If you have installed an SSL certificate for your Apache web-server with a pass-phrase setup on the server key, then when you start or restart apache server, this dialog pops up asking you to enter the pass-phrase for the private key. The RSA/DSA private key inside your server.key file is stored in encrypted format for security reasons. The pass-phrase is needed to be able to read and parse this file. When you are sure that your server is secure enough you can remove the pass-phrase from the server.key by performing the following steps:
Make a backup of the encrypted key
cp server.key server.key.encrypted
Export the key
openssl rsa -in server.key.encrypted -out server.key
Enter the pass-phrase at the prompt
Enter pass phrase for server.key.encrypted:
writing RSA key
Update the permissions to be Read-only by root user
chmod 400 server.key
So now when you start/restart the Apache server, you should not be prompted to enter the pass-phrase for the server key as it is not encrypted anymore.