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7940Re: [nslu2-general] Re: Problem after trying dd to clone new drive - wont boot on old disk

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  • Mike Westerhof (mwester)
    Dec 4 10:50 AM
      docbillnet wrote:
      >> Don't use dd to copy filesystems - it only works in very specific
      >> situations. You are far better off to format the target partition,
      >>
      >
      > That statement is completely absurd.

      Thanks for your polite response. Note that after that very strong
      statement you make, you then go on to (correctly) identify the very
      specific situations where dd *does* actually work.

      Thanks for your commentary.

      -Mike (mwester)

      > "dd" always works when copying filesystems, provided you use the correct block sizes. System administrators have been doing this to backup filesystems for more than 30 years. I have personally been doing it for more than 15 years, and I have never had problems.
      >
      > That said, chances are the problem is not copying the filesystem, but the disk image. e.g.
      >
      > dd if=/dev/sda1 of=/dev/sdb1 bs=2048
      >
      > works ok. But
      >
      > dd if=/dev/sda of=/dev/sdb bs=2048
      >
      > will only work if both hard drives have the same physical partitioning.
      >
      > However, you can still recover the data by dd'ing back to the original drive if you erased it...
      >
      > That said, I do NOT advice using dd to copy filesystems unless they contain features not supported by higher level programs. Usually "rsync" is both faster and better. However, a common exception to this rule is when copying the root partition of a file system with SELinux enabled. "dd" will preserve all the SELinux settings, "rsync" even with the appropriate settings might not be able to.
      >
      > I also tend to use "dd" when backing up windows partitions. The reason being is I've yet to find a linux method of copying windows file systems that preserves windows ACL's and such. Meaning if I want C: drive to boot and start, I better copy it with dd.
      >
      > Bill
      >
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