{ url: '4-20ma.io' }

Miscellaneous posts related to hardware / software development and industrial process control.

[4-20ma]

How to create an RPM package using Chef, Test Kitchen

This article describes how to leverage Chef and Test Kitchen to create a pristine virtual machine from which to create an RPM package.

Background

I needed customized versions of the FcgiWrap and Postfix RPM packages and preferred to develop a method that would allow me to periodically update the packages as new versions of the upstream source were released. Vagrant is a great tool for managing virtual machines and I was originally going to use this to provision a new VM to build the packages. I developed Chef cookbooks to provision the VMs, and while developing integration tests for the provisioners, I realized that it was more effective to use Test Kitchen to build and test my VMs (which itself uses Vagrant).

Prerequisites

The following are required:

Git (v2.2.1 used)

Ruby (v2.1.5 used)

Chef (v11.16.4 used)

Test Kitchen (v1.2.1 used)

Vagrant (v1.6.5 used)

Virtual machine (Parallels 10.0.0 used, but VirtualBox works as well)

FcgiWrap Example

Clone the repository:

$ git clone https://github.com/4-20ma/cookbook-fcgiwrap_rpm.git $ cd cookbook-fcgiwrap_rpm

Postfix Example

Clone the repository:

$ git clone https://github.com/4-20ma/cookbook-postfix_rpm.git $ cd cookbook-postfix_rpm

Both Examples

Use Test Kitchen to converge the node and retrieve the resultant RPM from .products/:

$ bundle exec kitchen converge

You can now transfer the .rpm file to the target machine(s) and install via rpm or yum.

Conclusion

Test Kitchen is not only effective at performing integration testing for a Chef cookbook, it is also useful to spin up a pristine virtual machine to perform tasks such as building an RPM package.

References

Cookbook Sources:

FcgiWrap RPM Cookbook -- builds FcgiWrap RPM

Postfix RPM Cookbook -- builds Postfix RPM

Software used (alphabetical):

Chef

FcgiWrap Source

Git

Parallels

Postfix

Ruby

Test Kitchen

Vagrant

VirtualBox

[4-20ma]

How to mount a remote file system over ssh

The following post describes how to mount a remote file system over ssh on Mac OS X 10.9.2. With minor modifications, the same thing can be achieved on other platforms.

Background

I recently needed to manipulate a sqlite database on a virtual machine and my gui tool lacked the ability to tunnel over ssh.

Enter sshfs: Secure SHell FileSystem -- a file system for Linux (and other operating systems with a FUSE implementation, such as Mac OS X or FreeBSD) capable of operating on files on a remote computer using just a secure shell login on the remote computer.

In the example below, I'm mounting a file system from a VirtualBox virtual machine controlled by vagrant (which happens to use port 2200 on the loopback address 127.0.0.1).

Prerequisites

Mac OS X 10.9.2

Homebrew

Installation

Install sshfs via Homebrew:

$ brew install sshfs

Follow instructions for osxfuse (refer to brew info osxfuse):

$ mount -t osxfusefs $ sudo kextunload -b com.github.osxfuse.filesystems.osxfusefs $ sudo /bin/cp -RfX /usr/local/Cellar/osxfuse/2.6.2/Library/Filesystems/osxfusefs.fs /Library/Filesystems $ sudo chmod +s /Library/Filesystems/osxfusefs.fs/Support/load_osxfusefs

Configuration

Replace mount_name with descriptive name indicating the name of the machine. Replace 2200 with the appropriate port on which sshd is listening.

$ mkdir /Volumes/mount_name $ sshfs [email protected]: /Volumes/mount_name -p 2200 [email protected]'s password: (enter password)

The remote file system is now mounted at /Volumes/mount_name and one can access files via Mac OS applications and/or the Finder.

Unmount

Close any open files and cd out of the mount_name directory before executing the following command to unmount the remote file system:

$ umount /Volumes/mount_name

Conclusion

sshfs is a lightweight solution to efficiently mount a remote file system for local access.

Reference(s)

SSH Filesystem

[4-20ma]

How to setup a new Mac

The following post describes basic components of the bootstrapping process I use to setup a new Mac.

Install the latest version of Xcode (available from the Mac App Store and Apple Developer).

Install Homebrew:

$ ruby -e "$(curl -fsSL https://raw.github.com/Homebrew/homebrew/go/install)"

Install Xcode tools; click Install when presented with the dialog:

$ xcode-select --install

Install rbenv:

$ brew install rbenv

Install libdvdcss:

$ brew install libdvdcss

Install iPhoto Library Manager (available from Fat Cat Software). Use a local Ethernet cable and iPhoto Library Manager to transfer photos to new machine.

Install any required apps via the Mac App Store.

Transfer any required files via Mac's built-in filesharing.

[4-20ma]

How to remove a submodule within git

This is an excellent article describing how to remove a submodule within git.

Short version below (in case original disappears):

Delete the relevant section from the .gitmodules file. The section would look similar to:

[submodule "vendor"] path = vendor url = git://github.com/some-user/some-repo.git

Stage the .gitmodules changes via command line using: git add .gitmodules

Delete the relevant section from .git/config, which will look like:

[submodule "vendor"] url = git://github.com/some-user/some-repo.git

Run git rm --cached path/to/submodule. Don't include a trailing slash -- that will lead to an error.

Run rm -rf .git/modules/submodule_name

Commit the change:

Delete the now untracked submodule files rm -rf path/to/submodule

[4-20ma]

How to package a jQuery plugin as a gem for Rails 3.1 asset pipeline

Follow the instructions to Gemify Assets for Rails. Refer to RailsCast #245 for more information on packaging a gem.

[4-20ma]

How to add Github Pages to a project

I occasionally need to add Github Pages (gh-pages) to a project. These instructions are based on a Github help [article](https://help.github.com/articles/creating-project-pages-manually) and have been customized for my use. Create orphan `gh-pages` branch in `doc/html` directory:

$ cd doc/html $ git init $ git remote add origin `git config --file ../../.git/config remote.origin.url` $ git checkout --orphan gh-pages $ git rm -rf .

Create initial commit:

$ touch index.html $ git add . $ git commit -m 'Initial commit'

Configure `gh-pages` branch:

$ git config branch.gh-pages.remote origin # optional $ git config branch.gh-pages.merge refs/heads/gh-pages # optional $ git push origin gh-pages

[4-20ma]

Arduino library for Texas Instruments PCF8575C 16-bit I2C I/O expander

[I2cDiscreteIoExpander](https://github.com/4-20ma/I2cDiscreteIoExpander) is an Arduino library for the Texas Instruments PCF8575C 16-bit I2C I/O expander. The PCF8575C provides general-purpose remote I/O expansion for most microcontroller families via the I2C interface serial clock (SCL) and serial data (SDA). The device features a 16-bit quasi-bidirectional input/output (I/O) port (P07..P00, P17..P10), including latched outputs with high-current drive capability for directly driving LEDs. Each quasi-bidirectional I/O can be used as an input or output without the use of a data-direction control signal. At power on, the I/Os are in 3-state mode. The strong pullup to VCC allows fast-rising edges into heavily loaded outputs. This device turns on when an output is written high and is switched off by the negative edge of SCL. The I/Os should be high before being used as inputs. After power on, as all the I/Os are set to 3-state, all of them can be used as inputs. Any change in setting of the I/Os as either inputs or outputs can be done with the write mode. If a high is applied externally to an I/O that has been written earlier to low, a large current (IOL) flows to GND. The fixed I2C address of the PCF8575C is the same as the PCF8575, PCF8574, PCA9535, and PCA9555, allowing up to eight of these devices, in any combination, to share the same I2C bus or SMBus. Full [source code documentation](http://4-20ma.github.com/I2cDiscreteIoExpander/) is available.

[4-20ma]

Arduino library for Texas Instruments ADS7828 12-bit, 8-channel I2C A/D converter

i2c_adc_ads7828 has a new home on github.com.

[4-20ma]

Arduino library for communicating with Modbus slaves over RS232/485 (via RTU protocol)

[ModbusMaster](https://github.com/4-20ma/ModbusMaster.git) has a new home on github.com.

[4-20ma]

How to embed a gist in tumblr

This simple gist describes how to embed a github gist in tumblr:

https://gist.github.com/1395926

[4-20ma]

[Solved] Error installing ruby-2.0.0-preview2 on OS X Mountain Lion (10.8.2) + RVM (1.17.6)

Attempt to install 2.0.0-preview2 via rvm:

https://gist.github.com/4388292

Note the error running 'make' (line 11, above). Inspect contents of `/Users/doc/.rvm/log/ruby-2.0.0-preview2/make.log`:

https://gist.github.com/4388316

Found solution to similar [problem](http://www.ruby-forum.com/topic/4407418):

https://gist.github.com/4388317

It seems to compile/install OK; test 2.0.0 via IRB:

https://gist.github.com/4388327

Interestingly, when I remove and reinstall 2.0.0-preview2, it works without setting `CONFIGURE_OPTS`:

https://gist.github.com/4388323