systemd/debian/udev.preinst

#!/bin/sh -e

# Hack to get the dpkg process' PID despite using debconf
if [ -z "$PARENT_PID" ]; then
  export PARENT_PID=$PPID
fi

. /usr/share/debconf/confmodule

# adapted from postinst
chrooted() {
  if [ "$(stat -c %d/%i /)" = "$(stat -Lc %d/%i /proc/1/root 2>/dev/null)" ];
  then
    return 1
  fi
  return 0
}

supported_kernel() {
  local version
  if [ "$1" ]; then
    version="$1"
  else
    version="$(uname -r)"
  fi

  case "$version" in
    2.[012345].*|2.6.[0-9]|2.6.[0-9][!0-9]*) return 1 ;;
    2.6.[12][0-9]|2.6.[12][0-9][!0-9]*) return 1 ;;
    2.6.3[0-1]|2.6.3[0-1][!0-9]*) return 1 ;;
  esac
  return 0
}

check_installed_kernel() {
  for ver in /lib/modules/*; do
    ver=${ver##*/}
    [ "$ver" = '*' ] && return 1
    supported_kernel "$ver" && return 0
  done
  return 1
}

check_installing_kernel() {
  for pkg in $(ps hp $PARENT_PID -o args); do
    ver=$(echo $pkg | sed -nr "s/^.*linux-image-(2\.6\.[0-9]+)-([0-9]+|trunk)-.*_.*_.*\.deb$/\1/p")
    [ "$ver" ] && supported_kernel "$ver" && return 0
  done
  return 1
}

check_kernel_version() {
  # skip the check if udev is not already active
  [ -d /dev/.udev/ -o -d /run/udev/ ] || return 0

  supported_kernel && return

  if [ -e /etc/udev/kernel-upgrade ]; then
    echo "This version of udev requires a kernel >= 2.6.32, but the upgrade was forced."
    # restart udevd which was killed by the old prerm
    udevd -d || true
    return 0
  fi
  
  db_settitle udev/title/upgrade

  if check_installed_kernel || check_installing_kernel; then
    db_fset udev/reboot_needed seen false
    db_input high udev/reboot_needed || true
    db_go
    db_stop
    echo "A reboot is needed, but proceeding with the upgrade."
    touch /etc/udev/kernel-upgrade
    # restart udevd which was killed by the old prerm
    udevd -d || true
    return 0
  fi

  db_fset udev/new_kernel_needed seen false
  db_reset udev/new_kernel_needed
  db_input critical udev/new_kernel_needed || true
  db_go
  db_get udev/new_kernel_needed
  if [ "$RET" = true ]; then
    db_stop
    echo "This version of udev requires a kernel >= 2.6.32, but the upgrade was forced."
    touch /etc/udev/kernel-upgrade
    # restart udevd which was killed by the old prerm
    udevd -d || true
    return 0
  fi
  db_stop
  exit 1
}

check_kernel_features() {
  # skip the check if udev is not already active
  [ -d /dev/.udev/ -o -d /run/udev/ ] || return 0

  # skip the check if check_kernel_version() decided that a new kernel is
  # being installed
  [ -e /etc/udev/kernel-upgrade ] && return 0

  local abort_install=0

  if [ -e /proc/kallsyms ]; then

  local needed_symbols='inotify_init signalfd accept4 open_by_handle_at timerfd_create epoll_create'
  local missing_symbol=0
  for symbol in $needed_symbols; do
    if ! egrep -q "^[a-fA-F0-9]+ T \.?sys_${symbol}$" /proc/kallsyms; then
      missing_symbol=1
      abort_install=1
      break
    fi
  done

  fi

  local missing_devtmpfs=0
  if ! grep -q '[[:space:]]devtmpfs$' /proc/filesystems; then
    missing_devtmpfs=1
    abort_install=1
  fi

  local sysfs_deprecated=0
  if [ -d /sys/class/mem/null -a ! -L /sys/class/mem/null ]; then
    sysfs_deprecated=1
  fi
  if [ -e /sys/block -a ! -e /sys/class/block ]; then
    sysfs_deprecated=1
  fi

  if [ "$missing_symbol" -eq 1 ]; then
    cat <<END
Since release 198, udev requires support for the following features in
the running kernel:

- inotify(2)            (CONFIG_INOTIFY_USER)
- signalfd(2)           (CONFIG_SIGNALFD)
- accept4(2)
- open_by_handle_at(2)  (CONFIG_FHANDLE)
- timerfd_create(2)     (CONFIG_TIMERFD)
- epoll_create(2)       (CONFIG_EPOLL)
END
  fi

  if [ "$missing_devtmpfs" -eq 1 ]; then
    cat <<END
Since release 176, udev requires support for the following features in
the running kernel:

- devtmpfs         (CONFIG_DEVTMPFS)
END
  fi

  if [ "$sysfs_deprecated" -eq 1 ]; then
    db_input critical udev/sysfs_deprecated_incompatibility || true
  fi

  if [ "$abort_install" -eq 0 ]; then
    return 0
  fi

  cat <<END

Please upgrade your kernel before or while upgrading udev.

AT YOUR OWN RISK, you can force the installation of this version of udev
WHICH DOES NOT WORK WITH YOUR RUNNING KERNEL AND WILL BREAK YOUR SYSTEM
AT THE NEXT REBOOT by creating the /etc/udev/kernel-upgrade file.
There is always a safer way to upgrade, do not try this unless you
understand what you are doing!


END

  db_stop
  exit 1
}

rm_conffile() {
  mv_conffile "$1" "$1.dpkg-bak"
}

mv_conffile() {
  local package='udev'
  local name="$1"
  local newname="$2"

  [ -e "$name" ] || return 0

  local md5="$(md5sum $name | sed -e 's/ .*//')"
  oldmd5="$(dpkg-query -W -f='${Conffiles}' $package | \
    sed -n -e "\' $name ' { s/ obsolete$//; s/.* //; p }")"

  if [ "$md5" = "$oldmd5" ]; then
    rm -f "$name"
  else
    mv "$name" "$newname"
  fi
}

mask_systemd_service() {
  if [ -x '/bin/systemctl' -a -d '/run/systemd/system/' ]; then
    ln -sf /dev/null /run/systemd/system/systemd-udevd.service
    ln -sf /dev/null /run/systemd/system/udev.service
    systemctl daemon-reload || true
  fi
}

stop_on_upstart_upgrade() {
  if which initctl >/dev/null && initctl version | grep -q upstart
  then
    # We have to stop udev before we can restart it under upstart in the
    # postinst.
    invoke-rc.d udev stop
  fi
}

check_version() {
  # $2 is non-empty when installing from the "config-files" state
  [ "$2" ] || return 0

  if dpkg --compare-versions $2 lt 204-4; then
    # these must be checked first to allow aborting before changing anything
    if chrooted; then
      echo 'Running in a chroot, skipping the kernel versions checks!'
    else
      check_kernel_version
      check_kernel_features
    fi
  fi # 168-2

  if dpkg --compare-versions $2 lt 175-1; then
    rm_conffile /etc/modprobe.d/blacklist.conf
  fi # 175-1

  if dpkg --compare-versions $2 lt 175-7.1; then
    stop_on_upstart_upgrade
  fi # 175-7.1

  if dpkg --compare-versions $2 lt 204-4; then
    # suppress errors when the new rules files contain options not supported by
    # the old daemon
    if ! chrooted; then
      udevadm control --log-priority=0 || true
    fi
  fi # 204-4
}

case "$1" in
    install)
    check_version "$@"
    ;;

    upgrade|abort-upgrade)
    check_version "$@"
    mask_systemd_service
    ;;

    *)
    echo "$0 called with unknown argument '$1'" >&2
    exit 1
    ;;
esac

#DEBHELPER#