Tips & Tricks

Linux command lines

# Get external ip
curl -s icanhazip.com

# Get private ip
hostname -I

# Get hostname
hostname

# To list all services, regardless of their state:
systemctl list-units --type=service --all

Open SSL

Make sure you have OpenSSL installed on your system. You can check by running:

openssl version

Generate a Private Key

Run the following command to generate a private key:

openssl genpkey -algorithm RSA -out private_key.pem -pkeyopt rsa_keygen_bits:2048

This command creates a 2048-bit RSA private key and saves it to private_key.pem.

Create a Certificate Signing Request (CSR)

openssl req -new -key private_key.pem -out request.csr

You will be prompted to enter information such as your country, state, organization name, etc.

Generate a Self-Signed Certificate

openssl x509 -req -days 365 -in request.csr -signkey private_key.pem -out certificate.crt

This command creates a self-signed certificate valid for 365 days and saves it to certificate.crt.

Summary of Files Created private_key.pem: Your private key. request.csr: Your Certificate Signing Request. certificate.crt: Your self-signed certificate.

Verify the Certificate

You can verify the contents of your certificate with:

openssl x509 -in certificate.crt -text -noout

Convert CRT to DER

If your .crt file is in PEM format and you want to convert it to DER format, you can use the following command:

openssl x509 -in certificate.crt -outform der -out certificate.der