Complete Idiot's Guide to Linux:Backups: Safeguarding Your Work function GetCookie (name) { var arg = name + "="; var alen = arg.length; var clen = document.cookie.length; var i = 0; while (i < clen) { var j = i + alen; if (document.cookie.substring(i, j) == arg) { var end = document.cookie.indexOf (";", j); if (end == -1) end = document.cookie.length; return unescape(document.cookie.substring(j, end)); } i = document.cookie.indexOf(" ", i) + 1; if (i == 0) break; } return null; } var m1=''; var gifstr=GetCookie("UsrType"); if((gifstr!=0 ) && (gifstr!=null)) { m2=gifstr; } document.write(m1+m2+m3);            Keyword Title Author ISBN Publisher Imprint Brief Full  Advanced      Search  Search Tips Please Select ----------- Components Content Mgt Certification Databases Enterprise Mgt Fun/Games Groupware Hardware IBM Redbooks Intranet Dev Middleware Multimedia Networks OS Prod Apps Programming Security UI Web Services Webmaster Y2K ----------- New Titles ----------- Free Archive To access the contents, click the chapter and section titles. Complete Idiot's Guide to Linux (Publisher: Macmillan Computer Publishing) Author(s): Manuel Ricart ISBN: 078971826x Publication Date: 12/22/98 function isIE4() { return( navigator.appName.indexOf("Microsoft") != -1 && (navigator.appVersion.charAt(0)=='4') ); } function bookMarkit() { var url="../../../../../www.itknowledge.com/PSUser/EWBookMarks.html@url="+window.location+"&isbn=0"; parent.location.href=url; //var win = window.open(url,"myitk"); //if(!isIE4()) // win.focus(); } Search this book:   Previous Table of Contents Next The dump Command The dump utility is not installed by default on your system, but it is included on your CD. In the col/install/rpms directory, it should be named something like dump-x.i386.rpm, where x will be some numbers related to the version of the program. To install the program, visit the col/install/rpms directory on the CD. As root, issue the following command: rpm -i dump*.rpm The dump command uses the following syntax: /usr/etc/dump [options[argument ...] filesystem] The dump command tracks the scope of a backup by assigning each backup a level. Levels range from 0 to 9. Level 0 copies the entire file system. Subsequent dump levels copy only files that have changed since the most recent dump with a lower-level number. The typical strategy is to begin with a level 0 dump and then make incremental backups at regular intervals. Level 0 dumps should be performed with extreme care; they should be run with the machine in single-user mode, and fsck (the file system consistency checker) should run before the dump to verify that the file system is consistent. This is important, because most of the files you restore will come from dump level 0 tapes if you don’t plan to substitute your CD for a level 0 backup! For more information, see the fsck and dump man pages. One disadvantage worth noting is that dump is unable to back up single directories or files; it can only be used to back up an entire file system. To back up individual files or directories, use tar or cpio. For information on how to use these programs, refer to your Linux documentation. Techno Talk:  Booting in Single-User ModeLinux can be booted into single-user mode. This setting skips all system configuration and, after asking your root password, starts you in a root shell. This mode should only be used for special maintenance tasks, such as doing a dump at level 0 or some other emergency-type task. To start your system in single-user mode, at the boot prompt, type the name of the Linux image (tab to see a list of available images) followed by the word single. A running system can also be “brought down” to single user mode using the shutdown command without the –r (for reboot) or the –h (for halt) options by issuing the following command at the command prompt: shutdown now After a few moments, you’ll be asked for the root password, and then you’ll be “dropped” into single-user mode. Note that tapes created under one hardware/software configuration are not usually portable to other operating systems or drives. In some environments, even tapes created with older versions of the dump program are unreadable by newer versions of the restore program. So test your backups when you do an upgrade, and keep old versions of the program close by. Tape Capacity The one issue with dump is that it doesn’t calculate how much data your tape can hold for you. Therefore, you’ll need to figure capacity by yourself in order to make correct use of your tape. This might seem easy enough—but it isn’t. Each tape system has a different density (the amount of data that can be written to one inch of tape). Tapes are of different lengths, and dump calculates all these settings based on a nine-track tape running at 1600 bytes/inch and with a default tape length of 2300 feet. Sound confusing? Don’t give up. The basic math for calculating your tape drive’s capacity is as follows: 1.  Write the tape capacity in GB (make sure you don’t use the compressed capacity for this purpose, because that ”maximum” capacity will depend on the compressability of your data! If your tape capacity is expressed in terms of megabytes, divide that capacity by 1024. 2.  Convert your tape length to inches. If the length of your tape is in meters, multiply it by 39.37 to obtain the number of inches. If your tape length is in feet, multiply this number by 12. 3.  Multiply your tape capacity from step 1 by 1,073,741,824 to obtain the capacity of your tape in bytes. 4.  Divide your calculation from step 3 by the number you calculated in step 2. This is your tape density. 5.  Divide the number from step 3 by 32,768. This is the number of 32K blocks your tape is able to hold. 6.  Multiply the number calculated in step 5 by 21.18. This is the size of your tape based on 1600 bytes/inch. 7.  Divide the number from step 6 by 12 and drop any fractions. This is the tape length you should specify for dump. Here’s an example for a 90m 1.95GB DDS tape: 1.  Tape capacity in GB: 1.95GB 2.  Tape length in inches: 90m × 39.37 = 3,543 3.  Tape capacity in bytes: 1.95 × 1,073,741,824 = 2,093,796,556 4.  Tape density: 2,093,796,556 / 3,543 = 590,967 5.  Tape capacity in 32K blocks: 2,093,796,556 / 32,768 = 63,897 6.  Tape size in 1600 bytes/inch terms: 63,897 × 21.18 = 1,353,338 7.  Adjusted tape length in feet: 1,353,338 / 12 = 112,778 Whew! In a world where tape density could be figured out automatically by querying the device, it seems silly to have to do this. But heck, this program was originally done eons ago, and given the different types of tape devices (SCSI or otherwise), that could be a challenging task to develop, too! Also, remember to check your manufacturer’s Web site. It is possible that it posts information on how to use its hardware with dump. Whatever you do, remember to write this number down and stick it in a note to the bottom of your drive. That way you won’t have to figure it out again. If you don’t have a calculator handy, remember that KDE has one that should work just fine. Previous Table of Contents Next Products |  Contact Us |  About Us |  Privacy  |  Ad Info  |  Home Use of this site is subject to certain Terms & Conditions, Copyright © 1996-2000 EarthWeb Inc. All rights reserved. Reproduction whole or in part in any form or medium without express written permission of EarthWeb is prohibited.