How do I fix the "You don't have write permissions into the /usr/bin directory" error when installing Rails?

I'm trying to install Rails 3 on a brand new MacBook Pro running OS X 10.6.3, Ruby 1.8.7, and Rails 2.3.5 and I'm wondering if I've hosed myself. So far, I've run these commands:

$ gem update --system
$ gem install arel tzinfo builder memcache-client rack rack-test rack-mount erubis mail text-format thor bundler i18n
$ gem install rails --pre

However, when I run the last command, I get this error:

ERROR:  While executing gem ... (Gem::FilePermissionError)
    You don't have write permissions into the /usr/bin directory.

I think it wants me to run the command with sudo so that it can write over /usr/bin/rails. But if I do that, won't I be overwriting my Rails 2.3.5 executable? I don't want to do that. Instead, I'd like to keep both versions of Rails. How do I do that?

use -n parameter to install like for cocoapods:

sudo gem install cocoapods -n /usr/local/bin

Using the -n /usr/local/bin flag does work, BUT I had to come back to this page every time I wanted to update a package again. So I figured out a permanent fix for this.

For those interested in fixing this permanently:

Create a ~/.gemrc file

vim .gemrc

With the following content:

:gemdir:
   - ~/.gem/ruby
install: -n /usr/local/bin

Now you can run your command normally without the -n flag.

Enjoy!

sudo gem install cocoapods --pre -n /usr/local/bin

This works for me.

You can use sudo gem install -n /usr/local/bin cocoapods

This works for me.

I'd suggest using RVM it allows you have multiple versions of Ruby/Rails installed with gem profiles and basically keep all your gems contained from one another. You may want to check out a similar post How can I install Ruby on Rails 3 on OSX

To fix your specific error you need to run that command as sudo, ie:

sudo gem install rails --pre

This Error hit me after installing RVM correctly. Solution: re-boot Terminal.

Reference RailsCast's RVM Install tutorial.

On macOS High Sierra, this solved my issue:

sudo gem update --system -n /usr/local/bin/gem

Problem: Performing some operations such as bundle installation / npm install on docker container prompts a lack of permissions error and preventing us accomplish applicative tasks. By default docker containers are "unprivileged" and not allow to accomplish out of scope administrator capabilities.

ERROR:  While executing gem ... (Gem::FilePermissionError)
    You don't have write permissions for the /usr/local/bundle directory.

Solution: Use --previliged flag to enable all devices and allow the container nearly all the same access to the host as processes running outside containers on the host. Pay attention this might be a security issue under some circumstances and recommended only on test/staging/development environments.

> By default, Docker containers are “unprivileged” and cannot, for example, run a Docker daemon inside a Docker container. This is because by default a container is not allowed to access any devices, but a “privileged” container is given access to all devices (see the documentation on cgroups devices). > > When the operator executes docker run --privileged, Docker will enable > access to all devices on the host as well as set some configuration in > AppArmor or SELinux to allow the container nearly all the same access > to the host as processes running outside containers on the host. > Additional information about running with --privileged is available on > the Docker Blog.

For additional reading about Runtime privilege and Linux capabilities read this Documentation.

For me, something different worked, that I found in on this answer from a similar question. Probably won't help OP, but maybe someone like me that had a similar problem.

You should indeed use rvm, but as no one explained to you how to do this without rvm, here you go:

sudo gem install tzinfo builder memcache-client rack rack-test rack-mount \
  abstract erubis activesupport mime-types mail text-hyphen text-format   \
  thor i18n rake bundler arel railties rails --prerelease --force