Guidelines for Package Builders

Purpose of this document

This document has hints and tips for those who manage their own Postfix distribution for internal use, and for those who maintain Postfix distributions for general use.

General distributions: please provide a small default main.cf file

The installed main.cf file must be small. PLEASE resist the temptation to list all 300+ parameters in the main.cf file. Postfix is supposed to be easy to configure. Listing all 300+ in main.cf defeats the purpose. It is an invitation for hobbyists to make random changes without understanding what they do, and gets them into endless trouble.

General distributions: please include README or HTML files

Please provide the applicable README or HTML files. They are referenced by the Postfix manual pages and by other files. Without README or HTML files, Postfix will be difficult if not impossible to configure.

Postfix Installation parameters

Postfix installation is controlled by a dozen installation parameters. See the postfix-install and post-install files for details. Most parameters have system-dependent default settings that are configurable at compile time, as described in the INSTALL file.

Preparing a pre-built package for distribution to other systems

You can build a Postfix package on a machine that does not have Postfix installed on it. All you need is Postfix source code and a compilation environment that is compatible with the target system.

You can build a pre-built Postfix package as an unprivileged user.

First compile Postfix. After successful compilation, execute:

 % sh postfix-install 

You will be prompted for installation parameters. Specify an install_root directory other than /. The mail_owner and setgid_group installation parameter settings will be recorded in the main.cf file, but they won't take effect until the package is unpacked and installed on the destination machine.

If you want to fully automate this process, specify all the non-default installation parameters on the command line:

 % sh postfix-install -non-interactive
install_root=/some/where ...  

Begin Security Alert

When building an archive for distribution, be sure to archive only files and symbolic links, not their parent directories. Otherwise, unpacking a pre-built Postfix package may mess up permission and/or ownership of system directories such as / /etc /usr /usr/bin /var /var/spool and so on. This is especially an issue if you executed postfix-install (see above) as an unprivileged user.

End Security Alert

Thus, to tar up the pre-built package, take the following steps:

% cd INSTALL_ROOT
% rm -f SOMEWHERE/outputfile
% find . \! -type d -print | xargs tar cf SOMEWHERE/outputfile
% gzip SOMEWHERE/outputfile 

This way you will not include any directories that might cause trouble upon extraction.

Installing a pre-built Postfix package

• To unpack a pre-built Postfix package, execute the equivalent of:

  # umask 022
  # gzip -d <outputfile.tar.gz | (cd / ; tar xvpf -) 

  The umask command is necessary for getting the correct permissions on non-Postfix directories that need to be created in the process.

• Create the necessary mail_owner account and setgid_group group for exclusive use by Postfix.

• Execute the postfix command to set ownership and permission of Postfix files and directories, and to update Postfix configuration files. If necessary, specify any non-default settings for mail_owner or setgid_group on the postfix command line:

  # postfix set-permissions upgrade-configuration \
         setgid_group=xxx mail_owner=yyy
  

  With Postfix versions before 2.1 you achieve the same result by invoking the post-install script directly.