Narasimhan, 
I've replied inline. 

On Tue, May 25, 2010 at 8:48 AM, Narasimhan Rajagopal <narasimhan1990@yahoo.co.in> wrote:
i have ubuntu 10.04. i have installed ROS using the precompiled binaries(karmic ubuntu 9.10) method. i installed ROS only(didn't install base and pr2).

i was following the tutorials when i came across a few problems.

1. in this http://www.ros.org/wiki/ROS/Tutorials/NavigatingTheFilesystem

the command
"rospack find roscpp"

returns

narasimhan@narasimhan-desktop:/opt/ros/boxturtle/ros$ rospack find roscpp
[rospack] opendir error [No such file or directory] while crawling /opt/ros/boxturtle/stacks
/opt/ros/boxturtle/ros/core/roscpp

and if i execute the same command again it returns

/opt/ros/boxturtle/ros/core/roscpp

why does the "[rospack] opendir error [No such file or directory] while crawling /opt/ros/boxturtle/stacks" occurs the first time but not the 2nd time.

It was expecting a directory /opt/ros/boxturtle/stacks which is installed with the boxturtle stacks.  You can remove it from your /opt/ros/boxturtle/setup.sh or add the directory or install more of the boxturtle packages.  TIcketed https://code.ros.org/trac/ros/ticket/2738 
2. the output of these commands
$ roscd roscpp
$ pwd
is
/opt/ros/boxturtle/ros/core/roscpp
but the one shown in the tutorial is
~/ros/ros/core/roscpp
and in the next tutorial http://www.ros.org/wiki/ROS/Tutorials/CreatingPackage
the output of commands
$ roscd beginner_tutorials
$ pwd
is
/home/narasimhan/ros-tutorials/ros_tutorials/beginner_tutorials
but the one shown in the tutorial is
~/ros/pkgs/ros_tutorials/beginner_tutorials
my guess is that the tutorials given in the website are written using some previous version of ros
The tutorials have been updated, to reflect the different possible locations of ros being installed. 

3.the command "ros log" gives
No active roscore
bash: cd: /home/narasimhan/.ros/log: No such file or directory
I'm assuming you're talking abour "roscd log" This will take you to the logging directory on the running core, which you're not running. So it takes you to the default ros logging directory ~/.ros/log which doesn't exist yet, because you may not have run anything that produced a log.

4.in this http://www.ros.org/wiki/ROS/Tutorials/NavigatingTheFilesystem
the following packages does not exist in my ROS
rosls ethercat_hardware/

rosls laser_
laser_assembler/ laser_geometry/
laser_camera_calibration/ laser_head_updater/
laser_cb_detector/ laser_joint_processor/
laser_cb_processing/ laser_pipeline/
laser_drivers/ laser_scan_publisher_tutorial/
laser_filters/

only laser_scan_publisher_tutorial/ exists.
The tutorial assumed you had more packages installed.  Fixed. 

5.in this tutorial http://www.ros.org/wiki/ROS/Tutorials/BuildingPackages
the command
"rosdep install turtlesim"
gives output as
"executing this script:
set -o errexit
#No Packages to install"

is this ok?
Yes, all things needed are already installed.   

6.the command
$ roscd turtle_teleop
$ svn up
gives output as
At revision 29804.

the command
$ roscd
$ svn up
gives output
Skipped '.'

is these outputs normal?

Yes 
7.the command
"rosdep install turtle_teleop rxtools"
gives output
narasimhan@narasimhan-desktop:/opt/ros/boxturtle/ros$ rosdep install turtle_teleop rxtools
"[rosstack] opendir error [No such file or directory] while crawling /opt/ros/boxturtle/stacks
Failed to find stack for package [joy]
Failed to load rosdep.yaml for package [joy]:Cannot locate installation of package joy: [rospack] opendir error [No such file or directory] while crawling /opt/ros/boxturtle/stacks
[rospack] couldn't find package [joy]. ROS_ROOT[/opt/ros/boxturtle/ros] ROS_PACKAGE_PATH[/home/narasimhan/ros-tutorials/ros_tutorials:/home/narasimhan/ros-tutorials/ros_pkg_tutorials:/opt/ros/boxturtle/stacks]
Failed to find stack for package [spacenav_node]
Failed to load rosdep.yaml for package [spacenav_node]:Cannot locate installation of package spacenav_node: [rospack] opendir error [No such file or directory] while crawling /opt/ros/boxturtle/stacks
[rospack] couldn't find package [spacenav_node]. ROS_ROOT[/opt/ros/boxturtle/ros] ROS_PACKAGE_PATH[/home/narasimhan/ros-tutorials/ros_tutorials:/home/narasimhan/ros-tutorials/ros_pkg_tutorials:/opt/ros/boxturtle/stacks]
Failed to find stack for package [ps3joy]
Failed to load rosdep.yaml for package [ps3joy]:Cannot locate installation of package ps3joy: [rospack] opendir error [No such file or directory] while crawling /opt/ros/boxturtle/stacks
[rospack] couldn't find package [ps3joy]. ROS_ROOT[/opt/ros/boxturtle/ros] ROS_PACKAGE_PATH[/home/narasimhan/ros-tutorials/ros_tutorials:/home/narasimhan/ros-tutorials/ros_pkg_tutorials:/opt/ros/boxturtle/stacks]
Failed to find stack for package [wiimote]
Failed to load rosdep.yaml for package [wiimote]:Cannot locate installation of package wiimote: [rospack] opendir error [No such file or directory] while crawling /opt/ros/boxturtle/stacks
[rospack] couldn't find package [wiimote]. ROS_ROOT[/opt/ros/boxturtle/ros] ROS_PACKAGE_PATH[/home/narasimhan/ros-tutorials/ros_tutorials:/home/narasimhan/ros-tutorials/ros_pkg_tutorials:/opt/ros/boxturtle/stacks]
[rosstack] opendir error [No such file or directory] while crawling /opt/ros/boxturtle/stacks
[rosstack] couldn't find dependency [joystick_drivers] of [ros_pkg_tutorials]
[rosstack] missing dependency
executing this script:
set -o errexit
#No Packages to install"

i think the problem here is in the manifest file of both turtle_teleop and rxtools there is no row specifying system dependencies.

thanks for reading and please help

The tutorials require packages from boxturtle-base.  Wiki notes as such now.

Thanks for the feedback, 
Tully 

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--
Tully Foote
Systems Engineer
Willow Garage, Inc.
tfoote@willowgarage.com
(650) 475-2827