To view the details of a certificate:
openssl x509 -in <certificate.cer> -text
To view the details of cacerts file:
keytool -list -keystore <cacerts>
To view the details of a specific certificate included in a cacerts file:
keytool -list -v -keystore <cacerts> -alias "<alias>"
To export, in a der format, a certificate from a cacerts file:
keytool -export -keystore <cacerts> -alias "<alias>" -file <certificate.der>
To convert a certificate from a der format into a pem format:
openssl x509 -inform der -in <certificate.der> -out <certificate.cer>
To generate a concatenate certificate chain:
cat certificate.cer intermediate.cer root.cer >combiner.cer