Introduction to the sg_write_same Command

The sg_write_same command is an SCSI generic utility that is used to quickly write data to multiple blocks of a disk. It is a useful tool for performing large writes to disk, such as restoring a disk image or writing a large file. This command is available on Linux systems and is part of the sg3_utils package.

Basic Usage and Syntax

The sg_write_same command is used with the following syntax:

sg_write_same [options] <device> <start> <length> <fill_pattern>

Where device is the device to write to, start is the starting block address, length is the number of blocks to write, and fill_pattern is the data to write.

Examples of Common Use Cases

• Write a disk image to a device: sg_write_same /dev/sdb 0 1024 image.img
• Write a large file to a device: sg_write_same /dev/sdb 1024 8192 file.dat
• Fill a device with zeroes: sg_write_same /dev/sdb 0 1024 0x00

Advanced Options and Flags

• -c: Use the SCSI command WRITE SAME 16 instead of WRITE SAME 10
• -f: Force the write even if the device is write protected
• -i: Display information about the device before writing
• -m: Use the SCSI command WRITE SAME 32 instead of WRITE SAME 10
• -n: Do not write data to the device, just display the command that would be used
• -v: Verbose output, display more information about the write operation

Examples in Real-World Scenarios

• Write a disk image to a device with verbose output: sg_write_same -v /dev/sdb 0 1024 image.img
• Write a large file to a device and display information about the device first: sg_write_same -i /dev/sdb 1024 8192 file.dat
• Fill a device with zeroes using the WRITE SAME 32 command: sg_write_same -m /dev/sdb 0 1024 0x00

Troubleshooting Tips and Potential Errors

• Make sure the device is writeable before attempting to write to it
• Make sure the device is large enough to fit the data you are writing to it
• Make sure the device is not write-protected, or use the -f flag to force the write
• If the command fails, make sure the syntax is correct and all the parameters are correct
• Make sure the device is ready before attempting to write to it
• If the command fails, make sure you have the necessary permissions to write to the device