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bs = buffer size (basically defined the size of a "unit" used by count and skip)
count = the number of buffers to copy (16m * 32 = 1/2 gig)
skip = (32 * 2) we are grabbing piece 3...which means 2 have already been written so skip (2 * count)
i will edit this later if i can to make this all more understandable
This is a more accurate way to watch the progress of a dd process. The $DDPID=$! is needed so that you don't get the PID of the sleep. The sleep 1 is needed because in my testing at least, if you run kill -USR1 against dd too quickly, it will kill it off instead of display the status. So you need to wait a second, probably so that it can configure itself to trap the USR1 signal.
The following command will clone usb stick inside /dev/sdc to /dev/sdd
Double check you got the correct usb sticks (origional-clone)with fdisk -l.
A bit different from some of the other submissions. Has bold and uses all c printable characters. Change the bs=value to speed up and increase the sizes of the bold and non-bold strings.
I wanted to create a copy of my whole laptop disk on an lvm disk of the same size.
First I created the logical volume: lvcreate -L120G -nlaptop mylvms
SOURCE: dd if=/dev/sda bs=16065b | netcat ip-target 1234
TARGET: nc -l -p 1234 | dd of=/dev/mapper/mylvms-laptop bs=16065b
to follow its process you issue the following command in a different terminal
STATS: on target in a different terminal: watch -n60 -- kill -USR1 $(pgrep dd)
If you have some drive imaging to do, you can boot into any liveCD and use a commodity machine. The drives will be written in parallel.
To improve efficiency, specify a larger block size in dd:
dd if=/dev/sda bs=64k | tee >(dd of=/dev/sdb bs=64k) | dd of=/dev/sdc bs=64k
To image more drives , insert them as additional arguments to tee:
dd if=/dev/sda | tee >(dd of=/dev/sdb) >(dd of=/dev/sdc) >(dd of=/dev/sdd) | dd of=/dev/sde
This is similar to how you would generate a file with all zeros
dd if=/dev/zero of=allzeros bs=1024 count=2k
For disk space constraint testing. Leaves a little space available for creating temp files, etc. Easily free up the used disk space again by deleting the dummy00 file. Can tailor the testing by building smaller 'blocks' to suit the needs of the testing.
WARNING: do not do this to the '/' (root) filesystem unless you know what you are doing... on some systems it could crash the OS.
If you leave out the block size it defaults to 512 bytes. I set it to 16 Megabytes and it was much faster...
This is an useful command for when your OS is reporting less free RAM than it actually has. In case terminated processes did not free their variables correctly, the previously allocated RAM might make a bit sluggis over time.
This command then creates a huge file made out of zeroes and then removes it, thus freeing the amount of memory occupied by the file in the RAM.
In this example, the sequence will free up to 1GB(1M * 1K) of unused RAM. This will not free memory which is genuinely being used by active processes.
See: http://imgur.com/JgjK2.png for example.
Do some serious benchmarking from the commandline. This will write to a file with the time it took to compress n bytes to the file (increasing by 1).
gnuplot -persist <(echo "plot 'lzma' with lines, 'gzip' with lines, 'bzip2' with lines")
To see it in graph form.
Intentional hash in the beginning. May run a looong time. Wipes your data for real. Was meant to be /dev/urandom - I mistyped it. :-)
You can use this to directly dump from machine A (with dvd drive) to machine B (without dvd drive) . I used this to copy dvd using my friend's machine to my netbook. Above command is to be issued on machine B.
1) No wasting time dumping first to machine A and then copying to Machine B.
2) You dont need to use space on Machine A. In fact, this will work even when Machine A doesnt have enough hdd space to dump the DVD.
Use -C ssh option on slow networks (enables compression).
you can replace "dd if=/dev/dvd" with any ripping command as long as it spews the iso to stdout.
Overwrites the boot sector. Since this doesn't overwrite any data, you can usually recover by re-creating the partition table exactly the same as before you zeroed it. This can also help sometimes if you install a new drive in a Windows machine which can't read it.
A dear friend of mine asked me how do I copy a DVD to your hard drive? If you want to make a copy of the ISO image that was burned to a CD or DVD, insert that medium into your CD/DVD drive and (assuming /dev/cdrom is associated with your computer?s CD drive) type the following command
This command clone the first partition of the primary master IDE drive to the second partition
of the primary slave IDE drive (!!! back up all data before trying anything like this !!!)