Using the dd command in Linux

Usage and code examples of the dd command in Linux

1. Command introduction
The dd command is a powerful disk copy command in the Linux system. It can copy an input file to an output file and copy it according to the Format conversion is required. It can be used to create image files, backup and restore disk data, clone disk partitions, etc. The dd command is very powerful, but it is also very dangerous because it can directly read and write disk operations without confirmation, so you should be very careful when using it.

2. Common usage and code examples

1. Copy disk partition
   The following is an example of copying one disk partition to another disk partition. Assume that /dev/sda1 is the source partition and /dev/sdb1 is the target partition.

   dd if=/dev/sda1 of=/dev/sdb1 bs=4M conv=notrunc,noerror

   Explanation:

2. if: input file, that is, the source partition
3. of: output file, that is, the target partition
4. bs: block size , used to specify the block size of read and write operations, here set to 4M

5. conv: used to specify format conversion options, here use notrunc and noerror

   • notrunc: no Truncate the output file; that is, if the output file is shorter than the input file, the output file will not be truncated, but will be written directly to the end of the file
   • noerror: Do not stop the operation when an error occurs and continue execution

6. Create a blank image file
   The following is an example of creating a blank image file. Create a blank image file with a size of 1GB as image.img.

   dd if=/dev/zero of=image.img bs=1M count=1024

   Explanation:

7. if: Input file, that is, /dev/zero. In Linux, /dev/zero is a special device file. When reading, it will return a string of characters all 0
8. of: output file, that is, image.img
9. bs: block Size, used to specify the block size for read and write operations, here set to 1M
10. count: The number of blocks to copy, here set to 1024, that is, copy 1GB of data

11. Create a disc Image file
    The following is an example of copying the contents of a CD to an image file. Assuming that the CD device is /dev/sr0, copy the CD content to isoimage.iso.

    dd if=/dev/sr0 of=isoimage.iso bs=2048

    Explanation:

12. if: input file, i.e. CD device/dev/sr0
13. of: output file, i.e. isoimage.iso
14. bs: block size, used to specify the block size for read and write operations, here set to 2048

15. Restore image files to disk partitions
    The following is a method to restore image files to a disk partition Example. Assume that the image file is image.img, restore to the target partition /dev/sdc1.

    dd if=image.img of=/dev/sdc1 bs=4M conv=notrunc,noerror

    Explanation:

16. if: input file, that is, the image file image.img
17. of: output file, that is, the target partition /dev/sdc1
18. bs: block size, used to specify the block size for read and write operations, here set to 4M
19. conv: used to specify format conversion options, here use notrunc and noerror

The above are some common usages and code examples of the dd command. In actual use, parameters need to be adjusted according to specific needs. At the same time, because the operation of the dd command is dangerous, please use it with caution, ensure that the operation object is correct and back up important data to prevent data loss.

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