The third medium is hard disk. This typically means one of three possibilities:
● Disk arrays with RAID or disk mirroring ● High-end disk arrays with business copy ● Removable USB disk storage
The first downside to this option is cost. The second (with the exception of USB disk storage) is the inability to have offsite backups. An offsite backup is vital. If a disaster destroys your datacenter, and you do not have offsite media storage, the disaster destroys all your backups. Offsite backups can be as simple as taking a briefcase of tapes home with you each day or as complex as shipping tapes daily to a hardened and secure third party. The one major exception to this limitation is mirroring data to a remote disk array. Most high-end disk array vendors offer this feature, but it is very expensive.
Copyright
Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and the publisher was aware of a trademark claim, the designations have been printed with initial capital letters or in all capitals.
Novell is a registered trademark of Novell, Inc. SUSE is a registered trademark of SUSE LINUX AG, a Novell business. Red Hat is a registered trademark of Red Hat, Inc. Linux is a registered trademark of Linus
Torvalds.
The authors and publisher have taken care in the preparation of this book, but make no expressed or implied warranty of any kind and assume no responsibility for errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of the use of the information or programs contained herein.
The publisher offers excellent discounts on this book when ordered in quantity for bulk purchases or special sales, which may include electronic versions and/or custom covers and content particular to your business, training goals, marketing focus, and branding interests. For more information, please contact:
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Library of Congress Cataloging-in-Publication Data
Linux troubleshooting for system administrators and power users / James Kirkland . . . [et al.]. p. cm.
ISBN 0-13-185515-8 (pbk. : alk. paper) 1. Linux. 2. Operating systems (Computers) I. Kirkland, James. QA76.76.O63L54875 2006
005.4'32dc22
2006000036
Copyright© 2006 Hewlett-Packard Development Company, L.P.
All rights reserved. Printed in the United States of America. This publication is protected by copyright, and permission must be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or likewise. For information regarding permissions, write to:
Pearson Education, Inc.
Rights and Contracts Department One Lake Street
Upper Saddle River, NJ 07458 Fax: (201) 236-3290
Text printed in the United States on recycled paper at R.R. Donnelley in Crawfordsville, IN.
First printing, May 2006
Dedication
To Kristine: Without your love and support, this book never would have happened. To my father and mother, for not killing me when I deserved it and loving me when I didn't. James
Stephanie, thank you for your effort and sacrifice, which made this book possible. You remind me every day how strong our love is by the things you do. Sarah and Shannon, thanks for being such sweet daughters and understanding when daddy had so much homework. Mom and Dad, thanks for buying me that Vic 20 back in high school to get me started.
Dave
Bonnie, my love, thank you for your understanding, sacrifice, and "word-smith" brilliance without which I would still be sitting under that tree in the back yard trying to figure out how to make task_struct flow into a discussion of threads. Steve, Robert, and Greg, you guys are the best. Mom and Dad, thanks for the love you've shown and the incredible work ethic that you have instilled.
Chris
Kristen, thank you for giving up so many weekends in order to make this effort successful. I also wish to thank my parents and brothers Robert Jr., Steve, and Chris, for being
understanding as I missed several family outings in 2005 while working on this endeavor. Greg
OS Hangs
OS hangs come in two types: interruptible and non-interruptible. The first step to remedying a hang is to identify the type of hang. We know we have an interruptible hang when it responds to an external
interrupt. Conversely, we know we have a non-interruptible hang when it does not.
To determine whether the hang responds to an external interrupt, attempt a ping test, checking for a response. If a keyboard is attached, perform a test by simply pressing the Caps Lock key to see whether the Caps Lock light cycles. If you have console access, determine whether the console gives you line returns when you press the Enter key. If one or more of these yields the sought response, you know you have an interruptible hang.
Note
Any time an OS hangs, one or more offending processes are usually responsible for the hang. This is true whether software or hardware is ultimately to blame for the OS hang. Even when a hardware problem exists, a process has made a request of the hardware that the hardware could not fulfill, so processes stack up as a result.