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- #!/bin/sh
- # This scripts makes a minimal bootable SD card image for the Chromebook.
- # The resulting file is called bootsd.img. It should be written directly
- # to the card:
- #
- # SD=/dev/mmcblk1 # check your device name!
- # dd if=output/images/bootsd.img of=$SD
- #
- # The partitions are created just large enough to hold the kernel and
- # the rootfs image. Most of the card will be empty, and the secondary
- # GPT will not be in its proper location.
- # cgpt does not create protective MBR, and the kernel refuses to read
- # GPT unless there's some kind of MBR in sector 0. So we need parted
- # to write that single sector before doing anything with the GPT.
- cgpt=$HOST_DIR/bin/cgpt
- parted=$HOST_DIR/sbin/parted
- kernel=$BINARIES_DIR/uImage.kpart
- rootfs=$BINARIES_DIR/rootfs.ext2
- run() { echo "$@"; "$@"; }
- die() { echo "$@" >&2; exit 1; }
- test -f $kernel || die "No kernel image found"
- test -f $rootfs || die "No rootfs image found"
- test -x $cgpt || die "cgpt not found (host-vboot-utils have not been built?)"
- # True file sizes in bytes
- kernelsize=`stat -t $kernel | cut -d\ -f2`
- rootfssize=`stat -t $rootfs | cut -d\ -f2`
- # The card is partitioned in sectors of 8KB.
- # 4 sectors are reserved for MBR+GPT. Their actual size turns out
- # to be 33 512-blocks which is just over 2 sectors, but we align
- # it to a nice round number.
- sec=8192
- kernelsec=$(((kernelsize+8191)>>13))
- rootfssec=$(((rootfssize+8191)>>13))
- headersec=4
- # There is also a copy of MBR+GPT at the end of the image.
- # It's going to be useless but both tools assume it's there.
- imagesec=$((2*headersec+kernelsec+rootfssec))
- bootsd="$BINARIES_DIR/bootsd.img"
- run dd bs=$sec count=$imagesec if=/dev/zero of=$bootsd
- # cgpt needs offsets and sizes in 512-blocks.
- block=512
- kernelstart=$((headersec<<4))
- kernelblocks=$((kernelsec<<4))
- rootfsblocks=$((rootfssec<<4))
- rootfsstart=$((kernelstart+kernelblocks))
- # This command initializes both GPT and MBR
- run $parted -s $bootsd mklabel gpt
- # The kernel partition must be marked as bootable, that's why -S -T -P
- run $cgpt add -i 1 -b $kernelstart -s $kernelblocks \
- -t kernel -l kernel \
- -S 1 -T 1 -P 10 $bootsd
- # It does not really matter where the rootfs partition is located as long
- # as the kernel can find it.
- # However, if anything is changed here, kernel.args must be updated as well.
- run $cgpt add -i 2 -b $rootfsstart -s $rootfsblocks \
- -t data -l rootfs $bootsd
- run dd bs=$block if=$kernel of=$bootsd seek=$kernelstart
- run dd bs=$block if=$rootfs of=$bootsd seek=$rootfsstart
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