Ruby RVM apt-get update error

RVM doesn't behave well if apt-get update has errors. If your apt sources have an invalid repository that gives 404 or GPG error, RVM will refuse to work. This can be confusing because it happens even if the faulty repository has nothing to do with ruby or RVM.

The following fix worked for me (Ubuntu):

Run apt-get update and see if there are any errors. Edit your sources.list and precise.list in /etc/apt to remove the faulty repositories. Repeat until apt-get update succeeds without any errors. Then try running RVM.

I also had to remove failing repositories but I had hard time spotting them and removing them based on instructions here. So I found this link which explains exactly why this happens and how to remove failing repositories:

In short, run following to find failing repositories:

sudo apt-get update | grep "Failed"

An example output can be like this:

:~# apt-get update  | grep "Failed"
W: Failed to fetch http://ppa.launchpad.net/upubuntu-com/web/ubuntu/dists/trusty/main/binary-amd64/Packages  404  Not Found

W: Failed to fetch http://ppa.launchpad.net/upubuntu-com/web/ubuntu/dists/trusty/main/binary-i386/Packages  404  Not Found

E: Some index files failed to download. They have been ignored, or old ones used instead.

And finally use this command to remove the failing repo(s):

sudo add-apt-repository --remove ppa:{failing ppa}

for the example here it will look like this:

sudo add-apt-repository --remove ppa:upubuntu-com/web

You can try to skip the rvm updating system so apt-get won't be called.

# Disable RVM from trying to install necessary software via apt-get
rvm autolibs disable

# Then try installing Ruby:
rvm install 2.4.0

See https://stackoverflow.com/a/16759839/1212791