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Similar to the original, but is much faster since it only needs to write the last byte as zero. A diff on testfile and testfile.seek will return that they are the same.
Useful for testing purposes
Will automatically take the size of the file but longer, usefull only if in an function.
Step#2 Create a copy of the bootload and partition table!
An alternative which does not require to be root
Acquires a bit-by-bit data image, gzip-compresses it on multiple cores (pigz) and encrypts the data for multiple recipients (gpg -e -r). It finally sends it off to a remote machine.
Install a basic FreeBSD system on a distant server. I use this to install FreeBSD on servers that can only boot a Linux rescue system. This sytem loads on ram when booted, so it is possible to install freely. You can even install on ZFS root !
Adjust "sleep X" to your needs.
*NOTE: First sleep is required because bash doesn't have a "post-test" syntax (do XXX while).
Sends random sounds to your sound card output (e.g. your speaker). Think... You can also run it remotely on another computer using SSH and scare its user!
Sends random beeps to your PC-speaker. Think... You can also run it remotely on another computer using SSH and scare its user! Don't forget to run it on your dedicated hosting server and watch sysadmin's action from data-center's live remote cameras!
If you're trying to create a sparse file, you can use dd by 'skip'ing to the last block instance.
ls -ls shows the actual size vs. the reported size
Change /dev/sda with the Disk or partition you want to back-up
To restore use:
dd if=~/backup-disk-YY-MM-DD.img of=/dev/sda
Once again change /dev/sda accordingly
Note: Replace 200000 with drive bytes/512, and /dev/sdx with the destination drive/partition. ;)
Note: You may need to install pipebench, this is easy with "sudo apt-get install pipebench" on Ubuntu.
The reason I hunted around for the pieces to make up this command is that I wanted to specifically flip all of the bits on a new HDD, before running an Extended SMART Self-Test (actually, the second pass, as I've already done one while factory-zeroed) to ensure there are no physical faults waiting to compromise my valuable data. There were several sites that came up in a Google search which had a zero-fill command with progress indicator, and one or two with a fill-with-ones command, but none that I could find with these two things combined (I had to shuffle around the dd command(s) to get this to happen without wasting speed on an md5sum as well).
For reference, these are the other useful-looking commands I found in my search:
Zero-fill drive "/dev/sdx", with progress indicator and md5 verification (run sudo fdisk -l to get total disk bytes, then divide by 512 and enter the resulting value into this command for a full wipe)
dd if=/dev/zero bs=512 count=<size/512> | pipebench | sudo tee /dev/sdx | md5sum
And this command for creating a file filled with ones is my other main source (besides the above command and man pages, that is - I may be a Linux newbie but I do read!):
tr '\000' '\377' < /dev/zero | dd of=allones bs=1024 count=2k
Hope someone finds this useful! :)
This command utilizes 'pv' to show dd's progress.
Notes on use with dd:
-- dd block size (bs=...) is a widely debated command-line switch and should usually be between 1024 and 4096. You won't see much performance improvements beyond 4096, but regardless of the block size, dd will transfer every bit of data.
-- pv's switch, '-s' should be as close to the size of the data source as possible.
-- dd's out file, 'of=...' can be anything as the data within that file are the same regardless of the filename / extension.
Use this if you're using vi editing mode.
Example use :
sudo vim /root/bin/ ##uh... autocomplete doesn't work... dd sudo ls /root/bin
##ah! that's the name of the file!
<p> sudo vim /root/bin/ ##resume here! Thanks readline!
read the memory from C:0000 to F:FFFF
without the need auf dmidecode
The above command will send 4GB of data from one host to the next over the network, without consuming any unnecessary disk on either the client nor the host. This is a quick and dirty way to benchmark network speed without wasting any time or disk space.
Of course, change the byte size and count as necessary.
This command also doesn't rely on any extra 3rd party utilities, as dd, ssh, cat, /dev/zero and /dev/null are installed on all major Unix-like operating systems.
Mac OS X needs some clean up. First command works in Linux, Solaris just needs the "0000000"'s removed
piping through 'pv' shows a simple progress/speed bar for dd. This is a replacement for my otherwise favorite 'while :;do killall -USR1 dd;sleep 1;done'