#!/bin/sh
# Start/stop/restart the BIND name server daemon (named).

# Start BIND. In the past it was more secure to run BIND as a non-root
# user (for example, with '-u daemon'), but the modern version of BIND
# knows how to use the kernel's capability mechanism to drop all root
# privileges except the ability to bind() to a privileged port and set
# process resource limits, so running as a non-root user is not needed.
# But if you want to run as a non-root user anyway, the command options
# can be set like this in /etc/default/named:
#       NAMED_OPTIONS="-u daemon"
# So you will not have to edit this script.
#
# Please note that if you run BIND as a non-root user, your files in
# /var/named may need to be chowned to this user or else named will
# refuse to start.

# You might also consider running BIND in a "chroot jail",
# a discussion of which may be found in
# /usr/doc/Linux-HOWTOs/Chroot-BIND-HOWTO.
 
# One last note: rndc has a lot of other nice features that it is not
# within the scope of this start/stop/restart script to support.
# For more details, see "man rndc" or just type "rndc" to see the options.

# Load command defaults:
if [ -f /etc/default/named ] ; then . /etc/default/named ; fi
if [ -f /etc/default/rndc ] ; then . /etc/default/rndc ; fi

# Sanity check. If /usr/sbin/named is missing then it
# doesn't make much sense to try to run this script:
if [ ! -x /usr/sbin/named ]; then
  echo "/etc/rc.d/rc.bind:  no /usr/sbin/named found (or not executable); cannot start."
  exit 1
fi

# Function to find the user BIND is running as in $NAMED_OPTIONS:
find_bind_user() {
  if echo $NAMED_OPTIONS | grep -wq "\-u" ; then
    unset BIND_USER USER_FOUND
    echo $NAMED_OPTIONS | tr ' ' '\n' | while read element ; do
      if [ "$USER_FOUND" = "true" ]; then
        BIND_USER="$element"
        echo $BIND_USER
        break
      elif [ "$element" = "-u" ]; then
        USER_FOUND="true"
      fi
    done
  else
    echo "root"
  fi
}

# Start BIND. As many times as you like. ;-)
# Seriously, don't run "rc.bind start" if BIND is already
# running or you'll get more than one copy running.
bind_start() {
  # Make sure /var/run/named exists:
  mkdir -p /var/run/named
  # If we are running as a non-root user, we'll need to be sure that
  # /var/run/named is chowned properly to that user. Your files in
  # /var/named may need to be chowned as well, but that will be up to
  # the sysadmin to do.
  BIND_USER="$(find_bind_user)"
  if [ ! "$BIND_USER" = "root" ]; then
    chown -R $BIND_USER /var/run/named
  else # prevent error if switching back to running as root:
    chown -R root /var/run/named
  fi
  # Start named:
  if [ -x /usr/sbin/named ]; then
    echo "Starting BIND:  /usr/sbin/named $NAMED_OPTIONS"
    /usr/sbin/named $NAMED_OPTIONS
    sleep 1
  fi
  # Make sure that named started:
  if ! ps axc | grep -q named ; then
    echo "WARNING:  named did not start."
    echo "Attempting to start named again:  /usr/sbin/named $NAMED_OPTIONS"
    /usr/sbin/named $NAMED_OPTIONS
    sleep 1
    if ps axc | grep -q named ; then
      echo "SUCCESS:  named started."
    else
      echo "FAILED: Sorry, a second attempt to start named has also failed."
      echo "There may be a configuration error that needs fixing. Good luck!"
    fi
  fi
}

# Stop all running copies of BIND (/usr/sbin/named):
bind_stop() {
  # If you've set up rndc, we can use this to make shutting down BIND faster.
  # If you have /etc/rndc.conf, or you have /etc/rndc.key, or $RNDC_OPTIONS is
  # not empty, we'll try it.
  if [ -r /etc/rndc.conf -o -r /etc/rndc.key -o ! -z "$RNDC_OPTIONS" ]; then
    if [ -z "$RNDC_OPTIONS" ]; then
      echo "Stopping BIND:  /usr/sbin/rndc stop"
    else
      echo "Stopping BIND:  /usr/sbin/rndc $RNDC_OPTIONS stop"
    fi
    /usr/sbin/rndc $RNDC_OPTIONS stop
    # Wait for up to $TIMEOUT seconds before moving on to try killall:
    TIMEOUT=${TIMEOUT:-10}
    while [ "$TIMEOUT" -gt "0" ]; do
      # Exit the timeout loop if there are no named processes:
      if ! ps axco command | grep -q -e "^named$"; then
        break
      fi
      sleep 1
      TIMEOUT=$(expr $TIMEOUT - 1)
    done
  fi
  # Kill named processes if there are any running:
  if ps axco command | grep -q -e "^named$"; then
    echo "Stopping all named processes in this namespace:  /bin/killall -SIGTERM --ns \$\$ named"
    /bin/killall -SIGTERM --ns $$ named 2> /dev/null
  fi
}

# Reload BIND:
bind_reload() {
  /usr/sbin/rndc $RNDC_OPTIONS reload
}

# Restart BIND:
bind_restart() {
  bind_stop
  bind_start
}

# Get BIND status:
bind_status() {
  /usr/sbin/rndc $RNDC_OPTIONS status
}

case "$1" in
'start')
  bind_start
  ;;
'stop')
  bind_stop
  ;;
'reload')
  bind_reload
  ;;
'restart')
  bind_restart
  ;;
'status')
  bind_status
  ;;
*)
  echo "usage $0 start|stop|reload|restart|status"
esac