Hi,

On 15.03.2012 22:05, Brad Morgan wrote:
> The BackupPC manual says: The best way to copy a pool file system, if
> possible, is by copying the raw device at the block level (eg: using dd).
> Could someone give an example of how to do this?

dd if=<source_partition> of=<target_partition> bs=4M

> Can someone explain why the output file system doesn't get reduced to the
> size of the input file system?

Actually the output-filesystem is an exact copy of the source. (Be 
careful with xfs filesystems here, they don't like to mount the same 
uuid on the same machine twice.)
If your target-partition is bigger, then you need to grow that 
filesystem after the dd-call finishes.

> For example, I have a 127GB disk, /dev/hdb1, mounted via fstab on
> /var/lib/backuppc. I have a new 200GB disk, /dev/hdd1, that I used fdisk to
> create a single partition, mkfs.ext4 to create the file system,

That mkfs-step is not necessary.


> and mounted it on /mnt/tempBackupPC.

this you should skip completely.

> If I use "dd if=/dev/hdb1 of=/dev/hdd1" doesn't
> this copy the partition table and file system metadata, superblocks, etc.
> such that the output device will now look exactly like the input device
> including being reduced in size from 200GB to 127GB?

Notice the 1's in your command? These say that only the partition is 
copied, not the mbr and partition-table.
But then the whole filesystem is copied exactly.

Be careful with your additional mkfs and mount from above: the os will 
access that filesystem and might destroy the parts you just copied with 
dd. If you copy while that fs is mounted...

Have fun,

Arnold
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