What is "cloning a hard drive" and how does one go about doing it?

What does cloning a hard drive mean? Is it just simply copying over all the "CONTENT" of the hard drive EXCLUDING the operating system, drivers, all the installed programs? or is it copying the ENTIRE hard drive BIT for BIT? Is the cloned hard drive bootable?

I have an external USB hard drive and trying to make a exact copy of my computer system by cloning, so that I can connect the cloned hard drive to another machine and boot into it, or install the cloned disk on another computer system and boot into it. Is this possible? Or am I going about this totally wrong?

What is ghosting a hard drive?

Cloning a hard drive means to make a duplicate copy of the original source data. This duplicate copy can be either bit for bit which will duplicate EVERYTHING on the disk. Another option is to clone individual partitions, this can be useful if you only want to copy specific data such as an OS or data partition.

If I make a clone of my computer's hard disk it will be an exact duplicate (of the data that is included. To clone a hard disk you need special software.

Some examples of cloning software:

• Clonezilla, a Linux based cloning utility
• Acronis True Image
• Norton Ghost

Once a drive is cloned you can use it as a bootable device (assuming you copied the bootloader data).

By the sound of it what you are trying to do is not a clone but instead what is called a sync. You want to have data reside on one computer. Then using a portable medium you want to take data to another computer for use. Yet you want both locations to remain identical.

Does that sound accurate?

Cloning a hard drive is the process of making an effective copy of the hard drive on another one. It doesn't necessarily mean that both drives are identical bit for bit, although that's an option.

Most of the time cloning means that the target drive is partitioned in a similar fashion, partitions are formatted with identical file systems and all data is copied over to analogous partitions on the target drive. Extra information that's not stored in files, such as MBR, VBRs, data hidden in partition tables are usually cloned too. (This data would be omitted in regular file system-level copy and target drive wouldn't be bootable.)

Making a bit for bit copy would count as cloning, but it's the slowest and least flexible way of doing that. It works only if target drive isn't smaller (any space surplus is wasted) and some gibberish is copied too (removed files, unused space etc.). This may be desired though, eg. when making a safe copy during recovery of a failed hard drive or in forensics.

The usually preferred way of cloning is to replicate source partitioning and copy files with consideration of file systems. If the cloning program understands how file system stores files, it can recreate a new one (possibly on a partition of different size) and copy only meaningful data. Even if both partitions have identical size, this process will most of the time result in partitions that aren't bit for bit identical, but contain exactly the same data nonetheless.

Booting a properly cloned hard drive in the same PC is possible. Using it in another machine is a different story. OS may be already configured for specific hardware configuration of original machine and may fail to boot. Linuxes don't have much problems booting after transplantation most of the time. Modern versions of Windows are quite good at this and will usually boot if hard disk controllers in both machines are similar and work in identical modes (ie. IDE/AHCI/RAID). Keep in mind that some software licenses don't allow transplantation or tie software to one specific machine - for example OEM versions of Windows do this.

Ghosting is probably just another term for cloning, I suppose it refers to Norton Ghost which was a de facto standard for disk cloning some 15-ish years ago.

What is cloning a disk?

Cloning a disk originally meant copying the contents of a disk at sector level, bit by bit, to an identical disk. At sector level, everything including partitioning, boot sectors, file systems, files, metadata and even deleted files gets copied. Cloning was used for mass-producing identical computers, mass-deploying identical configurations to identical computers, or for forensics.

Nowadays, however, people expect a cloning app to do more, e.g. clone to a dissimilar disk, clone to a virtual hard disk, defragment the disk upon cloning, speed up cloning by not bothering with free areas of the disk, or even prepare the clone for use on dissimilar hardware.

What happens if I transfer the clone to another system?

The same thing that happens if you transfer the original to another system.

Unless the other system is identical to the original, you can expect dissimilar hardware components to require new device drivers before they work. Also, some commercial closed-source computer programs might detect this new change and require additional licensing steps in order to work, as an anti-piracy measures. Windows comes with a sysprep utility that solves this problem for Windows only.

What is ghosting?

It is another name for cloning, derived from an app named Ghost, developed in 1995 by Murray Haszard. It is now discontinued; don't bother with it.