Ruby-on-rails – warning: Insecure world writable dir when I run a ruby or gem command

On Debian (or Ubuntu) systems, just install libmysqlclient-dev package using:

sudo apt-get install libmysqlclient-dev

and then:

gem install mysql

It will be installed without any error.

You will need to have root access to do this. If you aren't already the administrative user, login as the administrator. Then use 'sudo' to change the permissions:

sudo chmod go-w /usr/local/bin

Obviously, that will mean you can no longer install material in /usr/local/bin except via 'sudo', but you probably shouldn't be doing that anyway.