Q. Can you explain UUID concept related to Linux ext3 partitions and storage devices? How do I update /etc/fstab using UUID under Ubuntu Linux or any other Linux distro?
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)
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)
Q. My system comes with pre installed Linux and XP. Now I would like to delete a partition. How do I delete a partition?
A. Hard disks can be divided into one or more logical disks called partitions. This division is described in the partition table found in sector 0 of the disk.
You need to use fdisk command. It is a menu driven program for creation and manipulation of partition tables. However this program needs the device name (hard disk name) to manipulate partitions. Usually you use following names
=> /dev/hd[a-h] for IDE disks
=> /dev/sd[a-p] for SCSI disks
=> /dev/ed[a-d] for ESDI disks
=> /dev/xd[ab] for XT disks.
A device name refers to the entire hard disk. For more information see Linux partition naming convention and IDE drive mappings.
Before typing any one of the following command(s) make sure you have the backup of important data.
First, get a listing of your current partition scheme, type the following command:
# fdisk -l.
Disk /dev/hda: 20.0 GB, 20060651520 bytes 255 heads, 63 sectors/track, 2438 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/hda1 1 1024 8225248+ b W95 FAT32 /dev/hda2 * 1025 2438 11357955 c W95 FAT32 (LBA) Disk /dev/hdb: 80.0 GB, 80060424192 bytes 255 heads, 63 sectors/track, 9733 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/hdb1 * 1 2432 19535008+ 83 Linux /dev/hdb2 2433 2554 979965 82 Linux swap / Solaris /dev/hdb3 2555 6202 29302560 83 Linux /dev/hdb4 6203 9733 28362757+ 5 Extended /dev/hdb5 6203 9733 28362726 83 Linux
From above output I have two hard disks:
=> /dev/hda – 20 GB
=> /dev/hdb – 80 GB
Let us assume that you want to remove a partition from /dev/hdb disk. Type the following command:
# fdisk /dev/hdb
The number of cylinders for this disk is set to 9733. There is nothing wrong with that, but this is larger than 1024, and could in certain setups cause problems with: 1) software that runs at boot time (e.g., old versions of LILO) 2) booting and partitioning software from other OSs (e.g., DOS FDISK, OS/2 FDISK) Command (m for help):
Now type p command to list partition:
Command (m for help): p
Disk /dev/hdb: 80.0 GB, 80060424192 bytes 255 heads, 63 sectors/track, 9733 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/hdb1 * 1 2432 19535008+ 83 Linux /dev/hdb2 2433 2554 979965 82 Linux swap / Solaris /dev/hdb3 2555 6202 29302560 83 Linux /dev/hdb4 6203 9733 28362757+ 5 Extended /dev/hdb5 6203 9733 28362726 83 Linux
Now let us say you want to delete /dev/hdb3 (3rd partition). Type the d command to delete a partition:
Command (m for help): d
Partition number (1-4): 3
It will prompt you for the partition number. Type 3:
Verify that partition deleted:
Command (m for help): p
Now save the changes and exit to shell prompt. Type the w command:
Command (m for help): w
Reboot the system.