Puppet users - Apr 2013 - How to setup /etc/resolv.conf dependent on network

Hello,

I am a beginner in puppet so please excuse my lack of knowledge.
(I use puppet 3.1).

We have nodes in different networks - they use different DNS servers.
I''d like to set up its /etc/resolv.conf dependent on network they are
in.

What approach would you recommend to solve the problem ?

Thanks in advance 
Przemek

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On Friday, April 12, 2013 9:44:31 AM UTC+1, ForumUser wrote:
> We have nodes in different networks - they use different DNS servers.
> I''d like to set up its /etc/resolv.conf dependent on network they
are in.
>
Are you using Hiera? We run multiple datacentres that have different 
management networks, syslog servers and such, I provide the server with 
knowledge of the datacentre with a custom fact (which just reads a file in 
my case) and then in the hiera config I have:

:hierarchy:
  - nodes/%{hostname}
  - common/%{datacentre}

Then anything specific to the datacentre goes in that file. You could 
easily do something similar for the network.

Alternatively you might be able to define it all in a case statement 
matching the IP address of the server, although depending on how 
complicated your network architecture the regexs could become complicated:

case $::ipaddress_eth0 {
 /^192.168.1/: { $nameserver = ''192.168.1.254'' }
 /^192.168.2/: { $nameserver = ''192.168.2.254'' }
}

Josh

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We are not using Hiera yet (but it seems that this is what we should do in 
the close future ...)
At the moment the regexp expression is the simplest one.
Thank you :-)

On Friday, 12 April 2013 10:09:00 UTC+1, Josh wrote:
>
> On Friday, April 12, 2013 9:44:31 AM UTC+1, ForumUser wrote:
>
>> We have nodes in different networks - they use different DNS servers.
>> I''d like to set up its /etc/resolv.conf dependent on network
they are in.
>>
>
> Are you using Hiera? We run multiple datacentres that have different 
> management networks, syslog servers and such, I provide the server with 
> knowledge of the datacentre with a custom fact (which just reads a file in 
> my case) and then in the hiera config I have:
>
> :hierarchy:
>   - nodes/%{hostname}
>   - common/%{datacentre}
>
> Then anything specific to the datacentre goes in that file. You could 
> easily do something similar for the network.
>
> Alternatively you might be able to define it all in a case statement 
> matching the IP address of the server, although depending on how 
> complicated your network architecture the regexs could become complicated:
>
> case $::ipaddress_eth0 {
>  /^192.168.1/: { $nameserver = ''192.168.1.254'' }
>  /^192.168.2/: { $nameserver = ''192.168.2.254'' }
> }
>
> Josh
>
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Josh,

what if I have 192.168.* with exception of 192.168.100.* ?
Is the order in case statement important ?
E.g.:

case $::ipaddress_eth0 {
 /^192.168.100/: { $nameserver = ''192.168.100.254'' }
 /^192.168./: { $nameserver = ''192.168.1.254'' }
}



On Friday, 12 April 2013 10:09:00 UTC+1, Josh wrote:
>
> On Friday, April 12, 2013 9:44:31 AM UTC+1, ForumUser wrote:
>
>> We have nodes in different networks - they use different DNS servers.
>> I''d like to set up its /etc/resolv.conf dependent on network
they are in.
>>
>
> Are you using Hiera? We run multiple datacentres that have different 
> management networks, syslog servers and such, I provide the server with 
> knowledge of the datacentre with a custom fact (which just reads a file in 
> my case) and then in the hiera config I have:
>
> :hierarchy:
>   - nodes/%{hostname}
>   - common/%{datacentre}
>
> Then anything specific to the datacentre goes in that file. You could 
> easily do something similar for the network.
>
> Alternatively you might be able to define it all in a case statement 
> matching the IP address of the server, although depending on how 
> complicated your network architecture the regexs could become complicated:
>
> case $::ipaddress_eth0 {
>  /^192.168.1/: { $nameserver = ''192.168.1.254'' }
>  /^192.168.2/: { $nameserver = ''192.168.2.254'' }
> }
>
> Josh
>
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On Friday, April 12, 2013 3:54:16 PM UTC+1, ForumUser
wrote:
>
> what if I have 192.168.* with exception of 192.168.100.* ?
> Is the order in case statement important ?
> E.g.:
>
> case $::ipaddress_eth0 {
>  /^192.168.100/: { $nameserver = ''192.168.100.254'' }
>  /^192.168./: { $nameserver = ''192.168.1.254'' }
> }
>
It will choose the first match in the case statement.

You can also add a default (and I would always have a default anyway, even 
if it is just to fail with a sensible message)

case $::ipaddress_eth0 {
/^192.168.100/: { $nameserver = ''192.168.100.254'' }
/^192.168./: { $nameserver = ''192.168.1.254'' }
default: { fail("You shouldn''t get this far") }
}

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On 04/12/2013 10:44 AM, ForumUser wrote:
> Hello,
> 
> I am a beginner in puppet so please excuse my lack of knowledge.
> (I use puppet 3.1).
> 
> We have nodes in different networks - they use different DNS servers.
> I''d like to set up its /etc/resolv.conf dependent on network they
are in.
> 
> What approach would you recommend to solve the problem ?
Use facts about your network, like ip_address and netmask, and calculate
nameservers from that info:

$ facter -p | egrep "^(ipaddress |netmask )"
ipaddress => 192.168.0.164
netmask => 255.255.255.0

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