sudo dd if=/dev/sda of=/dev/sdb will create an exact replica of
sdb as long as
sdb is at least as big as
Plugin your hard disk to your system, make sure the BIOS is recognizing it correctly and boot normally to your system.
Check your hard disks with
Disk Utility(To launch
Disk Utility, you can use the dash),
make sure that your old hard disk is
sda and your new hard disk is
sdb (change the devices on the example command to reflect your hardware configuration), no need to mount the new disk (it should be empty anyways so there is nothing to mount).
Run the command with the right devices in a terminal wait until its finished and that's it.
PS: triple check the command and make sure that your old hard disk is in the
if part and that your new disk is in the
of part of the command.
Your partitions will be copied from your old disk to the new one byte by byte so no need to worry about reconfiguring / installing MBR and bootloader. The only thing you need to do after the disk is copied is to remove the old disk from the system or set the new disk as boot device in your BIOS.
Later on when you tested that all is ok you can resize your partitions on the new disk with
gparted, boot from a LiveCD, install
gparted and resize the partitions of your new disk to fit your needs.
This solution requires no installation of extra tools except for the installation of
gparted later on for resizing the partitions.