I created this SSL cert on Ubuntu to allow testing on F5 LTM

sudo apt-get install openssl

run the first two commands one by one as openssl will prompt for a passphrase.

openssl genrsa -des3 -out server.key 2048

openssl rsa -in server.key -out server.key

Replace 'localhost' with whatever domain you require.

openssl req -sha256 -new -key server.key -out server.csr -subj '/CN=testcert'

openssl x509 -req -days 365 -in server.csr -signkey server.key -out server.crt

To combine the two into a .pem file:

cat server.crt server.key > cert.pem