Before the explanation, i would still ask you to clarify, what you want to achieve: 1.Do you want to recover files on the former large MyDocs-partition or 2.Do you do not care about any data on that partition and just want to move on? Explanation: The sfdisk utility does not actually change anything on the internal card itself. It just creates or reads the partition table and offers the information to the kernel and the other utilities. You will have to create a fresh new file system every time you change the size of any partition or create new partitions. You do that with the mkfs.-$FILESYSTEM utilities, like mkfs.vfat. Basic steps: 1.Create the table, like the echo command to create the file - echo is a simple command to create text inside the "-characters, here, to a file, therefore >$FILENAME 2.Write the information from the file to the first sector of the internal card via the sfdisk command - sfdisk is the low level utility to access the first sectors of a sd-card like /dev/mmcblk0, --no-reread option tells sfdisk to do just that, do not try to read the partition table, because it would be useless right now, and table is the name of the file, which holds the information from which sfdisk reads 3.Reboot to have the changed geometry be known to the kernel 4.Now actually apply the file system, also named: format the partition