Managing Debian packages using debconf preseed
Problem
I want to install postfix on all my servers as a standalone mta that relays all mail to a central mta.
Normally you would just do something like the following:
package { "postfix": ensure => present }
service { "postfix": ensure => true, enable => true }
file { "/etc/postfix/main.cf":
backup => false,
content => template("daemons/mta/postfix/main.cf.erb"),
notify => Service["postfix"],
require => Package["postfix"],
}
So we are installing the package and a default main.cf is installed as part of that package installation, then we clobber that file with an erb template.
Why bother clobbering a config file that is automatically generated out of debconf anyway?
Solution
We can use a preseed file which is a list of responses that debconf can use to configure a package.
Firstly the easiest way to get your response file is by manually installing a package on a target system.
apt-get install postfix
During this process we get asked what type of mta we want to install, so for my purpose i selected Satellite and entered in my relay server.
Once that is done you will need to install debconf-utils which provides the command debconf-get-selections
After you have installed this package run the following:
debconf-get-selections | grep "postfix\/" > /tmp/postfix.preseed
If we look at the contents of that file:
postfix postfix/master_upgrade_warning boolean postfix postfix/db_upgrade_warning boolean true postfix postfix/mailname string /etc/mailname postfix postfix/tlsmgr_upgrade_warning boolean postfix postfix/recipient_delim string + postfix postfix/dynamicmaps_upgrade_warning boolean postfix postfix/main_mailer_type select Satellite system postfix postfix/transport_map_warning note postfix postfix/relayhost string someserver.domain.tld postfix postfix/procmail boolean false postfix postfix/bad_recipient_delimiter note postfix postfix/chattr boolean false postfix postfix/root_address string postfix postfix/rfc1035_violation boolean false postfix postfix/mydomain_warning boolean postfix postfix/mynetworks string 127.0.0.0/8 postfix postfix/destinations string puppet, localhost.localdomain, localhost postfix postfix/nqmgr_upgrade_warning boolean postfix postfix/not_configured note postfix postfix/mailbox_limit string 0 postfix postfix/protocols select all
NOTE: one line i changed in that file was "postfix postfix/mailname string XXXXX" from the server i generated this on to /etc/mailname as it sets the current hostname to that value.
Now that we have a preseed file we can then put that on our fileserver. Depending on your setup place this wherever you feel necessary.
define preseed_package ( $ensure ) {
file { "/var/local/preseed/$name.preseed":
source => "puppet://$server/rfile/daemons/$name/$name.preseed",
mode => 600,
backup => false,
}
package { "$name":
ensure => $ensure,
responsefile => "/var/local/preseed/$name.preseed",
require => File["/var/local/preseed/$name.preseed"],
}
Then we can just call this postfix package as the following:
class mta {
preseed_package {"postfix": ensure => present }
}
Now when you run the client you will see something like the following:
info: Package[postfix](provider=apt): Preseeding /var/local/preseed/postfix.preseed to debconf-set-selections notice: //Node[gbl-admin-01]/soe/daemon-mta-relay/Package[postfix]/ensure: ensure changed 'purged' to 'present'
