Puppet, Facter, looping through IPs

[Christian Reiß]

Hello all,

I am trying to set up ssh keys (sshkeys) for populate /etc/ssh/ssh_known_hosts. So far it works great, but I want to have aliases for all ips online on that host.

Two problems:

- The assumption is that the interface count and names are unknown. There can be one eth or many, none but a xapi device etc. There is, however, interfaces variable from facter, which holds all the interfaces.

- I need to loop through the array and use the contents of that variable, ie:

interfaces => eth0,eth1,lo,tun0
ipaddress => 46.229.47.132
ipaddress_eth0 => 46.229.47.132
ipaddress_eth1 => 10.1.0.2
ipaddress_lo => 127.0.0.1
ipaddress_tun0 => 10.10.0.1

So I would need to loop through interfaces, query the variable with the same name to get the ip address. All this by acoiding loopback.

- I dont know a good way to then add all compiled aliases into sshkeys.

Does anyone have a pointer / solution?

Thank you for your help in advance,
Chris.

[Dan White]

This might be better done with a shell script that calls facter

“Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us.”
Bill Waterson (Calvin & Hobbes)

---

From: "Christian Reiß" <reiss.s...@gmail.com>
To: puppet...@googlegroups.com
Sent: Wednesday, August 14, 2013 6:20:41 AM
Subject: [Puppet Users] Puppet, Facter, looping through IPs

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[jcbollinger]

I think you're saying you want to process the fact data to produce an array of the IP addresses (except of the loopback interface) to assign as the value of the 'host_aliases' parameter of an 'sshkey' resource.

You can obtain an array of the interface name from the $interfaces fact like so:

$interface_names = split($::interfaces, ',')

Given one interface name, you can interpolate the name into a string containing a template, then use the template to evaluate the desired Puppet variable, like so:

$interface_ipaddress = inline_template("<%= @ipaddress_${interface_name} %>")

But the inline_template() can produce only a string, not an array, and by itself that does not address processing all the interfaces.  I see three possible approaches:

1. Write a custom function that computes the array of IP addresses for you
   
2. Use "future" functions: especially reduce() and maybe reject().  This requires Puppet 3.2; see http://docs.puppetlabs.com/references/3.2.latest/function.html#reduce
3. Use an inline template to produce a delimited string of the IP addresses, then split that to get the array you want.

I present a possible implementation of (3):

$interface_addresses = inline_template('<%=
  @interface_names.reject{ |ifc| ifc == "lo" }.map{ |ifc| scope.lookupvar("ipaddress_#{ifc}") }.join(" ")
%>')

$interface_addr_array = split($interface_addresses, ' ')

Note the use of scope.lookupvar(), which is a different way to retrieve the value of a dynamically-chosen Puppet variable.


John