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It's kind of flawed where he says " If you pick x to be big enough, you should get the entire file, plus a bit of junk around the edges." - because this is simply not how filesystems work - if you manage to get the full file, it's by luck that it was small enough for the filesystem to allocate its contents contiguously on the block device.

Anything bigger and you're gonna quickly need something more sophisticated which can understand the filesystem it's dealing with, as it will need to collect the many pieces of your deleted file scattered across the block device and merge them. I'm sure that would be mountains of fun to do with bash.

And in this case, the "do one job well" program that you're gonna need is a program which specifically recovers deleted files from a specific filesystem.




I'm the author of the post -- that's good to know, thanks! :) I know embarrassingly little about filesystems. I'm glad you pointed this out.

EDIT: though, I'd point out that if you really wanted to recover the file you should probably try to use /proc or something (at the time I didn't know about this). This approach requires crawling the disk which is obv pretty slow. :) It's less of a "here's a useful thing" and more of an excited "HEY DID YOU KNOW THAT YOU CAN DO X".

EDIT 2: I updated the blog to link to your comment, because it's baller.


If processes which hold your file open are still running, then you can access the file via the /proc/<pid>/fd/ entries. Run an 'ls -l' in the proc directory of the process to see those.

You can simply copy the (proc) file to a new location to recover it.

Remember: open files keep the contents present on disk until the controlling process exists or closes the filehandle.

Since you're actually accessing the file on disk your issues of storage contingency don't come into play -- it's all read back to you in proper file order.

But yes, files (and virtual files) on Linux are pretty slick.

I also remember being really excited learning about disk image files and the ways in which they can be manipulated. Including the options of creating filesystems on virtual disks, partitioning them, and them mounting those partitions, etc. First tried with bootable floppy distros, but I've played around with them in a bunch of contexts since.


Last time I ran fsck on my ext2 partition the fragmentation ratio was pretty low, and I tend to fill up my disks. Fortunately, homework assignments tend to be shorter, and more likely to fit in a contiguous spot. Anyway, what else can you do?

From a different perspective, hopefully /tmp is on a different filesystem from /home, otherwise the reading the man pages might overwrite the blocks you need to recover with the temporary files they produce. (And less, more, sort, etc.) Also, doing Google/StackOverflow searches is probably unwise due to the browser writing stuff to the 50 MB disk cache (FF default, anyway) on the filesystem you want. Probably step 1 should be "remount the partition read-only". Or better yet, "find another computer to use for research" :)




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