Windows 7: format FAT32 Partition

1. run cmd.exe (in Administrative mode - use Ctrl+Shift+Enter)
2. format : /FS:FAT32

hope this little piece of information saves your time.

VMware ESXi 4.0 Headless (Unattended)Install

In order to achieve this you need to do some hacks and tricks with the vmware installer scripts

1. Modify the Installer-Steps

In order to achieve this you will need to modify the install.tgz file
--------------------------------------------------------------------------------------------------

- Extract ISO
- cd to the extracted directory

- mkdir tt
- cp install.tgz tt/
- cd tt/
- tar xvvf install.tgz

- $ ls
install.tgz sbin usr

- cd usr/lib/vmware/installer/
- chmod +w ThinESXInstall.py
- vi ThinESXInstall.py


modify following line (approx line 22 )

Steps = [ WelcomeStep, LicenseStep, TargetSelectionStep, ConfirmStep, \
WriteStep, PostConfigStep, CompleteStep, RebootStep ]
to

Steps = [ TargetSelectionStep, WriteStep, RebootStep ]

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

2. Automated the Disks Selection Step in the installer script

now go to ThinESX dircetory

- cd ThinESX/
- chmod +w ThinESXInstallSteps.py
- vi ThinESXInstallSteps.py


--- modify the target selection step (approx line 56)

copy paste the following lines in the Scripts :

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

def TargetSelectionStep(data):
"""TargetSelectionStep
This install step is responsible for presenting the user with the device
selection dialog and determining the target which is being installed to."""
targets = TargetEnumeration(NotPredicate(RACVirtualMediaFilter))

if len(targets) == 0:
raise NoValidDevicesException()

if len(targets) == 1 and targets[0].IsLocal():
data['Target'] = targets[0]
return data
else:
return LaunchDialog(DeviceSelectionDialog(targets, data))

--------------------------------------------------------------------------------------------------
- Save and Exit
- cd back to tt/ directory
- rm -rf install.tgz && tar -czvf install.tgz * && chmod 755 install.tgz

--------------------------------------------------------------------------------------------------
replace the existing install.tgz file to the modified one..

Your unattended installer is ready to go..

Script to display all duplicate line in a file once

this script will display all the duplicate lines only once

Example:

$cat file
I like oranges
I like apples
I like pears
I like apples
I like guavas
I like oranges
I like apples

$./test.pl file

I like apples
I like oranges

#!/usr/bin/perl
#
open(FILE,"$ARGV[0]");
my @contents = ;
my %dup;
foreach $line (@contents)
{
  @keyz = keys %dup;
  if(!(grep(/$line/, @keyz)) || $dup{$line})
  {
      $dup{$line}++;
      if($dup{$line} > 1)
  {
          print $line;
          $dup{$line} = 0;
      }
  }
}

Script to upload ssh key to skip password authentication

#!/bin/bash

## Script to auto upload ssh keys on the LINUX HOST

NO_ARGS=0
E_OPTERROR=65

if [ $# -eq "$NO_ARGS" ] # should check for no arguments
   then
   echo "Usage: `basename $0` -i   "
   exit $E_OPTERROR
fi

while getopts ":ih" Option

 do
 case $Option in
   
   i)
   remote_host_ipaddress="$2"
   ;;
 
   h)
   echo "Usage: `basename $0` -i  "
   exit $E_OPTERROR
   ;;
 esac
 done

 shift $(($OPTIND - 1))

 ## This will generate ssh key on the remote host
 echo "Generation ssh-keygen on remote linux host"
 echo $remote_host_ipaddress

 ssh root@$remote_host_ipaddress  /usr/bin/ssh-keygen -t dsa
 
 echo "uploading your ssh keys on remote linux host"
 scp ~/.ssh/id_dsa.pub root@$remote_host_ipaddress:/root/.ssh/authorized_keys

Expect - Sample Scripts

Following scripts will "ssh" into the remote machine and will "execute the command" that you pass to be executed on the remote system.

#!/usr/bin/expect -f
# USAGE:
#----------------------------------------------------
# ./ssh-expect.exp 'command to be executed on remote machine'
#----------------------------------------------------
# set Variables
set password [lrange $argv 0 0]
set remote_ipaddr [lrange $argv 1 1]
set scriptname [lrange $argv 2 2]
set arg1 [lrange $argv 3 3]
set timeout -1
spawn ssh root@$remote_ipaddr $scriptname $arg1
match_max 100000
# Look for passwod prompt
expect "*?assword:*"
# Send password to the remote machine
send -- "$password\r"
send -- "\r"
#terminate the connection
expect eof

Perl - Sample Scripts (useful for interview)

Script - to remove leading and trailing spaces from the passed string
--------------------------------------------------------------------------------------------------
#/usr/bin/perl

my $string = <>;
@temp = split / / , $string;
$string =~ s/^\s+//; #remove leading spaces
$string =~ s/\s+$//; #remove trailing spaces

print @temp
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Linux Admin - command line Interview questions

following are some sample question that you can get during a Linux command line interview

Question : In this system there is following directory structure.
-> 1 x Dir (main directory) -> 10 x Sub-Dir -> 10 x files in each subdirectories
Find out which file in the directory was lastly modified.

Answer :

$ find -type f -mtime -1

Exp : this command will find the lastly modified(within last 24 hours) file in the directory structure

Question: How can you send email from command line ??

Answer:

$ "mail e-mail @domain.com"
Subject:
Type in the Body "the message " that you want to send

press a Dott (.) when you are done.

Cc: "Leave it blank "

you can also put some one on the Cc list too..


Question: How can you create exactly 1MB sized file from command line ?

Answer :

$ dd if=/dev/zero of=output.file bs=1024 count=1024

Question: How can you find the largest file in a directory structure ?

Answer :

$ find /home/ -printf "%s:%p\n"|sort -k1n|tail -1

This will get you the largest sized file from the directory structure.

Question: How can you check what shell are you currently using

Answer:

$ echo $SHELL

or

$ ps | grep `echo $$`  | awk '{print $4}'