how to copy file on external hard drive?

Simply drag the file from one drive and drop it onto the other. This can also be done from a folder on one drive to a folder on the other drive.

You can also select a file or files to copy then press COMMAND-C to copy. Now move to the location on the other drive where you want the file or files to be and press COMMAND-V to paste them.

If you are talking about backing up one drive to another then see the following:

Basic Backup

For some people Time Machine will be more than adequate. Time Machine is part of OS X. There are two components:

1. A Time Machine preferences panel as part of System Preferences;

2. A Time Machine application located in the Applications folder. It is

used to manage backups and to restore backups. Time Machine

requires a backup drive that is at least twice the capacity of the

drive being backed up.

Alternatively, get an external drive at least equal in size to the internal hard drive and make (and maintain) a bootable clone/backup. You can make a bootable clone using the Restore option of Disk Utility. You can also make and maintain clones with good backup software. My personal recommendations are (order is not significant):

1. Carbon Copy Cloner

2. Data Backup

3. Deja Vu

4. SuperDuper!

5. Synk Pro

6. Tri-Backup

Visit The XLab FAQs and read the FAQ on backup and restore. Also read How to Back Up and Restore Your Files. For help with using Time Machine visit Pondini's Time Machine FAQ for help with all things Time Machine.

Although you can buy a complete external drive system, you can also put one together if you are so inclined. It's relatively easy and only requires a Phillips head screwdriver (typically.) You can purchase hard drives separately. This gives you an opportunity to shop for the best prices on a hard drive of your choice. Reliable brands include Seagate, Hitachi, Western Digital, Toshiba, and Fujitsu. You can find reviews and benchmarks on many drives at Storage Review.

Enclosures for FireWire and USB are readily available. You can find only FireWire enclosures, only USB enclosures, and enclosures that feature multiple ports. I would stress getting enclosures that use the Oxford chipsets especially for Firewire drives (911, 921, 922, for example.) You can find enclosures at places such as;

1. Cool Drives

2. OWC

3. WiebeTech

4. Firewire Direct

5. California Drives

6. NewEgg

All you need do is remove a case cover, mount the hard drive in the enclosure and connect the cables, then re-attach the case cover. Usually the only tool required is a small or medium Phillips screwdriver.

Is the external drive formatted so that you may 'write' to it? If not, open Disk Utility>Erase and format the drive to 'Mac OS Extended (Journaled)'. Note that when you format a drive, all data on that drive will be erased.

Ciao.