On Nov 23, 2010, at 4:53 PM, Adam Nielsen wrote: > Hi all, > > I've been reading up on Puppet but there are a few things I am unsure of, and > I'm hoping someone here can advise. > > As I understand it the idea behind Puppet is to describe how a machine should > be configured in a single place, and then let Puppet handle the actual set up > of the machine. > > How specific is this? For example, I use Exim as an e-mail MTA, with some > custom config rules related to SpamAssassin. Do I describe all these in > Puppet configuration files, so that Puppet can produce the correct Exim > config file? > > I'm also about to migrate a server onto new hardware and I would like to > upgrade the OS at the same time (change Linux distribution actually.) Would > it be possible to configure Puppet on the old server, run it in debug mode to > see what would be changed, then tweak the configuration until *nothing* would > be changed (so that the Puppet config exactly matches the current server > config) then apply that to the new server? Would this result in the new > server being set up exactly the same as the old one, with the same software > installed (albeit newer versions) and the same config set?
Nice idea, but not going to work. The problem is that an empty puppet config will also give you no changes. Doing this is a good idea, but you are almost sure to miss files that need to be changed that puppet is not changing because you didn't tell it to. As a simple example, suppose I need to change 3 files A, B, and C. When I first run puppet with an empty config, everything looks good because it tries to change nothing. Then I add A and B, but B has a mistake. I run puppet (with --noop) and puppet tells me it tried to change the file. I fix B and now I get no messages again, but I still don't realize that I missed C. In practice, there will often be a file you missed and you won't know until you try. Basically, I would try this, but expect that the new server will need a lot of runs with catalog treaking each time until it works. Once it works though, it makes disaster recovery much easier. (Although you still need a good backup plan for data.) -- You received this message because you are subscribed to the Google Groups "Puppet Users" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/puppet-users?hl=en.
