Forgot your password?
typodupeerror
Networking Software IT

Use BitTorrent To Verify, Clean Up Files 212

Posted by timothy
from the but-anything-bittorrent-is-for-terrorists dept.
jweatherley writes "I found a new (for me at least) use for BitTorrent. I had been trying to download beta 4 of the iPhone SDK for the last few days. First I downloaded the 1.5GB file from Apple's site. The download completed, but the disk image would not verify. I tried to install it anyway, but it fell over on the gcc4.2 package. Many things are cheap in India, but bandwidth is not one of them. I can't just download files > 1GB without worrying about reaching my monthly cap, and there are Doctor Who episodes to be watched. Fortunately we have uncapped hours in the night, so I downloaded it again. md5sum confirmed that the disk image differed from the previous one, but it still wouldn't verify, and fell over on gcc4.2 once more. Damn." That's not the end of the story, though — read on for a quick description of how BitTorrent saved the day in jweatherley's case.


jweatherley continues: "I wasn't having much success with Apple, so I headed off to the resurgent Demonoid. Sure enough they had a torrent of the SDK. I was going to set it up to download during the uncapped night hours, but then I had an idea. BitTorrent would be able to identify the bad chunks in the disk image I had downloaded from Apple, so I replaced the placeholder file that Azureus had created with a corrupt SDK disk image, and then reimported the torrent file. Sure enough it checked the file and declared it 99.7% complete. A few minutes later I had a valid disk image and installed the SDK. Verification and repair of corrupt files is a new use of BitTorrent for me; I thought I would share a useful way of repairing large, corrupt, but widely available, files."
This discussion has been archived. No new comments can be posted.

Use BitTorrent To Verify, Clean Up Files

Comments Filter:
  • Nice (Score:5, Interesting)

    by Goldberg's Pants (139800) on Sunday May 04, 2008 @07:31PM (#23295424) Journal
    Awesome idea. I've done this in the past with stuff. If a corrupt version was on one tracker, I'd save the files, get a new torrent and import the old files. Saves a lot of bandwidth wasting.
    • Re: (Score:2, Interesting)

      by Jarik_Tentsu (1065748)
      Mmm, in my experience, Firefox's Download Manager occassionally leaves me with incompletely downloaded files - especially when they're big. Dunno whether this is a bad connection (Telstra, I wouldn't be surprised) or an issue with the actual Download Manager, but I don't get these isseues when using Free Download Manager.

      Anyways, I've done this before for a different thing.

      There was a rare file I was trying to get my hands on, which was fairly large, but corrupted. There was a torrent which had it too, but
    • Re:Nice (Score:4, Insightful)

      by Jurily (900488) <jurily@noSpAM.gmail.com> on Monday May 05, 2008 @03:02AM (#23297870)
      Me too. But I never thought about the endless possibilities here.
      Just ship everything with a .torrent to verify.

      (Wow, all the authorities we could annoy with one minor change!)
  • by b4dc0d3r (1268512) on Sunday May 04, 2008 @07:36PM (#23295460)
    If I happen to see a stuck torrent (many leechers, no seeds), sometimes I can find a good version of the file I already have - so I start the torrent, stop it, replace the single good file (sometimes you need more if the file is smaller than the part size), and upload a few Kb to finish the torrent. Then sit back and watch as everyone fills up.
    • by Scaba (183684)

      Then sit back and watch as everyone fills up.

      You really need a girlfriend or some hobbies or something...

  • Anonymous Coward (Score:3, Informative)

    by Anonymous Coward on Sunday May 04, 2008 @07:37PM (#23295468)
    Those of us who use BitTorrent for *ahem* illegal purposes have been doing this since the beginning. The only way to get rare and complete downloads was to take the files to other trackers and match them against another md5 to finish the download.

    It's like getting parity files over on usenet to fix that damned .r23 file which is just a bit too short for some reason :)
  • Scheduling (Score:4, Informative)

    by FiestaFan (1258734) on Sunday May 04, 2008 @07:38PM (#23295476) Homepage

    Many things are cheap in India, but bandwidth is not one of them. I can't just download files > 1GB without worrying about reaching my monthly cap, and there are Doctor Who episodes to be watched. Fortunately we have uncapped hours in the night
    I don't know about other bittorrent clients, but uTorrent lets you set download speed caps by hour(like 0 during the day and unlimited at night).
  • !new (Score:2, Insightful)

    by gustgr (695173)
    For heavy BT users this tactic is very common, provided the file(s) you are willing to download is fairly well available from different sources.
    • Re: (Score:3, Insightful)

      It's an older concept than that, even. Goes back to the strange Debian habit of using a tool called Jigdo -- it would provide essentially a recipe for building an ISO out of all the files needed, where the files were mostly available from standard Debian mirrors. ISOs were available from far fewer mirrors than standard Debian packages, you see.

      So, you'd use Jigdo, and if all went well, it'd assemble a working image. But if a few packages couldn't be downloaded, you could always take your mostly-complete Jig
      • Re:!new (Score:5, Informative)

        by Anonymous Coward on Sunday May 04, 2008 @10:09PM (#23296454)

        I don't think this tactic is very common, though, as most people seem to have no fucking clue how BitTorrent works. I've seen torrents with gigantic multipart RARs, with an SFV of those. Let's see... so, my torrent software is already checksumming everything, and RAR has a builtin checksum too, or at least, acts like it does (it says "ok" or not) -- and on top of that, there's an SFV checksum (crappy CRC32), too. Never mind that RAR saves you at most a few megabytes (video is already compressed), which, based on the size of these files, you'll spend more time unpacking the RAR than you would downloading the extra couple megs. Or that, once you unpack and throw away the RAR, you can't seed that torrent from the working video. Or that multipart anything is retarded on BitTorrent, as the torrent is splitting it into 512k-4meg chunks anyway.
        People who aren't aware of the full situation often make this complaint. These multipart rar files are "scene releases".

        First of all, scene releases are _never_ compressed; it's always done with the -0 argument, this makes is basically equivalent to the unix split program. If a file is to be compressed, it is done with a zip archive, and the zip archive is placed inside the rar archive. This is because rar archives can be created/extracted easily with FOSS software, but cannot easily be de/compressed. This was more of an issue before Alexader Roshal released source code (note:not FOSS) to decompress rar archives.

        Second, people often have parts of, or complete, scene releases and they are unwilling to unrar them (often because it's an intermediary, like a shell account somewhere where law isn't a problem).

        Third, people follow "the scene" and try and download the exact releases that are chosen by the social customs of the scene (I am not going to detail those here), thus, "breaking up" (ie, altering) the original scene release is seen as rude.

        Fourth, the archive splitting is in precise sizes so that fitting the archives onto physical media works better; typically the archive size is some rough factor of 698, ~4698 and ~8500.

        Fifth, archives are split due to poor data integrity on some transfer protocols (though this is largely historical nowadays); redownloading a corrupted 14.3mb archive is easier than redownloading a 350mb file.

        Sixth, traffic of the size is measured in terabytes, with some releases being tens, or sometimes hundreds of gigabytes in size. Thus, there become efficiency arguments for archive splitting; effective use of connections, limited efficiency of software(sftp scales remarkably poorly, though that is beginning to change - not that sftp is used everywhere), use of multiple coordinated machines and so on. This is an incomplete list of reasons; it is almost as though every time a new challenge is presented to the scene, splitting in some way helps to solve it.

        AC because I'm not stupid enough to expose my knowledge of this either to law enforcement, or to the scene (who might just hand me over for telling you this - it has been done). Suffice to say that this is more complex than you understand, and that even this level of incomplete explanation is rare.
        • Ah, thanks for the enlightening post. Someone mod this informative. I thought I saw a comment along those lines, presumably by a "scene" person, on a torrent once, but I didn't remember the exact details.
        • Re:!new (Score:5, Informative)

          by dk.r*nger (460754) on Monday May 05, 2008 @07:07AM (#23298764)

          First of all, scene releases are _never_ compressed; it's always done with the -0 argument, [...] This was more of an issue before Alexader Roshal released source code (note:not FOSS) to decompress rar archives.
          So, historical, and pointless. And anyway, just an excuse if there's any point in using RAR anyway. Let's see..

          Second, people often have parts of, or complete, scene releases and they are unwilling to unrar them (often because it's an intermediary, like a shell account somewhere where law isn't a problem).
          So they should use BitTorrent. Run a seed on your [strike]compromised windows host[/strike] "shell account".

          Third, [....] social customs of the scene (I am not going to detail those here), thus, "breaking up" (ie, altering) the original scene release is seen as rude.
          Oh, I think we're at the core of the problem. Pale teenagers in their mothers basements getting hurt feelings. I appreciate that someone will rip the Lost episodes in HD pretty much as they are being broadcast, and I actually look for some "group names" in the torrents I get - because they provide one file, not a RAR. In other words, provide what people want, and they will respect you for that. Make their life hard, and they will not care about your 1998 social customs. Like anything else in life.

          Fourth, [...]fitting the archives onto physical media works better
          Yawn. 1998 called, they want their infrastructure back. Harddrives are cheaper than dirt. Five years ago "the scene" at my college exchanged 250 gb harddrives.

          Fifth, archives are split due to poor data integrity on some transfer protocols
          SO USE BITTORRENT! It easier and faster and better and more fun, but of course less 'leet than using [strike]compromised windows hosts[/strike] "shell accounts"

          Sixth, [...] Thus, there become efficiency arguments for archive splitting;[...]it is almost as though every time a new challenge is presented to the scene, splitting in some way helps to solve it.
          No, BitTorrent does ALL this for you. ALL of it.

          AC because I'm not stupid enough to expose my knowledge of this either to law enforcement, or to the scene (who might just hand me over for telling you this - it has been done).
          Badass gangster!

          Suffice to say that this is more complex than you understand, and that even this level of incomplete explanation is rare.
          What? Moving files around on the internet is "more complex" than we understand? It probably the simplest fucking thing there is. Let me put it very simple for you: 1) Multi-file RARs made sense back when people got their stuff from FTPs and newsgroups. 2) It's the past. It's pure nostalgia. Get over it. If you're not using your "scene" FTP servers as Torrent seeds instead, you're wasting your resources.
          • Re: (Score:3, Interesting)

            I actually look for some "group names" in the torrents I get - because they provide one file, not a RAR. In other words, provide what people want, and they will respect you for that. Make their life hard, and they will not care about your 1998 social customs. Like anything else in life.

            Firstly, if you use torrents than nobody in the "Scene" gives a flying toss about whether you respect them or not. I have nothing to do with the Scene, and even I know that. They are not ripping things for us, they're ripping things for themselves. We're feeding from their scraps, if you like.

            Once you understand that, all the other arguments become moot. Yes, multi-part RARs in torrents annoys me as well, but the people making them aren't doing it for us. Most (all?) Scene members would much prefer thei

        • by ccguy (1116865)

          scene releases are _never_ compressed; it's always done with the -0 argument
          [citation needed]
  • by CSMatt (1175471) on Sunday May 04, 2008 @07:40PM (#23295486)
    Are their even MD5 hashes on Apple's download pages for such large files? Jusging by how the article was written and the lack of hashes on the QuickTime and iTunes download sites, it doesn't seem like they even bother.
    • I would think that the only reasonable thing to do would be to have md5s because they are such large files after all, they could be corrupted.
    • Re: (Score:3, Informative)

      by Anonymous Coward
      Yes, there are- though most of the latest ones are SHA-1 digests. They're not usually seen in the "public front page" download areas and aren't universal, but are generally present for the downloads for updates and security patches through links from the tech literature and developer sections.
  • by Bazar (778572) on Sunday May 04, 2008 @07:43PM (#23295508)
    One should be more concerned as to why your files are becoming corrupted.

    I'd say its a safe bet that the files from apple.com are in perfect condition.

    Which means it either became corrupted in transit to, or on arrival to your machine.

    Which leads the question, is your memory defective
    run memtest86 to check your memory.
    http://www.memtest86.com/ [memtest86.com]

    Check if your Harddrives have SMART and are reporting anything. A disk checker would also be a good idea.

    The other idea that springs to mind is if your behind some proxy with the above problems, although i doubt anyone would want to proxy a 1.5gig file.

    Fact is, if files are being corrupted on your disk, its just a matter of time before something more important is hit by corruption.
    • by Anonymous Coward on Sunday May 04, 2008 @07:50PM (#23295590)
      could also be one's routers.

      There was a problem w/ dlink routers back in the day that hit alot of p2p users. If you placed your machine in the dmz, the router basically did a search and replace on all packets replacing the bitstring representing the global address w/ the bitstring representing the local address. On large files, this didn't just hit in the ip header, but in the data as well corrupting it. If you didn't use dmz functionality, just port mapping, it worked fine, so if you were using bittorrent, you'd get repeated hash fails on some parts that would never fix, because bitorrent has no capability to work around that (as opposed to eMule's extensions)
      • by log0n (18224)
        As per the topic, Bittorrent fixed the problems - didn't cause them - so a failing router is not likely the problem. 99% likely it's bad ram.
        • by BobPaul (710574) * on Sunday May 04, 2008 @08:44PM (#23295942) Journal

          As per the topic, Bittorrent fixed the problems - didn't cause them - so a failing router is not likely the problem.
          You misunderstood his comment; please read it again. In his story, bittorrent didn't cause any problem either--it identified a problem by use of the same mechanism (hash checks of file parts) that it solved the problem in the OP.

          While I agree that bad ram is most likely the issue, it's still possible bad ram in a router or even something goofy going on in a router, such as the firmware bug described, could have caused problems. The bits were mangled before they were written to the disk. They could have been mangled by anything that processed those bits as they traversed from apple's website to his HD, including Apple's website and the HD itself. That embedded devices tend to be more reliable does not mean they don't break and do weird things sometimes.
        • Bad RAM would be surprising as the machine is stable. I'm more inclined to believe that it is a case of 'shit happens' with networking. As others have pointed out there is a not insignificant chance of an error slipping through with gigabyte sized files. I don't think the router is in the clear either. BitTorrent fixed the problem, but the protcol will keep trying until it gets the correct data. Safari, which is what I used for the original download, only gets one chance.
      • by gozu (541069)
        This has happened to me using a linksys router a few years ago. Hexadecimal values equivalent to my internal IP (and another nonexistent internal IP, oddly enough) would get corrupted on large files consistently until I figured it out.

        No such problems on the Tomato firmware I'm using now :)
    • by cheesybagel (670288) on Sunday May 04, 2008 @08:38PM (#23295898)
      Maybe, maybe not.

      IIRC TCP/IP has a guaranteed maximum error rate of at least 10^-5 bits. Well, the thing is, 1.5 Gigabytes is over 10^10 bits in length. So even at such an error rate, it is not guaranteed that your file will arrive without bit errors.

      • by nguy (1207026)
        That's basically extrapolating from the TCP checksum. But if the raw error rate is so high that you get a TCP error rate of 10^-5, then there is something else wrong with the link.
      • by Srin Tuar (147269)
        But TCP does error checking per packet, not for the whole file at once. (so once per 1460bytes or so)

        its unlikely that TCP is the culprit here, but with a file that big, there are many many places where things could
        go wrong, and a single bit error is all it takes to mess things up in a compressed file.

        I would bet on the HTTP client/server software being involved.

    • by icebike (68054)

      One should be more concerned as to why your files are becoming corrupted.

      I'd say its a safe bet that the files from apple.com are in perfect condition.

      Which means it either became corrupted in transit to, or on arrival to your machine.

      Which leads the question:
      Is the OP or any of the seeders on Comcast?

      • Pretty sure they don't have Comcast in India...
        • by BobPaul (710574) *
          Lucky bastards.
          • Hah, funny. But if the internet situation in India is anything like that in Bangladesh, they've got a lot of crappy ISPs that sell "broadband" which is pretty much dialup-speeds through ethernet connected to a local hub somewhere. My family's from Bangladesh and we visit every summer or so, and this last summer they had their new "broadband" which was exactly the same speed as their dialup they had earlier, but through ethernet. It was through a proxy server too, which made it really annoying to configure p
            • by icebike (68054)
              Bringing this back on topic....

              The point of my post was to remind people that Comcast in the USA has been inserting reset commands into Bit Torrent (as well as other P2P protocols) as a way of "managing the network" (what ever the hell that means).

              If the seeders were on comcast, some of the problem getting complete downloads could be due to that practice.

              Of course Comcast both 1)denies they were doing this and 2)has promised to stop.
    • I have certain people who play my game who simply _cannot_ download from my website--although it works great for me and most others.

      I generally suspect malware on their clients, but I don't know for sure and it has long baffled me, because it is not rare at all.  Something like 40% or so.  Surely the malware problem is not so bad that 40% of net users can't download a 130 MB file via http without corruption?
  • by DiSKiLLeR (17651) on Sunday May 04, 2008 @07:46PM (#23295552) Homepage Journal
    I've used bittorrent for this purpose many times in years gone by.

    Especially with our slow links, or worse yet, on dialup (if I go enough years back) in Australia.

    Before bittorrent I would use rsync. That required me to download the large file to a server in the US on a fast connection, then rsync my copy to the server's copy to fix what is corrupt in my copy.

    It works beautifully. :)
    • Rsync also works nicely for "upgrading" CD images of beta Ubuntu releases to the final version, and for, say, making a Kubuntu Live CD out of the normal GNOME-based Ubuntu one. It has the advantage that it can spot blocks that have moved around in the new version but are still the same, even if they're no longer on block boundaries.
  • by trawg (308495) on Sunday May 04, 2008 @07:47PM (#23295560) Homepage
    We have been doing this for ages [ausgamers.com] for certain high-demand games file that we mirror. While offering torrents for some of our download mirrors is only mildly useful (as we're in Australia we're trying to keep bandwidth on-shore to cut down international traffic, and BT doesn't really help this), it is extremely helpful for the VAST amount of users that appear to either have massively crazy Internet problems or are simply unable to drive a HTTP based downloader and resume downloads.

    When a large number of users are having problems downloading or resuming a particular file, I simply create a torrent for them and give them some vague instructions about how to resume it and then generally I never hear from them again. They're happy because they don't have to download a 4gb game client again from scratch, they don't have to worry about resuming/corrupt downloads, and because its a torrent it probably feels like they're getting something for free that they shouldn't be.
  • by greerga (2924) on Sunday May 04, 2008 @08:01PM (#23295658)
    For even more fun, if you have two differently-corrupted copies of a file and a torrent to go with it, then you can have BitTorrent stitch them together into a valid file without involving any third parties.

    I used Azureus's internal tracker ability and two computers on a local network with the torrent modified to track on one of the machines, and one corrupted copy of the file on each.

    Obviously only works if they don't have corruption in common, but it also doesn't require the original torrent file tracker to work anymore.
    • by BobPaul (710574) *

      but it also doesn't require the original torrent file tracker to work anymore
      More importantly, this can be done without access to the internet. The lack of an available tracker is already made unnecessary by DHT. Just on the internet, it sometimes takes a while for Azureus to find someone else with the file through DHT.
    • For even more fun, if you have two differently-corrupted copies of a file and a torrent to go with it, then you can have BitTorrent stitch them together into a valid file without involving any third parties.

      It would be cool if someone built a small utility to do just that, built off of something like cfv [sourceforge.net], which only does torrent (+sfv,crc,csv,md5,etc.) verification.

      Torrents are really just fancy networked .par/.par2 files, but it would be nice to have a tool for torrent repairing that works as well as something like QuickPar [quickpar.org.uk] does for newsgroup files.

  • What a novel idea!!! (Score:3, Interesting)

    by WarJolt (990309) on Sunday May 04, 2008 @08:06PM (#23295706)
    Using bit torrent for it's actual legal intended use. I love it!!!

    I'm not a lawyer though. I just hope it doesn't violate apples NDA. Please please please follow the rules. Don't want to see you in prison or slapped with a large fine.

    Bit torrent has received a bad reputation because of pirates. There are legitimate uses though. I do believe that doctor who episodes aren't public domain, so shame on you for that. Might want to be careful what you admit to on /.
    • I have never used BitTorrent to download anything that I did not already have the legal right to possess. That is basically what the OP did. He had a legal right to possess the file, just the technical inability to get it officially.

      Most of my BitTorrenting is "100% legal" (Linux distros, UBCD, publicly released media (new NIN, Star Trek fan films,) etc.) Those I make sure to seed to at least a 2:1 ratio, often more. But some of it is to download items that I have the legal right to have, but do not hav
      • by Hatta (162192)
        Most of my BitTorrenting is "100% legal"

        And 50% of the time it works every time.
  • I wrote this bash script [vftp.net] to do basically the same thing. It uses openssl (built into most unix and OS X in specific) to create 1mb check files basically the same as torrent files. Follow the instructions and its easy to fix a corrupt download from someone that has a good copy, with the minimum required data transfer. The person with the bad file runs option 1 to make the check file and sends that to the person with the good file. They run option 2 which identifies bad chunks and exports them, which they
    • Re: (Score:3, Insightful)

      by Just Some Guy (3352)

      The person with the bad file runs option 1 to make the check file and sends that to the person with the good file. They run option 2 which identifies bad chunks and exports them, which they send back to the first person. Run option 3 and the exports are patched into their download and it's fixed.

      Isn't that almost exactly how rsync works?

  • This is not really anything BitTorrent specific, but good use of available tools. However, I hope you then checksum verified the completed file with an MD5 from Apple or somebody who has downloaded directly from them. While you probably weren't a target of an attack, you did download software from an unknown source. An attacker could download the SDK, insert malicious code, compute a new set of MD5 sums for the torrent file, upload to pirate bay or some tracker, and then seed the torrent expecting that no
  • OK, maybe not tonight-at-eleven news, but this is a totally clever hack, which is exactly what many people on Slashdot live for.

    On a related note, I came up with a roundabout way to do something similar to help a friend who was having trouble moving large files. On the remote end, split [hmug.org] the file into small chunks. Then md5 [hmug.org] them all and save those results into a text file. Then, ftp them, and when they arrive, md5 them all again and compare your values to what's in the text file. If any don't match, re-downl
    • Re: (Score:2, Insightful)

      To be honest, when I saw this story I was shocked it had shown up. I thought that using BitTorrent to repair mostly-whole files was obvious for this crowd. It's like "Using Water to Nourish Your Plants" showing up on a horticulturist site. If you know anything about how BitTorrent works then you should immediately realize that it will fix up mostly-good files for you.

      The subsequent discussion has revealed that a large chunk of the slashdot population not only doesn't understand how BitTorrent works but does
  • by erexx23 (935832) on Sunday May 04, 2008 @10:44PM (#23296652)
    I have been using Torrents for this very reason.

    I was being required to copy sometimes 10-20GB of Virtual Machine Image Files from Server to PC or PC to PC on up 40 machines at one time.
    This was taking way too long and copies were not perfect.
    Restoration of VM images presented the same problem.
    Updating a VM meant redistribution of the entire file to all machines again.

    Using (Micro) Torrent and my own tracker changed all that.

    I came up with the following solution using all available resources.
    First I started by copying all images to workstations to a separate partition. (about 200GB of VM's.)
    Then I created created my own internal Tracker and Web Page to host torrents.

    The results were:
    1. Extremely efficient use of all available network hard drive space.
    2. Utilities every machine on the network to distribute the files.
    3. Works extremely well restoring or redistributing the VM's to any one machine or several machines at once. (The more the better)
    4. 100% accuracy in distribution.
    5. The ability to quickly modify any one image on any machine, recreate the torrent(hash) and then update that image across hundreds of machines very quickly.
    In other words, modifying a file only means that the machines only have to download the bits that changed not the whole image again.
    6. With Micro Torrent any machine can be used as the tracker.
    7. The Tracker is also the "master" file server, however any machine can be used to modifiy and upload a change
    Just recreate and re-upload the new torrent replacing the old one. Remember that a torrent file serving network is Not a server centric file sharing system.
  • I used to download Linux ISO files directly from FTP or web sites.

    Nothing upset me more than downloading an ISO only to find out that after I burned it to CD/DVD, it had CRC errors and random lockups during an install.

    After BitTorrent with error correcting, the problem was solved. It works for other things as well.

    Commercial software companies can offer ISO downloads via BitTorrent trackers and send the install CD Key via email. That way customers just burn the CD/DVD and install the key they got in email.

    S
    • Even piracy doesn't hurt that much as most people want to try the software before they buy it. It is like kicking the tires before buying a car and taking it out for a test drive before signing the papers to buy it.

      Nope, better. Kicking the tires and test-driving the car add tiny amounts of wear and tear.

  • I've used it to finish up the last 3% of a jigdo build when I was missing a file or two. Worked great.
  • I wonder if you could legitimately argue that you were verifying the data in a personal backup of media that you had?

    Unless I am mistaken, it is perfectly legal to make a backup of data that you own right? So, if you already own an item, would downloading it to have a backup be a legal thing to do?

    And if that's the case, I wonder what the legal implications are in cases where the RIAA comes down on people who have been "participating in file sharing" activities.
  • Assuming you can find a source that serves a known-good file via rsync, it's a very efficient way to fix up a damaged copy.

    I once had to download a CD image over a dialup connection when I was at a client site in Mexico. I did the initial download via FTP, but it got corrupted and the MD5 sum didn't match the correct value. It had taken almost two full days to download the first time (over a weekend, so shipping a CD wouldn't have been faster), but rsync was able to find and correct the corrupted sectio

  • I tried using it on our current administration. It showed up as being 29% complete, but unfortunately nobody's seeding the uncorrupted parts that we're missing. :(

Any sufficiently advanced technology is indistinguishable from a rigged demo. - Andy Finkel, computer guy

Working...