Running Linux, 5th Edition - Matthias Kalle Dalheimer [435]
On Debian, you can use dpkg to see if the libraries are installed:
# dpkg -l libdb4.3-dev
If you download a prepackaged Postfix, use your package manager (described in Chapter 12) to install it. If you download the source postfix-2.2.5.tar.gz, move that file to a suitable directory (such as your home directory) to unpack it. The numbers in the name of the file represent the version of this release. Your file may have different numbers depending on the current release when you download it.
Follow this basic procedure to build Postfix. Note that you'll have to be the root user to create the user and group and to install the package.
Rename your sendmail binaries as described earlier.
Create a user account called postfix and a group called postdrop. See "Managing User Accounts" in Chapter 11 for information on setting up accounts and groups.
Run gunzip on the compressed file to produce a file named postfix-2.2.5.tar.
Execute tar -xvf postfix-2.2.5.tar
to unpack the source into a directory called postfix-2.2.5.
Move to the directory created when you unpacked the file. You'll find a file called INSTALL with detailed instructions about building your Postfix system. In most cases, building Postfix should be as simple as typing make in the directory.
If your build completes without any errors, type make install to install Postfix on your system. You should be able to accept all the defaults when prompted by the installation script.
After installation, you will have Postfix files in the following directories:
/usr/libexec/postfix
This directory contains the various Postfix daemons. Postfix uses a split architecture in which several discrete programs handle separate tasks. The master daemon is started first. It deals with starting other programs as they are needed. For the most part, you don't need to worry about any of the programs here. Stopping and starting Postfix is handled with the postfix command found in the /usr/sbin directory.
/etc/postfix
Typically this directory contains dozens of Postfix configuration files, but only master.cf and main.cf and a few lookup tables are used by Postfix. The rest of the files are examples that document the various parameters used for configuration.
The master.cf file controls the various Postfix processes. It includes a line for each component of Postfix. The layout of the file is described by comments in the file itself. Usually, you shouldn't have to make any changes to run a simple Postfix installation.
The main.cf file is the global SMTP configuration file. It includes a list of parameters set to one or more values using the format
parameter = value
Comments are marked with a hash mark (#) at the beginning of the line. You cannot put comments on the same line as parameters. Commented lines can begin with whitespace (spaces or tabs), but they must appear on lines by themselves.
Multiple values for parameters can be separated by either commas or whitespace (including newlines), but if you want to have more than one line for a parameter, start the second and subsequent lines with whitespace. Values can refer to other parameters by preceding the parameter name with a dollar sign ($).
Here's an example of an entry that includes comments, multiple lines, and a parameter reference:
# Here are all the systems I accept mail from.
mynetworks = $myhostname
192.168.75.0/24
10.110.12.15
/usr/sbin
All the Postfix commands are located in /usr/sbin and have names starting with post. There are commands to create index files, manage the mail queue, and otherwise administer your Postfix system. The postfix command, which is used to stop and start Postfix (described later), is found here.
/var/spool/postfix
The Postfix queue manager is an important component of the Postfix system that accepts incoming email messages and arranges with other Postfix components to deliver them. It maintains its files under the /var/spool/postfix directory. The queues