Is the same DD command appropriate for writing EMMC and SD cards
09-23-2021, 09:32 AM
dd has been nicknamed as DESTROYER OF DISKS. and i have full experience 
, i have destroyed one harddisk in the past. (good time for remind others, did you do your backups, i did not).
"sudo dd if=/dev/mmcblk2 of=/dev/mmcblk1 bs=1M status=progress"
previous command works if both disks are exactly same size by bytes. bs=1M was good, because default is 512 and it's suboptimal and slow. "fdisk -l" shows some info. also "lsblk" and "blkid". linux does not always guarantee same order for disks, so be very careful.
few things for dd command. users need to know difference between disk, partition and file. one could backup whole disk to as file.
linux booting uses uuid's in most cases, can be shown by "blkid". uuid's are relative, so booting works in other disks or memories. some rare cases absolute paths are used, then booting won't work on other disks or media.
, i have destroyed one harddisk in the past. (good time for remind others, did you do your backups, i did not)."sudo dd if=/dev/mmcblk2 of=/dev/mmcblk1 bs=1M status=progress"
previous command works if both disks are exactly same size by bytes. bs=1M was good, because default is 512 and it's suboptimal and slow. "fdisk -l" shows some info. also "lsblk" and "blkid". linux does not always guarantee same order for disks, so be very careful.
few things for dd command. users need to know difference between disk, partition and file. one could backup whole disk to as file.
linux booting uses uuid's in most cases, can be shown by "blkid". uuid's are relative, so booting works in other disks or memories. some rare cases absolute paths are used, then booting won't work on other disks or media.