I just ran 'chmod -x /bin/chmod'. What did I do? How do I recover?

( or )

What to do if you cannot execute CHMOD?

This is a tricky question.. you have just removed execute permission on chmod.
Result of that is you cannot modify file permissions . Not even for chmod itself .
chmod remains usless on your system.

Here is the solution for the problem

sudo /lib/ld-linux.so.2 /bin/chmod 755 /bin/chmod

or

perl -e 'chmod(0755, "/bin/chmod")'

Solution : Backtrack 5 Live blank screen

I have downloaded backtrack 5 DVD and was trying to live boot from my Laptop.

Once i am in text mode and as root user.

I gave command startx

Just to turn command mode to GUI mode .

My system was showing a blank screen .. Searched online but did not find solutions

So I have tried my own troubleshooting methods and found that it was Graphics related issue.

Fix : Hope problem is because you are using a laptop with graphic card and BT is not able to
load specific drivers for your graphic card.
So go to BIOS either disable graphic card or

Change Graphic mode from Switching to discrete

for me it worked !! let me know if you still have problems will come up with other solutions...

Rsync current directory using SSH port to remote host

/usr/bin/rsync -rave "ssh -p 22222 -l root" --delete . 192.168.1.111:/tmp

Bash script to check command-line arguments and set default if not present

if [ -n "$1" ]
# Test whether command-line argument is present (non-empty).
then
lines=$1
else
lines=$LINES # Default, if not specified on command-line.
fi

how to encrypt your scripts using sch

Dont want to give your scripts to any one but want to give someone to execute for specific period of time then this is what you are looking for .
We can also give timeline in which the script can be used.

Also you will not be revealing you passwords in the script.

SCH will encrypt shell scripts using RC4 and make executable binary.

http://www.datsi.fi.upm.es/~frosal/sources/shc-3.8.7.tgz

shc [ -e date ] [ -m addr ] [ -i iopt ] [ -x cmnd ]
[ -l lopt ] [ -ACDhTv ] -f script

shc -e date ( script will not run afterdate specified )
-m "Please contact support " (message to display after we run the expired scirpt)

shc -e 01/06/2010 -m "You are late to run this script." -f script.sh

./script.sh.x



http://www.datsi.fi.upm.es/~frosal/sources/shc.html

I have tried to hack the encrypted binary that came as output, but was not successful
I used bashdb and GDB

Per user mac based bandwidth monitor for routers

Want to calculate how much bandwidth each user (mac address) is using


    ./wrtbwmon setup
   ./wrtbwmon update /tmp/usage.db offpeak
   ./wrtbwmon publish /tmp/usage.db /www/user/usage.htm /jffs/users.txt

Here is open source solution ClickHere

Below is the script  (wrtbwmon )

---------------------------

LAN_IFACE=$(nvram get lan_ifname)

lock()

{

while [ -f /tmp/wrtbwmon.lock ]; do

if [ ! -d /proc/$(cat /tmp/wrtbwmon.lock) ]; then

echo "WARNING : Lockfile detected but process $(cat /tmp/wrtbwmon.lock) does not exist !"

rm -f /tmp/wrtbwmon.lock

fi

sleep 1

done

echo $$ > /tmp/wrtbwmon.lock

}

unlock()

{

rm -f /tmp/wrtbwmon.lock

}

case ${1} in

"setup" )

#Create the RRDIPT CHAIN (it doesn't matter if it already exists).

iptables -N RRDIPT 2> /dev/null

#Add the RRDIPT CHAIN to the FORWARD chain (if non existing).

iptables -L FORWARD --line-numbers -n | grep "RRDIPT" | grep "1" > /dev/null

if [ $? -ne 0 ]; then

iptables -L FORWARD -n | grep "RRDIPT" > /dev/null

if [ $? -eq 0 ]; then

echo "DEBUG : iptables chain misplaced, recreating it..."

iptables -D FORWARD -j RRDIPT

fi

iptables -I FORWARD -j RRDIPT

fi

#For each host in the ARP table

grep ${LAN_IFACE} /proc/net/arp | while read IP TYPE FLAGS MAC MASK IFACE

do

#Add iptable rules (if non existing).

iptables -nL RRDIPT | grep "${IP} " > /dev/null

if [ $? -ne 0 ]; then

iptables -I RRDIPT -d ${IP} -j RETURN

iptables -I RRDIPT -s ${IP} -j RETURN

fi

done

;;

"update" )

[ -z "${2}" ] && echo "ERROR : Missing argument 2" && exit 1

# Uncomment this line if you want to abort if database not found

# [ -f "${2}" ] || exit 1

lock

#Read and reset counters

iptables -L RRDIPT -vnxZ -t filter > /tmp/traffic_$$.tmp

grep -v "0x0" /proc/net/arp  | while read IP TYPE FLAGS MAC MASK IFACE

do

#Add new data to the graph. Count in Kbs to deal with 16 bits signed values (up to 2G only)

#Have to use temporary files because of crappy busybox shell

grep ${IP} /tmp/traffic_$$.tmp | while read PKTS BYTES TARGET PROT OPT IFIN IFOUT SRC DST

do

[ "${DST}" = "${IP}" ] && echo $((${BYTES}/1000)) > /tmp/in_$$.tmp

[ "${SRC}" = "${IP}" ] && echo $((${BYTES}/1000)) > /tmp/out_$$.tmp

done

IN=$(cat /tmp/in_$$.tmp)

OUT=$(cat /tmp/out_$$.tmp)

rm -f /tmp/in_$$.tmp

rm -f /tmp/out_$$.tmp

if [ ${IN} -gt 0 -o ${OUT} -gt 0 ];  then

echo "DEBUG : New traffic for ${MAC} since last update : ${IN}k:${OUT}k"

LINE=$(grep ${MAC} ${2})

if [ -z "${LINE}" ]; then

echo "DEBUG : ${MAC} is a new host !"

PEAKUSAGE_IN=0

PEAKUSAGE_OUT=0

OFFPEAKUSAGE_IN=0

OFFPEAKUSAGE_OUT=0

else

PEAKUSAGE_IN=$(echo ${LINE} | cut -f2 -s -d, )

PEAKUSAGE_OUT=$(echo ${LINE} | cut -f3 -s -d, )

OFFPEAKUSAGE_IN=$(echo ${LINE} | cut -f4 -s -d, )

OFFPEAKUSAGE_OUT=$(echo ${LINE} | cut -f5 -s -d, )

fi

if [ "${3}" = "offpeak" ]; then

OFFPEAKUSAGE_IN=$((${OFFPEAKUSAGE_IN}+${IN}))

OFFPEAKUSAGE_OUT=$((${OFFPEAKUSAGE_OUT}+${OUT}))

else

PEAKUSAGE_IN=$((${PEAKUSAGE_IN}+${IN}))

PEAKUSAGE_OUT=$((${PEAKUSAGE_OUT}+${OUT}))

fi

grep -v "${MAC}" ${2} > /tmp/db_$$.tmp

mv /tmp/db_$$.tmp ${2}

echo ${MAC},${PEAKUSAGE_IN},${PEAKUSAGE_OUT},${OFFPEAKUSAGE_IN},${OFFPEAKUSAGE_OUT},$(date "+%d-%m-%Y %H:%M") >> ${2}

fi

done

#Free some memory

rm -f /tmp/*_$$.tmp

unlock

;;

"publish" )

[ -z "${2}" ] && echo "ERROR : Missing argument 2" && exit 1

[ -z "${3}" ] && echo "ERROR : Missing argument 3" && exit 1

USERSFILE="/etc/dnsmasq.conf"

[ -f "${USERSFILE}" ] || USERSFILE="/tmp/dnsmasq.conf"

[ -z "${4}" ] || USERSFILE=${4}

[ -f "${USERSFILE}" ] || USERSFILE="/dev/null"

# first do some number crunching - rewrite the database so that it is sorted

lock

touch /tmp/sorted_$$.tmp

cat ${2} | while IFS=, read MAC PEAKUSAGE_IN PEAKUSAGE_OUT OFFPEAKUSAGE_IN OFFPEAKUSAGE_OUT LASTSEEN

do

echo ${PEAKUSAGE_IN},${PEAKUSAGE_OUT},${OFFPEAKUSAGE_IN},${OFFPEAKUSAGE_OUT},${MAC},${LASTSEEN} >> /tmp/sorted_$$.tmp

done

unlock

        # create HTML page

        echo "

Total Usage :

" >> ${3}

        echo "" >> ${3}

        echo "

User	Peak download	Peak upload	Offpeak download	Offpeak upload	Last seen

" >> ${3}

        echo "
This page was generated on `date`" 2>&1 >> ${3}

        echo "" >> ${3}

        #Free some memory

        rm -f /tmp/*_$$.tmp

        ;;

*)

echo "Usage : $0 {setup|update|publish} [options...]"

echo "Options : "

echo "   $0 setup"

echo "   $0 update database_file [offpeak]"

echo "   $0 publish database_file path_of_html_report [user_file]"

echo "Examples : "

echo "   $0 setup"

echo "   $0 update /tmp/usage.db offpeak"

echo "   $0 publish /tmp/usage.db /www/user/usage.htm /jffs/users.txt"

echo "Note : [user_file] is an optional file to match users with their MAC address"

echo "       Its format is : 00:MA:CA:DD:RE:SS,username , with one entry per line"

exit

;;

esac

How to extract 7zip files in ubuntu

First install 7zip package

sudo apt-get install p7zip  

( you will need universal repository to run the above command )


after installing

7z x my7Zzipfile