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author53hornet <atc@53hor.net>2021-07-28 10:58:58 -0400
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-
- <article>
- <h1>How I Do Data Recovery</h1>
-
- <p>
- This week Amy plugged in her flash drive to discover that there were no
- files on it. Weeks before there had been dozens of large cuts of footage
- that she needed to edit down for work. Hours of recordings were
- seemingly gone. And the most annoying part was the drive had worked
- perfectly on several other occasions. Just not now that the footage was
- actually needed of course. Initially it looked like everything had been
- wiped clean, however both Amy's Mac and her PC thought the drive was
- half full. It's overall capacity was 64GB but it showed only about 36GB
- free. So there still had to be data on there if we could find the right
- tool to salvage it.
- </p>
-
- <p>
- Luckily this wasn't the first time I had to recover accidentally (or
- magically) deleted files. I had previously done so with some success at
- my tech support job, for some college friends, and for my in-laws'
- retired laptops. So I had a pretty clear idea of what to expect. The
- only trick was finding a tool that knew what files it was looking for.
- The camera that took the video clips was a Sony and apparently they
- record into <code>m2ts</code> files, which are kind of a unique format
- in that they only show up on Blu-Ray discs and Sony camcorders. Enter my
- favorite two tools for dealing with potentially-destroyed data:
- <code>ddrescue</code> and <code>photorec</code>.
- </p>
-
- <h2>DDRescue</h2>
-
- <p>
- <code>ddrescue</code> is a godsend of a tool. If you've ever used
- <code>dd</code> before, forget about it. Use <code>ddrescue</code>. You
- might as well <code>alias dd=ddrescue</code> because it's that great. By
- default it has a plethora of additional options, displays the progress
- as it works, recovers and retries in the event of I/O errors, and does
- everything that good old <code>dd</code> can do. It's particularly good
- at protecting partitions or disks that have been corrupted or damaged by
- rescuing undamaged portions first. Oh, and have you ever had to cancel a
- <code>dd</code> operation? Did I mention that <code>ddrescue</code> can
- pause and resume operations? It's that good.
- </p>
-
- <h2>PhotoRec</h2>
-
- <p>
- <code>photorec</code> is probably the best missing file recovery tool
- I've ever used in my entire life. And I've used quite a few. I've never
- had as good results as I've had with <code>photorec</code> with other
- tools like Recuva et. al. And <code>photorec</code> isn't just for
- photos, it can recover documents (a la Office suite), music, images,
- config files, and videos (including the very odd
- <code>m2ts</code> format!). The other nice thing is
- <code>photorec</code> will work on just about any source. It's also free
- software which makes me wonder why there are like $50 recovery tools for
- Windows that look super sketchy.
- </p>
-
- <h2>In Practice</h2>
-
- <p>
- So here's what I did to get Amy's files back. Luckily she didn't write
- anything out to the drive afterward so the chances (I thought) were
- pretty good that I would get <em>something</em> back. The first thing I
- always do is make a full image of whatever media I'm trying to recover
- from. I do this for a couple of reasons. First of all it's a backup. If
- something goes wrong during recovery I don't have to worry about the
- original, fragile media being damaged or wiped. Furthermore, I can work
- with multiple copies at a time. If it's a large image that means
- multiple tools or even multiple PCs can work on it at once. It's also
- just plain faster working off a disk image than a measly flash drive. So
- I used <code>ddrescue</code> to make an image of Amy's drive.
- </p>
-
- <pre><code>
-$ sudo ddrescue /dev/sdb1 amy-lexar.dd
-GNU ddrescue 1.24
-Press Ctrl-C to interrupt
- ipos: 54198 kB, non-trimmed: 0 B, current rate: 7864 kB/s
- opos: 54198 kB, non-scraped: 0 B, average rate: 18066 kB/s
-non-tried: 63967 MB, bad-sector: 0 B, error rate: 0 B/s
- rescued: 54198 kB, bad areas: 0, run time: 2s
-pct rescued: 0.08%, read errors: 0, remaining time: 59m
- time since last successful read: n/a
-Copying non-tried blocks... Pass 1 (forwards)
- </code></pre>
-
- <p>
- The result was a very large partition image that I could fearlessly play
- around with.
- </p>
-
- <pre>
- <code>
-$ ll amy-lexar.dd
--rw-r--r-- 1 root root 60G Sep 24 02:45 amy-lexar.dd
- </code>
- </pre>
-
- <p>
- Then I could run <code>photorec</code> on the image. This brings up a
- TUI with all of the listed media that I can try and recover from.
- </p>
-
- <pre><code>
-$ sudo photorec amy-lexar.dd
-
-PhotoRec 7.0, Data Recovery Utility, April 2015
-http://www.cgsecurity.org
-
- PhotoRec is free software, and
-comes with ABSOLUTELY NO WARRANTY.
-
-Select a media (use Arrow keys, then press Enter):
->Disk amy-lexar.dd - 64 GB / 59 GiB (RO)
-
->[Proceed ] [ Quit ]
-
-Note:
-Disk capacity must be correctly detected for a successful recovery.
-If a disk listed above has incorrect size, check HD jumper settings, BIOS
-detection, and install the latest OS patches and disk drivers.
- </code></pre>
-
- <p>
- After hitting proceed <code>photorec</code> asks if you want to scan
- just a particular partition or the whole disk (if you made a whole disk
- image). I can usually get away with just selecting the partition I know
- the files are on and starting a search.
- </p>
-
- <pre><code>
-PhotoRec 7.0, Data Recovery Utility, April 2015
-http://www.cgsecurity.org
-
-Disk amy-lexar.dd - 64 GB / 59 GiB (RO)
-
- Partition Start End Size in sectors
- Unknown 0 0 1 7783 139 4 125042656 [Whole disk]
-> P FAT32 0 0 1 7783 139 4 125042656 [NO NAME]
-
->[ Search ] [Options ] [File Opt] [ Quit ]
- Start file recovery
- </code></pre>
-
- <p>
- Then <code>photorec</code> asks a couple of questions about the
- formatting of the media. It can usually figure them out all by itself so
- I just use the default options unless it's way out in left field.
- </p>
-
- <pre><code>
-PhotoRec 7.0, Data Recovery Utility, April 2015
-http://www.cgsecurity.org
-
- P FAT32 0 0 1 7783 139 4 125042656 [NO NAME]
-
-To recover lost files, PhotoRec need to know the filesystem type where the
-file were stored:
- [ ext2/ext3 ] ext2/ext3/ext4 filesystem
->[ Other ] FAT/NTFS/HFS+/ReiserFS/...
- </code></pre>
-
- <p>
- Now this menu is where I don't just go with the default path.
- <code>photorec</code> will offer to search just unallocated space or the
- entire partition. I always go for the whole partition here; sometimes
- I'll get back files that I didn't really care about but more often than
- not I end up rescuing more data this way. In this scenario searching
- just unallocated space found no files at all. So I told
- <code>photorec</code> to search everything.
- </p>
-
- <pre><code>
-PhotoRec 7.0, Data Recovery Utility, April 2015
-http://www.cgsecurity.org
-
- P FAT32 0 0 1 7783 139 4 125042656 [NO NAME]
-
-
-Please choose if all space need to be analysed:
- [ Free ] Scan for file from FAT32 unallocated space only
->[ Whole ] Extract files from whole partition
- </code></pre>
-
- <p>
- Now it'll ask where you want to save any files it finds. I threw them
- all into a directory under home that I could zip up and send to Amy's
- Mac later.
- </p>
-
- <pre><code>
-PhotoRec 7.0, Data Recovery Utility, April 2015
-
-Please select a destination to save the recovered files.
-Do not choose to write the files to the same partition they were stored on.
-Keys: Arrow keys to select another directory
- C when the destination is correct
- Q to quit
-Directory /home/adam
- drwx------ 1000 1000 4096 28-Sep-2019 12:10 .
- drwxr-xr-x 0 0 4096 26-Jan-2019 15:32 ..
->drwxr-xr-x 1000 1000 4096 28-Sep-2019 12:10 amy-lexar-recovery
- </code></pre>
-
- <p>
- And then just press <code>C</code>. <code>photrec</code> will start
- copying all of the files it finds into that directory. It reports what
- kinds of files it found and how many it was able to locate. I was able
- to recover all of Amy's lost footage this way, past, along with some
- straggler files that had been on the drive at one point. This has worked
- for me many times in the past, both on newer devices like flash drives
- and on super old, sketchy IDE hard drives. I probably won't ever pay for
- data recovery unless a drive has been physically damaged in some way. In
- other words, this software works great for me and I don't foresee the
- need for anything else out there. It's simple to use and is typically
- pretty reliable.
- </p>
- </article>
- </body>
-</html>