sudo su -

でrootになる

curl -L get.rvm.io | bash -s stable

とするが、下記エラーが発生

GPG signature verification failed for '/usr/local/rvm/archives/rvm-1.26.11.tgz' - 'https://github.com/rvm/rvm/releases/download/1.26.11/1.26.11.tar.gz.asc'!
try downloading the signatures:

    gpg2 --keyserver hkp://keys.gnupg.net --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3

or if it fails:

    command curl -sSL https://rvm.io/mpapis.asc | gpg2 --import -

curl -sSL https://rvm.io/mpapis.asc | gpg2 --import -

2020-09-20以降では下記

    command curl -sSL https://rvm.io/mpapis.asc | gpg2 --import -
    command curl -sSL https://rvm.io/pkuczynski.asc | gpg2 --import -

を実行する

再度、

curl -L get.rvm.io | bash -s stable

で、インストール完了

完了時のログ

# curl -L get.rvm.io | bash -s stable
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   194  100   194    0     0    593      0 --:--:-- --:--:-- --:--:--   593
100 24535  100 24535    0     0  45267      0 --:--:-- --:--:-- --:--:-- 45267
Downloading https://github.com/rvm/rvm/archive/1.29.10.tar.gz
Downloading https://github.com/rvm/rvm/releases/download/1.29.10/1.29.10.tar.gz.asc
gpg: Signature made Wed 25 Mar 2020 09:58:42 PM UTC using RSA key ID 39499BDB
gpg: Good signature from "Piotr Kuczynski <piotr.kuczynski@gmail.com>"
gpg: WARNING: This key is not certified with a trusted signature!
gpg:          There is no indication that the signature belongs to the owner.
Primary key fingerprint: 7D2B AF1C F37B 13E2 069D  6956 105B D0E7 3949 9BDB
GPG verified '/usr/local/rvm/archives/rvm-1.29.10.tgz'
Creating group 'rvm'
Installing RVM to /usr/local/rvm/
Installation of RVM in /usr/local/rvm/ is almost complete:

  * First you need to add all users that will be using rvm to 'rvm' group,
    and logout - login again, anyone using rvm will be operating with `umask u=rwx,g=rwx,o=rx`.

  * To start using RVM you need to run `source /etc/profile.d/rvm.sh`
    in all your open shell windows, in rare cases you need to reopen all shell windows.
  * Please do NOT forget to add your users to the rvm group.
     The installer no longer auto-adds root or users to the rvm group. Admins must do this.
     Also, please note that group memberships are ONLY evaluated at login time.
     This means that users must log out then back in before group membership takes effect!
Thanks for installing RVM ?
Please consider donating to our open collective to help us maintain RVM.

?  Donate: https://opencollective.com/rvm/donate

exit

で、通常ユーザに変更

source /usr/local/rvm/scripts/rvm
rvm list known
rvm install 2.2.2
rvm use 2.2.2 --default

.bashrcまたは.bash_profileに下記を追記する

. /usr/local/rvm/scripts/rvm

・

rvm use 2.2.2 --default

も追記してもいい

Railsを使用しているなら、rootで

gem install rails