dd, a super powerful Linux command!

In Linux systems, the dd command is a highly respected tool with powerful and diverse functions, mainly used for file copying and conversion. Because it is widely used in disk copy and data copy operations, it is named the "disk copy" or "data copy" command. This article aims to comprehensively introduce the various uses of the dd command and provide rich sample code to help readers fully appreciate its functions and potential. ddThe flexibility and customizability of the command make it a powerful tool for processing data conversion between files and devices, showing strong application value in various scenarios.

Copy file

dd command can be used to copy files.

The following example copies a file to another location:

dd if=input.txt of=output.txt

This will copy the data from input.txt and write it to output.txt.

Backup and restore hard drive

dd command can be used to create a full backup of a hard drive and restore backup data to a new hard drive.

The following example demonstrates how to create a hard drive backup:

# Create hard disk backup
dd if=/dev/sda of=backup.img bs=4M

This will copy the contents of /dev/sda to a file named backup.img.

To restore the backup to a new hard drive, you can perform the following operations:

# Restore backup to new hard drive
dd if=backup.img of=/dev/sdb bs=4M

This will copy the data from backup.img and write it to the new hard drive /dev/sdb.

Random data generation

dd The command can also generate random data.

The following example generates a file containing random data:

dd if=/dev/urandom of=random_data.bin bs=1M count=10

This will generate a file called random_data.bin containing 10 megabytes of random data.

Adjust block size

The block size of the dd command can be adjusted to optimize copy performance by specifying the bs (block size) parameter.

The following example sets the block size to 1K:

dd if=input.txt of=output.txt bs=1K

Display progress information

To display progress information during the execution of the dd command, you can use the status=progress parameter.

For example:

dd if=input.txt of=output.txt bs=1M status=progress

This will display the progress information of the copy, including the number of bytes copied and the speed.

Skip and truncate data

dd command can be used to skip a portion of a file or truncate a file.

The following example will skip the first 1GB of the file:

dd if=input.txt of=output.txt bs=1G skip=1

This will copy the data from input.txt, skipping the first 1GB, and then write to output.txt.

Modify file size

dd The command can also be used to modify the file size. The following example truncates a file to a specific size:

dd if=/dev/null of=output.txt bs=1M seek=100

This will truncate output.txt to 100 megabytes, and if the file is originally larger, the excess data will be removed.

Copy and convert data format at the same time

dd The command can not only copy data, but also convert the data format while copying.

For example, you can convert the case of a file to uppercase:

dd if=input.txt of=output.txt conv=ucase

This will read data from input.txt, convert it to uppercase and write it to output.txt.

Skip the beginning of the input file

Sometimes, you may want to skip the beginning of the input file. This can be easily achieved using the skip parameter.

The following example skips the first 1GB of data in the input file:

dd if=input.txt of=output.txt bs=1G skip=1

This will read the data from input.txt, skipping the first 1GB, and then write output.txt.

Limit the size of data copy

dd The command can also limit the size of copied data.

For example, to copy the first 5GB of data in a file:

dd if=input.txt of=output.txt bs=1G count=5

This will read the data from input.txt, copy the first 5GB of data, and write to output.txt.

Summarize

dd The command is a very powerful tool in Linux that can be used to copy, convert, generate and modify files and device data. Its functionality is very diverse, but it also needs to be used with care, as incorrect command parameters can lead to data loss or unrecoverable damage. When using the dd command, always make sure you understand its functionality and carefully check the command parameters so that you can perform the required tasks safely and efficiently.

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