How to get home directory of a prticular user in bash scripting or a single command

The below command gets the home directory of user if at all the user exists
 
getent passwd naresh | cut -f6 -d:

Bash script to add some line to a file at specific line number

I wrote this example to show how to append JAVA_OPTS parameters to startup.sh of tomcat



#!/bin/bash

NLINE=2
s=" export JAVA_OPTS=\"$JAVA_OPTS -Xms1024m -Xmx1024m -XX:MaxPermSize=256m\""
sp=" "
awk -vn="$NLINE" -vs="$s" -vsp="$sp" 'NR==n{$0=$0 sp s}1' startup.sh >temp
mv temp startup.sh



Sp is space given so that if something exists in that line it will give some space and
append our command or string

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