RVM and Parallella: What a Difference a Shell Makes

RVM is an effective way to manage Ruby versions on Linux or OS X. RVM was working well on my Ubuntu-based Parallella, until one day it stopped:

linaro-nano:~> rvm list
rvm: Command not found.
linaro-nano:~>

rvm: Command not found. Fortunately, Zach Briggs and I were pairing at a joint OpenHack - ChicagoRuby event when the problem occurred. Zach is an ideal pairing partner; troubleshooting was smooth because he was there. Time to investigate.

Explicit Path

After a few experiments, we discovered that we could run RVM by explicitly specifying the path to the executable:

linaro-nano:~> ~/.rvm/bin/rvm list

rvm rubies

   ruby-2.0.0-p481 [ armv7l ]

# Default ruby not set. Try 'rvm alias create default <ruby>'.

# => - current
# =* - current && default
#  * - default

linaro-nano:~>

Therefore, it appeared that the Ubuntu/Linux $PATH variable was being ignored. Google led us to consider the shell in use on the Parallella.

Which Shell Is In Use?

The shell is just a program that lets humans talk to the Linux operating system through a command line interface. Several shell programs exist. Linux users tend to prefer one shell or another. The $SHELL environmental variable points to the one in use.

linaro-nano:~> echo $SHELL
/bin/tcsh
linaro-nano:~>

Very interesting. tcsh was the current Parallella shell. I’m more accustomed to bash. Could RVM prefer bash too? We changed one line of /etc/passwd to tell the Parallella to start with bash instead of tcsh and rebooted the Parallella.

linaro-nano:~> echo $SHELL
/bin/bash
linaro-nano:~>

…and now RVM works normally.

linaro-nano:~> rvm list

rvm rubies

   ruby-2.0.0-p481 [ armv7l ]

# Default ruby not set. Try 'rvm alias create default <ruby>'.

# => - current
# =* - current && default
#  * - default

linaro-nano:~>

Consider Fish?

Right after this exercise, Zach and Josh Cheek had a Twitter conversation about a shell called fish. Something new and shiny to explore!

Original Plan: Rubinius

Did I mention that we originally planned to install Rubinius on the Parallella? Where there are goals, there are yaks waiting to be shaved!