How to install Puppet server and client on CentOS and RHEL

As a system administrator acquires more and more systems to manage, automation of mundane tasks gets quite important. Many administrators adopted the way of writing custom scripts, that are simulating complex orchestration software. Unfortunately, scripts get obsolete, people who developed them leave, and without an enormous level of maintenance, after some time these scripts will end up unusable. It is certainly more desirable to share a system that everyone can use, and invest in tools that can be used regardless of one's employer. For that we have several systems available, and in this howto you will learn how to use one of them - Puppet.

What is Puppet?

Puppet is an automation software for IT system administrators and consultants. It allows you to automate repetitive tasks such as the installation of applications and services, patch management, and deployments. Configuration for all resources are stored in so called "manifests", that can be applied to multiple machines or just a single server. If you would like to know more information, The Puppet Labs site has a more complete description of what Puppet is and how it works.

What are we going to achieve in this tutorial?

We will install and configure a Puppet server, and set up some basic configuration for our client servers. You will discover how to write and manage Puppet manifests and how to push it into your servers.

Prerequisites

Since Puppet is not in basic CentOS or RHEL distribution repositories, we have to add a custom repository provided by Puppet Labs. On all servers in which you want to use Puppet, install the repository by executing following command (RPM file name can change with new release):

On CentOS/RHEL 6.5:

# rpm -ivh https://yum.puppetlabs.com/el/6.5/products/x86_64/puppetlabs-release-6-10.noarch.rpm

On CentOS/RHEL 7:

# rpm -ivh https://yum.puppetlabs.com/el/7/products/x86_64/puppetlabs-release-7-10.noarch.rpm

Server Installation

Install the package "puppet-server" on the server you want to use as a master.

# yum install puppet-server

When the installation is done, set the Puppet server to automatically start on boot and turn it on.

# chkconfig puppetmaster on
# service puppetmaster start

Now when we have the server working, we need to make sure that it is reachable from our network.

On CentOS/RHEL 6, where iptables is used as firewall, add following line into section ":OUTPUT ACCEPT" of /etc/sysconfig/iptables.

-A INPUT -m state --state NEW -m tcp -p tcp --dport 8140 -j ACCEPT

To apply this change, it's necessary to restart iptables.

# service iptables restart

On CentOS/RHEL 7, where firewalld is used, the same thing can be achieved by:

# firewall-cmd --permanent --zone=public --add-port=8140/tcp
# firewall-cmd --reload

Client Installation

Install the Puppet client package on your client nodes by executing the following:

# yum install puppet

When the installation finishes, make sure that Puppet will start after boot.

# chkconfig puppet on

Your Puppet client nodes have to know where the Puppet master server is located. The best practice for this is to use a DNS server, where you can configure the Puppet domain name. If you don't have a DNS server running, you can use the /etc/hosts file, by simply adding the following line:

1.2.3.4 server.your.domain
2.3.4.5 client-node.your.domain

1.2.3.4 corresponds to the IP address of your Puppet master server, "server.your.domain" is the domain name of your master server (the default is usually the server's hostname), "client-node.your.domain" is your client node. This hosts file should be configured accordingly on all involved servers (both Puppet master and clients).

When you are done with these settings, we need to show the Puppet client what is its master. By default Puppet looks for a server called "puppet", but this setting is usually inappropriate for your network configuration, therefore we will exchange it for the proper FQDN of the Puppet master server. Open the file /etc/sysconfig/puppet and change the "PUPPET_SERVER" value to your Puppet master server domain name specified in /etc/hosts:

PUPPET_SERVER=server.your.domain

The master server name also has to be defined in the section "[agent]" of /etc/puppet/puppet.conf:

server=server.your.domain

Now you can start your Puppet client:

# service puppet start

We need to force our client to check in with the Puppet master by using:

# puppet agent --test

You should see something like the following output. Don't panic, this is desired as the server is still not verified on the Puppet master server.

Exiting; no certificate found and waitforcert is disabled

Go back to your puppet master server and check certificate verification requests:

# puppet cert list

You should see a list of all the servers that requested a certificate signing from your puppet master. Find the hostname of your client server and sign it using the following command (client-node is the domain name of your client node):

# puppet cert sign client-node

At this point you have a working Puppet client and server. Congratulations! However, right now there is nothing for the Puppet master to instruct the client to do. So, let's create some basic manifest and set our client node to install basic utilities.

Connect back to your Puppet server and make sure the directory /etc/puppet/manifests exists.

# mkdir -p /etc/puppet/manifests

Now create the manifest file /etc/puppet/manifests/site.pp with the following content

node 'client-node' {
        include custom_utils
}

class custom_utils {
        package { ["nmap","telnet","vim-enhanced","traceroute"]:
                ensure => latest,
                allow_virtual => false,
        }
}

and restart the puppetmaster service.

# service puppetmaster restart

The default refresh interval of the client configuration is 30 minutes, if you want to force the application of your changes manually, execute the following command on your client node:

# puppet agent -t

If you would like to change the default client refresh interval, add:

runinterval = <yourtime>

to the "[agent]" section of /etc/puppet/puppet.conf on your client node. This setting can be a time interval in seconds (30 or 30s), minutes (30m), hours (6h), days (2d), or years (5y). Note that a runinterval of 0 means "run continuously" rather than "never run".

Tips & Tricks

1. Debugging

It can happen from time to time that you will submit a wrong configuration and you have to debug where the Puppet failed. For that you will always start with either checking logs in /var/log/puppet/ or running the agent manually to see the output:

# puppet agent -t

By default "-t" activates verbose mode, so it allows you to see the output of Puppet. This command also has several parameters that might help you identify your problem a bit more. The first useful option is:

# puppet agent -t --debug

Debug shows you basically all steps that Puppet goes through during its runtime. It can be really useful during debug of really complicated rules. Another parameter you might find really useful is:

# puppet agent -t --noop

This option sets puppet in so called dry-run mode, where no changes are performed. Puppet only writes what it would do on the screen but nothing is written on the disk.

2. Modules

After some time you find yourself in the situation where you will want to have more complicated manifests. But before you will sit down and start to program them, you should invest some time and browse https://forge.puppetlabs.com. Forge is a repository of the Puppet community modules and it's very likely that you find the solution for your problem already made there. If not, feel free to write your own and submit it, so other people can benefit from the Puppet modularity.

Now, let's assume that you have already found a module that would fix your problem. How to install it into the system? It is actually quite easy, because Puppet already contains an interface to download modules directly. Simply type the following command:

# puppet module install <module_name> --version 0.0.0

<module_name> is the name of your chosen module, the version is optional (if not specified then the latest release is taken). If you don't remember the name of the module you want to install, you can try to find it by using module search:

# puppet module search <search_string>

As a result you will get a list of all modules that contain your search string.

# puppet module search apache
Notice: Searching https://forgeapi.puppetlabs.com ...
NAME                               DESCRIPTION                                                                                         AUTHOR          KEYWORDS                                        
example42-apache                   Puppet module for apache                                                                            @example42      example42, apache                               
puppetlabs-apache                  Puppet module for Apache                                                                            @puppetlabs     apache web httpd centos rhel ssl wsgi proxy     
theforeman-apache                  Apache HTTP server configuration                                                                    @theforeman     foreman apache httpd DEPRECATED               

And if you would like to see what modules you already installed, type:

# puppet module list

Summary

By now, you should have a fully functional Puppet master that is delivering basic configuration to one or more client servers. At this point feel free to add more settings into your configuration to adapt it to your infrastructure. Don't worry about experimenting with Puppet and you will see that it can be a genuine lifesaver.

Puppet labs is trying to maintain a top quality documentation for their projects, so if you would like to learn more about Puppet and its configuration, I strongly recommend visiting the Puppet project page at http://docs.puppetlabs.com.

If you have any questions feel free to post them in the comments and I will do my best to answer and advise.

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Jaroslav Štěpánek

Jaroslav Štěpánek is a 26-year-old self taught GNU/Linux and UNIX enthusiast from Czech Republic. He first came in contact with Linux 17 years ago. Currently, he works full-time as a Configuration Manager at a German company, while still keeping up-to-date with the latest open source news and releases.
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9 thoughts on “How to install Puppet server and client on CentOS and RHEL

  1. Hi,
    Your tutorial is very interesting.
    I just wanted to tell you that there is a small mistake. In RHEL7, you don't update the firewall configuration with "service firewalld restart" but with "firewall-cmd --reload".
    In one case, you stop everything, in the other, you update the firewall configuration without stopping it which is all the purpose of this new firewall version.
    Regards.

    • Hi Udaya,

      that is not necessary. Client nodes are periodically connecting to master node. So the only machine that has to have this port open is the master node.

      Best regards,
      Jaroslav

  2. Thanks for your useful article, by the way, could you please suggest me a master puppet GUI to easily monitoring list of puppet agents in a dashboard view ?

    Thanks

  3. Yes, maybe puppet is useful for some people, but in my opinion, is not a good tool, and I write some "minor example" from my own experience with puppet (official repo - last stable version, and 3 days wasted for this .... ) - and this is my own opinion:

    - poor official documentations (some of the topics are outdated or wrong. simple examples are not common, for example not any kind of "Hello World" setup);
    - it is a tool created by some developers (with very good software skills) but they do not know best practice/rules on linux;
    - the messages in the logs are very few, and messages are only useful for a developer, not for a linux admin (for example you will not see message like "file access denied", or "file not found" - something normal with any decent software on linux)
    - the logs are not in the /var/log/puppet/, but in /var/lib/puppet/, and are in a dedicate format .... especially for linux administrators: yaml
    - on the server side I seen only syntactic errors, nothing else, but on the client side you will see other errors (for example, because a file does not exist on server ... and the client cannot copy this file from the server);
    - the puppet server package comes with a web-server, which can serve only 10-15 puppet clients
    - the logs of this super web-server has its own format ... not like any normal http server
    - on the server side if you install the server package, you also get the client .... and the same config file (indeed with 2 section for server = main and another section for the client ..... )
    - on the client side if you install the client package you get the same config file, like on the server
    - if you make some changes on your config on the server, you need to "compile" this new configuration (example: puppet apply -v /etc/puppet/manifests/site.pp), and not /etc/init.d/.... reload
    - no "man puppet", no "puppet --help" or "puppet -help", only "puppet help"
    - examples which are in the config files (with comments), (at least some of them) are wrong;
    - and take a look on this ... I am not the only one who spent a lot of time for some "puppet errors":

    http://www.mail-archive.com/puppet-users@googlegroups.com/msg54296.html

    Maybe in another life I will meet again with puppet ;) In the meantime, my old bash scripts work very well for at least 5-6 years .... on several servers, and did not mess any of my server (yet).

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