56rawdevices S60lpd S75keytable
S80sendmail S85gpm S85httpd S90crond
S90xfs S95anacron S97rhnsd S99linuxconf
S99local

The first letter, S, indicates that the script should be started. The 2nd and 3rd number tell the order
where 01 would be the first service to start. The rest is the name of the script in the ../init.d/ directory. If
we would configure a service to stop (such as in runlevels 0 and 6) we would use a K instead of a S at
the beginning.

In our case I would tell named to start before xinetd, using the number 47. I will have named start in
runlevels 3 and 5. So we type

ln –s /etc/rc.d/init.d/named /etc/rc.d/rc3.d/S53named
ln –s /etc/rc.d/init.d/named /etc/rc.d/rc5.d/S53named

To start named in runlevel 3 and 5 automatically. To stop named everytime we make a reboot or halt
or system, we add the following if it doesn't already exist (please check)

ln –s /etc/rc.d/init.d/named /etc/rc.d/rc0.d/K45named
ln –s /etc/rc.d/init.d/named /etc/rc.d/rc6.d/K45named

Now reboot by typing

shutdown –r now

If we find named started automatically after the login, we are already 25% on our way. You can see if
the process is active by typing ps –A | grep named

If we were going from San Diego to Miami, we would probably be somwhere in New Mexico.



6 Sendmail
6.1 Configuring sendmail
On our Redhat installation we will find sendmail's configuration file as /etc/sendmail.cf. If you
download and compile sendmail you would find it in /etc/mail/sendmail.cf. However, we stay with the
former. Redhat 7 comes with sendmail version 8.11.0-8.

To configure sendmail you have basically 2 options. Either you edit the sendmail.cf file directly or
you create the sendmail.cf from a m4 file such as sendmail.mc. Sendmail uses the macro language
m4 to create the configuration file from an easier to read .mc file. I highly recommend using the latter
approach in order to keep administration of this configuration overseeable. Our version of sendmail is
already configured well so we don't have to change anything.

However, to explain the process I will list the steps to procuce a custom sendmail.cf file. Don't do this
right now please, just save it for later reference! Redhat comes with a working configuration from the
file redhat.mc. We will use this file as our template and modify it to our needs. This file should reside
in /usr/lib/sendmail-cf/cf/. If you can't find it there you can search for it by typing

cd /
find –name *.cf

Now let's copy the template to a new file sendmail-config.mc by typing

cp /usr/lib/sendmail-cf/cf/redhat.mc /usr/lib/sendmail-cf/cf/sendmail-conf.mc

Now we edit the file by typing

vi /usr/lib/sendmail-cf/cf/sendmail-conf.mc

Now we add the following lines to our configuration file. Please note that some of these settings might
not be suitable for your configuration or use:
MASQUERADE_AS(organicbrownsuger.com)dnl # mails always appear to come from
# this domain
Define('confMAX_MESSAGE_SIZE','3145728')dnl # maximum message size of ~3Mb

Now we create the a file readable by sendmail with

cd /usr/lib/sendmail-cf/cf
sh Build sendmail-conf.cf

Isn't it easy? Now we create a backup copy of our current sendmail.cf file (just in case we messed
up) and copy our new file over the old one.
cp /etc/sendmail.cf /etc/sendmail.cf.original
cp /usr/lib/sendmail-cf/cf/sendmail-conf.cf /etc/sendmail.cf

Now we're almost there. For sendmail to know what the local email domain is, we have to configure
the file /etc/mail/local-host-names by typing

vi /etc/mail/local-host-names


Sendmail 21

and appending the lines

organicbrownsugar.com
us.organicbrownsugar.com

to it. Now we're done. To activate the changes we restart sendmail. We will use the init script, just like
explained when configuring DNS for automatic startup in 3.4.

/etc/rc.d/init.d/sendmail restart

If we didn't get an error message here it at least means that our configuration file is ok. Now let's see if
we can actually use sendmail as we would like to.

6.2 Testing the sendmail configuration
We telnet to port 25 (SMTP) of our machine and try to send our test user testuser (created during
installation) an email. Let's type

telnet localhost 25

and we should see something like

220 email.organicbrownsugar.com ESTMP Sendmail 8.11.0/8.11.0; Mon, 30 Oct 2000
16:56:36 –0500

Type in the following lines:

mail from: root@organicbrownsugar.com
rcpt to: testuser@organicbrownsugar.com
data
subject: I love the world and the world loves me!
Cool, I just installed and configured sendmail. Wow!!
.

and you should now see something like

250 2.0.0 e9UmxRw01218 Message accepted for delivery

Now enter

quit

Now log in as testuser on a different console (by pressing ALT+F2 for example) and type

mail

At the command prompt. You should see something like
Mail version 8.1 6/6/92. Type ? for help.
"/var/spool/mail/testuser": 1 message 1 new
>N 1 root@organicbrownsugar.com Mon Oct 30 16:59 13/571 "Hello from telnet"
& _

Now simply type 1 and enter to read the message. q exits from the mail application. Voila! We're half
way and almost out of Texas.

Now compared to almost 5 pages DNS configuration this was pretty straightforward. Time to install
POP3 and IMAP! Don't forget to logout again as the testuser and switch to your root console,
otherwise our imap experience is not going to last very long …



7 POP3 and IMAP
7.1 Installing the Washington IMAP and POP3 services
We download the latest version of the Washington IMAP from
ftp://ftp.cac.washington.edu/imap/imap-2000.tar.Z

to one of our computers that is connected to the internet. Then we create a directory on our linux box
with

mkdir /usr/software

and copy the file imap-2000.tar.Z into this directory. You can do this with ftp, floppies and so on. You
don't have to create the directory in the /usr folder – but I will reference to this folder in this chapter.
Now "cd" into this directory and decompress the archive by typing

cd /usr/software
tar –xvzf imap-2000.tar.Z

The source should now have been extracted properly and we are ready to install. The decompression
created a directory imap-2000 which we will use to install. Let's do that! Imap's root folder is the user's
home folder by default. Some people like that, I however prefer the imap root to be in a subfolder of
the home directory, imap in our scenario. We achive this by editing the file Makefile

vi /usr/software/imap-2000/Makefile

And changing the following line from

EXTRACFLAGS=

to

EXTRACFLAGS=-DMAILSUBDIR="imap"

You can quickly find the line in the file by typing

/EXTRACFLAGS=

while in command mode of vi.

If you edit the file Makefile and modify the root directory of imap, you have to make sure that the
subdirectory actually exists in every users homedirectory. Forgetting this will yield to unpredictable
results according to the documentation.

To automate the procedure of creating an imap directory everytime we can create a user, we will
modify the template directory /etc/skel/ by creating a directory there with:

mkdir /etc/skel/imap

Now, everytime you create a user make sure you will use the –m option with the useradd program.
However, for the user we created during installation the above procedure will not work so we create it
manually one time with

mkdir /home/testuser/imap

So to finally start the installation we type


POP3 and IMAP 23

cd imap-2000
make slx

This means that we are installing on an up to date Linux box. This should go well without problems
and will create the executables that we need (yes, there is nothing more to do except the make
command):

ls /usr/software/imap-2000/imapd/imapd
ls /usr/software/imap-2000/ipopd/ipop3d

Those files of course would be better located in a directory that is designed for little daemons, so we
copy them to the /etc/sbin directory with

cp /usr/software/imap-2000/imapd/imapd /usr/sbin
cp /usr/software/imap-2000/ipopd/ipop3d /usr/sbin

7.2 Configuring IMAP and POP3
What now? Are we done? Are we finally getting near Florida? Almost. Those two daemons will be
invoked by the service xinetd so we have to tell xinetd where to find them and how to start them. But
first we make sure the both services are registered in the /etc/services file by typing

cat /etc/services | grep pop3
cat /etc/services | grep imap

this should result in lines like this ones (unimportant ones omitted)
pop3 110/tcp pop-3 # POP version 3
imap2 143/tcp imap # Interim Mail Access Proto
v2

If you don't see those lines, please add them with vi /etc/services. Xinetd loads all daemons which
are properly configured in the directory /etc/xinetd.d/. Since neither pop3 nor imap are configured
there, we will have to create 2 files. Lets create ourselves a template by copying the configuration of
telnet and editing it

cp /etc/xinetd.d/telnet /etc/xinetd.d/pop3
vi /etc/xinetd.d/pop3

Then edit the file /etc/xinetd.d/pop3 so it will look like this:

# default: on
# description: The pop3 server serves pop3 connections; it uses
# unencrypted username/password pairs for authentication
#
service pop3
{



socket_type = stream
wait = no
user = root
server = /usr/sbin/ipop3d
log_on_failure += USERID
}
Then we do the same for imap

cp /etc/xinetd.d/pop3 /etc/xinetd.d/imap
vi /etc/xinetd.d/imap

And the file should look like this

# default: on
# description: The pop3 server serves pop3 connections; it uses
# unencrypted username/password pairs for authentication
#
service imap2
{
socket_type = stream
wait = no
user = root
server = /usr/sbin/imapd
log_on_failure += USERID
}

You should be careful and make sure that the name that's listed next to service is the one you found /
entered in the file /etc/services. Once the configuration files exist we can restart xinetd and see if we
can use those services. We simply type

/etc/rc.d/init.d/xinetd restart

and see what happens.

7.3 Testing the POP3 and IMAP configuration
To start testing pop3, we simply type

telnet localhost 110

and should see an output similar to this:

+OK POP3 email.organicbrownsugar.com v2000.69 server ready

and type

quit

to exit again. To see if we actually can read email with our pop3 connection, we will send another
email via SMTP. Please repeat the steps listed at 3.2 where we telnetted to port 25 and sent an email
to testuser@organicbrownsugar.com. After we did that, we connect again with with telnet localhost
110 and issue the following commands
user testuser
pass usertest
list


POP3 and IMAP 25

we should then see something like

+OK Mailbox scan listing follows
1 708
.

Now we can retrieve the mail by typing

retr 1

Which should display the message in it's raw format. You will probably appreciate an email client here
that does not use HTML… Ok, pop3 hopefully works and we quickly see if imap works as well. If you
cannot establish a connection to port 110 for some mean reason, make sure your entries in the xinetd
configuration file match the proper service name in the /etc/services file and that the executables
actually point to existing files! Now lets logout with quit and quickly type

telnet localhost 143

and we should see an output similar to this:

OK [CAPABILITY IMAP4 IMAP4REV1 LOGIN-REFERRALS AUTH=LOGIN]
email.organicbrownsugar.com IMAP4rev1 2000.293 at Mon, 30 Oct 2000 18:47:11 –0500
(CST)

and type

. logout

to leave imap at it's peace. To really test imap you will have to launch your imap cabable email client
and connect to the server, at this point I am not listing all the imap commands here which are more
complex than the ones used in pop3.

Good! DNS is working, we can send mail via sendmail / smtp and we can read our emails happily
with either pop3 or imap4. Wonderful. We're through Lousiana and will now enter Florida. 75%. But
wait!

7.4 Enabling quotas to limit the mailbox size
Our linux distribution comes with quota support, so we might want to enable it. If you trust your users
and/or have unlimited disk space, you can simply skip this step. Knowing how to turn on quotas won't
hurt I would say anyways. First we have to activate the quotas in 3 steps. First we enable quota on our
machine during the boot-up, then we enable a volume / mount point for quotas and finally we add the
quota database files. So we add the following lines to the end of the file /etc/rc.d/rc.local just before
the last fi command

vi /etc/rc.d/rc.local
# Check quota and then turn it on
if [ -x /sbin/quotacheck ]
then
echo "Checking quotas …"
/sbin/quotacheck –avug
echo "Done"
fi
if [ -x /sbin/quotaon ]
then
echo "Turning quota on …"
/sbin/quotaon –avug
fi



Now we will enable the /home mountpoint for quotas. This is done by adding some stuff to the
/etc/fstab file:

vi /etc/fstab

Now look for the line that starts with "LABEL=/home" and change the word defaults to
defaults,usrquota,grpquota so that it looks like this:

LABEL=/home /home ext2 defaults,usrquota,grpquota 1 2

Now we have to create the quota database files in the root of the directory with

cd /home
touch quota.user
touch quota.group
chmod 600 quota.*

That's all. We make a reboot and our system is at least ready to accept our quota commands! So let's
add those commands for our testuser by typing:

edquota –u testuser

And we will see something like this (hda5 will most likely be different for you):

Quotas for user testuser:
/dev/hda5: blocks in user: 28, limits (soft = 0, hard = 0)
inodes in use: 7, limits (soft = 0, hard = 0)

As you see the edquota command has launched the vi editor for you automatically. Whenever you're
done with the changes just save them as you would usually with ZZ. But what changes ? First the
explanation of a hard and soft limit. A soft limit let's a user exceed this limit for a limited amount of
time, called the grace period. You can notifiy the user that this is happening. The hard limit is a limit
that can not be exceeded at any costs – unless it is changed. If the user exceeds it, he can not write to
the directory anymore – unless he cleans up or the administrator changes the hard limit.

But what are blocks and i-nodes? 1 block in linux is 1kb. So if you want to limit the quota to 1 Mb you
will just use 1024 blocks. I-nodes are control structures that point to other i-nodes or to the file itself.
So one file has one or more I-nodes assigned to it. I prefer to change only the block use.
So to limit the testuser's mailbox size (and everything else as well) to a soft limit (warning) of
reasonable 10Mb, and an ultimate hard limit of 15Mb, we change the above output in vi to:

Quotas for user testuser:
/dev/hda5: blocks in user: 28, limits (soft = 10240, hard = 15360)
inodes in use: 7, limits (soft = 0, hard = 0)

Pretty neat, hmm? Never mind the filename vi displays while you edit, edquota manages all this for
you. So how do you know what user used to be a mailman in his previous life? The program
quotacheck lets you check the quota dat abase, and the program repquota shows you some current
statistics. Just type

edquota –a

And you see the current status for everybody. With perl you can run a daily job that sends emails to
users or to you. The grace period is set to 7 days, by the way. If you want to change it for all users,
type

edquota –g –t

To change it for all users, type


POP3 and IMAP 27

edquota –u –t

For users to view their quota information, they can use the program
quota

With the switch –g the user can view statistics. The –q switch prints a message to the user if
he is over quota.



8 LDAP from OpenLDAP
8.1 Installing LDAP
We download the latest version of OpenLDAP from

ftp://ftp.openldap.org/pub/OpenLDAP/openldap-stable/openldap-stable-20000704.tgz

and copy it just like before to our favorite software directory, /usr/software. Then we uncompress it by
typing
cd /usr/software
tar –xvzf openldap-stable-20000704.tgz

Please note that the file mentioned above was the most stable version available as of 30th October
2000. You might want to check for a newer version at http://www.openldap.org/. Now that we have
unpacked it we are ready to configure, so lets type

cd openldap-1.2.11
./configure
make depend
make

Now we will test our installation with
cd tests
make

which hopefully turns out well. To finish the installation we do
cd ..
make install

and LDAP should now be installed properly and we can start configuring it. Not exactly the easiest and
most obvious thing to do, but I'll guide you through everything.


LDAP from OpenLDAP 29

8.2 Configuring LDAP
LDAP comes with a couple of configuration files, which are

/etc/openldap/ldap.conf
/usr/local/etc/openldap/slapd.conf
/usr/local/etc/openldap/slapd.at.conf
/usr/local/etc/openldap/slapd.oc.conf

ldap.conf does not have to be changed for our installation, so we continue with slapd.conf. We edit the
file with vi by typing

vi /usr/local/etc/openldap/slapd.conf

and should have a slapd.conf file that will look like this

#
# See slapd.conf(5) for details on configuration options.
# This file should NOT be world readable.
#
include /usr/local/etc/openldap/slapd.at.conf
include /usr/local/etc/openldap/slapd.oc.conf
schemacheck off
#referral ldap://root.openldap.org/

pidfile /usr/local/var/slapd.pid
argsfile /usr/local/var/slapd.args

#######################################################################
# ldbm database definitions
#######################################################################

database ldbm
suffix ""
suffix "dc=organicbrownsugar, dc=com"
suffix "o=Organic Brown Sugar, c=US"
#rootdn "cn=Manager, dc=organicbrownsugar, dc=com "
rootdn "cn=Manager, o=Organic Brown Sugar, c=US"
# cleartext passwords, especially for the rootdn, should
# be avoid. See slapd.conf(5) for details.
rootpw secret
# database directory
# this directory MUST exist prior to running slapd AND
# should only be accessable by the slapd/tools Mode 700 recommended.
directory /usr/local/var/openldap-ldbm
index cn,sn,mail pres,eq,app

The first change we applied concerns the suffix value. The suffix determines to which kind of queries
our ldap server will response. In order to use automatic name resolution from various email clients,
we need to add the line
suffix ""

Since the email client does not include a search base (like o=Organic Brown Suger,c=US) we have to
add this line. Otherwise our queries will always be unsuccessful. The next two line include two other
search bases that might be used. The line rootdn specifies the LDAP administrator – the user who
has the right to update and change the database. Please note the following password that goes with
the username. At the end of the document we have a few indexes for searches.

Now we'll take a look at the next document with



vi /usr/local/etc/openldap/slapd.at.conf

where we will add an attribute for email addresses. We append the line

attribute mail dn
attribute ou dn

to the file. Now ldap knows about the mail attribute, but we have to tell ldap that we want to use it
with the person objectclass. What is an objectclass? It's a collection of attributes, an objectclass
person e.g. would need a lastname, firstname, email and so on. An organization objectclass would
probably need attributes like street, telephone number, state and so on. Whenever we add an object
to the ldap database, it has to be in an object class. Let's open the file slapd.oc.conf with

vi /usr/local/etc/openldap/slapd.oc.conf

and look for the line objectclass person which should look like this after our modifications:

objectclass person
requires
objectClass,
sn,
cn
allows
description,
seeAlso,
telephoneNumber,
userPassword,
mail,
ou

We now edited most of our configuration files and are now ready to move on and create our first
entries. For this reason we will create a ldif file that contains the records in readable format. Let's type
vi /tmp/root.ldif and create the following file:

dn: o=Organic Brown Sugar, c=US
objectclass: organization
o: Organic Brown Sugar

I choose to use an LDAP hirachy that is based on organzation and country rather than email domains.
If I would want to add both, I could create a file that looks like this:

dn: o=Organic Brown Sugar, c=US
objectclass: organization
o: Organic Brown Sugar

dn: dc=organicbrownsugar,dc=com
objectclass: dcObject
dc: organicbrownsugar

Now we are almost in LDAP land. We will now configure ldap to automatically everytime we boot. For
this reason we will create a file ldap in the directory /etc/rc.d/init.d/ by typing

cd /etc/rc.d/init.d/

And creating the /etc/rc.d/init.d/ldap file:

#!/bin/sh
#
# ldap This shell script takes care of starting and stopping
# ldap servers (slapd and slurpd).
#



# chkconfig: - 39 61
# description: LDAP stands for Lightweight Directory Access Protocol, used
# for implementing the industry standard directory services.
# processname: slapd
# config: /usr/local/libexec/slapd.conf
# pidfile: /usr/local/var/slapd.pid

# Source function library.
. /etc/init.d/functions

# Source networking configuration and check that networking is up.
if [ -r /etc/sysconfig/network ] ; then
. /etc/sysconfig/network
[ ${NETWORKING} = "no" ] && exit 0
fi

slapd=/usr/local/libexec/slapd
slurpd=/usr/local/libexec/slurpd
[ -x ${slapd} ] || exit 0
[ -x ${slurpd} ] || exit 0

RETVAL=0

function start() {
# Start daemons.
echo -n "Starting slapd:"
daemon ${slapd}
RETVAL=$?
echo
if [ $RETVAL -eq 0 ]; then
if grep -q "^replogfile" /usr/local/etc/openldap/slapd.conf; then
echo -n "Starting slurpd:"
daemon ${slurpd}
RETVAL=$?
echo
fi
fi
[ $RETVAL -eq 0 ] && touch /var/lock/subsys/ldap
return $RETVAL
}

function stop() {
# Stop daemons.
echo -n "Shutting down ldap: "
killproc ${slapd}
RETVAL=$?
killproc ${slurpd}
RETVAL=$?
fi
fi
echo
[ $RETVAL -eq 0 ] && rm -f /var/lock/subsys/ldap /var/run/slapd.args
return $RETVAL
}

# See how we were called.
case "$1" in
start)
start
;;
stop)
stop
;;
status)



status ${slapd}
if grep -q "^replogfile" /usr/local/etc/openldap/slapd.conf ; then
status ${slurpd}
fi
;;
restart)
stop
start
;;
reload)
killall -HUP ${slapd}
RETVAL=$?
killall -HUP ${slurpd}
RETVAL=$?
fi
fi
;;
condrestart)
if [ -f /var/lock/subsys/ldap ] ; then
stop
start
fi
;;
*)
echo "Usage: $0 start|stop|restart|status|condrestart}"
RETVAL=1
esac

exit $RETVAL

Of course you can download this file from http://www.netikus.net/. Make sure this file has the same
permissions assigned to it as all the other startup files in this directory. If it does not, enter

chmod 755 /etc/rc.d/init.d/ldap

However, this file does not start our ldap server by itself, we have to invoke it just like we did with our
DNS service. So we create the necessary symbolic links with

ln –s /etc/rc.d/init.d/ldap /etc/rc.d/rc3.d/S54ldap
ln –s /etc/rc.d/init.d/ldap /etc/rc.d/rc5.d/S54ldap

for starting the service and with

ln –s /etc/rc.d/init.d/ldap /etc/rc.d/rc0.d/K41ldap
ln –s /etc/rc.d/init.d/ldap /etc/rc.d/rc6.d/K41ldap

we stop the services when our machine shuts down or reboots.
You should now reboot your system – I experienced some problems without doing a reboot. So type
shutdown –r now

and wait until our system is back up. Now login again as root.

8.3 Testing the LDAP configuration
To finally add the entry to the ldap database, we will use a programm called ldapadd by typing

ldapadd –D "cn=Manager,o=Organic Brown Suger,c=US" –W –f /tmp/root.ldif



When asked for a password, please enter secret. This should produce an output similar to:
adding new entry o=Organic Brown Sugar, c=US

If your output matches and you didn't get any error messages, verify it with the ldapsearch
commando like this:

ldapsearch –u –b '' –s sub '(objectclass=*)'

This should display the one or two entries you created for the root of the hirarchy. To make things a
little more fun we will add another entry that has a telephonenumber and an email address. Create a
file /tmp/entry1.ldif and enter the following data:

dn: cn=Buffalo Bill,o=Organic Brown Sugar,c=US
objectclass: person
cn: Buffalo Bill
cn: Bill Buffalo
sn: Buffalo
mail: buffalo.bill@organicbrownsugar.com
mail: buffalo.bill@animalhunting.com
telephonenumber: +001 (987) 654-3210

Note here that you can have multiple attributes defined, cn and mail show up twice here. Make sure
you separate multiple entries with a blank line. dn stands for distinguished name and should be
unique for every entry. I could have also used dn: cn=Buffalo Bill,
dc=organicbrownsugar,dc=com instead in the first line, or a combination. Now type

ldapadd –D "cn=Manager,o=Organic Brown Suger,c=US" –W –f /tmp/entry1.ldif

and if you don't see any errors, type immediately: ldapsearch –u –b '' –s sub
'(objectclass=*)'
Do you see Buffalo Bill? If yes, we both have succeeded. Now delete the entry by typing:

ldapdelete –D "cn=Manager,o=Organic Brown Suger,c=US" "cn=Buffalo Bill,o=Organic
Brown Sugar, c=US" –W

One last word on ldap. Befory you start adding entries to an organizational unit, make sure you
create the organizational unit itself first with the objectclass=organizationalUnit objectclass.

Congratulations! Stand up, have your favorite drink and call your computer friends to tell them that you
escaped the
magic powers of Bill Gates and is supporters J



9 Administration with Perl
9.1 Installing the necessary Modules
To ease administration I wrote a perl script that let's you create and modify users with a perl script. To
make the user interface a little bit more appealable, you will need to install several modules for PERL.
Simply go to http://www.cpan.org and search for all the modules listed below, download them, and
copy them to the /usr/software directory. Those modules are needed (and included in the netikus
package):

1. Term::ReadKey TermReadKey-2.14.tar.gz
2. Passwd::Linux Passwd-Linux-0.70.tar.gz
3. Convert::ASN1 Convert-ASN1-0.07.tar.gz
4. Net::LDAP perl-ldap-0.22.tar.gz

The installation procedure is the same for all of those modules (and for most other ones). Please note
that you will have to substitute the correct file- and directory names to make it work. Also make sure
you install the modules in the order showed above. I showed one example with real filenames on the
right side with the Term::ReadKey Module:

tar –xvzf filename.tar.gz tar –xvzf TermReadKey-2.14.tar.gz
cd directory cd TermReadKey-2.14
perl Makefile.PL perl Makefile.PL
make make
make test make test
make install make install

Do this for every modele and the modules should now all be installed correctly!

9.2 Installing the perl script
Now copy the file useradministration.pl and usermanager.sh from the downloaded package to the
(recommended) the /root directory.

You can launch the usermanager anytime by typing

/root/usermanager.sh

To change default values (like the password for the ldap server) edit lines 33 to 37 of the file
useradministration.pl.

To make sure that only our holy root user has access to this valuable file(s), we type the following:

cd /root
chmod 700 useradministration.pl
chmod 700 usermanager.sh

which will only give the root user read, write and execute access.


Setting up a simple webpage 35

10 Setting up a simple webpage
Since our webserver should already be up and running, we will use some standard unix commands to
make administration bearable. We will

- Create a group for content administrators and adding a user
- Modify the file permissions
- Create a symbolic link in a users homedirectory that points to the content

10.1 Creating a group
That's as easy as it can be. All we do is type

groupadd htmladmins

and we have group for all of those html administrators (to see all groups look into /etc/group). Of
course we have to add user to this group, so we edit the /etc/group file, look for the line with our new
group and simply append testuser to it. The line should then look something like this:

htmladmins:x:501:testuser

The only thing that might look different on your installation might be the running number 501. If you
don't specify a GID, this number is always increased by one.

10.2 Modifying file permissions
Now we have to tell our directory that we have group we want to assign to it (and it's subdirectories).
By default the group root is assigned to that directory, but we don't want that. The html files for our
apache server are in the /var/www/html directory, so we have to go /var/www and change the group:

cd /var/www
chgrp –R htmladmins html

And that's it! So now every file and directory below (or above, depends on how you see it) has
htmladmins as it's group. Now we change the file permissions and give full rights to our new group.
We type

chmod –R 775 html

And off we go, it's done. If you wonder what the –R switch means … it stands for Recursive and
applies to all subdirectories as well. Bueno.

10.3 Creating a symbolic link
This will be short. Simply go into our testuser directory and we type

cd /home/testuser
ln –s /var/www/html html

This creates a symbolic with the name html (you can call it whatever you want) that redirects us to the
root directory of our webserver.


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