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    Booting into Xen with grub2-mkconfig 2.03 on centos8 x86_64

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    • brunocekB
      brunocek
      last edited by 

      Linux localhost.localdomain 4.18.0-394.el8.x86_64 #1 SMP Tue May 31 16:19:11 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

grub2-mkconfig (GRUB) 2.03

      On my centos8, I have installed centos-release-openstack-xena.noarch

      But I cannot boot into Xen, please help.

      Theoretically, after installing Xen, I should only run

      grub2-mkconfig -o /boot/efi/EFI/centos/grub.cfg

      As my /etc/grub.d has a linux_xen file and antoher large number of files hanging there:

      [root@localhost ~]# ls /etc/grub.d/
00_header  01_users              10_linux               11_linux_xen       20_linux_xen     30_os-prober      35_fwupd   41_custom
00_tuned   08_fallback_counting  10_reset_boot_success  12_menu_auto_hide  20_ppc_terminfo  30_uefi-firmware  40_custom  README

      (11_linux_xen is a symlink I created pointing to 20_linux_xen)

      Unfortunately, grub.cfg will have nothing in the linux_xen section.

      I added echo << EOF and EOF to the linux_xen file and I got some errors, but I wonder if debugging this complexity is the best way forward or if there is something simpler I can do.

      /etc/grub.d/11_linux_xen file contents:

      
#! /bin/sh
set -e

# grub-mkconfig helper script.
# Copyright (C) 2006,2007,2008,2009,2010  Free Software Foundation, Inc.
#
# GRUB is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# GRUB is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with GRUB.  If not, see <http://www.gnu.org/licenses/>.

cat << EOF
prefix="/usr"
exec_prefix="/usr"
datarootdir="/usr/share"

. "$pkgdatadir/grub-mkconfig_lib"

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

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

if [ "x${GRUB_DISTRIBUTOR}" = "x" ] ; then
  OS="$(sed 's, release .*$,,g' /etc/system-release)"
else
  OS="${GRUB_DISTRIBUTOR}"
  CLASS="--class $(echo ${GRUB_DISTRIBUTOR} | tr 'A-Z' 'a-z' | cut -d' ' -f1|LC_ALL=C sed 's,[^[:alnum:]_],_,g') ${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/^[^(]*(\([^)]\+\)).*/\1/"`
  ;;
esac

# Default to disabling partition uuid support to maintian compatibility with
# older kernels.
GRUB_DISABLE_LINUX_PARTUUID=${GRUB_DISABLE_LINUX_PARTUUID-true}

# btrfs may reside on multiple devices. We cannot pass them as value of root= parameter
# and mounting btrfs requires user space scanning, so force UUID in this case.
if ( [ "x${GRUB_DEVICE_UUID}" = "x" ] && [ "x${GRUB_DEVICE_PARTUUID}" = "x" ] ) \
    || ( [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ] \
	&& [ "x${GRUB_DISABLE_LINUX_PARTUUID}" = "xtrue" ] ) \
    || ( ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" \
	&& ! test -e "/dev/disk/by-partuuid/${GRUB_DEVICE_PARTUUID}" ) \
    || ( test -e "${GRUB_DEVICE}" && uses_abstraction "${GRUB_DEVICE}" lvm ); then
  LINUX_ROOT_DEVICE=${GRUB_DEVICE}
elif [ "x${GRUB_DEVICE_UUID}" = "x" ] \
    || [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ]; then
  LINUX_ROOT_DEVICE=PARTUUID=${GRUB_DEVICE_PARTUUID}
else
  LINUX_ROOT_DEVICE=UUID=${GRUB_DEVICE_UUID}
fi

# Allow overriding GRUB_CMDLINE_LINUX and GRUB_CMDLINE_LINUX_DEFAULT.
if [ "${GRUB_CMDLINE_LINUX_XEN_REPLACE}" ]; then
  GRUB_CMDLINE_LINUX="${GRUB_CMDLINE_LINUX_XEN_REPLACE}"
fi
if [ "${GRUB_CMDLINE_LINUX_XEN_REPLACE_DEFAULT}" ]; then
  GRUB_CMDLINE_LINUX_DEFAULT="${GRUB_CMDLINE_LINUX_XEN_REPLACE_DEFAULT}"
fi

case x"$GRUB_FS" in
    xbtrfs)
	if [ "x${SUSE_BTRFS_SNAPSHOT_BOOTING}" = "xtrue" ]; then
	GRUB_CMDLINE_LINUX="${GRUB_CMDLINE_LINUX} \${extra_cmdline}"
	else
	rootsubvol="`make_system_path_relative_to_its_root /`"
	rootsubvol="${rootsubvol#/}"
	if [ "x${rootsubvol}" != x ]; then
	    GRUB_CMDLINE_LINUX="rootflags=subvol=${rootsubvol} ${GRUB_CMDLINE_LINUX}"
	fi
	fi;;
    xzfs)
	rpool=`${grub_probe} --device ${GRUB_DEVICE} --target=fs_label 2>/dev/null || true`
	bootfs="`make_system_path_relative_to_its_root / | sed -e "s,@$,,"`"
	LINUX_ROOT_DEVICE="ZFS=${rpool}${bootfs}"
	;;
esac

title_correction_code=

linux_entry ()
{
  os="$1"
  version="$2"
  xen_version="$3"
  type="$4"
  args="$5"
  xen_args="$6"
  if [ -z "$boot_device_id" ]; then
      boot_device_id="$(grub_get_device_id "${GRUB_DEVICE}")"
  fi
  if [ x$type != xsimple ] ; then
      if [ x$type = xrecovery ] ; then
	  title="$(gettext_printf "%s, with Xen %s and Linux %s (recovery mode)" "${os}" "${xen_version}" "${version}")"
      else
	  title="$(gettext_printf "%s, with Xen %s and Linux %s" "${os}" "${xen_version}" "${version}")"
      fi
      replacement_title="$(echo "Advanced options for ${OS}" | sed 's,>,>>,g')>$(echo "$title" | sed 's,>,>>,g')"
      if [ x"Xen ${xen_version}>$title" = x"$GRUB_ACTUAL_DEFAULT" ]; then
         quoted="$(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)' ${CLASS} \$menuentry_id_option 'xen-gnulinux-$version-$type-$boot_device_id' {" | sed "s/^/$submenu_indentation/"
  else
      title="$(gettext_printf "%s, with Xen hypervisor" "${os}")"
      echo "menuentry '$(echo "$title" | grub_quote)' ${CLASS} \$menuentry_id_option 'xen-gnulinux-simple-$boot_device_id' {" | sed "s/^/$submenu_indentation/"
  fi
  if [ x$type != xrecovery ] ; then
      save_default_entry | grub_add_tab | sed "s/^/$submenu_indentation/"
  fi

  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/^/$submenu_indentation/"
  xmessage="$(gettext_printf "Loading Xen %s ..." ${xen_version})"
  lmessage="$(gettext_printf "Loading Linux %s ..." ${version})"
  sed "s/^/$submenu_indentation/" << EOF
	echo	'$(echo "$xmessage" | grub_quote)'
        if [ "\$grub_platform" = "pc" -o "\$grub_platform" = "" ]; then
            xen_rm_opts=
        else
            xen_rm_opts="no-real-mode edd=off"
        fi
	insmod ${module_loader}
	insmod ${xen_loader}
	${xen_loader}	${rel_xen_dirname}/${xen_basename} placeholder ${xen_args} \${xen_rm_opts}
	echo	'$(echo "$lmessage" | grub_quote)'
	${module_loader}	${rel_dirname}/${basename} placeholder root=${linux_root_device_thisversion} ro ${args}
EOF
  if test -n "${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)'
	insmod ${module_loader}
	${module_loader}	--nounzip   ${rel_dirname}/${initrd}
EOF
  fi
  sed "s/^/$submenu_indentation/" << EOF
}
EOF
}

linux_list=
for i in /boot/vmlinu[xz]-* /vmlinu[xz]-* /boot/kernel-*; do
    if grub_file_is_not_garbage "$i"; then
    	basename=$(basename $i)
	version=$(echo $basename | sed -e "s,^[^0-9]*-,,g")
	dirname=$(dirname $i)
	config=
	for j in "${dirname}/config-${version}" "${dirname}/config-${alt_version}" "/etc/kernels/kernel-config-${version}" ; do
	    if test -e "${j}" ; then
		config="${j}"
		break
	    fi
	done
        if (grep -qx "CONFIG_XEN_DOM0=y" "${config}" 2> /dev/null || grep -qx "CONFIG_XEN_PRIVILEGED_GUEST=y" "${config}" 2> /dev/null); then linux_list="$linux_list $i" ; fi
    fi
done
if [ "x${linux_list}" = "x" ] ; then
    exit 0
fi

file_is_not_sym () {
    case "$1" in
	*/xen-syms-*)
	    return 1;;
	*)
	    return 0;;
    esac
}

xen_list=
for i in /boot/xen*; do
    if grub_file_is_not_garbage "$i" && file_is_not_sym "$i" ; then xen_list="$xen_list $i" ; fi
done
prepare_boot_cache=
boot_device_id=

title_correction_code=

machine=`uname -m`

case "$machine" in
    i?86) GENKERNEL_ARCH="x86" ;;
    mips|mips64) GENKERNEL_ARCH="mips" ;;
    mipsel|mips64el) GENKERNEL_ARCH="mipsel" ;;
    arm*) GENKERNEL_ARCH="arm" ;;
    *) GENKERNEL_ARCH="$machine" ;;
esac

# 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_top_level=true

while [ "x${xen_list}" != "x" ] ; do
    list="${linux_list}"
    current_xen=`version_find_latest $xen_list`
    xen_basename=`basename ${current_xen}`
    xen_dirname=`dirname ${current_xen}`
    rel_xen_dirname=`make_system_path_relative_to_its_root $xen_dirname`
    xen_version=`echo $xen_basename | sed -e "s,.gz$,,g;s,^xen-,,g"`
    if [ -z "$boot_device_id" ]; then
	boot_device_id="$(grub_get_device_id "${GRUB_DEVICE}")"
    fi
    if [ "x$is_top_level" != xtrue ]; then
	echo "	submenu '$(gettext_printf "Xen hypervisor, version %s" "${xen_version}" | grub_quote)' \$menuentry_id_option 'xen-hypervisor-$xen_version-$boot_device_id' {"
    fi
    if ($grub_file --is-arm64-efi $current_xen); then
	xen_loader="xen_hypervisor"
	module_loader="xen_module"
    else
	if ($grub_file --is-x86-multiboot2 $current_xen); then
	    xen_loader="multiboot2"
	    module_loader="module2"
	else
	    xen_loader="multiboot"
	    module_loader="module"
        fi
    fi
    while [ "x$list" != "x" ] ; do
	linux=`version_find_latest $list`
	gettext_printf "Found linux image: %s\n" "$linux" >&2
	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}"

	initrd=
	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}-${alt_version}" ; do
	    if test -e "${dirname}/${i}" ; then
		initrd="$i"
		break
	    fi
	done
	if test -n "${initrd}" ; then
	    gettext_printf "Found initrd image: %s\n" "${dirname}/${initrd}" >&2
	else
    # "UUID=" magic is parsed by initrds.  Since there's no initrd, it can't work here.
	    if [ "x${GRUB_DEVICE_PARTUUID}" = "x" ] \
		|| [ "x${GRUB_DISABLE_LINUX_PARTUUID}" = "xtrue" ]; then

		linux_root_device_thisversion=${GRUB_DEVICE}
	    else
		linux_root_device_thisversion=PARTUUID=${GRUB_DEVICE_PARTUUID}
	    fi
	fi

	if [ "x$is_top_level" = xtrue ] && [ "x${GRUB_DISABLE_SUBMENU}" != xy ]; then
	    linux_entry "${OS}" "${version}" "${xen_version}" simple \
		"${GRUB_CMDLINE_LINUX} ${GRUB_CMDLINE_LINUX_DEFAULT}" "${GRUB_CMDLINE_XEN} ${GRUB_CMDLINE_XEN_DEFAULT}"

	    submenu_indentation="$grub_tab$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 (with Xen hypervisor)" "${OS}" | grub_quote)' \$menuentry_id_option 'gnulinux-advanced-$boot_device_id' {"
	echo "	submenu '$(gettext_printf "Xen hypervisor, version %s" "${xen_version}" | grub_quote)' \$menuentry_id_option 'xen-hypervisor-$xen_version-$boot_device_id' {"
	   is_top_level=false
	fi

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

	list=`echo $list | tr ' ' '\n' | fgrep -vx "$linux" | tr '\n' ' '`
    done
    if [ x"$is_top_level" != xtrue ]; then
	echo '	}'
    fi
    xen_list=`echo $xen_list | tr ' ' '\n' | fgrep -vx "$current_xen" | tr '\n' ' '`
done

# If at least one kernel was found, then we need to
# add a closing '}' for the submenu command.
if [ x"$is_top_level" != xtrue ]; then
  echo '}'
fi

echo "$title_correction_code"

EOF

      Error message generated when running grub2-mkconfig -o /boot/efi/EFI/centos/grub.cfg :

      [root@localhost ~]# grub2-mkconfig -o /boot/efi/EFI/centos/grub.cfg
Generating grub configuration file ...
losetup: /dev/nvme0n1p3: failed to use device: No such device
/etc/grub.d/11_linux_xen: line 20: make_system_path_relative_to_its_root: command not found
/etc/grub.d/11_linux_xen: line 20: make_system_path_relative_to_its_root: command not found
/etc/grub.d/11_linux_xen: line 20: grub_get_device_id: command not found
/etc/grub.d/11_linux_xen: line 20: gettext_printf: command not found
/etc/grub.d/11_linux_xen: line 20: gettext_printf: command not found
/etc/grub.d/11_linux_xen: line 20: grub_quote: command not found
/etc/grub.d/11_linux_xen: line 20: grub_quote: command not found
/etc/grub.d/11_linux_xen: line 20: gettext_printf: command not found
/etc/grub.d/11_linux_xen: line 20: grub_quote: command not found
/etc/grub.d/11_linux_xen: line 20: gettext_printf: command not found
/etc/grub.d/11_linux_xen: line 20: grub_quote: command not found
/etc/grub.d/11_linux_xen: line 20: prepare_grub_to_access_device: command not found
/etc/grub.d/11_linux_xen: line 20: grub_add_tab: command not found
/etc/grub.d/11_linux_xen: line 20: gettext_printf: command not found
/etc/grub.d/11_linux_xen: line 20: gettext_printf: command not found
/etc/grub.d/11_linux_xen: line 20: grub_quote: command not found
/etc/grub.d/11_linux_xen: line 20: grub_quote: command not found
/etc/grub.d/11_linux_xen: line 158: syntax error near unexpected token `}'

      This question was also published at: https://unix.stackexchange.com/questions/710283/booting-into-xen-with-grub2-mkconfig-2-03-on-centos8-x86-64

      And: https://forums.centos.org/viewforum.php?f=54

      1 Reply Last reply Reply Quote 0
      • DanpD Danp moved this topic from Installation on
      • brunocekB
        brunocek
        last edited by

        Our wiki needs some updates on what is supported. I will try to help there.

        Is Xen alive? Or is it now OpenStack?

        Which Linuxes are native Xen? I guess Gentoo is, but are Debian and Fedora the same?

        On the question I asked, on stackoverflow I have got:
        Note that RHEL/CentOS 8 has no support for Xen PV or PVH modes at all, as RedHat favors KVM over Xen. You could run CentOS 8's standard kernel in HVM mode, but I've understood that would probably be less efficient than the PV/PVH modes. Or you could install kernel-ml from ElRepo; that would allow you to run CentOS 8 within Xen, but would be a necessary but not sufficient step in setting up a CentOS 8-based Xen host.

        1 Reply Last reply Reply Quote 0
        • olivierlambertO
          olivierlambert Vates 🪐 Co-Founder CEO
          last edited by

          PV mode is dead, HVM is faster anyway (with PV drivers).

          Note this is not posted in the right category, since we talk mainly about XCP-ng and not Xen in a general distro 🙂

          1 Reply Last reply Reply Quote 0
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