To unpack a pre-built Postfix package, execute the equivalent
# 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
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
setgid_group on the postfix command line:
# postfix set-permissions upgrade-configuration \
With Postfix versions before 2.1 you achieve the same result
by invoking the post-install script directly.