Linux Copy One Hard Disk to Another Using dd Command

Posted on in Categories , , , , , , , , , , , , , last updated February 5, 2008

Q. How can I copy one hard disk to another using dd command?

A. dd command can copy disk in raw format. It will copy partition table and bootloader and all partitions within this disk. For example, you can copy /dev/sda to /dev/sdb (same size) using the following dd command. dd should complete with no errors, but output the number of records read and written.

Login as the root user (use sudo or su command)

WARNING! These examples may result into data loss, ensure there are good backups before doing this, as using dd wrong way can be dangerous.

Open terminal or shell prompt and type the following dd command:
# dd if=/dev/sda of=/dev/sdb

  • if=/dev/sda : Input disk (source)
  • of=/dev/sdb : Output disk (destination)

You can also copy hard disk or partition image to another system using a network and netcat (nc) command.

OpenBSD set up default boot time by modifying boot.conf file

Posted on in Categories last updated September 19, 2007

Q. I’m using OpenBSD as VPS os (guest os) under VMWARE server. However OpenBSD pauses for a few seconds to give me a chance to provide parameters to the kernel at boot> prompt. I’d like to force boot loader to wait for 30 seconds instead of default timeout. How do I setup bootloader timeout?

A. OpenBSD uses boot program. The main purpose of this program is to load the system kernel while dealing with the downfalls of the PC BIOS architecture. This program acts as an enhanced boot monitor for PC systems, pro viding a common interface for the kernel to start from. By default, boot attempts to load the kernel executable /bsd. If it fails to find the kernel and no alternative kernel image has been specified, the system will be unable to boot.

/etc/boot.conf file and timeout parameter

/etc/boot.conf is configuration file for bootloader. Open file using text editor:
$ sudo vi /etc/boot.conf
Append / modify timeout parameter as follows:
set timeout 30
Save and close the file. Above line set the 30 second pause at boot-time.