Ninad, thanks for the valuable guidance. Since I am newbie to linux i did not experiment but followed as per your guidance. extract of terminal reproduced below: sriranga@ubuntu:~$ cd tesseract-ocr-read-only-408/ sriranga@ubuntu:~/tesseract-ocr-read-only-408$ sudo password [sudo] password for sriranga: sudo: password: command not found sriranga@ubuntu:~/tesseract-ocr-read-only-408$ sudo passwd Enter new UNIX password: Retype new UNIX password: passwd: password updated successfully sriranga@ubuntu:~/tesseract-ocr-read-only-408$ sudo ldconfig sriranga@ubuntu:~/tesseract-ocr-read-only-408$ sudo usage: sudo -h | -K | -k | -L | -l | -V | -v usage: sudo [-bEHPS] [-p prompt] [-u username|#uid] [VAR=value] {-i | -s | <command>} usage: sudo -e [-S] [-p prompt] [-u username|#uid] file ... sriranga@ubuntu:~/tesseract-ocr-read-only-408$ sudo ldconfig sriranga@ubuntu:~/tesseract-ocr-read-only-408$ su Password: root@ubuntu:/home/sriranga/tesseract-ocr-read-only-408# ldconfig root@ubuntu:/home/sriranga/tesseract-ocr-read-only-408# Nothing displayed for ldconfig. where I made a mistake? -sriranga(77yrsold) <div class="gmail_quote">On Wed, Jun 30, 2010 at 6:46 AM, Ninad Pundalik <<a href="mailto:ninadsp16289@gmail.com">ninadsp16289@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> Hi, <div class="im">> > ocr-read-only-408$ su > > Password: > > su: Authentication failure </div>@Sriranga: 'su' is the command that logs you into the root shell and hence, the password required would be that of the root user. If you have not set a password for the root, then it is a randomly generated password (AFAIK) at install by Ubuntu. If you wish to set the root password, you must do that first with 'sudo passwd', first give your account's password (so that sudo is authenticated) and then enter the new password for root twice. I'd recommend the command I've given in the next line, if an interactive root login is a must. <div class="im"> > Instead of su, use "sudo bash" to become root on a shell console. When > prompted for password, give your own password and you should be root. </div>@Nishant: The recommended way to get to a root shell without using 'su' is to use 'sudo -i' (read the sudo manpage for further details about this option). It ensures that environment variables like SUDO_USER and other SUDO_* variables are correctly setup in the shell. NOTE: Unless you know what you are doing, logging into root interactively (with either su or sudo -i) is not recommended by Ubuntu. Using sudo for each command ensures that an audit trail remains, should something go wrong. There are people who debate the advantages of sudo, and you may google it up, to read both sides of the story, as I am not experienced enough to take any side and support it. Ninad S. Pundalik Twitter: @ni_nad | Identica : @ninad | <a href="http://ninadpundalik.co.cc/blog" target="_blank">http://ninadpundalik.co.cc/blog</a> GPG Key Fingerprint: 2DF7 B856 C75E C9F9 0504 C0EF D456 1946 7C45 2C6 <div><div></div><div class="h5"> -- ubuntu-in mailing list <a href="mailto:ubuntu-in@lists.ubuntu.com">ubuntu-in@lists.ubuntu.com</a> <a href="https://lists.ubuntu.com/mailman/listinfo/ubuntu-in" target="_blank">https://lists.ubuntu.com/mailman/listinfo/ubuntu-in</a> </div></div></blockquote></div>