dd if=/dev/sda bs=512 count=1 | hexdump -C

nebo

dd if=/dev/sda bs=512 count=1 of=sdambr.bin
file sdambr.bin
 
sdambr.bin: x86 boot sector; 
partition 1: ID=0xfd, active, starthead 32, startsector 2048, 195309568 sectors; 
partition 2: ID=0x5, starthead 254, startsector 195313662, 1758210050 sectors, code offset 0x0