Previously we talked about the Differences Between RVM, Rbenv and RubyInstaller and also I wrote a post about Creating a Linux Virtual Machine in AWS. For this post we’ll have to use these entries as the necessary context to install Ruby on a Linux environment using RVM. So, I’ll assume on this post that you have:

Because we’re using a virtual environment for this post, and we’re giving continuity to this post: Creating a Linux Virtual Machine in AWS we have to first access to this machine using our terminar and SSH:

$ ssh -p 22 -i ~/.ssh/ubuntu-webserver-rails.pem [email protected]  

Note: here is where we finished in the post mentioned

This step helps us to up update linux and create the environment

$ sudo apt-get update

apt-get update downloads the package lists from the repositories and "updates" them to get information on the newest versions of packages and their dependencies. It will do this for all repositories and PPAs. From http://linux.die.net/man/8/apt-get

$ sudo apt-get install -y curl gnupg build-essential

The build-essentials packages are meta-packages that are necessary for compiling software. They include the GNU debugger, g++/GNU compiler collection, and some more tools and libraries that are required to compile a program. For example, if you need to work on a C/C++ compiler, you need to install essential meta-packages on your system before starting the C compiler installation. When installing the build-essential packages, some other packages such as G++, dpkg-dev, GCC and make, etc. also install on your system.

As a next step install GPG keys used to verify installation package:

$ sudo gpg --keyserver keyserver.ubuntu.com --recv-key 409B6B1796C275462A1703113804BB82D39DC0E3 7D2BAF1CF37B13E2069D6956105BD0E739499BDB

GPG is the Gnu Privacy Guard and it is an implementation of OpenPGP (Open Pretty Good Privacy). It is an encryption technique that was originally developed for use in e-mail exchanges that is now used in a number of different applications such as code signing for Linux code repositories and source code repositories like github. 

OpenPGP is a hybrid of the two-key cryptography approach where the message to be exchanged (called plaintext) is first compressed and then a session key is created as a one-time use secret key. The compressed plaintext is then encrypted with the session key. The session key is then encrypted with the destination’s public key and bundled with the encrypted message (called ciphertext). The destination can decrypt the session key with their private key then decompress it to recover the original plaintext.

There are several different ways to create a GPG key. The easiest is with the “gpg” or “gpg2” commands available on many major operating systems. Many commercial encryption programs also include a way to generate a GPG key. You can then store the public version on a public key server so folks can start sending you encrypted files/message traffic. Only you will be able to decrypt it because only you have the associated private key.

Step #4- Install RVM

Curl is used for transferring data using various network protocols. The name stands for "Client URL”. Using this tool we can access to the RVM webpage to get the last and stable version of RVM

$ curl -sSL https://get.rvm.io | sudo bash -s stable

Then we can add the current/root user to a group with the command

$ sudo usermod -a -G rvm `whoami`

whoami It is a concatenation of the words "Who am I?" and prints the effective username of the current user when invoked. More info here: https://en.wikipedia.org/wiki/Whoami

$ if sudo grep -q secure_path /etc/sudoers; then sudo sh -c "echo export rvmsudo_secure_path=1 >> /etc/profile.d/rvm_secure_path.sh" && echo Environment variable installed; fi

This last command seems a little bit cryptic than the other ones, so I’ll try to explain it: In Linux and other Unix-like operating systems, only the root user can run all commands and perform certain critical operations on the system such as install and update, remove packages, create users and groups, modify important system configuration files and so on.

However, a system administrator who assumes the role of the root user can permit other normal system users with the help of sudo command and a few configurations to run some commands as well as carry out a number of vital system operations including the ones mentioned above.

Alternatively, the system administrator can share the root user password (which is not a recommended method) so that normal system users have access to the root user account via su command.

sudo allows a permitted user to execute a command as root (or another user), as specified by the security policy:

Below are ten /etc/sudoers file configurations to modify the behavior of sudo command using Defaults entries.

$ sudo cat /etc/sudoers

#

# This file MUST be edited with the 'visudo' command as root.

#

# Please consider adding local content in /etc/sudoers.d/ instead of

# directly modifying this file.

#

# See the man page for details on how to write a sudoers file.

#

Defaults env_reset

Defaults mail_badpass

Defaults secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin"

# Host alias specification

# User alias specification

# Cmnd alias specification

# User privilege specification

root ALL=(ALL:ALL) ALL

# Members of the admin group may gain root privileges

%admin ALL=(ALL) ALL

# Allow members of group sudo to execute any command

%sudo ALL=(ALL:ALL) ALL

# See sudoers(5) for more information on "#include" directives:

#includedir /etc/sudoers.d

We can now see that we have a secure path to execute RVM. It’s mandatory now to exit the system and with that we can have the environment ready to install Ruby

$ exit

And then, we enter again

$ ssh -p 22 -i ~/.ssh/ubuntu-webserver-rails.pem [email protected]  

Step #5- Install Ruby

Now we can use the command rvm

$ rvm install ruby-2.6.8

You can replace the version number for whatever you want or need. After a while, we can check the installation of ruby with the next commands

$ rvm list

$ ruby -v

$ irb

“rvm list” command will list all the ruby versions that we have in the machine. Now we’ve just the version 2.6.8. Irb will enter you to the Interactive Ruby Console

Let’s install other 2 versions of Ruby to see the behavior of RVM

Step #6- Install other Ruby Versions and Change versions

On the very same machine, let’s install other 2 versions of Ruby

$ rvm install ruby-2.7.0

$ rvm install ruby-3.0.3

As you can see, we’ve installed other 2 versions of ruby 2.7.0 and 3.0.3. The question now is how to deal with these versions according to the project you’re working on?

Let’s execute a couple of other commands

$ rvm list

 * ruby-2.6.8 [ x86_64 ]

   ruby-2.7.0 [ x86_64 ]

=> ruby-3.0.3 [ x86_64 ]

# => - current

# =* - current && default

#  * - default

When we execute rvm list we can see at the final of the output these symbols:

# => - current

# =* - current && default

#  * - default

In our current state we have the default ruby version in * ruby-2.6.8 [ x86_64 ] (the first that we’ve been installed) and the current version in => ruby-3.0.3 [ x86_64 ] (the last we’ve been installed)

Now what happens if we run

$ ruby -v

The output will be something like this: 

ruby 3.0.3p157 (2021-11-24 revision 3fb7d2cadc) [x86_64-linux]

That means that any project we create now, it will be created with the current version. The default version is loaded just when we restart the machine. Let’s say now that we want to create a project with the last version that we have in the machine and at the same time we want this version as the default version. We have to do this:

$ rvm --default use ruby-3.0.3

Using /usr/local/rvm/gems/ruby-3.0.3

Now let’s check the list again

$ rvm list

   ruby-2.6.8 [ x86_64 ]

   ruby-2.7.0 [ x86_64 ]

=* ruby-3.0.3 [ x86_64 ]

# => - current

# =* - current && default

#  * - default

Do you see something different? Yes, we have now =* ruby-3.0.3 [ x86_64 ] as current && default

As you can see is quite easy to jump between Ruby versions, you just have to take care about the current and the default version

Step #7- Other RVM commands

To change just the current version (not the default version)

$ rvm use 2.7.0

Others

$ rvm list known

$ rvm version

$ rvm current

$ rvm list rails