Boot

https://help.ubuntu.com/community/UbuntuBootupHowto

Restore grub:
01. Boot the system using live cd
02. Mount the /boot partion of the hard drive as /mnt

  sudo mount /dev/sda1 /mnt

03. Install grub on the system

  sudo grub-install --root-directory=/mnt/ /dev/sdX  

04. Reboot the system

Controlling Services
All the startup scripts are in /etc/init.d/ directory

To add a service (services must be in /etc/init.d folder

  update-rc.d <nameoftheservice> defaults

To remove it

  update-rc.d <nameoftheservice> remove