How to configure fan in Dell laptop on Debian

For people who run Linux on their dell laptops have a problem that their fan is running noisily all the time. So the fix is to install a tool "i8kutils" which can be used to control fan depending on temperature of CPU.
First make sure that your current user is sudo user and install the tool:

sudo apt-get install i8kutils

Add a line "i8k" in /etc/modules:

sudo vim /etc/modules

Add a line "options i8k force=1" in a new file /etc/modprobe.d/options:

sudo vim /etc/modprobe.d/options

Run:

sudo modprobe i8k force=1

Open a new file called /etc/i8kmon.conf:

sudo vim /etc/i8kmon.conf

Copy the following to it:

# Run as daemon, override with --daemon option
set config(daemon) 0

# Automatic fan control, override with --auto option
set config(auto) 1

# Report status on stdout, override with --verbose option
set config(verbose) 1

# Status check timeout (seconds), override with --timeout option
set config(timeout) 20

# Temperature thresholds: {fan_speeds low_ac high_ac low_batt high_batt}
set config(0) {{-1 0} -1 40 -1 40}
set config(1) {{-1 1} 40 60 40 60}
set config(3) {{-1 2} 60 128 60 128}

# For computer with 2 fans, use a variant of this instead:
# Temperature thresholds: {fan_speeds low_ac high_ac low_batt high_batt}
# set config(0) {{-1 0} -1 52 -1 65}
# set config(1) {{-1 1} 41 66 55 75}
# set config(2) {{-1 1} 55 80 65 85}
# set config(3) {{-1 2} 70 128 75 128}

To run i8kmon daemon on startup, make a new file /etc/init.d/i8kmon:

sudo vim /etc/init.d/i8kmon

Then add the following to it:
(in my case debian-8 jessie, this file was created automatically when the tool was installed)

#!/bin/sh

### BEGIN INIT INFO
# Provides: i8kmon
# Required-Start:
# Required-Stop:
# Should-Start: $local_fs
# Should-Stop: $local_fs
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Dell Inspiron fan/cpu-temperature monitor
### END INIT INFO

# i8kmon Dell Inspiron fan/cpu-temperature monitor
#
# Written by Miquel van Smoorenburg .
# Modified for Debian GNU/Linux
# by Ian Murdock .
#
# Modified for i8kutils by Karl E. Jørgensen ,
# Massimo Dal Zotto and
# Bradley Smith

PATH=/sbin:/bin:/usr/sbin:/usr/bin

. /lib/lsb/init-functions

NAME=i8kmon
DAEMON=/usr/bin/i8kmon
PROC_I8K=/proc/i8k
DESC="Dell Inspiron fan/cpu-temperature monitor"
# DAM orig: "--daemon --nouserconfig"
I8KMON_ARGS="--auto --daemon"
PIDFILE=/var/run/$NAME.pid
ENABLED=0

test -x $DAEMON || exit 5

if [ -f /etc/default/$NAME ] ; then
. /etc/default/$NAME
fi

case "$1" in
start)
if [ "$ENABLED" = 0 ]; then
log_warning_msg "Not starting. Disabled via /etc/default/$NAME."
exit 0
fi
log_daemon_msg "Starting $DESC" "$NAME"
modprobe i8k >/dev/null 2>&1 || true
if [ ! -f "$PROC_I8K" ]; then
log_progress_msg "Could not find $PROC_I8K."
log_end_msg 1
exit 1
fi
start-stop-daemon --start --quiet --pidfile $PIDFILE \
--background --make-pidfile --exec $DAEMON -- $I8KMON_ARGS
log_end_msg $?
;;
stop)
log_daemon_msg "Stopping $DESC" "$NAME"
start-stop-daemon --oknodo --stop --quiet --pidfile $PIDFILE
log_end_msg $?
rm -f $PIDFILE
;;
restart|reload|force-reload)
$0 stop && sleep 2 && $0 start
;;
*)
echo "Usage: $0 {start|stop|restart|reload|force-reload}" >&2
exit 2
;;
esac

then restart the machine.