![]() Why dont windows/Linux/macOS do it right themselves? My guess? Separation of concerns. Lacking those commands, it is as if the secure area doesn’t exist.Ħ. This tool and basically any device you’ll ever encounter in your everyday life do not use them. Secure area exists on all cards (yes you are paying for flash you cannot use). Costs a lot of money to license the SD security stuff. What is this about the secure area? The tool just says it doesn’t touch it. Thus we have this tool and ones like it.ĥ. Why not sd? There isn’t a command in the spec for that and adding it now is too late - nobody will use it. Why doesn’t the card just do it in firmware all by itself? Curiously sony memory stick does this. What about my gopro, my phone, or $DEVICE-X that can format SD cards? Well, most device firmwares DO indeed do this correctly as the SD spec advises to do.Ĥ. Why not just mkfs.vfat? You can, but unless you do some of the above work yourself and some math, you’re unlikely to get the alignment right and will suffer because of it, especially on small or random writes. How? Well in the CSD register (accessible using SD commands), the NAND geometry is given, so all it takes is reading that and creating a file system that is properly aligned.Ģ. Aligning your file system clusters with these flash pages will allow SIGNIFICANTLY better performance and lower wear. But as per spec SD cards must allow writes at 512 byte granularity. NAND in SD cards has page size (minimum writeable piece) something like 4kB or 8KB, or maybe even 64KB. Let me try to clarify (all of this is very very simplified).ġ. The file system is new (just formatted) and clean (properly unmounted).So much confusion in this discussion. The device is a USB pen drive initialized with Disk Utility on macOS. This line tells you the cluster size is 4096 bytes: 4096 bytes per clusterĮxecute the following command: sudo minfo -i /dev/sdb1 Here is the result for the same USB pen drive, partitioned and formatted on Ubuntu Linux: fsck.fat 4.2 ()ĭata area starts at byte 1064960 (sector 2080) This line tells you the cluster size is 512 bytes: 512 bytes per cluster Root directory start at cluster 2 (arbitrary size)ĭata area starts at byte 3243008 (sector 6334) Media byte 0xf0 (5.25" or 3.5" HD floppy)įirst FAT starts at byte 16384 (sector 32) The result looks like this: fsck.fat 4.2 ()Ĭhecking we can access the last sector of the filesystem The file system is new (just formatted) and clean (properly unmounted). ![]() Mkdosfs / mkfs.msdos / mkfs.vfat → mkfs.fatĮxecute the following command: sudo fsck.fat -n -v /dev/sdb1 Other names are just symlinks: dosfslabel → fatlabelĭosfsck / fsck.msdos / fsck.vfat → fsck.fat In fact, there are only 3 executables in the dosfstools package. Please note that dosfsck (as mentioned in Cyan's answer) is a symbolic link to fsck.fat. As you can see in the examples below, dosfstools feels much cleaner, while mtools provides more low-level information. Since dosfstools is installed by default on Ubuntu (and many other distributions, I bet), it is recommended. Use the minfo command from the mtools packageīoth dosfstools and mtools are FAT-specific utilities.Use the fsck.fat command from the dosfstools package.There are more than one way to find the cluster size of a FAT file system:
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