Format Entire Disk FAT32 Script (otimização de Fat32)

#! /bin/sh
# fdisk portion of script based on mkcard.sh v0.4
# (c) Copyright 2009 Graeme Gregory <dp@xora.org.uk>
# Additional functionality by Steve Sakoman
# (c) Copyright 2010-2011 Steve Sakoman <steve@sakoman.com>
# Licensed under terms of GPLv2
#
# Parts of the procudure base on the work of Denys Dmytriyenko
# http://wiki.omap.com/index.php/MMC_Boot_Format
# Official Site: http://3gfp.com/wp/2014/07/formatting-sd-cards-for-speed-and-lifetime/

export LC_ALL=C

format_whole_disk_fat32() {
    if ! id | grep -q root; then
        echo "This utility must be run prefixed with sudo or as root"
        return 1
    fi

    local DRIVE=$1
    local PART1=$2

    #make sure that DRIVE isn't mounted before we start
    if [ -b ${DRIVE}1 ]; then
        umount ${DRIVE}1
        umount ${DRIVE}2
    elif [ -b ${DRIVE}p1 ]; then
        umount ${DRIVE}p1
        umount ${DRIVE}p2
    else
        umount ${DRIVE}
    fi

    # Erase first 8MiB of DRIVE
    dd if=/dev/zero of=$DRIVE bs=1024 count=8192

    # Get disk size in bytes
    local SIZE=$(fdisk -l $DRIVE | grep Disk | grep bytes | awk '{print $5}')
    echo DISK SIZE – $SIZE bytes

    # Note: I'm changing our default cluster size to 32KiB since all of
    # our 8GiB cards are arriving with 32KiB clusters. The manufacturers
    # may know something that we do not *or* they're trading speed for
    # more space.
    local CLUSTER_SIZE_KB=32
    local CLUSTER_SIZE_IN_SECTORS=$(( $CLUSTER_SIZE_KB * 2 ))

    # This won't work for drives bigger than 32GiB because
    # 32GiB / 64kiB clusters = 524288 FAT entries
    # 524288 FAT entries * 4 bytes / FAT = 2097152 bytes
    # 2097152 bytes / 512 bytes = 4096 sectors for FAT size
    # 4096 * 2 = 8192 sectors for both FAT tables which leaves no
    # room for the BPB sector
    if [ $SIZE -ge $(( ($CLUSTER_SIZE_KB / 2) * 1024 * 1024 * 1024 )) ]; then
        echo -n "This drive is too large, >= $(($CLUSTER_SIZE_KB / 2))GiB, for this "
        echo "formatting routine."
        return 1
    fi

    # Calculate number of cylinders based on "255 heads, 63 sectors/track"
    local CYLINDERS=""
    if [ "$CYLINDERS" = "" ] && which bc >/dev/null 2>&1; then
        CYLINDERS=$(echo $SIZE/255/63/512 | bc)
    fi
    if [ "$CYLINDERS" = "" ] && which dc >/dev/null 2>&1; then
        CYLINDERS=$(echo "$SIZE 255 / 63 / 512 / p" | dc | sed -e 's,\..*$,,')
    fi
    if [ "$CYLINDERS" = "" ]; then
        echo "Failed to calculate CYLINDERS=$SIZE/255/63/512"
        return 1
    fi
    echo CYLINDERS – $CYLINDERS

    # Align partitions for SD card performance/wear optimization
    # Summary: start 1st partition at sector 8192 (4MiB) and align FAT32
    #          data to start at 8MiB (4MiB logical)
    #          There's a document that explains why, but its too long to
    #          reproduce here.
    {
    echo 8192,,0x0C,*
    } | sfdisk --force -D -uS -H 255 -S 63 -C $CYLINDERS -q $DRIVE

    sleep 1

    if [ "$PART1" = "" ]; then
        if [ -b ${DRIVE}1 ]; then
            PART1=${DRIVE}1
        elif [ -b ${DRIVE}p1 ]; then
            PART1=${DRIVE}p1
        else
            echo "Improper partitioning on $DRIVE"
            return 1
        fi
    fi

    # Format FAT32 with 64kiB clusters (128 * 512)
    # Format once to get the calculated FAT size
    local FAT_SIZE=$(mkdosfs -F 32 -s $CLUSTER_SIZE_IN_SECTORS -n boot -v ${PART1} | \
        sed -n -r -e '/^FAT size is/ s,FAT size is ([0-9]+) sectors.*$,\1,p')

    # Calculate the number of reserved sectors to pad in order to align
    # the FAT32 data area to 4MiB
    local RESERVED_SECTORS=$(( 8192 - 2 * $FAT_SIZE ))

    # Format again with padding
    mkdosfs -F 32 -s $CLUSTER_SIZE_IN_SECTORS -n boot -v -R $RESERVED_SECTORS ${PART1}
}

#set -x

format_whole_disk_fat32 "$@"