[Techtalk] finding bad files

Miriam English mim at miriam-english.org
Mon Apr 13 22:05:46 UTC 2015

Lots of great suggestions. Thanks.
Using tar was a terrific idea. Using find and cat to send to /dev/null 
was the perfect solution.

I should have waited longer before trying what I did. I ran e2fsck to 
check for errors, then thought, hell, I might as well get it to fix all 
the errors at the same time and then I could restore the files from my 
backup because now the damaged files will be different from the backups. 
But I didn't think long enough about this, because I also have some new 
files that haven't yet been backed up from that drive. And some will 
almost certainly be affected by the errors, with no chance of recovering 
them now. Oops.

The good news is that although many blocks had erroneous data, there 
were none listed as "bad blocks". I assume that bad blocks are 
physically faulty regions on the disk.

The drive may be failing, though it isn't terribly old and being an 
external drive I only connect and switch it on when I actually need to 
read or write data from/to it. The data may have become affected during 
one of the very frequent blackouts we have here. Or I wonder if dust on 
the USB connectors could have damaged the data, though I think that they 
use checksums to guard against that. Looks like I'll have to save the 
money to buy another 2 terabyte (or larger) drive. (I wish solid state 
drives would get cheaper more quickly.)

I used to have an uninterruptible power supply, but it got destroyed a 
while back when lightning struck while I was shutting everything down 
because I heard a storm approaching. Since then I've become a big fan of 
ultra-low-power computing and want to move entirely to solar panels and 
batteries in the near future. I'm sick of having thousands of dollars in 
computers and other equipment destroyed by the electrical grid over the 

There is also the human-unfriendly problem of unmounting a drive before 
disconnecting it. Everybody knows this must be done, but everybody has 
lost data because of it. I have, on odd occasions, usually when 
over-tired, made the mistake of pulling out the wrong USB connector or 
switching off the wrong external drive.

<rant>I'm certain the design of peripherals could have been made to take 
account of the flawed nature of humans so that data was buffered in 
drive electronics, and capacitors supplied just enough power to ensure 
pointers were updated correctly. But USB, while having terrific 
advantages over previous kinds of data connectors, was nevertheless a 
good example of an over-complex, yet flawed, spec designed by committee. 
The main USB document is more than 600 pages long!</rant>


	- Miriam

If you don't have any failures then you're not trying hard enough.
  - Dr. Charles Elachi, director of NASA's Jet Propulsion Laboratory
Website: http://miriam-english.org
Blogs:   http://miriam-e.dreamwidth.org

More information about the Techtalk mailing list