After installing GRUB, Ubuntu will request a reboot to complete its installation running from the hard drive. On both of my systems, the reboot produced the ominous message “Missing operating system.” This message is the result of Ubuntu having set its own partition as the active partition. The Windows bootloader, which is still installed in the master boot record, cannot boot Windows because the Windows partition is not flagged as active; the Windows bootloader also has no knowledge of the Ubuntu operating system, so that cannot boot either.
RPM Package Manager (originally Red Hat Package Manager, abbreviated RPM) is a package management system. The name RPM refers to two things: a software package file format, and a free software tool which installs, updates, uninstalls, verifies and queries software packaged in this format.
MySQL vs. PostgreSQL