ProfitPress Mega CDROM2 Shareware Freeware (MSDOS)(1992)(Eng)

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Text File | 1990-07-21 | 26.9 KB | 533 lines

CoverUp.DOC Copyright (C) 1990 Jay Vanderbilt CoverUp.COM 10819 bytes Erases all data in free space on a disk Erases the data in a cluster beyond the file end Overwrites all data in erased directory entries Reports the number of bytes in bad sectors [Does not deal with data in clusters marked bad] Preserves time, date, and all attributes of files Sets errorlevel for use in batch files Reports on progress as it runs Exits on start-up if problems detected Exits after clean-up on all disk errors Should handle any standard hard or floppy disk Requirements DOS 2.00+ 192k free memory Speed 1.2meg floppy, 72 files, 720k, 3 directories 1 m 28 s 360k floppy, 24 files, 240k, 1 directory 35 s 32meg hard, 980 files, 23meg, 18 directories 4 m 6 s [Times for 12 mhz AT Clone MS-DOS 3.30 VERIFY = OFF Your times will vary.] Erases with 0f6h for data Meaningless name for directories TABLE OF CONTENTS Bug Reports.........................................................2 What CoverUp Does And Why...........................................3 WARNINGS............................................................4 How To Use The Program..............................................5 What Is Happening While The Program Runs?...........................6 Program Speed.......................................................6 Hard Disks..........................................................7 Unusual Drives......................................................8 Error Messages......................................................9 Message In A Box...................................................10 Revisions..........................................................11 CoverUp Version 1.01 Copyright (c) 1990, Jay Vanderbilt CoverUp may be freely distributed provided that it is unaltered and that the complete, unaltered documentation is included. CoverUp may not be sold or included in any commercial package without written permission. CREDITS The program was originally named and specified on BIX by Roedy Green. Roedy Green, Robert Babcock, and David Holm among others on BIX helped at various stages with the design and testing. All mistakes, bugs, and design errors are entirely my own. -2- A Special Plea (From The Heart Of Anyone Who Has Written Freeware) Programmers who write and distribute freeware do not have the resources to test every possible combination of equipment and software; they must rely on cautious programming to avoid fatal errors and user feedback to find and fix special cases. Consider the record some of the biggest software houses have with compatibility problems. Consider the disdain with which they treat bug reports. Remember that the people who write the programs you get for free always want to hear from you. If you have a problem, let me know. If you like the program, let me know. If you hate it, let me know. If it isn't what you wanted, let me know. Whatever you have to say, I want to hear it. Report bugs and make suggestions for improvements to: Jay Vanderbilt 3 Calvin #1 Somerville, Ma 02143 617-776-5792 (reasonable hours please) j_vanderbilt on BIX -3- What CoverUp Does and Why This program erases everything from a floppy disk except the structure of the disk (directories and file allocation table) and the actual data in the files. This is every bit as useless as it sounds 99% of the time. However, when you send a disk out to be duplicated or to a customer you might be surprised to find what can be lurking unnoticed beyond the ends of files or in the unused areas of the disk. What DOS Does When It Erases and Copies When DOS erases a file it does not touch any of the data; all it does is mark the directory entry and the disk space as available. Until that space is overwritten the original file is still there and can be read by anyone with a file uneraser or disk browser. When DOS writes to a file it only allocates space in discrete chunks (clusters). The unused space at the end of a cluster contains whatever was there before the file was written and that also can be read by anyone with a disk browser. When DOS writes or copies anything less than a full sector (512 bytes, the smallest unit the disk drive deals with) it does so through its own internal buffers. This includes the end of any file that is not an exact multiple of the size of a sector. The sector will be filled out with whatever happened to be in the buffer from the last time it was used. It is also possible, though unlikely, for data to be concealed in clusters marked bad. Because the program avoids using direct writes, CoverUp ignores this possibility. Most of the time this means nothing. Nonetheless it could be embarrassing to send out half your mailing list or the save files for Zork with a disk of data for your customers. People using disk- browsing utilities could be confused by random gibberish at the ends of programs. If you need to do something about it CoverUp is for you. -4- WARNINGS Please read this section before you use the program. It's important. The program checks for dangerous conditions as well as it can, but it can't do everything. With a little care you should never have a problem. NEVER use CoverUp on the only copy of a disk! This is so simple and obvious that it has to go first. It's too easy to forget how hard it is to recover the original of a file, and how easy it is just to make another copy if something goes wrong. NEVER use CoverUp on the original copy of copy-protected software! This is a corollary of the first warning. A copy-protection method may work by hiding data in unusual places or modifying the disk layout. CoverUp will not remove the protection, but it may destroy the hidden data and make the program useless. A legitimate copy of the software which has been installed on another disk will not be affected by CoverUp. NEVER use CoverUp with drive-aliasing active (JOIN ASSGN or SUBST)! ASSIGN, JOIN, and SUBST are utilities provided with DOS for use with old programs that insist on having files on particular drives or do not work with directories. They work by faking the drive or directory name to the operating system. These, and any similar utilities, will give CoverUp severe problems because it will not be working on the drive it thinks it is. A simple test is to read the directory of the disk you are going to use. If another drive lights up, or the directory doesn't match what should be on the disk, stop and disable the drive-aliasing. NEVER use CoverUp on a network drive! CoverUp reads and writes every file on a drive. It writes a file that fills all the empty space on the drive. The network administrator will be seriously annoyed if you use anything like CoverUp. The program will in any case stop as soon as it reaches a file it doesn't have access to. It will do nothing useful for a user on a network drive. So don't try. NEVER use CoverUp while a background process is active! There are a number of programs that run in the background doing things like formatting disks or downloading or printing files while the normal programs run. They should be disabled. CoverUp needs exclusive access to the drive while it is running. If it is run in the OS/2 compatibility box no other processes that use the disk should be running. The same applies to Desqview and any other program which allows multiple processes. -5- How To Use The Program Disable any drive aliasing. Read the directory of the drive you are using to make sure. Put the disk in the drive and close the door. Type: COVERUP [Drive]:/Y <ENTER> There is nothing magic about the 'Y'. It is there only to make sure that no one uses the program without reading a little about using it. It's short for "Yes, I have looked at the manual." Thank you. The program will run from one to five minutes depending on the size of the disk and the number of files. Do not open the door until you see the DOS prompt. If you need to stop the program before it ends hit the <CONTROL> and <BREAK> keys together. (On some keyboards <BREAK> is called <PAUSE>.) The program will exit as soon as it can. If CoverUp runs into any error reading or writing the disk it will attempt to clean up before quitting. If it cannot clean up (perhaps because the door was opened) it will report on what needs to be done. It is usually easier to recopy the disk and start again. If the error was not due to an open door, the disk may have been defective. Throw it away and try a new one. NEVER use CoverUp on an original disk. NEVER use it if you may want to recover erased files on a disk. ALWAYS check that the files are still good before you send out the disk. If you want to run CoverUp from a batch file, it sets the errorlevel to zero for a clean finish and one for any failure. Any important disk should be checked against the original with a file comparison utility after the program is run. -6- What Is Happening While The Program Runs? Start Up The program checks for sufficient memeory, checks the DOS version, installs the critical error handler and the other traps needed for safe operation, and then checks the data it needs to read the disk. Generally takes less than four seconds. Erasing Data in Free Space on Disk The program finds an unused filename and opens a dummy file in the root directory. It then allocates all the available space on the disk to this file (1 to 4 seconds) and writes the erasing data to the file. Progress is marked by the row of large or small arrowheads. The size changes solely to make the progress more visible. When the file is full it is erased. The result is that all the free space has been overwritten and released to be used again. Erasing File Tails and Overwriting Old Directory Entries. The program starts with the root directory and looks at every entry. Unless the data exactly fills the last sector, each file is opened, and the unused space between the end of the data and the end of the space allocated to the file is overwritten, and then the file is truncated to its original length and the original time, date, and attribute restored. Whenever a subdirectory is found it is done and then the program resumes with the parent. A count of the erased entries is kept, and when the end of a directory is reached the program opens as many zero-length files with dummy names as there are erased entries and then erases them. The result is that the names of erased files are overwritten. Progress is marked by an 'F' or 'f' for each file and an 'E' or 'e' for each erased directory entry. The distinction between the large and small letters is meaningless; it simply makes the progress more visible. Note that there will always be at least one file entry to erase. This is the dummy file that was created to overwrite all the free space. The only exception is a disk that has no free space to begin with. Checking for Data in Bad Sectors The program counts the sectors marked bad in the File Allocation Table and reports the number of bytes in them. A floppy disk with any bad sectors at all should never be used for anything important. Many hard disks have some bad sectors; this report should be ignored unless the number is very large or starts changing from one run to the next. This number should be the same as CHKDSK reports. PROGRAM SPEED The speed of the program is not simple to predict. On a floppy it will run about the same amount of time it took to copy the disk. There is much more uncertainty with a hard disk. In general a 32 meg -7- disk with 1000 to 2000 files on a 12mhz AT will take less than ten minutes. If the program slows down abruptly (by about a factor of five) while doing a hard disk the problem is likely to be too few buffers. These are the buffers DOS uses in reading the directories and file allocation tables. When directories and files get too large the buffers overflow and DOS has to go back to the disk at every read. You could increase the number of buffers in CONFIG.SYS or break up very large directories into smaller ones. Or you can just be patient; the program will still work properly. If you have a good disk cache this may not be a problem. HARD DISKS There are a few reasons to use CoverUp on a hard disk. If it is necessary to give a hard drive with confidential data on it to someone else the usual procedure would be to do a complete back-up, low-level format the drive, and restore only what is necessary. This is at best tedious. A few manufacturers tell you to never redo the the low-level format. If you use CoverUp after the confidential files have been erased they will not be recoverable by any ordinary means. Do so only immediately after you have made a good back-up. If you run CoverUp once in a while it will make it easier to recover erased files. This is not as screwy as it sounds, even though the primary purpose of the program is to make it impossible to recover erased files. File un-erasers generally work by finding the entry of the file in the directory (this is possible because DOS only erases the first character) and hunting for the pieces of the erased file on the disk. (They are still there, for a while, because DOS frees the space without erasing the data.) After the first chunk the data could be anywhere on the disk. The un-eraser will show you chunks of file and ask if this is what you want. The fewer unallocated clusters with old data on the disk the easier it is to find the ones with your data. If you ran CoverUp recently, but NOT AFTER you erased the file you want to recover, there will be very few clusters with data in them to look at. This is an extreme measure; it's easier to keep good back-ups and be careful. Only run CoverUp after you have made a good back-up. WORMS Don't ever try to use CoverUp on a WORM. You will end up with an expensive and useless cartridge full of bad data. BACKING-UP FIRST Why do I insist on only running CoverUp immediately after a back-up? Do I lack confidence in the safety of the program? The program is conservatively designed, and I hope bug-free. Even with a flawless program I would still recommend backing-up before running it. Why? Because the program spends anywhere from a minute to half an hour (for a really enormous disk) writing to the disk. If DOS is interrupted during a write (by a power failure or by resetting the computer) the likely result is a corrupt disk, which may -8- be difficult to fix. Any program that spends a lot of time writing (a disk testing program like SpinRite or HDTEST, or a disk defragger) runs the same risk. Any such program will do more writing in a few minutes than a word processor would in a month. So back-up. The peace of mind is wonderful. If it seems like too much trouble, think about buying a tape drive. It will be a lot cheaper than replacing your data. How To Run CoverUp On A Hard Disk Now that you have read the warnings, start it by typing COVERUP [Drive]:/Y/+ The program will pause and give you a chance to quit before going on. The plus sign was deliberately chosen to be awkward and nonintuitive. UNUSUAL DRIVES CoverUp tries to identify disks before running and checks to be sure the data it needs is in the right place. Unfortunately there are cases where the drive cannot be dealt with easily. Ramdisks and certain floppy disks (e.g. an add-on for Sanyo) identify themselves as hard drives. If you get an error message for what you know is a floppy or a ramdisk you can force the program to treat it as a floppy as long as it is smaller than 1 megabyte. Add /S to the command line. That is, COVERUP [Drive]:/Y/S If a disk does not identify itself as a hard disk but is larger than 4 megabytes the program will always treat it as a hard disk. See the previous section, HARD DISKS. If a disk seems to have only one File Allocation Table, which is the case with some ramdisks, and is unlikely but possible with other drives, you can force CoverUp to run by adding /! to the command line. That is, COVERUP [Drive]:/Y/! Do so only if you are sure the disk was actually written in the drive you are using. CoverUp will refuse to deal with any other disk it sees as odd. If you have a drive CoverUp won't work with let me know and I'll see what can be done. [A note on ramdisks. The only case where CoverUp might be useful on a ramdisk would be on one used as a master for track-by- track duplicating. A ramdisk set up this way will look exactly like a floppy to CoverUp, and will generate no errors.] -9- ERROR MESSAGES Most of the error messages are self-explanatory or refer to a section in the manual. Some explanation for the others may be useful. Most of them are in the program to cover unlikely cases. These messages are presented in roughly the order the order they might occur. If you have a reasonably standard system, keep the drive door closed, keep the drive clean, and only use decent quality disks you will probably never see any of these messages. 'Unable to find critical error flag. Program cannot run without it.' 'Unable to install critical error handler. Program cannot run without it.' CoverUp uses a critical error handler that provides a functional equivalent of FAIL for versions of DOS before 3.1. This means that the program can handle disk errors without help from the user and without corrupting DOS's internal tables. The problem is that the installation is complicated and relies on undocumented features of DOS. If you ever get either of these two messages let me know so I can work on a fix. 'The cluster-size is too big for CoverUp to handle.' If you have a drive with clusters bigger than 32k and you want to use CoverUp please let me know. The program can be rewritten to cover the case, but I have never heard of such a beast. 'CoverUp has found inconsistencies in the data...' 'The File Allocation Tables are not where CoverUp expects to find them or they are mismatched.' Caused either by a programming error or a completely non- standard disk layout. Let me know and I'll see what can be done. May also be a corrupt File Allocation Table. Run CHKDSK and see what it says. If it's a floppy disk erase it and reformat and start again. If it's a hard disk get expert help. -10- 'Disk error during start up.' 'Disk missing, unformatted, or unreadable.' 'CoverUp has encountered an error with the disk and is exiting.' These are general error messages. The most likely causes are an open drive door or a bad disk. Disks are not as interchangeable as they should be. In particular 360k disks that have been written in 1.2 meg drives are frequently unreliable in 360k drives. Floppy disks which have any bad sectors at all may cause problems; FORMAT does not do a good job of rejecting marginal sectors. As a general rule any floppy disk that shows bad sectors after formatting should be thrown away (or at least never used for data you want to see again). The drive may be dirty, try cleaning it according to the manufacturer's instructions. If you see these messages on a hard disk there is either a bug in the program, or a serious problem with the drive. Read/write errors should be VERY rare with any decent hard drive. If this happens to you, make sure you have a back-up, run any diagnostics you have, and keep an eye out for any repetition. If you suspect CoverUp rather than your disk let me know, with the most detailed possible account of the problem. If you have any of these errors without an obvious reason check the data on the disk carefully before you use it again. 'CoverUp has had a disk error which it cannot clean up.' If CoverUp runs into an error at a time the disk has been altered by the program it makes one attempt to clean up before exiting. If it fails it gives instructions for finishing the clean-up. If you have the choice start over with a newly copied disk; otherwise follow the instructions given. If the program was interrupted while writing the File Allocation Table or directory the damage may be difficult to fix and the instructions given will not be adequate. The only likely causes of such an interruption are a power-failure, turning off or re-setting the computer, or opening the drive door. The result will be the same with any program that is caught writing the disk. At this point you need something like Norton Disk Doctor and expert help. MESSAGE IN A BOX If the program encounters a fatal error after the start-up, a neatly boxed message full of register values will appear. If the error seems to have been caused by a bug, and not by something obvious like a bad disk or open door, copy them down carefully and send them to me. This information will tell me where the error happened and the error codes returned by DOS, and give me a good start on fixing it. -11- REVISIONS 7/11/90 Version 1.00 First distributed version. 7/20/90 Version 1.01 Bug-fix and small improvements. Fixed unexpected incompatibility with SHARE. If SHARE is loaded and a program attempts to change the attribute of a file (which CoverUp must do) and the file is open, changing the attribute will seem to work, but when the file is closed DOS will return an error 'Invalid Handle'. Fixed by changing the attribute only when a file is not open. Added improved error reporting to make bugs easier to track. Except for the start-up errors, where the messages are quite specific, fatal errors now generate a neatly boxed report of the error codes returned by the function itself and by INT 021 AH=059 (in versions of DOS where it is available), and the address of the function that had the error. Revised manual. Added report of number of files checked and bytes and directory entries erased. Improved messages.