Dumb question - linux dd write 0s to multiples disks at once

travisdh1

@dustinb3403 said in Dumb question - linux dd write 0s to multiples disks at once:

@travisdh1 said in Dumb question - linux dd write 0s to multiples disks at once:

@dustinb3403 said in Dumb question - linux dd write 0s to multiples disks at once:

@scottalanmiller said in Dumb question - linux dd write 0s to multiples disks at once:

With a single command, no. But you can run several commands at once.

That would suffice, what would it look like?

tack a ; to the end of each dd command and put them all on a single line

as

dd if=/dev/zero of=/dev/sdb bs=4k; dd if=/dev/zero of=/dev/sdc bs=4k; dd if=/dev/zero of=/dev/sdd bs=4k; dd if=/dev/zero of=/dev/sde bs=4k

right?

yes

DustinB3403

It works!

Now just to go home and drink and come back to this Monday.

Thanks guys!

scottalanmiller

@dustinb3403 said in Dumb question - linux dd write 0s to multiples disks at once:

@travisdh1 said in Dumb question - linux dd write 0s to multiples disks at once:

@dustinb3403 said in Dumb question - linux dd write 0s to multiples disks at once:

@scottalanmiller said in Dumb question - linux dd write 0s to multiples disks at once:

With a single command, no. But you can run several commands at once.

That would suffice, what would it look like?

tack a ; to the end of each dd command and put them all on a single line

as

dd if=/dev/zero of=/dev/sdb bs=4k; dd if=/dev/zero of=/dev/sdc bs=4k; dd if=/dev/zero of=/dev/sdd bs=4k; dd if=/dev/zero of=/dev/sde bs=4k

right?

That makes one run right after the other, they don't run at the same time.

scottalanmiller

@travisdh1 said in Dumb question - linux dd write 0s to multiples disks at once:

dd if=/dev/zero of=/dev/sdb bs=4k

nohup dd if=/dev/zero of=/dev/sdb bs=4k &
nohup dd if=/dev/zero of=/dev/sdc bs=4k &
nohup dd if=/dev/zero of=/dev/sdd bs=4k &

Like that

DustinB3403

@scottalanmiller but nohup from the live us isn't an option.

scottalanmiller

@dustinb3403 said in Dumb question - linux dd write 0s to multiples disks at once:

@scottalanmiller but nohup from the live us isn't an option.

Oh, what shell are you in?

black3dynamite

@dustinb3403 said in Dumb question - linux dd write 0s to multiples disks at once:

@scottalanmiller but nohup from the live us isn't an option.

Using Ubuntu live usb?

DustinB3403

Centos 7

scottalanmiller

What is the result of this command..

echo $0

DustinB3403

@scottalanmiller said in Dumb question - linux dd write 0s to multiples disks at once:

What is the result of this command..
echo $0

Not at the office, so I don't know

black3dynamite

https://unix.stackexchange.com/revisions/284489/1

dd if=/dev/zero | tee >(dd of=/dev/sdb) >(dd of=/dev/sdc) | dd of=/dev/sdd

Obsolesce

@dustinb3403 said in Dumb question - linux dd write 0s to multiples disks at once:

Is it possible to use linux DD to write 0's to multiple disks at once?

The goal would be to wipe 4 drives at once.

What if you create a SW RAID 10 with them quick, then write zeros?

Alex Sage

Does writing zeros to an SSD drive affect the drive life?

1337

No need to wipe all the disks. It's a waste of time.

If you wanted to erase the partition table you don't have to erase the whole disk. Just the first / last bytes of the drive. Or just remove it with fdisk or parted.
If you wanted to remove superblocks after an earlier md raid installation you wouldn't need to wipe the disk either. You do: mdadm --zero-superblock /dev/sdX

You could also use wipefs -a /dev/sdX to remove just partition tables and raid signatures - if you have it installed.

And as soon as you put together a raid-10 it will start synchronizing the disk and write the same zeros one more time.

If you really, really wanted to wipe the drive so no residual data where on them, wipe just what is needed to make a raid-10 array out of it. Then wipe the array with zeros, as a block device. It will save a lot of time. As the synchronization process will write the zeros for you on the other drives.

scottalanmiller

@obsolesce said in Dumb question - linux dd write 0s to multiples disks at once:

@dustinb3403 said in Dumb question - linux dd write 0s to multiples disks at once:

Is it possible to use linux DD to write 0's to multiple disks at once?

The goal would be to wipe 4 drives at once.

What if you create a SW RAID 10 with them quick, then write zeros?

That would be faster. Or RAID 1. Any RAID, actually.

scottalanmiller

@aaronstuder said in Dumb question - linux dd write 0s to multiples disks at once:

Does writing zeros to an SSD drive affect the drive life?

No, shouldn't affect anything unless you are trying to obfuscate the old data

manxam

"screen" is available within the bootable USB.
screen dd if=/dev/zero of=/dev/sda1 bs=1M
Ctrl-A then D to detach
Up arrow then enter 3 more times...

This will continue to run even if the console is lost (ssh) or if the user logs out
screen -R to re-attach a session if you want to check the status

Having said that:
dd if=/dev/zero of=/dev/sda bs=512 count=1 conv=notrunc
Should take only seconds and delete the partition table and is less work than using fdisk in the event that wipefs isn't available on the bootable USB.

travisdh1

@scottalanmiller said in Dumb question - linux dd write 0s to multiples disks at once:

@travisdh1 said in Dumb question - linux dd write 0s to multiples disks at once:

dd if=/dev/zero of=/dev/sdb bs=4k
nohup dd if=/dev/zero of=/dev/sdb bs=4k &
nohup dd if=/dev/zero of=/dev/sdc bs=4k &
nohup dd if=/dev/zero of=/dev/sdd bs=4k &
Like that

Dang it, I'm always mixing those up.

stacksofplates

@scottalanmiller said in Dumb question - linux dd write 0s to multiples disks at once:

@travisdh1 said in Dumb question - linux dd write 0s to multiples disks at once:

dd if=/dev/zero of=/dev/sdb bs=4k
nohup dd if=/dev/zero of=/dev/sdb bs=4k &
nohup dd if=/dev/zero of=/dev/sdc bs=4k &
nohup dd if=/dev/zero of=/dev/sdd bs=4k &
Like that

And if you're set on a one-liner like before:

for i in {b..d}; do nohup dd if=/dev/zero of=/dev/sd$i bs=4k &; done

stacksofplates

Another way would be to use make. Just create a makefile with:

all: disk1 disk2 disk3 

.PHONY: disk1
disk1:
    dd if=/dev/zero of=/dev/sdb bs=4k

.PHONY: disk2
disk2:
    dd if=/dev/zero of=dev/sdc bs=4k

.PHONY: disk3
disk3:
    dd if=/dev/zero of=/dev/sdd bs=4k

Then just run make -j and it will run all of the targets in parallel. If you want them to loop then just don't give the -j flag.

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