RHEL7 – How to Set Your Hostname in Redhat Enterprise Linux 7

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Setting a server’s hostname used to be as simple as running the ‘hostname’ command and adding a “HOSTNAME” entry in /etc/sysconfig/network. However things have changed quite a bit in RHEL7. Apparently, systemd now controls setting a server’s hostname. The ‘hostname‘ command no longer works to set your hostname, however the command is still available just to confuse you.

Now in RHEL 7 you use the command ‘hostnamectl‘. Below is an example of how it works.

Here I have logged into my a RHEL 7.1 VM. You can see that the system appears to have the hostname of node1.

[root@node1 ~]# hostname
node1

However upon further inspection, I find that this is not the case. Rather, the server has a static hostname of localhost.localdomain.

[root@node1 ~]# hostnamectl
Static hostname: localhost.localdomain
Transient hostname: node1
Icon name: computer-vm
Chassis: vm
Machine ID: 4c26a2a3101947bfa2ec7d9c16824ca4
Boot ID: f58707942bd1458da48680025b6f1a53
Virtualization: vmware
CPE OS Name: cpe:/o:redhat:enterprise_linux:7.1:GA:server
Kernel: Linux 3.10.0-229.el7.x86_64
Architecture: x86_64

So lets set the hostname permanently using ‘hostnamectl’.

[root@node1 ~]# hostnamectl set-hostname node1.packy.lab.localdomain

As you can see the hostname shows correct in the output of the ‘hostname’ command

[root@node1 ~]# hostname
node1.packy.lab.localdomain

… and in the output from ‘hostnamectl’

[root@node1 ~]# hostnamectl
Static hostname: node1.packy.lab.localdomain
Icon name: computer-vm
Chassis: vm
Machine ID: 4c26a2a3101947bfa2ec7d9c16824ca4
Boot ID: f58707942bd1458da48680025b6f1a53
Virtualization: vmware
Operating System: Employee SKU
CPE OS Name: cpe:/o:redhat:enterprise_linux:7.1:GA:server
Kernel: Linux 3.10.0-229.el7.x86_64
Architecture: x86_64

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Redhat 6 Minimal Kickstart Configuration with VMware Tools and Puppet Agent Install

smartaHere is my small, crude, little Kickstart configuration and post install script that I have up and running in my lab at home. Don’t expect to find anything too fancy here, as this Kickstart was purposefully built to be small and to the point. Here, the point was to spin up a VM, run through a basic install of CentOS/Redhat Linux,  and install VMware Tools along with a Puppet agent.

Note that this post assumes that you have a working Kickstart server.

First lets take a look at our kickstart file, CentOS-6.6-x86_64-minimal.ks

The section directly below kicks off our kickstart ks file. Here we set our root password (no that’s not my hash) and setup our network interface for DHCP. We do a tiny bit of disk partitioning, and setup very simple LVM. Then we choose our packages. As you can see my package list is not at all fancy, I just want to make sure that I have pretty much every package that might need for a lab VM.

[code language=”bash”]
# Kickstart file for RHEL 6 Minimal
# Small Disk

text
install
url –url=http://10.1.0.106/ks/loop/CentOS-6.6-x86_64-bin-DVD1
lang en_US.UTF-8
keyboard us
network –onboot yes –device eth0 –bootproto dhcp –noipv6
rootpw –iscrypted $6$X/4YYZPN$4Sv.khxXms8N8vRssR/Vl35w/m80FF5P6p7aX0D7EFfD9p734F6tU4kXdcSCoOjPiXLrVxqfKxxxxxxxxxxxq5551
firewall –disabled
authconfig –enableshadow –passalgo=sha512
selinux –permissive
timezone America/New_York

# Disk
bootloader –location=mbr –driveorder=sda –append="crashkernel=auto rhgb"
zerombr
clearpart –all –drives=sda
part pv.1 –grow –size=1
part /boot –fstype=ext4 –size=1024
volgroup VolGroup pv.1
logvol / –fstype=ext4 –name=lv_root –vgname=VolGroup –size=1024 –grow
logvol swap –name=lv_swap –vgname=VolGroup –size=1024

#Network
network –device=eth0 –bootproto=dhcp –nameserver=10.1.0.110

# Package Selection
%packages –nobase –excludedocs
@Base
@core
kernel-headers
wget
perl
sysstat
bind-utils
tcpdump
[/code]

Now let me pause to point out the section below. This is the %pre script that I am using to prompt me for the VM hostname before the install begins. The hostname needs to be set before you install puppet on the VM, otherwise you are going to have to recreate your puppet certificates after you set properly set your hostname post install and reboot.

[code language=”bash”]
%pre –log=/root/ks_pre.log
#change to tty6 to get input
chvt 6
exec </dev/tty6 > /dev/tty6

#Prompt for hostname
echo "What is my hostname?"
read NAME
echo "NETWORKING=yes
HOSTNAME=${NAME}" > network
chvt 1
[/code]

Now we run a simple post install, along with a custom post install script. It is this script that will install Vmware tools and Puppet. Myself, I prefer keeping most of my code out of the actual Kickstart ks file, however you can always jam all your code into it if you like. You will just need to validate your syntax first, as I have not tested my config this way.

[code language=”bash”]
%post –nochroot
# bring in hostname collected from %pre, then source it
cp network /mnt/sysimage/etc/sysconfig/network
. /mnt/sysimage/etc/sysconfig/network
# force hostname change
/mnt/sysimage/bin/hostname $HOSTNAME
#Post Install
%post –log=/root/ks-post.log
cd /root
echo "Getting the post install script – if this takes a long time check network or path"
wget http://10.1.0.106/ks/scripts/centos-6-postinstall.bash
echo "Running the post install script"
/bin/bash centos-6-postinstall.bash
[/code]

Ok, so below is the post install script that I am calling in the section above. After a quick modification of my hosts file, I pull down the Puppet installer from my local Puppet server. Next we install the open source VMware tools packages, after creating the required yum repofile.

 

[code language=”bash”]
#!/bin/bash
#centos-6-postinstall.bash

#Switch to the 6th console and redirect all i/o
exec < /dev/tty6 > /dev/tty6 2> /dev/tty6
chvt 6

# Lets make sure we know who the puppet server is before we get too far
echo "Adding hosts entry for puppet master"
echo "10.1.0.115 puppet puppet.lab.localdomain" >> /etc/hosts

## Update Via Yum – not doing this for now in order to save time
#yum -y update
# Install puppet from local puppet master
echo "Downloading and running Puppet installer"
curl -k https://10.1.0.115:8140/packages/current/install.bash | sudo bash
#Install Open Source VMware Tools
rpm –import http://packages.vmware.com/tools/keys/VMWARE-PACKAGING-GPG-DSA-KEY.pub
rpm –import http://packages.vmware.com/tools/keys/VMWARE-PACKAGING-GPG-RSA-KEY.pub

echo -e "[vmware-tools]\nname=VMware Tools\nbaseurl=http://packages.vmware.com/tools/esx/5.1latest/rhel6/$HOSTTYPE\nenabled=1\ngpgcheck=1" > /etc/yum.repos.d/vmware-tools.repo

echo "Installing Vmware Tools"
yum -y install vmware-tools-esx-nox

#Minor grub.conf modifications
sed -i ‘s/rhgb quiet//’ /boot/grub/grub.conf
sed -i ‘s/hiddenmenu//’ /boot/grub/grub.conf
sed -i ‘s/timeout=5/timeout=10/’ /boot/grub/grub.conf

#Kick off first puppet run, for some reason I think you might need to do this twice.
sleep 5
echo "Running Puppet for the first time"
puppet agent –test
puppet agent –test

#Tell us we have reached the end
echo "We have reached the end of the post-install script"
[/code]

A couple of additional details to note about the post install script above. I like to modify the grub.conf so that I unhide the menu and increase the time out. I also like to make sure that we disable the Redhat graphical boot screen… I want to make sure its easy to catch any errors or miss-configurations in my kickstarts.
 

Puppet: How Not To Generate a Certificate with Your Correct Hostname

954f7381089ac290b4690c5ffd9dd7d3_400x400So, I’ve been hacking away in my homelab as of late, building out a CentOS kickstart server, a Git server, and a puppet server. Right now, I am working on how to roll my puppet agent installs into my kickstart process. I just started on this, so I have yet to nail it down.

So currently, when kicking a VM, I am not yet setting my new CentOS node’s hostname before the install process. Sadly I am setting it manually as I am still building my kickstarts, and they are no where near where I want them to be.

Well, this whole hostname mumbo-jumbo just creates all sorts of issues for puppet… the hostname is one thing initially, then puppet installs as part of the post, and the hostname is set manually to finalize the install. Well this is no good, as you are are not going to be able to add your new node properly until you step in and provide a bit of manual persuasion.

Now while its not hard to find documentation on how to troubleshoot puppet node and master certificate issues — see here and here for example — none of it was written to help troubleshoot the mess that I had created.

Here was my specfic error.

Error: Could not request certificate: The certificate retrieved from the master does not match the agent’s private key.
Certificate fingerprint: BE:B6:B6:5E:AC:B8: ..truncated

And here verbatim, is the output that you get in response to the error above.

To fix this, remove the certificate from both the master and the agent and then start a puppet run, which will automatically regenerate a certficate.

On the master:
  puppet cert clean localhost.localdomain

On the agent:
  rm -f /etc/puppetlabs/puppet/ssl/certs/localhost.localdomain.pem
  puppet agent -t

So we try that and it doesn’t work. The next cert I generate identifies my node as localhost again.

So heres how to fix the issue.

# rm -rf /etc/puppetlabs/puppet/ssl

Now before we generate another certificate for our node, lets test what hostname a new cert would have using the command below.

#puppet agent –verbose –configprint certname

If the command above does not spit out the correct hostname, then you my friend, are in luck. Edit the file below

# vi /etc/puppetlabs/puppet/puppet.conf

Now change the entry below by removing the localhost.localdomain, and replacing that mess with the correct hostname

certname = correcthostname.localdomain

Now kickoff a puppet run on the node

#puppet agent -t

Log into the UI, or ssh into the puppet master, and accept the new node request.

Kick off another puppet run after you have accepted the request to seal the deal and update the new node properly.

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