If you're about to handle X509 certificates and don't want to remember/google a handful of openssl commands you can use the graphical tool XCAShow archive.org snapshot.
Setup
Install XCA sudo apt install xca
Create a new database with a strong master password
Features
Create CSR
Verify SSL private key matches SSL certificate
enable Key name column
import certificate and private key
Import, export and convert PKCS#12, PKCS#7, PEM chain, DER and more
Check issuer chain
import certificate, intermediate and root ca
they get automatically chained
View certificates and export openssl config
Check revocation lists
Setup a private PKI
A lot more...
Rails Long Term Support
Rails LTS provides security patches for old versions of Ruby on Rails (2.3, 3.2, 4.2 and 5.2)
Prevents you from data breaches and liability risks