Re: [gentoo-user] Testing a used hard drive to make SURE it is good.

[Dale]

David Haller wrote:
> Hello,
>
> On Mon, 15 Jun 2020, Dale wrote:
> [..]
>> While I'm at it, when running dd, I have zero and random in /dev.  Where
>> does a person obtain a one?  In other words, I can write all zeros, I
>> can write all random but I can't write all ones since it isn't in /dev. 
>> Does that even exist?  Can I create it myself somehow?  Can I download
>> it or install it somehow?  I been curious about that for a good long
>> while now.  I just never remember to ask. 
> I've wondered that too. So I just hacked one up just now.
>
> ==== ones.c ====
> #include <unistd.h>
> #include <stdlib.h>
> #include <stdio.h>
> static unsigned int buf[BUFSIZ];
> int main(void) {
>     unsigned int i;
>     for(i = 0; i < BUFSIZ; i++) { buf[i] = (unsigned int)-1; }
>     while( write(STDOUT_FILENO, buf, sizeof(buf)) );
>     exit(0);
> }
> ====
>
> Compile with:
>     gcc $CFLAGS -o ones ones.c
> or
>     gcc $(portageq envvar CFLAGS) -o ones ones.c
>
> and use/test e.g. like
>
>     ./ones | dd of=/dev/null bs=8M count=1000 iflag=fullblock
>
> Here, it's about as fast as
>
>     cat /dev/zero | dd of=/dev/null bs=8M count=1000 iflag=fullblock
>
> (but only about ~25% as fast as
>     dd if=/dev/zero of=/dev/null bs=8M count=1000 iflag=fullblock
> for whatever reason ever, but the implementation of /dev/zero is
> non-trivial ...)
>
> HTH,
> -dnh
>


Thanks David for the reply and others as well.  I got some good ideas
from some experts plus gave me things to google.  More further down.

For the /dev/one, I found some which seems to work.  They listed further
down.  I think my google search terms was poor.  Google doesn't have ESP
for sure.  O_o

I mentioned once long ago that I keep a list of frequently used
commands.  I do that because, well, my memory at times isn't that
great.  Here is some commands I ran up on based on posts here and what
google turned up when searching for things related on those posts.  I
wanted to share just in case it may help someone else.  ;-)  dd commands
first. 


root@fireball / # cat /root/freq-commands | grep dd
dd commands
dd if=/dev/zero of=/dev/sd bs=4k conv=notrunc
dd if=/dev/zero of=/dev/sd bs=4k conv=notrunc oflag=direct  #disables cache
dd if=/dev/zero of=/dev/sd bs=1M conv=notrunc
dd if=<(yes $'\01' | tr -d "\n") of=
dd if=<(yes $'\377' | tr -d "\n") of=
dd if=<(yes $'\xFF' | tr -d "\n") of=
root@fireball / #


The target device or file needs to be added to the end of course on the
last three.  I tend to leave out some of the target to make sure I don't
copy and paste something that ends badly.  dd can end badly if targeting
the wrong device. 


root@fireball / # cat /root/freq-commands | grep smartctl
smartctl -t long /dev/sd
smartctl -t full  ##needs research
smartctl -c -t short -d sat /dev/sd  ##needs research
smartctl -t conveyance -d sat /dev/sd  ##needs research
smartctl -l selftest -d sat /dev/sd  ##needs research
smartctl -t <short|long|conveyance|select> /dev/sd  ##needs research
smartctl -c /dev/sd  ##displays test times in minutes
smartctl -l selftest /dev/sd
root@fireball / #


The ones where I have 'needs research' on the end, I'm still checking
the syntax of the command.  I haven't quite found exact examples of them
yet.  This also led to me wanting to print the man page for smartctl. 
That is a task in itself.  Still, google found me some options which are
here:


root@fireball / # cat /root/freq-commands | grep man
print man pages to text file
man <command> | col -b > /home/dale/Desktop/smartctl.txt
print man pages to .pdf but has small text.
man -t <command> > /home/dale/Desktop/smartctl.pdf
root@fireball / #


It's amazing sometimes how wanting to do one thing, leads to learning
how to do many other things, well, trying to learn how anyway.  LOL 

I started the smartctl longtest a while ago.  It's still running but it
hasn't let the smoke out yet.  It's a good sign I guess. I only have one
SATA port left now.  I got to order another PCI SATA card I guess.  :/ 
I really need to think on the NAS project. 

Thanks to all. 

Dale

:-)  :-)