[ale] Copying config files to DHCP peer

[Todor Fassl]

It occurs to me that my question has a basic push/pull problem. I could 
make it so my co-workers don't know they are updating the peer.  That is 
the way it is now. They type "service dhcp start" just as they have 
always done. So that's nice when I am on vacation but what if I get hit 
by a bus? New guy comes in and has no idea how the peer is getting 
updated. Maybe its bad that I'm making this so easy.

Well, if I stick with the make it easy approach, what about adding a 
execstart post script to the systemd config file?

https://www.freedesktop.org/software/systemd/man/systemd.service.html#ExecStartPre=




On 12/19/19 11:20 AM, Bryan L. Gay via Ale wrote:
> Using a config manager would be perfect, but that's a long row to hoe
> if not already using a config manager.
> Personally, I'd use Chef above ansible or puppet, but that's just me.
> There's a learning curve for the people who want to make config
> changes using either of these tools.
> 
> On Thu, Dec 19, 2019 at 12:17 PM Joey Kelly via Ale <ale at ale.org> wrote:
>>
>> On Thursday, December 19, 2019 10:58:03 AM Todor Fassl via Ale wrote:
>>> I have been running peered ISC dhcp servers for years. The problem is
>>> that you need copies of the config files on both machines. Say you want
>>> to assign an IP address to a new machine. You add a stanza to a config
>>> file but then you then have to get a copy of the modified config file to
>>> the peer. If you forget to do that, you are going to screw things up
>>> pretty badly.
>>
>> So write a wrapper that fetches your stanzas or the complete config file, pushes
>> them to the servers, then restarts the servers. ansible/puppet can be your
>> friend here.
>>
>> --Joey
>>
>>
>>> Other people in my department occasionally need to make these config
>>> changes. So I need a way to guarantee that the config files get copied
>>> over. Googling showed me lots of articles on configuring a peer in
>>> isc-dhcp but only one on syncing the config files. That person was doing
>>> it via rsync and a script in cron.hourly.
>>>
>>> What I have done, at least for now, is to replace the init script with
>>> my own script. This script uses an ssh key to copy the files to the peer
>>> and then restarts dhcp on the peer. If somebody types "service dhcp
>>> restart", it runs my script. But now with systemd, it is going to be harder.
>>>
>>> Fortunately, for now, my co-workers are still typing "service bind9
>>> restart" and the like. So "service dhcp restart" is not a problem --
>>> yet. But if somebody types "systemctl restart isc-dhcp-server", it is
>>> not going to work.
>>>
>>>
>>> Its interesting that bind9 and slapd handle this under the covers.
>>
>> --
>> Joey Kelly
>> Minister of the Gospel and Linux Consultant
>> http://joeykelly.net
>> 504-239-6550
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-- 
Todd