Archive for March, 2011


Friday, March 25th, 2011

Primary Domain Controller
First, install Samba,

[root@linux10 ~]#apt-get install samba

Configure Samba by editing /etc/samba/smb.conf.
My smb.conf file is shown below. Make changes according to your requirement.

[root@linux10 ~]#vi /etc/samba/smb.conf

#======================= Global Settings =======================


## Browsing/Identification ###

# Change this to the workgroup/NT-domain name your Samba server will part of
workgroup = TVIN

# server string is the equivalent of the NT Description field
server string = %h server (Samba, Ubuntu)

# Windows Internet Name Serving Support Section:
# WINS Support – Tells the NMBD component of Samba to enable its WINS Server
# wins support = no

# WINS Server – Tells the NMBD components of Samba to be a WINS Client
# Note: Samba can be either a WINS Server, or a WINS Client, but NOT both
; wins server = w.x.y.z

# This will prevent nmbd to search for NetBIOS names through DNS.
dns proxy = no

# What naming service and in what order should we use to resolve host names
# to IP addresses
; name resolve order = lmhosts host wins bcast

#### Networking ####

# The specific set of interfaces / networks to bind to
# This can be either the interface name or an IP address/netmask;
# interface names are normally preferred
; interfaces = eth0

# Only bind to the named interfaces and/or networks; you must use the
# ‘interfaces’ option above to use this.
# It is recommended that you enable this feature if your Samba machine is
# not protected by a firewall or is a firewall itself. However, this
# option cannot handle dynamic or non-broadcast interfaces correctly.
; bind interfaces only = yes

#### Debugging/Accounting ####

# This tells Samba to use a separate log file for each machine
# that connects
log file = /var/log/samba/log.%m

# Cap the size of the individual log files (in KiB).
max log size = 1000

# If you want Samba to only log through syslog then set the following
# parameter to ‘yes’.
# syslog only = no

# We want Samba to log a minimum amount of information to syslog. Everything
# should go to /var/log/samba/log.{smbd,nmbd} instead. If you want to log
# through syslog you should set the following parameter to something higher.
syslog = 0

# Do something sensible when Samba crashes: mail the admin a backtrace
panic action = /usr/share/samba/panic-action %d

####### Authentication #######

# “security = user” is always a good idea. This will require a Unix account
# in this server for every user accessing the server. See
# /usr/share/doc/samba-doc/htmldocs/Samba3-HOWTO/ServerType.html
# in the samba-doc package for details.
security = user

# You may wish to use password encryption. See the section on
# ‘encrypt passwords’ in the smb.conf(5) manpage before enabling.
encrypt passwords = true

# If you are using encrypted passwords, Samba will need to know what
# password database type you are using.
passdb backend = tdbsam

obey pam restrictions = yes

# This boolean parameter controls whether Samba attempts to sync the Unix
# password with the SMB password when the encrypted SMB password in the
# passdb is changed.
unix password sync = yes

# For Unix password sync to work on a Debian GNU/Linux system, the following
# parameters must be set (thanks to Ian Kahan < for
# sending the correct chat script for the passwd program in Debian Sarge).
passwd program = /usr/bin/passwd %u
passwd chat = *Entersnews*spassword:* %nn *Retypesnews*spassword:* %nn *passwordsupdatedssuccessfully* .

# This boolean controls whether PAM will be used for password changes
# when requested by an SMB client instead of the program listed in
# ‘passwd program’. The default is ‘no’.
pam password change = yes

# This option controls how unsuccessful authentication attempts are mapped
# to anonymous connections
map to guest = bad user

########## Domains ###########

# Is this machine able to authenticate users. Both PDC and BDC
# must have this setting enabled. If you are the BDC you must
# change the ‘domain master’ setting to no
domain logons = yes
domain master = yes
local master = yes
preferred master = yes
os level = 64

# The following setting only takes effect if ‘domain logons’ is set
# It specifies the location of the user’s profile directory
# from the client point of view)
# The following required a [profiles] share to be setup on the
# samba server (see below)
; logon path = \%Nprofiles%U
# Another common choice is storing the profile in the user’s home directory
# (this is Samba’s default)
logon path = \%N%Uprofile

# The following setting only takes effect if ‘domain logons’ is set
# It specifies the location of a user’s home directory (from the client
# point of view)
logon drive = H:
logon home = \%N%U

# The following setting only takes effect if ‘domain logons’ is set
# It specifies the script to run during logon. The script must be stored
# in the [netlogon] share
# NOTE: Must be store in ‘DOS’ file format convention
; logon script = logon.cmd

# This allows Unix users to be created on the domain controller via the SAMR
# RPC pipe. The example command creates a user account with a disabled Unix
# password; please adapt to your needs
; add user script = /usr/sbin/adduser –quiet –disabled-password –gecos “” %u

# This allows machine accounts to be created on the domain controller via the
# SAMR RPC pipe.
# The following assumes a “machines” group exists on the system
add machine script = /usr/sbin/useradd -g machines -c “%u machine account” -d /var/lib/samba -s /bin/false %u

# This allows Unix groups to be created on the domain controller via the SAMR
# RPC pipe.
; add group script = /usr/sbin/addgroup –force-badname %g

########## Printing ##########

# If you want to automatically load your printer list rather
# than setting them up individually then you’ll need this
# load printers = yes

# lpr(ng) printing. You may wish to override the location of the
# printcap file
; printing = bsd
; printcap name = /etc/printcap

# CUPS printing. See also the cupsaddsmb(8) manpage in the
# cupsys-client package.
; printing = cups
; printcap name = cups

############ Misc ############

# Using the following line enables you to customise your configuration
# on a per machine basis. The %m gets replaced with the netbios name
# of the machine that is connecting
; include = /home/samba/etc/smb.conf.%m

# Most people will find that this option gives better performance.
# See smb.conf(5) and /usr/share/doc/samba-doc/htmldocs/Samba3-HOWTO/speed.html
# for details
# You may want to add the following on a Linux system:
# socket options = TCP_NODELAY

# The following parameter is useful only if you have the linpopup package
# installed. The samba maintainer and the linpopup maintainer are
# working to ease installation and configuration of linpopup and samba.
; message command = /bin/sh -c ‘/usr/bin/linpopup “%f” “%m” %s; rm %s’ &

# Domain Master specifies Samba to be the Domain Master Browser. If this
# machine will be configured as a BDC (a secondary logon server), you
# must set this to ‘no'; otherwise, the default behavior is recommended.
# domain master = auto

# Some defaults for winbind (make sure you’re not using the ranges
# for something else.)
; idmap uid = 10000-20000
; idmap gid = 10000-20000
; template shell = /bin/bash

# The following was the default behaviour in sarge,
# but samba upstream reverted the default because it might induce
# performance issues in large organizations.
# See Debian bug #368251 for some of the consequences of *not*
# having this setting and smb.conf(5) for details.
; winbind enum groups = yes
; winbind enum users = yes

# Setup usershare options to enable non-root users to share folders
# with the net usershare command.

# Maximum number of usershare. 0 (default) means that usershare is disabled.
; usershare max shares = 100

# Allow users who’ve been granted usershare privileges to create
# public shares, not just authenticated ones
usershare allow guests = yes

#======================= Share Definitions =======================

# Un-comment the following (and tweak the other settings below to suit)
# to enable the default home directory shares. This will share each
# user’s home directory as \serverusername
comment = Home Directories
browseable = no
writeable = yes

# By default, the home directories are exported read-only. Change the
# next parameter to ‘no’ if you want to be able to write to them.
; read only = yes

# File creation mask is set to 0700 for security reasons. If you want to
# create files with group=rw permissions, set next parameter to 0775.
; create mask = 0700

# Directory creation mask is set to 0700 for security reasons. If you want to
# create dirs. with group=rw permissions, set next parameter to 0775.
; directory mask = 0700

# By default, \serverusername shares can be connected to by anyone
# with access to the samba server. Un-comment the following parameter
# to make sure that only “username” can connect to \serverusername
# This might need tweaking when using external authentication schemes
; valid users = %S

# Un-comment the following and create the netlogon directory for Domain Logons
# (you need to configure Samba to act as a domain controller too.)
comment = Network Logon Service
path = /home/samba/netlogon
guest ok = yes
read only = yes
share modes = no

# Un-comment the following and create the profiles directory to store
# users profiles (see the “logon path” option above)
# (you need to configure Samba to act as a domain controller too.)
# The path below should be writable by all users so that their
# profile directory may be created the first time they log on
comment = Users profiles
path = /home/samba/profiles
guest ok = no
browseable = no
create mask = 0600
directory mask = 0700

comment = All Printers
browseable = no
path = /var/spool/samba
printable = yes
guest ok = no
read only = yes
create mask = 0700

# Windows clients look for this share name as a source of downloadable
# printer drivers
comment = Printer Drivers
path = /var/lib/samba/printers
browseable = yes
read only = yes
guest ok = no
# Uncomment to allow remote administration of Windows print drivers.
# You may need to replace ‘lpadmin’ with the name of the group your
# admin users are members of.
# Please note that you also need to set appropriate Unix permissions
# to the drivers directory for these users to have write rights in it
; write list = root, @lpadmin

# A sample share for sharing your CD-ROM with others.
; comment = Samba server’s CD-ROM
; read only = yes
; locking = no
; path = /cdrom
; guest ok = yes

# The next two parameters show how to auto-mount a CD-ROM when the
# cdrom share is accesed. For this to work /etc/fstab must contain
# an entry like this:
# /dev/scd0 /cdrom iso9660 defaults,noauto,ro,user 0 0
# The CD-ROM gets unmounted automatically after the connection to the
# If you don’t want to use auto-mounting/unmounting make sure the CD
# is mounted on /cdrom
; preexec = /bin/mount /cdrom
; postexec = /bin/umount /cdrom

Save the file.
Then create a group named machines.

[root@linux10 ~]#groupadd -g 201 machines

Create the netlogon directory for Domain Logons.

[root@linux10 ~]#mkdir -m 0775 /home/netlogon

Create the profiles directory to store users profiles.

[root@linux10 ~]#mkdir /home/samba /home/samba/profiles

Set permission on profiles directory.

[root@linux10 ~]#chmod 1757 /home/samba/profiles

Create users, passwords and smbpasswords.

[root@linux10 ~]#useradd -m tactical
[root@linux10 ~]#passwd tactical
[root@linux10 ~]#smbpasswd -a tactical
[root@linux10 ~]#useradd -m swat
[root@linux10 ~]#passwd swat
[root@linux10 ~]#smbpasswd -a swat

Set root password for samba authentication while matchine joininig the domain.

[root@linux10 ~]#smbpasswd -a root

Final Step to Restart Samba Service.

[root@linux10 ~]#service smbd restart
[root@linux10 ~]#service nmbd restart

Samba Primary Domain Controller is ready to accept client requests.
Joining a Windows machine to Samba PDC.
1.Right Click on Mycomputer.
2.Go to Properties select the Computer Name tab.
3.Click Change.
4.Click Domain radio button, enter the Domain name like TVIN, then click ok.
5.At the prompt, enter the user name root and root smbpassword and then click OK.
6.Click OK twice to return to the System Properties dialog box.
7.Click OK, and then click Yes to restart the computer.

Windows xp is ready to login with samba user and make sure you should use smbpassword while user login.

Process Address Space – Code, gvar, BSS, Heap & Stack

Wednesday, March 23rd, 2011

Almost all modern operating systems implement Memory Protection to protect access to a private address allocated to a process by other processes to avoid storage violation. this private space is called Process Address Space.

Process Address Space partitioned into various memory areas or segments based on the functional differences.

Text/Code Segment

This segment, also known as the code segment, holds the executable instructions of a program.

  • execute-only
  • fixed size

Data Segment

The data area contains global and static variables used by the process that are initialized. This segment can be further classified into initialized read-only area and initialized read-write area.

  • Gvar Section
    A global variable that is initialized and stored in the data segment. This section has read/write attributes but cannot be shared among processes running the same program.
  • BSS Section
    This section holds uninitialized data. This data consists of global variables that the system initializes with 0s upon program execution. Another name for this section is the zero-initialized data section.
  • Heap Section
    This is used to grow the linear address space of a process. When a program uses malloc() to obtain dynamic memory, this memory is placed in the heap.The heap area begins at the end of the BSS segment and “grows up” to larger addresses from there. The Heap area is shared by all shared libraries and dynamically loaded modules in a process.

    • read/write
    • variable size
    • dynamic allocation by request

Stack Segment

This contains all the local variables that get allocated. When a function is called, the local variables for that function are pushed onto the stack. As soon as a function ends, the variables associated with the function are popped from the stack. Other information, including return addresses and parameters, is also stored in the stack. The stack is a LIFO structure, typically located in the higher parts of memory. It usually “grows down” with every register, immediate value or stack frame being added to it.

  • read/write, variable size
  • automatic growth/shrinkage

popen() – execute shell command from C/C++

Wednesday, March 23rd, 2011

The popen() function executes a command and pipes the executes command to the calling program, returning a pointer to the stream which can be used by calling program to read/write to the pipe.
Below are the C/C++ snippets to run a simple command, read the stream from pipe and then write to console.

C Implementation

#include <stdio.h>

int main(void) {
	FILE *in;
	extern FILE *popen();
	char buff[512];

	if(!(in = popen("ls -sail", "r"))){

	while(fgets(buff, sizeof(buff), in)!=NULL){
		printf("%s", buff);


C++ Implementation

#include <iostream>
#include <stdio.h>

using namespace std;

int main() {
	FILE *in;
	char buff[512];

	if(!(in = popen("ls -sail", "r"))){
		return 1;

	while(fgets(buff, sizeof(buff), in)!=NULL){
		cout << buff;

	return 0;

popen() is included in SUS version 2. More details can be found at http://pubs.opengroup.org/onlinepubs/007908799/xsh/popen.html

SQL Server Comma Delimited to table

Tuesday, March 1st, 2011
One of the frequently asked questions in a lot of SQL Server forums is how to handle a comma-delimited value passed as a parameter in a stored procedure.
To better illustrate the question, let’s say you have a website wherein you have a page that lets the users select data items which are sent back to the database for further processing in variety of formats, and of all the formats, comma separated is probably the format which developers struggle with most if they do not know how to consume this structure.

Databases do not understand data arranged horizontally, so how to convert the data from CSV (horizontal) to a table (vertical) ?

Fortunately there are a couple of tricks up database’s sleeve.

1. Dynamic SQL Approach
This method involves creating a SQL statement during execution time to evaluate the where condition. But this approach is as ugly as it sounds nasty. Creating SQL statments on the the fly would results in lot of activity in shared pool. i.e. Compilation of statement, execution plan generation and final execution of query. All of these consume precious server resources and hence should avoided if at all possible.
Due to the obvious pit-falls in this approach I am not even going to attempt to show how-to.
2. Common Table Expression (CTE) based Approach
Comman table expressions (CTE) is probably one of the most powerful programming construct introduced in the SQL Server 2005. It can be used in hierarchical queries, special aggregations and various other problem solving. Various uses of CTE are discussed elsewhere in my blog, which can be found using the search button on the blog homepage.
Below is a CTE based implementation. The good aspect about this approach is that it is completely object independent so the function can be used for any table in any schema of the database as long as you have sufficient permissions.

USE [AdventureWorks]
IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N‘[dbo].[ufnCSVToTable]’)
AND type in (N‘FN’, N‘IF’, N‘TF’, N‘FS’, N‘FT’))
DROP FUNCTION [dbo].[ufnCSVToTable]
CREATE FUNCTION [dbo].[ufnCSVToTable](@str VARCHAR(4000), @sep CHAR(1))
( [colx] VARCHAR(4000) NULL )
SELECT 1 n,1 m
FROM r0 WHERE n<=LEN(@str)
SELECT SUBSTRING(@str,MIN(n), MAX(n)-MIN(n)) colx
–Independent usage
SELECT * FROM [dbo].[ufnCSVToTable](this,is,a,comma,separated,sentence,‘,’)

–Usage with table
DECLARE @str VARCHAR(1000); SET @str = ‘1,2’;
FROM Person.Address Ad
INNER JOIN [dbo].[ufnCSVToTable](@str,‘,’) CSV ON Ad.AddressID = CSV.colx


I hope you find this function useful.
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