rsync trick of the day
I have all the ISOs for a previous release of software, and I want to get the next release from a remote machine. Since some packages probably have not changed, I want to use rsync to find the common parts and avoid transferring them.
mkchdir rhel4b1 cat ../rhel4a4/*.iso > nahant-ia64-AS-disc1.iso cp nahant-ia64-AS-disc1.iso nahant-ia64-disc2.iso cp nahant-ia64-AS-disc1.iso nahant-ia64-disc3.iso cp nahant-ia64-AS-disc1.iso nahant-ia64-disc4.iso cp nahant-ia64-AS-disc1.iso nahant-ia64-disc5.iso rsync -avP remote::iso/rhel4b1/ ./
This uses a lot of disk while making the big temporary files but allows rsync to find matches even for data that has moved between disks.
If you do this, try not to interrupt rsync in the middle of the transfer. It will recover, but it will throw away all of the basis data for the iso that was in flight.
On reflection I think we can be even more clever by making hardlinks rather than copies for each disk. rsync will use the concatenated version for a basis version, and then break the link for the updated version.
posted Mon 25 Oct 2004 in /software/rsync | link
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