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I have this "disk list" table:

   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *16.4 GB    disk2
   1:                      Linux                         536.9 MB   disk2s1
   2:                  Linux_LVM                         15.9 GB    disk2s2

the partition I am trying to DD is only 536MB, but when I try to dd it takes me more than one hour. my question is there a way to make the dd fast, and copy only what's important but to keep the new disk functional and have the same partition scheme.


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Did you try setting a block size? dd if=/dev/disk2s1 of=<destination> bs=1M – Darth Android Aug 26 '14 at 18:53
@DarthAndroid Yes I did set "bs", not a big difference, I am trying to see if it's possible to dd only what it matters. – Midimo Aug 26 '14 at 18:56
Also, you can try cat /dev/source_disk > /dev/dest_disk – Denilson Sá Aug 26 '14 at 18:56
I'm curious what hardware you're doing this on, because dd'ing a ~500 MB disk image onto a disk taking an hour is a new phenomenon for me to hear about. If it's something particularly low powered, it may not be that odd, but if it's a desktop computer from the last decade or so, it sounds like something fishy is going on here. – 0xDAFACADE Aug 26 '14 at 18:58
up vote 3 down vote accepted

No; dd is a dumb tool - you tell it were to start, where to stop, and it copies everything in between. It has no knowledge of partitions, partition maps, drives, filesystems, or what remotely might constitute valuable or important data (other than everything between aforementioned start and finish).

If you have a partition with low filesystem utilization (i.e., the 536MB partition only has 100MB in use, the rest is free space), then you need a partition imaging tool which supports sparse images. OSX's disk utility can do this, as well as PartImage on linux/unix and Ghost on Windows. However, this may not be any faster; it will take up less space though.

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dd doesn't interpret data, it's just dumping bytes from source to target. It doesn't know what it's copying or if it matters.

If you want to make an intelligent copy (ie. skip empty space etc.) you can use partclone, partimage or Clonezilla (which is, in fact, just a more convenient wrapper to those two tools).

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