Useful commands

Using GPG to share secrets

# Install GPG (sender and Recipient) 
sudo apt install gnupg 
 
# Generate key (Recipient) 
gpg --full-generate-key 
 
# Export public Key (Recipient) 
gpg --armor --export your.email@example.com > public-key.asc 

# Import the public key (sender) 
gpg --import public-key.asc 

# Encrypt the secret (sender) 
echo "your-secret-password" > password.txt 
gpg --armor --encrypt --recipient Recipient@example.com password.txt 

# Decrypt the secret (Recipient) 
gpg --decrypt password.txt.asc

OpenSSL commands to create certificates

# Create CA certificate and key
openssl req -new -x509 -days 3650 -extensions v3_ca -keyout private/cakey.pem -out cacert.pem

# Create Certificate Signing Request
$ openssl req -new -nodes -out example.com.csr -keyout private/example.com.key

# Create extension file
cat > example.com.ext << EOF
authorityKeyIdentifier=keyid,issuer
basicConstraints=CA:FALSE
keyUsage = digitalSignature, nonRepudiation, keyEncipherment, dataEncipherment
subjectAltName = @alt_names

[alt_names]
DNS.1 = example.com
EOF

# Sign CSR file using CA key/certificate
openssl x509 -req -in example.com.csr \
-CA cacert.pem -CAkey private/cakey.pem \
-CAcreateserial -out example.com.crt \
-days 500 -sha256 -extfile example.com.ext

Open SSL Convert

openssl x509 -inform DER -in ssl_certificate.cer -out ssl_certificate.cr
openssl pkcs12 -export -out my-cert-and-key.pfx -inkey key.pem -in cert.pem --passin pass:changeit --passout pass:changeit -name "alias to be set in here"
openssl pkcs7 -inform der -in a.p7b -out a.cer
openssl pkcs7 -inform der -in a.p7b -print_certs -out a.pem

openssl x509 -inform der -in cert.crt -out cert.pem

# convert Windows CRL to PEM
openssl crl -in your_current.crl -inform DER -out crl.pem
# view text content
openssl crl -in crl.pem  -noout -text

GNome swithc to windows on the same workspace only

gsettings set org.gnome.shell.app-switcher current-workspace-only true

Update java CACerts

keytool -import -noprompt -cacerts -storepass changeit -alias alias-for-self-generated-ca-cert -file /path/to/ca.der.or.cer.file

Install packages on Debian using not-very-well-mirrored repository

apt --allow-unauthenticated --allow-insecure-repositories update 
apt install -y --allow-unauthenticated

Configure PIP for private CA and mirrored Pypi

pip3 config set global.cert my-ca-chain.pem 
pip3 config set global.index-url https://my-mirrored-repository/simple 
pip3 config set global.timeout 90