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https://github.com/linuxkit/linuxkit.git
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105 lines
2.9 KiB
Bash
Executable File
105 lines
2.9 KiB
Bash
Executable File
#!/bin/sh
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set -e
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# for debugging
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[ -n "$DEBUG" ] && set -x
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IMGFILE=$PWD/disk.img
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# we want everything except the final result to stderr
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( exec 1>&2;
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ESP_FILE=$PWD/boot.img
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mkdir -p /tmp/bios
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cd /tmp/bios
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# input is a tarball of filesystem on stdin with kernel in /boot
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# output is an iso on stdout
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# extract. BSD tar auto recognises compression, unlike GNU tar
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# only if stdin is a tty, if so need files volume mounted...
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[ -t 0 ] || bsdtar xzf -
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INITRD="$(find . -name '*.img')"
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KERNEL="./kernel"
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CMDLINE_FILE="$(find . -name cmdline)"
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CMDLINE="$(cat $CMDLINE_FILE )"
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cat >> syslinux.cfg <<EOF
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DEFAULT linux
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LABEL linux
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KERNEL /kernel
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INITRD /initrd.img
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APPEND ${CMDLINE}
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EOF
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# now build an img file
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KERNEL_FILE_SIZE=$(stat -c %s "$KERNEL")
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INITRD_FILE_SIZE=$(stat -c %s "$INITRD")
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# minimum headroom needed in ESP, in bytes
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# 511KiB headroom seems to be enough
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ESP_HEADROOM=$(( 1024 * 1024 ))
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ESP_FILE_SIZE=$(( $KERNEL_FILE_SIZE + $INITRD_FILE_SIZE + $ESP_HEADROOM ))
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# (x+1024)/1024*1024 rounds up to multiple of 1024KB, or 2048 sectors
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# some firmwares get confused if the partitions are not aligned on 2048 blocks
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# we will round up to the nearest multiple of 2048 blocks
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# since each block is 512 bytes, we want the size to be a multiple of
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# 2048 blocks * 512 bytes = 1048576 bytes = 1024KB
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ESP_FILE_SIZE_KB=$(( ( ( ($ESP_FILE_SIZE+1024-1) / 1024 ) + 1024-1) / 1024 * 1024 ))
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# and for sectors
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ESP_FILE_SIZE_SECTORS=$(( $ESP_FILE_SIZE_KB * 2 ))
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# create a raw disk with an EFI boot partition
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# Stuff it into a FAT filesystem, making it as small as possible.
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mkfs.vfat -v -C $ESP_FILE $(( $ESP_FILE_SIZE_KB )) > /dev/null
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echo "mtools_skip_check=1" >> /etc/mtools.conf && \
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mcopy -i $ESP_FILE syslinux.cfg ::/
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mcopy -i $ESP_FILE $KERNEL ::/kernel
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mcopy -i $ESP_FILE $INITRD ::/initrd.img
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# install syslinux
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syslinux --install $ESP_FILE
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# now make our actual filesystem image
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# how big an image do we want?
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# it should be the size of our ESP file+1MB for BIOS boot + 1MB for MBR + 1MB for backup
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ONEMB=$(( 1024 * 1024 ))
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SIZE_IN_BYTES=$(( $(stat -c %s "$ESP_FILE") + 4*$ONEMB ))
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# and make sure the ESP is bootable for BIOS mode
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# settings
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BLKSIZE=512
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MB_BLOCKS=$(( $SIZE_IN_BYTES / $ONEMB ))
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# make the image
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dd if=/dev/zero of=$IMGFILE bs=1M count=$MB_BLOCKS
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echo "w" | fdisk $IMGFILE || true
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# format one large partition of the apprropriate size
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echo ","$ESP_FILE_SIZE_SECTORS",;" | sfdisk $IMGFILE
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# of course, "one large partition" means minus the 2048 at the beginning
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ESP_SECTOR_START=2048
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# copy in our EFI System Partition image
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dd if=$ESP_FILE of=$IMGFILE bs=$BLKSIZE count=$ESP_FILE_SIZE_SECTORS conv=notrunc seek=$ESP_SECTOR_START
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# install mbr
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#dd if=/usr/share/syslinux/mbr.bin of="$IMGFILE" bs=440 count=1 conv=notrunc
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dd if=/usr/share/syslinux/altmbr.bin bs=439 count=1 conv=notrunc of=$IMGFILE
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printf '\1' | dd bs=1 count=1 seek=439 conv=notrunc of=$IMGFILE
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sfdisk -A "$IMGFILE" 1
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)
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cat $IMGFILE
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