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 Extracting from a Device Extracting from a device is done much the same way as from a file: tar xvf device path If you don’t provide a destination, all files are extracted to the current directory while preserving their path organization. If you provide an absolute or relative path, files will be put there. If the path you provide is neither absolute nor relative, it is taken to mean a file in the archive to extract. When extracting from a multiarchive tape, remember to use the nonrewinding interface and mt to forward the tape. Spanning Multiple Disks or Tapes If the file you are trying to archive doesn’t fit onto a single floppy or tape, you’ll need to specify the M option to tar. The M option tells the device to span multiple disks or tapes. Each tape or disk is a complete and standalone archive (with the sole exception that the last file on any disk or tape might be split between disks or tapes). This means that you can extract and work with each disk or tape as if it were its own archive. To back up my nsmail directory onto multiple floppies, I type this: tar cMvf /dev/fd0 /home/alberto/nsmail When the first floppy disk gets full, it will ask you to insert a new one. It is important that you number each floppy or tape in the order they were written so that when you extract them, data won’t be corrupted. To extract a multivolume archive, enter the following: tar xMvf /dev/fd0 Tar will ask for each of the volumes (in this case, floppies) in order. Make sure you have all of them. The one drawback with tar is that it doesn’t keep track of files that need backing up. In order to use tar, you need to decide which files you want to back up and provide a list of these files to the program. Although it offers some facilities to address this limitation, there are better programs for this task. If you want to do incremental backups and have a program keep track of files that need to be backed up, you’ll need to use dump. A Backup Strategy Doing incremental backups under UNIX/Linux means using the dump utility. This utility is powerful. It can handle backups that span multiple tapes and can create incremental backups. If you can fit your entire backup onto a single tape, you’ll be able to automate your backups. Just start up the backup, and let it run. Because dump actually keeps track of what was dumped before and only backs up things that have changed, there are a couple of tricks that you can use to back up only those items that you have added and modified since you installed your system (not including the ”unconfigured” operating system). My strategy is to back up at well-defined times: •  Right after the system software is installed but before anything is configured •  After the system software is installed and configured •  Any time additional software is installed and configured Using this strategy, the order of things is to back up your system right after installing it. This is done to a special device file called /dev/null, which simply discards any data that you send to it. Because dump will keep track of the date it last dumped, subsequent backups will only store things that have been modified after that date. This is a neat trick because your backup set won’t include your system’s software distribution. This will set the beginning of time for the dump utility to operate. The backup level for this dump should be at level 0; it must include everything in the newly installed system. Dump uses the concept of levels to determine what to back up. Level 0 (zero) backs up everything. Level 1 backs up everything modified after the level 0 dump. Level 2 dumps only backup items that have changed since the last lower-level dump, and so on. Subsequent backups should be performed at level 8 or 9. This will effectively back up everything that has been modified in the machine since the first backup was made. To restore files stored in a tape created with the dump utility, use the restore program described later in this chapter, in the section “The restore Command.” 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. 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