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Exam LFCS topic 1 question 38 discussion

Actual exam question from Linux Foundation's LFCS
Question #: 38
Topic #: 1
[All LFCS Questions]

Which of the following commands overwrites the bootloader located on /dev/sda without overwriting the partition table or any data following it?

  • A. dd if=/dev/zero of=/dev/sda bs=512
  • B. dd if=/dev/zero of=/dev/sda bs=512 count=1
  • C. dd if=/dev/zero of=/dev/sda bs=440 count=1
  • D. dd if=/dev/zero of=/dev/sda bs=440
Show Suggested Answer Hide Answer
Suggested Answer: C 🗳️

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Buruguduystunstugudunstuy
1 year, 4 months ago
Selected Answer: C
The command that overwrites the bootloader located on '/dev/sda' without overwriting the partition table or any data following it is 'dd if=/dev/zero of=/dev/sda bs=440 count=1'. The correct answer is Option C. The 'dd' command is a utility for copying data from one location to another. It can be used to overwrite data on a device, such as a hard drive or a bootloader. The 'if' option specifies the input file, and the 'of' option specifies the output file. The 'bs' option specifies the block size, and the 'count' option specifies the number of blocks to copy. In this case, the command will copy a single block of data ('count=1') from '/dev/zero' (a special file that provides an endless stream of zero bits) to '/dev/sda' using a block size of '440' bytes. This will overwrite the bootloader located on '/dev/sda' without overwriting the partition table or any data following it.
upvoted 1 times
Buruguduystunstugudunstuy
1 year, 4 months ago
The other options will overwrite more data on the device, potentially causing data loss or corruption. Option C will overwrite the first 440 bytes of the device, which is the correct block size to overwrite the bootloader without overwriting the partition table or any data following it. Option A will overwrite the entire device, including the partition table and all data. Option B will overwrite the first 512 bytes of the device, potentially causing data loss or corruption. Option D will overwrite the entire device, including the partition table and all data.
upvoted 1 times
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Flubu
1 year, 11 months ago
For example in Windows, “the 4 bytes following the first 440 bytes contain the Windows Unique Disk Signature” -> https://unix.stackexchange.com/questions/254657/mbr-size-is-440-bytes-or-512-bytes#254662
upvoted 1 times
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Flubu
1 year, 11 months ago
None, is correct. ... it is composed of 3 parts: the boot code (446 bytes long), the partition table (64 bytes long) and the boot code signature (2 bytes long) -> https://unix.stackexchange.com/questions/252509/using-dd-in-order-to-save-and-restore-a-boot-sector
upvoted 1 times
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ignou143
3 years, 6 months ago
Right Answer is : dd if=/dev/zero of=/dev/sda bs=512 count=1
upvoted 3 times
Funkslinger
2 years, 2 months ago
Do we want to overwrite the bootloader or the whole MBR? Answer is C
upvoted 1 times
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B (20%)
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