关于grub的那些事（三）

　　接着第二篇的研究，继续分析/etc/grub.d/10_linux。

#! /bin/sh
set -e

prefix="/usr"
exec_prefix="${prefix}"
datarootdir="/usr/share"

. "${datarootdir}/grub/grub-mkconfig_lib"

export TEXTDOMAIN=grub
export TEXTDOMAINDIR="${datarootdir}/locale"

CLASS="--class gnu-linux --class gnu --class os"

#这里开始用到GRUB_DISTRIBUTOR变量了，从第一篇中可以找到这个变量的内容
if [ "x${GRUB_DISTRIBUTOR}" = "x" ] ; then
  OS=Linux
else
  OS="${GRUB_DISTRIBUTOR} Linux"
  CLASS="--class $(echo ${GRUB_DISTRIBUTOR} | tr 'A-Z' 'a-z' | cut -d' ' -f1) ${CLASS}"
fi

# loop-AES arranges things so that /dev/loop/X can be our root device, but
# the initrds that Linux uses don't like that.
case ${GRUB_DEVICE} in
  /dev/loop/*|/dev/loop[0-9])
    GRUB_DEVICE=`losetup ${GRUB_DEVICE} | sed -e "s/^[^(]*(\([^)]\+\)).*/\/"`
  ;;
esac

#在第二篇中研究了一个对策，那就是将这个变量取消注释了，这个变量的作用可以看第二篇的解说
if [ "x${GRUB_DEVICE_UUID}" = "x" ] || [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ] \
    || ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" \
    || uses_abstraction "${GRUB_DEVICE}" lvm; then
  LINUX_ROOT_DEVICE=${GRUB_DEVICE}
else
  LINUX_ROOT_DEVICE=UUID=${GRUB_DEVICE_UUID}
fi

GRUBFS="`${grub_probe} --device ${GRUB_DEVICE} --target=fs 2>/dev/null || true`"

if [ x"$GRUBFS" = x ]; then
    GRUBFS="$(stat -f --printf=%T / || true)"
fi

case x"$GRUBFS" in
    xbtrfs)
    rootsubvol="`make_system_path_relative_to_its_root /`"
    rootsubvol="${rootsubvol#/}"
    if [ "x${rootsubvol}" != x ]; then
        GRUB_CMDLINE_LINUX="rootflags=subvol=${rootsubvol} ${GRUB_CMDLINE_LINUX}"
    fi;;
    xzfs)
    rpool=`${grub_probe} --device ${GRUB_DEVICE} --target=fs_label >/dev/null || true`
    bootfs="`make_system_path_relative_to_its_root / | sed -e "s,@$,,"`"
    LINUX_ROOT_DEVICE="ZFS=${rpool}${bootfs}"
    ;;
esac

title_correction_code=

linux_entry ()
{
  os="$1"
  version="$2"
  type="$3"
  args="$4"

  if [ -z "$boot_device_id" ]; then
      boot_device_id="$(grub_get_device_id "${GRUB_DEVICE}")"
  fi
  if [ x$type != xsimple ] ; then

#这里开始设置菜单模式了
      case $type in
      recovery)
          title="$(gettext_printf "%s, with Linux %s (recovery mode)" "${os}" "${version}")" ;;
      fallback)
          title="$(gettext_printf "%s, with Linux %s (Fallback initramfs)" "${os}" "${version}")" ;;
      *)
          title="$(gettext_printf "%s, with Linux %s" "${os}" "${version}")" ;;
      esac
      if [ x"$title" = x"$GRUB_ACTUAL_DEFAULT" ] || [ x"Previous Linux versions>$title" = x"$GRUB_ACTUAL_DEFAULT" ]; then
      replacement_title="$(echo "Advanced options for ${OS}" | sed 's,>,>>,g')>$(echo "$title" | sed 's,>,>>,g')"
      quoted="$(echo "$GRUB_ACTUAL_DEFAULT" | grub_quote)"
      title_correction_code="${title_correction_code}if [ \"x\$default\" = '$quoted' ]; then default='$(echo "$replacement_title" | grub_quote)'; fi;"
      grub_warn "$(gettext_printf "Please don't use old title \`%s' for GRUB_DEFAULT, use \`%s' (for versions before 2.00) or \`%s' (for 2.00 or later)" "$GRUB_ACTUAL_DEFAULT" "$replacement_title" "gnulinux-advanced-$boot_device_id>gnulinux-$version-$type-$boot_device_id")"
      fi
      echo "menuentry '$(echo "$title" | grub_quote)' ${CLASS} \$menuentry_id_option 'gnulinux-$version-$type-$boot_device_id' {" | sed "s/^/$submenu_indentation/"
  else
      echo "menuentry '$(echo "$os" | grub_quote)' ${CLASS} \$menuentry_id_option 'gnulinux-simple-$boot_device_id' {" | sed "s/^/$submenu_indentation/"
  fi
  if [ x$type != xrecovery ] && [ x$type != xfallback ] ; then
      save_default_entry | grub_add_tab
  fi

  # Use ELILO's generic "efifb" when it's known to be available.
  # FIXME: We need an interface to select vesafb in case efifb can't be used.
  if [ "x$GRUB_GFXPAYLOAD_LINUX" = x ]; then
      echo "    load_video" | sed "s/^/$submenu_indentation/"
      if grep -qx "CONFIG_FB_EFI=y" "${config}" > /dev/null \
      && grep -qx "CONFIG_VT_HW_CONSOLE_BINDING=y" "${config}" > /dev/null; then
      echo "    set gfxpayload=keep" | sed "s/^/$submenu_indentation/"
      fi
  else
      if [ "x$GRUB_GFXPAYLOAD_LINUX" != xtext ]; then
      echo "    load_video" | sed "s/^/$submenu_indentation/"
      fi
      echo "    set gfxpayload=$GRUB_GFXPAYLOAD_LINUX" | sed "s/^/$submenu_indentation/"
  fi

  echo "    insmod gzio" | sed "s/^/$submenu_indentation/"

  if [ x$dirname = x/ ]; then
    if [ -z "${prepare_root_cache}" ]; then
      prepare_root_cache="$(prepare_grub_to_access_device ${GRUB_DEVICE} | grub_add_tab)"
    fi
    printf '%s\n' "${prepare_root_cache}" | sed "s/^/$submenu_indentation/"
  else
    if [ -z "${prepare_boot_cache}" ]; then
      prepare_boot_cache="$(prepare_grub_to_access_device ${GRUB_DEVICE_BOOT} | grub_add_tab)"
    fi
    printf '%s\n' "${prepare_boot_cache}" | sed "s/^/$submenu_indentation/"
  fi

  message="$(gettext_printf "Loading Linux %s ..." "${version}")"
  sed "s/^/$submenu_indentation/" << EOF
    echo    '$(echo "$message" | grub_quote)'
    linux    ${rel_dirname}/${basename} root=${linux_root_device_thisversion} rw ${args}
EOF
  if test -n "${initrd}" ; then
    # TRANSLATORS: ramdisk isn't identifier. Should be translated.
    message="$(gettext_printf "Loading initial ramdisk ...")"
    sed "s/^/$submenu_indentation/" << EOF
    echo    '$(echo "$message" | grub_quote)'
    initrd    ${rel_dirname}/${initrd}
EOF
  fi
  sed "s/^/$submenu_indentation/" << EOF
}
EOF
}

#下面开始设置寻找内核的范围，从命名上可以看出，不能直接将内核命名为vmlinuz，
#建议按照下面的方式命名，除非你一定要使用vmlinuz这个文件名。你可以修改这个文件
machine=`uname -m`
case "x$machine" in
    xi? | xx86_64)
    list=`for i in /boot/vmlinuz-* /vmlinuz-* /boot/kernel-* ; do
                  if grub_file_is_not_garbage "$i" ; then echo -n "$i " ; fi
              done` ;;
    *)
    list=`for i in /boot/vmlinuz-* /boot/vmlinux-* /vmlinuz-* /vmlinux-* /boot/kernel-* ; do
                  if grub_file_is_not_garbage "$i" ; then echo -n "$i " ; fi
         done` ;;
esac

case "$machine" in
    i?) GENKERNEL_ARCH="x86" ;;
    mips|mips64) GENKERNEL_ARCH="mips" ;;
    mipsel|mips64el) GENKERNEL_ARCH="mipsel" ;;
    arm*) GENKERNEL_ARCH="arm" ;;
    *) GENKERNEL_ARCH="$machine" ;;
esac

prepare_boot_cache=
prepare_root_cache=
boot_device_id=
title_correction_code=

# Extra indentation to add to menu entries in a submenu. We're not in a submenu
# yet, so it's empty. In a submenu it will be equal to '\t' (one tab).
submenu_indentation=""

is_first_entry=true
while [ "x$list" != "x" ] ; do
  linux=`version_find_latest $list`
  gettext_printf "Found linux image: %s\n" "$linux" >&
  basename=`basename $linux`
  dirname=`dirname $linux`
  rel_dirname=`make_system_path_relative_to_its_root $dirname`
  version=`echo $basename | sed -e "s,^[^0-9]*-,,g"`
  alt_version=`echo $version | sed -e "s,\.old$,,g"`
  linux_root_device_thisversion="${LINUX_ROOT_DEVICE}"

  if test -e "/etc/arch-release" ; then
    if echo "${basename}" | grep -q 'vmlinuz-linux' ; then
      version="`echo "${basename}" | sed -e 's,vmlinuz-linux,,g'`"

      if [ "x${version}" = "x" ] ; then
        version="core repo kernel"
      else
        version="`echo "${version}" | sed -e 's,-,,g'`"
        version="${version} kernel"
      fi
    fi
  fi

#这里开始设置initrd参数，从命名上看，似乎无法查找initrd这个文件名，
#最好的做法是将你的文件按照下面的其中一种方式命名
  initrd=
  initrd_arch="`echo "${basename}" | sed -e 's,vmlinuz,initramfs,g'`"

  for i in "initrd.img-${version}" "initrd-${version}.img" "initrd-${version}.gz" \
       "initrd-${version}" "initramfs-${version}.img" \
       "initrd.img-${alt_version}" "initrd-${alt_version}.img" \
       "initrd-${alt_version}" "initramfs-${alt_version}.img" \
       "initramfs-genkernel-${version}" \
       "initramfs-genkernel-${alt_version}" \
       "initramfs-genkernel-${GENKERNEL_ARCH}-${version}" \
       "initramfs-genkernel-${GENKERNEL_ARCH}-${alt_version}" \
       "${initrd_arch}.img" ; do
    if test -e "${dirname}/${i}" ; then
      initrd="$i"
      break
    fi
  done

  config=
  for i in "${dirname}/config-${version}" "${dirname}/config-${alt_version}" "/etc/kernels/kernel-config-${version}" ; do
    if test -e "${i}" ; then
      config="${i}"
      break
    fi
  done

  initramfs=
  if test -n "${config}" ; then
      initramfs=`grep CONFIG_INITRAMFS_SOURCE= "${config}" | cut -f2 -d= | tr -d \"`
  fi

  if test -n "${initrd}" ; then
    gettext_printf "Found initrd image: %s\n" "${dirname}/${initrd}" >&
  elif test -z "${initramfs}" ; then
    # "UUID=" and "ZFS=" magic is parsed by initrd or initramfs.  Since there's
    # no initrd or builtin initramfs, it can't work here.
    linux_root_device_thisversion=${GRUB_DEVICE}
  fi

  if test -e "/etc/arch-release" ; then
    is_first_entry="false"

    linux_entry "${OS}" "${version}" true \
              "${GRUB_CMDLINE_LINUX} ${GRUB_CMDLINE_LINUX_DEFAULT}"

    for i in "${initrd_arch}-fallback.img" "initramfs-${version}-fallback.img" ; do
      if test -e "${dirname}/${i}" ; then
        initrd="${i}"
        linux_entry "${OS}" "${version}" fallback \
                    "${GRUB_CMDLINE_LINUX} ${GRUB_CMDLINE_LINUX_DEFAULT}"
        break
      fi
    done
  fi

  if [ "x$is_first_entry" = xtrue ]; then
    linux_entry "${OS}" "${version}" simple \
    "${GRUB_CMDLINE_LINUX} ${GRUB_CMDLINE_LINUX_DEFAULT}"

    submenu_indentation="$grub_tab"

    if [ -z "$boot_device_id" ]; then
    boot_device_id="$(grub_get_device_id "${GRUB_DEVICE}")"
    fi
    # TRANSLATORS: %s is replaced with an OS name
    echo "submenu '$(gettext_printf "Advanced options for %s" "${OS}" | grub_quote)' \$menuentry_id_option 'gnulinux-advanced-$boot_device_id' {"
  fi

  if ! test -e "/etc/arch-release" ; then
  linux_entry "${OS}" "${version}" advanced \
              "${GRUB_CMDLINE_LINUX} ${GRUB_CMDLINE_LINUX_DEFAULT}"
  fi

  if [ "x${GRUB_DISABLE_RECOVERY}" != "xtrue" ]; then
    linux_entry "${OS}" "${version}" recovery \
                "single ${GRUB_CMDLINE_LINUX}"
  fi

  list=`echo $list | tr ' ' '\n' | grep -vx $linux | tr '\n' ' '`
  is_first_entry=false
done

# If at least one kernel was found, then we need to
# add a closing '}' for the submenu command.
if ! test -e "/etc/arch-release" ; then
if [ x"$is_first_entry" != xtrue ]; then
  echo '}'
fi
fi

echo "$title_correction_code"

　　从代码里可以看到，如果没有找到到内核文件，也许是命名的问题。如果想修改启动菜单的顺序，只需要修改/etc/grub.d/目录里的文件名的序号就好了。

　　这个10_linux脚本的效果可以看/boot/grub/grub.cfg文件的内容。