full ddrescue manual

This is the sum of the sizes of all the non-trimmed, non-scraped, andThis is theThis is theThis is the size of the part of the rescue domainThe total error size is the sum of theIt increases during the trimming andA sector isNon-trimmed and non-scraped blocks are not considered bad areas. See --max-bad-areas.See --max-error-rate.The remaining time is calculated using the average rate of the last 30Therefore itIn particular it may go down toSuch is the nature of ddrescue; the goodPrevious: Output. Up: Top If mapfile does not exist, ddrescue will create it. Be careful to notWithout a mapfile,This version number should be included in all bug reports.The skipped blocks are tried in additionalTry this if the drive stopsDefaults to 512.SI prefixes (powers of 1000) are used by default. (See table below). Try smaller values for slow drives. The number of sectors per track (18 orThis is useful when readingSector size must beNot all systems support this.Some OSs have a bug that prevents them fromDefaults toThe rate being measured is that ofNeeded when outfile is not aThis option is just a safeguardSee the chapter Fill mode (see Fill mode ) forNote that you must keep theSee the chapter. Generate mode (see Generate mode ) for a complete description of theThe blocks marked as finishedAll other block types will beUse ' - ' as file to readDefaults to 0. This is not the point from which ddrescue starts copying. In fill mode itExit with status 2 if the read fails orExit with status 1 if a read error happensYou may need to power cycle the drive beforeAt least one ofThe values given will be rounded to the nextThe skip size will be doubled for each readValid values range from 64 KiB An initial value of 0 disablesInversely, if ddrescue is skipping too much, leaving large non-triedThis optionUse ' - ' as file to read the domain mapfile from standard input.

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Up: (dir) Previous: Top. Up: Top That is, you don't haveAlso you may interrupt theThe mapfile is anUse it unless you know what youSo, every timeThis is so because the probability of having the same area damaged in allUsing the mapfile, onlySee lziprecover-example.SCSI, old MFM drives, floppy discs, or even flash media cards like SD).Previous: Introduction. Up: Top A block is described by its starting position andThe end of the block is its starting positionHard disc drives, cdrom drives, USBDevices and partitions are accessedA partition normally contains aThe rescue domain defaults to the whole inputIf it does, please, report it as a bug.Smallest accessible amount of data on a device.Previous: Basic concepts. Up: Top You need to understand what itThe resulting copy may beIf you reboot, check the device names before restarting ddrescue.Previous: Important advice. Up: Top But that caused a lot of headTherefore, newer versions try toThis maximizes the amount of data that can beThis is a bad idea because it means spending moreIf no mapfile is specified, or is empty, orThe second passThe first two passes alsoThe skipped areas are tried later in one orThe copying direction isThe last pass is a sweepingThe purpose of the multiple passes is toTrimming, scraping, andEach sector is tried at most twoThen read backwards oneScraping is done in one pass. EachThe direction isEvery bad sector is tried only once in eachIf the output file is a regular fileSo in case of aThe default intervalSee --mapfile-interval.Previous: Algorithm. Up: Top Pass 1 (forwards)The position in the input file where data are beingThe position in the output file where data are beingThis is theThis is the sum of the sizes of all the finished blocks.See --min-read-rate.

Up: Top It is formed by threeThey are intended as information forIt contains aThe status character is one ofThe status characterPass 1 (forwards)Previous: Mapfile structure. Up: Top Ddrescue will try toPrevious: Emergency save. Up: Top Also dd may create an image larger than theAfter that time, data loss develops slowly withSee thePrevious: Optical media. Up: Top Because of this, you should rescue the data from a drive as soon as youBe diligent because every time a physicallyAt least not with ddrescue.Note: you need to know the offset of the partition sda1 in the drive sdaPrevious: Examples. Up: Top In this case you may want to use direct discThis is the only caseIf direct disc access is notRead your systemFor efficiency reasons, alsoOn some systems, ddrescue can't determine the size of a raw device, so anPrevious: Direct disc access. Up: Top In this mode commands are read from the standard input and executed to copyDdrescue's responses are written toOnly one command is allowed per line. Ddrescue recognizes the following commands:Copies a block of data from infile to outfile andThe areas already marked asThen prints. On startup, the mapfile is firstIf writing mapfile See Emergency save.Writes to standard output one or more lines in mapfileWrites the internal copy of the mapfile toIf update mapfilePrevious: Command mode. Up: Top That is, in. It only fills with data readIf it is too big, only the dataThen the same data will beThe status line is the only part ofSee the following examples:For example, the following command line fillsThis way, the drive will still test bad (i.e., with unreadable sectors). This is the fastest way of wiping a failing drive, and is especiallyWARNING! This may not work on your drive.Don't use sparseThose files containing theNote that ifPrevious: Fill mode.

Specialized tools like ddrutility or partclone can produce a domainAvoids spending a lot of time trying to rescueEspecially useful in the first parts of aThe bytes below bytes If ' --min-read-rate ' is set, also closeUse this option if you notice aBut be warned that most probably the slowing-down is intentionallyOnly space for regular filesIf ddrescue can't determine the size toValid values for lines range from 1 to 32. IfSuppress all messages. Defaults to 0. -1 meansTo retry badIt limits the amount ofIf ddrescue can't determine the size of theNote that thisMay save a lot of disc space in some cases. Not all systems support this. Only regular files can be sparse.Only works forDefaults to infinity.Forwards by default, or backwardsFurther -v's (up to 4) increase the verbosity level. Some large numbers in messages (like device sizes) are printed in groups ofThis is useful to avoid ddrescueFill mode normally writes to outfile With this option, after the first write error isIf the size of outfile is already equal or longer than bytes,Use this option to guarantee a minimumDefaults toIf bytes is too small, theUse this option to limit the bandwidth used byIf the first letterElse it exits withDdrescue also shows the size in bytes ofThe format used isCommand line arguments controling the display (likeSee Command mode,Valid pass valuesThe ' end of run ' line also contains the current position andEvery time the screen is updatedThis allows a posterior analysis of the drive to see if it has any weakIf file already exists, itFinally, a line with a timeIntervals are formatted as in the option ' --timeout ' above.The time needed to write the mapfile is excluded from the mapfile saveDefaults toDefaults to 0. Defaults to 0. interval is formattedWith this option, ddrescue only exitsIt may also be usedIf the data to be copied overlap with theThe ' s ' multiplier may beFor example, ' ks ' meansPrevious: Invoking ddrescue.

Technibble and SilverLeaf take no responsibility for the loss of any data, business, reputation etc. It seems that a guide for using ddrescue might be of some benefit to many members who may be shy of the linux terminal. So, I’ve decided to document some real-world examples from in the shop. I plan on doing this in 3 parts to cover the most common scenarios. I usually PXE boot (or boot from a live CD) the machine that I am working on to Parted Magic for this purpose. If you run linux on your test bench machine and prefer to attach the failing drives to it, this guide will give you the basics, but obviously the screenshots will be different. Hard drives are usually denoted with the “sd” prefix, followed by an incremental alphabetical designation, beginning with “a”. Furthermore, the partitions on a particular drive are represented by incremental numbers. If you just need to recover files from a Windows partition, it is advisable to only image that particular partition (as opposed to the entire disk). If, on the other hand, you intend to rescue the whole drive, replace the failing drive, and re-image; then certainly image the whole drive so you get the MBR, etc. Be aware, that if you have multiple drives installed, it is possible that these designations can change after a reboot; so be sure to double check before you proceed. In this example, we are going to image the whole Windows8 drive in the laptop to an image file stored on the attached USB hard drive. In this example, I will be storing the image in the root directory of the USB drive. Make sure the drive you plan to store the image on has sufficient capacity. If you are rescuing a 500gb drive, you must have at least 500gb free to store the image. Note: On a failing drive you may want to eliminate this option the first time so as to not waste time hammering on bad sectors and risking drive failure. Always use a logfile.

Up: Top It only tries toNow, two days later, your computer crashed and you can't know how much dataAnd even worse, you can't resume the rescue; youIn this case, note thatDdrescue can in some cases generate an approximateIt makes this by simplyThe reason is that old data may be present in thePrevious: Generate mode. Up: Top DdrescuelogArguments to options ' -i ' and ' -s ' are the starting positionsPrevious: Ddrescuelog. Up: Top This version number should be included in all bug reports.Depending on the requested operation itDefaults to 512.SI prefixes (powers of 1000) are used by default. (See table above,If not specified, type1 All gaps in mapfile are filled. Domain options are ignored.The exit status is 0 if mapfile Defaults to 0. ItThe blocks in the mapfile must be strictlyThis option allows making quick edits to a mapfile without all the sizeDefaults to ' --input-position '.Two files comparing equalSuppress all messages. It refers to a size in theIf the domainFurther -v's (up to 4) increase the verbosity level.In other words, in the resulting mapfile aEither ' --input-position ' orAny blocks beyondPrevious: Invoking ddrescuelog. Up: Top There are certainly errors andIf you report them, they will get fixed. IfUp: Top. You will find written articles and podcasts starting from “making the jump” from your full time job, all the way up to looking after other businesses with managed services. Bryce Whitty Founder, Technibble Guide to Using DDRescue to Recover Data November 14, 2013 8 COMMENTS 0 Shares This guide was written by one of our forum members SilverLeaf and was originally written as a forum post. This guide is intended for people who are looking to do quality data recovery using free tools. This guide is fairly technical requiring you to deal with the Linux command line. Some paid software is more straight forward than the steps here, but this is a great way to get the job done for free. Use at you own risk.

Or we discover after the image is finished, that ddrescue reports too much damage to justify attempting to clone it to a new disk and hope that Windows will have enough integrity to operate. So, how do we then use the image files to retrieve the data contained therein. Actually we have a few options here. Firstly, some file recovery tools will support working with these image files directly, R-studio for example. So, you may be able to point your recovery software to the image file and go to work. Another option is to mount the image file using linux (either natively or from a live environment like Parted Magic) using the mount command. This is why I made the earlier statement: “ If you just need to recover files from a Windows partition, it is advisable to only image that particular partition (as opposed to the entire disk).” We will cover this scenario first. Part 3a: Working with image files containing a single partition With Parted Magic booted and your image file available (from USB disk, etc), we first need to create a suitable place to mount the image file. Open “File Manager” from the Parted Magic desktop, and browse to the location of your image file, As you can see from the screenshot below, I have an image file named “partition.img” stored on my attached USB hard drive. Next I will create two new folders on the USB drive: One named “mountpoint” in which to temporarily mount the image file, and one called “recovery” in which to copy and store the recovered files from the mounted image. Notice the two new folders in the screenshot: Next, we just need to issue the proper mount command. Note: The “ro” switch mounts the image as read only. You could explicity specify the filesystem type by using the “-t ntfs” switch as well, but the mount command is pretty good at automatically determining this. Simply browse to that directory, and you should see the contents of the Windows8 partition we rescued.

Now you can simply copy the files you need to the “recovery” directory we created earlier. There is a reason for this. In order to use any other file system (another partition, cdrom, USB drive, floppy, etc), it needs to be attached to a place in the current filesystem that the OS already knows about. This is the mount point. It’s kind of like hooking up a stereo receiver. The receiver has input jacks on the back to plug the components into (CD player, cassette deck, turntable, etc.). The receiver cant use any of these components however, until the patch cables are plugged into the corresponding input jacks in the patch panel on the receiver. Mounting an image containing multiple partitions is similar to attempting to plug multiple components into the same input jack on the stereo receiver. Here’s what happens when you try this. This screenshot is when I attempted to mount an image file (test.img) that contains multiple partitions: Fear not, there is still a way to mount the individual partition(s) contained in the image file. What we need to do is to tell the mount command where within the image file it needs to look to find the partition we are interested in. We do this by specifying an offset. In order to determine the offset of the partition in question, we use a command line tool called parted. At the prompt, type: unit then B then print and you should be presented with something resembling this: As you can see, this image has two partitions. The first has on offset of 32256, the second 7355760640. As the second partition is the Windows partition in this case, this is the one I’m after. Simply type quit to exit the parted prompt. When I open the “mountpoint” folder where we just mounted the image, I’m presented with the Windows8 partition contained in the full disk image. Now it’s just a matter of copying the files I want to another folder before I unmount the image.

This allows you to resume an interrupted image at the point you left off, or to retry bad sectors after an initial pass. Without a logfile, you will have to start over again. Notice the appearance of the new files in the File Manager pane (test.img and test.logfile). This process will take a good while. It’s not uncommon for a large drive with lots of damage to take days to complete. If our intention is to replace a defective drive and restore the image, then obviously the next step is to install the new drive. A word of caution here: the new drive must be at least as large as the original. If ddrescue runs out of space, it will fail at the very end, even if it is only a few bytes shy. I prefer a drive that is larger, just in case. Another consideration is the integrity of the image file. When ddrescue has done all it can, you may still have a significant amount of errors. The terminal window that you started the rescue process in will display the number and size of the errors when ddrescue has finished running. If there are any, it is possible that the damage could be enough to render Windows unstable when cloned to a new drive, depending on where the damage is. Sometimes running CHKDSK and SFC on the new drive afterwards will take care of it, sometimes not. It’s a judgment call at this point. As you can see in this screenshot, ddrescue failed to recover 512 bytes. Depending on which file, if any, this 512 bytes is from, this may, or may not be a problem. So, assuming everything is OK, install the new drive, connect the USB drive containing the image file, and boot up Parted Magic again. Now, we have a few options on how to image the new drive. Again, be sure to triple check your device names, especially if you have rebooted. They may be different now. This will take a while, and dd doesn’t really provide any progress info, so be patient. When the process is finished, reboot and you should be good to go. You don’t want to reuse the old one by mistake.

Furthermore, do not use the -d switch that we used earlier. This option is only applicable when the source is a block device, not a file. Cloning directly to a new disk Now, knowing what we do about ddrescue so far, it is entirely possible to rescue directly from one drive to another, rather than to an image file. Again, be sure to make sure the new drive is an appropriate size as mentioned earlier. Both drives must be connected to the machine that is running linux, either natively or from a live environment like Parted Magic. Using the command from Part 1 to view the attached block devices, determine the correct names for the drive to be rescued and the drive to be imaged to. Be careful here. If you get this wrong, you could easily image the wrong device to the wrong device, and have a real problem on your hands. You can store the logfile anywhere to which you have write access, just not to either of the two drives involved in the imaging process. And again, the same caveats apply to the -r3 switch as in the example from Part 1. Finally, a note about resizing partitions after restoring an image to a new drive that is larger than the original. For example: the failing drive that you rescued was 500gb; the new drive that you used is 750gb. After the restore process, you will now have a 750gb drive with 500gb used, and 250gb as unpartitioned space. You have a few options here: You could just leave it as-is You could take the 250gb of unallocated space and create a new empty partition You could choose to resize the existing partitions to include the extra space. Although outside of the scope of this guide, the tool called gparted (also on the Parted Magic CD, the “Partition Editor” icon), is a great tool for this. Part 3: Working with image files Many times we need to use ddrescue to create an image for file recovery purposes, rather than use it to replace a failing disk.

Again, you can see why it is much easier to have recovery software (like R-studio) that can open these whole disk images for you; and why it is easier to mount single partition images (as opposed to whole disk images) for file recovery. Anyway, that’s the basics. Maybe this will help some to better take advantage of the great tools that are ddrescue and Parted Magic. Finally, as an aside, I would encourage anyone who finds Parted Magic as useful as I do, to support the developer with a donation. I am not affiliated with the project in any way, but I really believe that it is worthwhile, and would like to see it continue. Related Posts 19 Nov, 2019 One Touch is Not Enough 14 Nov, 2019 How to Create Unique Managed Service Offerings Easily 31 Oct, 2019 Motivational Quote for MSP’s Rincon Dynamic says: November 14, 2013 at 10:10 am Awesome guide, ddrescue always saves the day but can be kind of a rough start. If I had this when i first started using it i would have had less headaches. Great guide. mraikes says: November 15, 2013 at 9:33 am I used SilverLeaf’s guide when it was just a thread in the forums. It’s a lifesaver for anyone unfamiliar with DDR or who just doesn’t use it often enough to remember everything. Excellent work SilverLeaf and thanks for sharing. Geranium says: November 16, 2013 at 4:21 am How timely. I’m just in the throes of learning how to work with ddrescue, and this guide REALLY clarifies things for me. Big thanks! SilverLeaf says: November 16, 2013 at 4:56 am Thanks for the comments. I’m glad you all found it helpful.It’s just 1’s and 0’s whether it’s encrypted or not.If I did not have a hardware imager, I would not use anything else other than ddrescue(even if someone else bought it) redmon says: November 30, 2013 at 8:21 am Maybe some of the paid software for making a hard drive image is easier to use, but not as effective as ddrescue. All Rights Reserved Close dialog Session expired Please log in again. The login page will open in a new tab.

GNU ddrescue - Data recovery tool. Copies data from one file or block device to another, trying hard toThere is NO WARRANTY, to the extent permitted by law.The full documentation for ddrescue is maintained as a Texinfo manual. If the info and. It copies data from one file or block device (hard disc, cdrom, etc) to another, trying to rescue the good parts first in case of read error. Also you can interrupt the rescue at any time and resume it later at the same point. The mapfile is an essential part of ddrescue's effectiveness. Use it unless you know what you are doing. However, if you intend to clone hard disks for any reason, it is important to use a safe process that will not introduce unnecessary risks to your data.It is extremely efficient, and because it doesn’t truncate files or write zeroes to its output file, it can be run successively to fill in bad sectors that were missed in earlier passes. There are risks to consider — see the last section of this article for some important precautions — and it is no substitute for professional data recovery services, but it is an effective option for restoring low-priority data from a failing hard disk. This guide will explain how the utility works and how different commands can affect the tool’s functionality.Likewise, you should not use this utility if you are at all confused by the command parameters discussed below. Cloning Hard Drives with ddrescue Before starting this process, you will need a copy of ddrescue (preferably on a CD or DVD), a fully functional hard drive, and the damaged drive. You can download the latest version of ddrescue here, or click here to download SystemRescueCD, a system rescue disk for Linux that can be used as a bootable USB stick or CD. Of these options, we’d recommend using the SystemRescueCD, since it provides for a fairly simple hard disk cloning process with ddrescue.

Forcing a malfunctioning drive to read damaged areas without first repairing it can cause further damage, resulting in irreversible data loss.You can name the logfile anything. Without a logfile, you can’t make additional passes on areas of your disk with bad sectors. Some other useful command options for the process include: -r3 Tells ddrescue to keep retrying damaged areas until 3 passes have been completed. This sets “verbose” mode, providing additional details. However, it can only be used for regular files, and it is not an available option on all operating systems. A full list of usable commands can be found here in the ddrescue manual. Precautions When Cloning with ddrescue ddrescue is a powerful utility and should only be utilized by experienced Linux users. It can cause damage to a failing hard drive in some circumstances. It can also overwrite data when used incorrectly. We want to reiterate — if you really need your data and your hard drive is failing, your best bet is a professional data recovery service. You should immediately turn off your computer if the failing hard drive seems to get worse, for instance if sounds get louder or if successive passes result in a larger number of bad sectors. Be sure that the good drive doesn’t have any important data that might be overwritten. Make sure that you properly identify the good and bad drives when using the utility. Check for capitalization errors before starting the process, and don’t leave the hard drives unattended (if you do, you won’t be able to turn off the computer if serious errors occur). If you have questions that weren’t answered by this article, you can find the full ddrescue manual here. You can also contact us at 1-800-237-4200 for more assistance or to set up a free evaluation for a failing hard drive. Recent Is Underwater Data Storage the Next Big Thing. Copies data from one file or block device to another,NOTE: In versions of ddrescue prior to 1.

20 the mapfile was calledDon't use options '-F' or '-G' without reading the manual first.There is NO WARRANTY, to the extent permitted by law.Linux Man Pages Copyright Respective Owners. All Rights Reserved. It copies data from one file or block device (hard disc, cdrom, etc) to another, trying hard to rescue data in case of read errors. That is, you don't have to wait for an error, stop the program, read the log, run it in reverse mode, etc. Also you can interrupt the rescue at any time and resume it later at the same point. So, every time you run it on the same output file, it tries to fill in the gaps without wiping out the data already rescued. This is so because the probability of having damaged areas at the same places on different input files is very low. Using the logfile, only the needed blocks are read from the second and successive copies. After that time, data loss develops slowly with read errors growing from the outer media region towards the inside.So in case of a crash you can resume the rescue with little recopying. Because of this, you should rescue the data from a drive as soon as youBe diligent because every time a physicallyNote: you need to know the offset of the partition sda1 in the drive sda. Copies data from one file or block device to another,If you reboot, check theDo not use options '-F' or '-g' without readingTime intervals have theThere is NO WARRANTY,If the info andUbuntu and Canonical are registered trademarks of Canonical Ltd. Copies data from one file or block device to another,Without a mapfile, ddrescue can'tNOTE: In versions of ddrescue prior to 1.20 theThe format is the same; only the name has changed.Don't use options '-F'Time intervals have the formatThere is NO WARRANTY,If the info andUbuntu and Canonical are registered trademarks of Canonical Ltd.

It copies data from one file or block device (hard disc, cdrom, The basic operation of ddrescue So, every time you run it on the Using the logfile, only the needed blocks are read from the second A block is described by its starting position and its size.Hard disc drives, cdrom drives, USB pendrives, Devices are accessed by means of their associated file names. A partition normally contains a filesystem. DVDs can be mounted Smallest accessible amount of data on a device. This behavior reduces the chances of rescuing the remaining If no logfile is specified or is empty or does not exist, mark all the rescue domain as non-tried.Only non-tried areas are read in large blocks. Trimming, Each sector is tried at most two times; the first After a number of consecutive bad sectors is found in a block large enough, the block is split by half This recursively splits the largest failed blocks without Note that as ddrescue splits the failed blocks, making them smaller, the total error size may diminish See this example: Defaults to 512. SI prefixes (powers of 1000) are used by default. (See table below). Try smaller The number of sectors per track (18 or 9) is a good value for floppies.Do not read new data beyond logfile Sector size must Not all systems support this.If the sector size May be useful Defaults to infinity. If n Defaults to infinity.Needed when the output file is not a regular file, but a device See the chapter Defaults to 0. In fill mode it refers to the original Avoids spending a lot of time trying to rescue the most difficult Else they are Only space for regular files can be preallocated. If ddrescue can't Defaults to 0. -1 means infinity. Every bad sector is To retry bad sectors detected on a previous run, you must specify a This means the copy of the non-tried blocks, splitting If ddrescue can't determine the size of Note that this option specifies the So, for example, the following Not all systems support this.