Deploying Multiple files using Chef and Arrays

This post is one of a number of posts I’m making on nifty little tricks for Chef beginners.  These posts will try and detail solutions to common problems I found when learning Chef.  Hopefully I will save some people some time.

When I first started using Chef I would write the same lines of code over and over again to deploy files to a server.  This code would look something like the following:

cookbook_file "/etc/test/file1.txt"
   source "/my/files/file1.txt"
end

While this works for a few files it soon becomes unmanageable when you need to deploy more than a few.  The easiest way to keep your recipe nice and tidy is to create an array of the files and loop through the array performing the Chef action on the file that’s needed.  This will reduce the number of lines in your recipe and will be easier to maintain going forward.  This looks like this:

# Location of the files and templates within the cookbook
# the following location would translation to files/default/my/files
files_directory="/my/files"

# Location to deploy to
etc_directory="/etc/test"

# Array of the files that require to be deployed
file_array = [
'file1.txt',
'file1.txt',
'file1.txt',
'file1.txt']

# For each file in the array
file_array.each do |this_file|
   cookbook_file "#{etc_directory}/" + this_file do
      source "#{files_directory}/#{this_file}"
   end
end

The inner code works with cookbook_file, template or anything else you may need to do multiple times.

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RHEL Linux VMware migration eth0 eth1 problems…

I’ve recently had an incident where a Red Hat Enterprise Linux server that had been migrated between two VMware clusters (in this case dev to live) had no network connectivity after the migration.  The server had lost eth0 and had gained an unconfigured eth1 instead.  After a little bit of research I found that this was because the UUID and the MAC address had changed on the virtual hardware making the ifcfg-eth0 configuration file invalid

The fix was fairly simple – remove the UUID from ifcfg-eth0, delete the udev rules for the the network card, correct the MAC address and restart the network service.

I wrote this simple script for others to use:

#!/bin/bash

# Backup all files first
mkdir nic_change_backup
cp /etc/sysconfig/network-scripts/ifcfg-eth0 nic_change_backup
cp /etc/udev/rules.d/70-persistent-net.rules nic_change_backup
tar jcpvf nic_change_backup.tar.bz2 nic_change_backup
rm -rf nic_change_backup

# Remove the udev rule
# They are re-created on boot up
rm -f /etc/udev/rules.d/70-persistent-net.rules

# Fix the eth0 file
# This involves removing the UUID and
# updating the HWADDR with the MAC
# address of the new card.
grep -v UUID /etc/sysconfig/network-scripts/ifcfg-eth0 | sed '/HWADDR/c\'$(echo "HWADDR:$(echo "$(ip addr | grep ether | cut -d\  -f 6)" | tr '[:lower:]' '[:upper:]')") > /etc/sysconfig/network-scripts/ifcfg-eth0

# Restart networking, or in this case the server
shutdown -r now
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