dd command examples

 Learning Linux dd command with examplesLinux command syntaxLinux command descriptionFile systems

dd if=/dev/urandom of=/dev/sda bs=4k

Fills the drive with random data

dd if=/dev/sda of=/dev/sdb bs=4096 

Drive-to-drive duplication

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

Clean up a hard drive (may need to be repeated)

dd if=inputfile of=/dev/st0 bs=32k conv=sync

Copy from file to tape device

dd if=/dev/st0 of=outfile bs=32k conv=sync

The above, reversed

dd if=/dev/sda | hexdump -C | grep [^00] 

Check if drive is really zeroed out

dd if=/dev/urandom of=/home/$user/hugefile\
 bs=4096

Fills out a partition (careful with system partitions!)

ls -l myfile
-rw-r--r-- 6703104 Oct 31 18:25 myfile
dd if=/dev/urandom of=myfile bs=6703104 count=1

Scramble a file (maybe before deleting it)

dd if=/dev/sda3 of=/dev/sdb3 bs=4096 \
conv=notrunc,noerror

Copy a partition to another partition

dd if=/proc/filesystems | hexdump -C | less

View available filesystems

dd if=/proc/partitions | hexdump -C | less

View availble partitions in kb

dd if=/dev/sdb2 ibs=4096 | gzip > partition.image.gz \
conv=noerror

Creates a gzipped image of the second partition 
of the second disk

dd bs=10240 cbs=80 conv=ascii,unblock\
 if=/dev/st0 of=ascii.out

Copy the contents of a tape drive to a file, converting
from EBCDIC to ASCII

dd if=/dev/st0 ibs=1024 obs=2048 of=/dev/st1

Copy from 1KB block device to 2KB block device

dd if=/dev/zero of=/dev/null bs=100M count=100
100+0 records in
100+0 records out
10485760000 bytes (10 GB) copied,

5.62955 s, 1.9 GB/s

Copy 10 GB of zeros to the garbage can.

dd if=/dev/zero of=/dev/sda bs=512 count=2
fdisk -s /dev/sda
dd if=/dev/zero of=/dev/sda seek=\
(number_of_sectors - 20) bs=1k

Erase GPT from disk. Since GPT writes data at the beginning
AND at the end of the drive, after 
erasing from the beginning, we need to find out the number 
of sectors (second command), then erase the last 20 sectors.

dd if=/home/$user/bootimage.img of=/dev/sdc 

Create bootable USB drive (here shown as /dev/sdc)

dd if=/dev/sda of=/dev/null bs=1m 

A good way to check for bad blocksBackup and system-related

dd if=/dev/sda of=/dev/fd0 bs=512 count=1

Copies the MBR to a floppy

dd if=/dev/sda1 of=/dev/sdb1 bs=4096 

Drive-to-drive duplication

dd if=/dev/sr0 of=/home/$user/mycdimage.iso\
 bs=2048 conv=nosync

Create an image of a CD

mount -o loop /home/$user/mycdimage.iso\
 /mnt/cdimages/

Mount said image locally

dd if=/dev/sda of=/dev/sdb bs=64k conv=sync

Useful when replacing a disk with another of identical size

dd if=/dev/sda2 of=/home/$user/hddimage1.img\
 bs=1M count=4430
dd if=/dev/sda2 of=/home/$user/hddimage2.img\
 bs=1M count=8860
[...]

Create DVD images of a partition (useful for backing up)

dd if=/$location/hddimage1.img of=/dev/sda2\
 bs=1M
dd if=/$location/hddimage2.img of=/dev/sda2\
 seek=4430 bs=1M
dd if=/$location/hddimage3.img of=/dev/sda2\
 seek=8860 bs=1M
[and so on...]

Restore from above backup

dd if=/dev/zero count=1 bs=1024 seek=1 of=/dev/sda6 

Destroy the superblock

dd if=/dev/zero count=1 bs=4096 seek=0 of=/dev/sda5 

Another way to destroy the superblock

dd if=/home/$user/suspicious.doc | clamscan -

Check file for viruses (needs ClamAV)

dd if=/home/$user/binary file | hexdump -C | less

Look at the contents of a binary file (needs hexdump)

dd if=/home/$user/bigfile of=/dev/null
dd if=/dev/zero of=/home/$user/bigfile \
bs=1024 count=1000000

Benchmarks hard drive for read/write speed

dd if=/dev/sda of=/dev/sda

Gives new life to older hard drives that haven't been used for a while (disk must be unmounted)

dd if=/dev/mem | strings | grep 'string_to_search'

Examine memory contents (human-readable, that is)

dd if=/dev/fd0 of=/home/$user/floppy.image\
 bs=2x80x18b conv=notrunc

Copy a floppy disk

dd if=/proc/kcore | hexdump -C | less

View virtual memory

dd if=/proc/filesystems | hexdump -C | less

View available filesystems

dd if=/proc/kallsyms | hexdump -C | less

View loaded modules

dd if=/proc/interrupts | hexdump -C | less

View interrupt table

dd if=/proc/uptime | hexdump -C | less

View uptime in seconds

dd if=/proc/partitions | hexdump -C | less

View availble partitions in kb

dd if=/proc/meminfo | hexdump -C | less

View memstats

dd if=/dev/urandom of=/home/$user/myrandom \
bs=100 count=1

Creates a 1kb file of random gibberish

dd if=/dev/mem of=/home/$user/mem.bin\
 bs=1024

Creates an image of the actual state of your system memory

dd if=/home/$user/myfile

Prints the file to stdout

dd if=/dev/sda2 bs=16065 | hexdump -C\
 | grep 'text_to_search'

Search an entire partition for a string; even if it's secured,
you can boot a liveCD

dd if=/home/$user/file.bin skip=64k bs=1\
 of=/home/$user/convfile.bin

Copy file.bin to convfile.bin skipping the first 64 kB

dd if=/home/$user/bootimage.img of=/dev/sdc 

Create bootable USB drive (here shown as /dev/sdc)

dd if=/dev/mem bs=1k skip=768 count=256 \
2>/dev/null | strings -n 8

Read BIOS.

dd bs=1k if=imagefile.nrg of=imagefile.iso skip=300k

Convert Nero image into ISO standard image. 
This is possible because the only difference between 
the two is a 300 kB header Nero adds to a standard ISO file.

echo -n "hello vertical world" | dd cbs=1 \
conv=unblock 2> /dev/null

Try it, it's safe. :-)

dd if=/dev/sda1 | gzip -c | split -b 2000m - \
/mnt/hdc1/backup.img.gz

Create a gzipped image of a partition using split

cat /mnt/hdc1/backup.img.gz.* | gzip -dc |\
 dd of=/dev/sda1

Restore above backup

dd if=/dev/zero of=myimage bs=1024 count=10240

Create an empty disk image

dd ibs=10 skip=1

Strip first 10 bytes of stdin

dd bs=265b conv=noerror if=/dev/st0 \
of=/tmp/bad.tape.image

Make image of a tape drive with bad spots

dd if=/dev/sda count=1 | hexdump -C

View your MBR

dd if=/dev/sda | nc -l 10001 
nc $system_to_backup_IP 10001 | dd\
 of=sysbackupsda.img 

Fast network backup using netcat

dd if=/dev/zero of=/dev/sdX\
 bs=1024000 count=1

Clear first 10MB of the partition

dd if=/dev/zero of=tmpswap bs=1k\
 count=1000000
chmod 600 tmpswap
mkswap tmpswap
swapon tmpswap

Create temporary swap space

dd if=/dev/sda of=/dev/null bs=1024k \
count=1024
1073741824 bytes (1.1 GB) copied, 
24.1684 s, 44.4 MB/s

Determine sequential I/O speed of your drive. Reading 1GB file

dd if=/dev/random count=1 2>/dev/null | od -t u1 |\
 awk '{ print $2}' | head -1

Generate random number

dd if=/dev/mem of=myRAM bs=1024

Copy RAM memory to a file

dd if=/dev/sda bs=512 count=1 | od -xa

See content of your MBR in hex and ASCII format

dd if=/my/old/mbr of=/dev/sda bs=446 count=1

Restore MBR without disturbing partition table record 
which is between 447 - 511 bytes

dd if=/dev/sda1 | split -b 700m - sda1-image

Create a partition copy and save images where maximum
volume size is 700MBText manipulation

ls -l | dd conv=ucase

Convert the output of a command to uppercase

echo "MY UPPER CASE TEXT" | dd conv=lcase

Convert any text to lowercase

dd if=/etc/passwd cbs=132 conv=ebcdic of=/tmp/passwd.ebcdic

Convert the system password file to fixed-length EBCDIC-format file

dd if=text.ascii of=text.ebcdic conv=ebcdic

Convert from ASCII to EBCDIC

dd if=myfile of=myfile conv=ucase

Convert a file to uppercase (simple sed or tr replacement)