isabella232 / sysctl-1

sysctl cookbook for chef

sysctl

Description

Set sysctl system control parameters via Opscode Chef

Platforms

• Debian/Ubuntu
• RHEL/CentOS
• Scientific Linux
• PLD Linux (not tested)

Usage

There are two main ways to interact with the cookbook. This is via chef attributes or via the provided LWRP.

Attributes

• node['sysctl']['params'] - A namespace for setting sysctl parameters. These will be set during convergence, but will not be automatically persisted into a configuration file. The resource ruby_block[save-sysctl-params] is provided via the default recipe, which you can notify in order to persist these values.
• node['sysctl']['conf_dir'] - Specifies the sysctl.d directory to be used. Defaults to /etc/sysctl.d on the Debian and RHEL platform families, otherwise nil
• node['sysctl']['allow_sysctl_conf'] - Defaults to false. Using conf_dir is highly recommended. On some platforms that is not supported. For those platforms, set this to true and the cookbook will rewrite the /etc/sysctl.conf file directly with the params provided. Be sure to save any local edits of /etc/sysctl.conf before enabling this to avoid losing them.

LWRP

sysctl_param

Actions

• apply (default)
• remove
• nothing

Attributes

• key
• value

Persistence rules

sysctl values will be persisted to the filesystem (so that they can be initialized at boot) by this cookbook under the following conditions:

• You use an LWRP to declare the value, or you declare its value via a node attribute (node['sysctl']['param']) and invoke ruby_block[save-sysctl-params'] via a notification; and

• node['sysctl']['conf_dir'] is defined, in which case they are written to VALUE/99-chef-attributes.conf; or node['sysctl']['allow_sysctl_conf'] is set to true, in which case they are written to /etc/sysctl.conf.

Examples

# set vm.swapiness to 20 via attributes

node.default['sysctl']['params']['vm']['swappiness'] = 20

# set vm.swapiness to 20 via sysctl_param LWRP
sysctl_param 'vm.swappiness' do
  value 20
end

# remove sysctl parameter and set net.ipv4.tcp_fin_timeout back to default
sysctl_param 'net.ipv4.tcp_fin_timeout' do
  value 30
  action :remove
end

Development

We have written unit tests using chefspec and integration tests in bats executed via test-kitchen. Much of the tooling around this cookbook is exposed via guard and test kitchen, so it is highly recommended to learn more about those tools.

Vagrant Plugin Dependencies

The integration tests can be run via test-kitchen using vagrant, but it depends on the following vagrant plugins:

vagrant plugin install vagrant-omnibus
vagrant plugin install vagrant-berkshelf

Tested with

• Vagrant (version 1.4.3)
• vagrant-berkshelf (1.3.5)
• vagrant-omnibus (1.1.2)

Running tests

The following commands will run the tests:

bundle install
bundle exec rubocop
bundle exec foodcritic .
bundle exec rspec
bundle exec kitchen test default-ubuntu-1204
bundle exec kitchen test default-centos-65

The above will do ruby style (rubocop) and cookbook style (foodcritic) checks followed rspec unit tests ensuring proper cookbook operation.Integration tests will be run next on two separate linux platforms (Ubuntu 12.04 LTS Precise 64-bit and CentOS 6.5). Please run the tests on any pull requests that you are about to submit and write tests for defects or new features to ensure backwards compatibility and a stable cookbook that we can all rely upon.

Running tests continuously with guard

This cookbook is also setup to run the checks while you work via the guard gem.

bundle install
bundle exec guard start

ChefSpec LWRP Matchers

The cookbook exposes a chefspec matcher to be used by wrapper cookbooks to test the cookbooks LWRP. See library/matchers.rb for basic usage.

Links

There are a lot of different documents that talk about system control parameters, the hope here is to point to some of the most useful ones to provide more guidance as to what the possible kernel parameters are and what they mean.

• Linux Kernel Sysctl
• Linux Kernel IP Sysctl
• THE /proc FILESYSTEM (Jun 2009)
• RHEL 5 VM/Page Cache Tuning Presentation (2009) pdf
• Arch Linux SysCtl Tutorial (Feb 2013)
• Old RedHat System Tuning Overview (2001!)
• Tuning TCP For The Web at Velocity 2013 (video), slides
• Adventures in Linux TCP Tuning (Nov 2013)
• Part 1: Lessons learned tuning TCP and Nginx in EC2 (Jan 2014)