How to View the Contents of a Master Boot Record

By Andrew Mikael

The master boot record of a hard drive -- also called the boot sector -- stores information about installed operating systems. This small, 512-byte section exists outside the storage of a disk’s partitions; it tells the machine how to boot an operating system and where individual partitions are stored. It contains a table of partitions and a code for the program used by the BIOS to boot the system. You can view the raw contents of the master boot record using tools included with the Linux operating system or using third-party programs in Windows; the latter method offers the ability to alter the record, which could seriously damage the system if performed incorrectly.

Linux

Step 1

Open a file-explorer application and navigate to a storage folder on the hard drive; this process will export a text copy of the master boot record to whichever folder you choose.

Step 2

Open a terminal and type “# dd if=/dev/sda of=mbr.bin bs=512 count=1.” If your primary disk does not use the “/dev/sda” location, replace this section with the correct disk location.

Step 3

Open the new file in a binary editor program or print it to an ASCII format using the “# od -xa mbr.bin” command.

Windows

Step 1

Download the Partition Table Editor from the Symantec website (see "Resources" below) and unzip the downloaded file. Double-click the “PTEDIT32” file.

Step 2

Select a hard disk from the drop-down menu to view the boot record for that device. Only physical disks -- not individual disk partitions -- contain boot records.

Step 3

Click inside a text box to change the value or configure a certain element of the boot record. Note that changing these values can result in an inoperable system.

Tips & Warnings

  • If you do not need to view the specific values of the master boot record’s tables, you can find more user-friendly versions of the information in partitioning tools. Windows comes with the Disk Management feature that's designed for viewing disk information, and third-party programs such as Partition Manager (see "Resources" below) also include these features.