delta rpms - can we turn them off

[Reindl Harald]

Am 02.07.2014 16:46, schrieb Richard W.M. Jones:
> Doesn't the current process assume that xz always 
> produces the same output?

hopefully not

> What would happen if a newer version of xz/lzma comes out which (for
> example) produces better compressed output while still remaining
> compatible with the file format and older decompression tools?

XZ and BZ2 seems to have predictable results

but it's just dangerous to assume that will be forever true
and as you can see below with gzip you have *always*
different results for the same data

not sure about XZ, other compressors support different
levels and so if you change decisions in favour to
size/performance you are already lost if you can't
make sure that the rebuild process is using the same

[harry at srv-rhsoft:~/Desktop]$ tar -p -cJf 1.tar.xz test.bin
[harry at srv-rhsoft:~/Desktop]$ tar -p -cJf 2.tar.xz test.bin
[harry at srv-rhsoft:~/Desktop]$ tar -p -cJf 3.tar.xz test.bin
[harry at srv-rhsoft:~/Desktop]$ tar -p -cJf 4.tar.xz test.bin
[harry at srv-rhsoft:~/Desktop]$ tar -p -cJf 5.tar.xz test.bin
[harry at srv-rhsoft:~/Desktop]$ md5sum *.xz
244b1e8e64686007acec1cc17928223c  1.tar.xz
244b1e8e64686007acec1cc17928223c  2.tar.xz
244b1e8e64686007acec1cc17928223c  3.tar.xz
244b1e8e64686007acec1cc17928223c  4.tar.xz
244b1e8e64686007acec1cc17928223c  5.tar.xz

[harry at srv-rhsoft:~/Desktop]$ tar -p -cjf 1.tar.bz2 test.bin
[harry at srv-rhsoft:~/Desktop]$ tar -p -cjf 2.tar.bz2 test.bin
[harry at srv-rhsoft:~/Desktop]$ tar -p -cjf 3.tar.bz2 test.bin
[harry at srv-rhsoft:~/Desktop]$ tar -p -cjf 4.tar.bz2 test.bin
[harry at srv-rhsoft:~/Desktop]$ tar -p -cjf 5.tar.bz2 test.bin
[harry at srv-rhsoft:~/Desktop]$ md5sum *.bz2
10abef602d3eba260b97c339a40936e8  1.tar.bz2
10abef602d3eba260b97c339a40936e8  2.tar.bz2
10abef602d3eba260b97c339a40936e8  3.tar.bz2
10abef602d3eba260b97c339a40936e8  4.tar.bz2
10abef602d3eba260b97c339a40936e8  5.tar.bz2

[harry at srv-rhsoft:~/Desktop]$ tar -p -czf 1.tar.gz test.bin
[harry at srv-rhsoft:~/Desktop]$ tar -p -czf 2.tar.gz test.bin
[harry at srv-rhsoft:~/Desktop]$ tar -p -czf 3.tar.gz test.bin
[harry at srv-rhsoft:~/Desktop]$ tar -p -czf 4.tar.gz test.bin
[harry at srv-rhsoft:~/Desktop]$ tar -p -czf 5.tar.gz test.bin
[harry at srv-rhsoft:~/Desktop]$ md5sum *.gz
8f132cafffe6d7a613a480a5e593abc8  1.tar.gz
3cf402bbbde27db631a2896af9365275  2.tar.gz
5cb1fc9f6628a41d71572862ea4c19a1  3.tar.gz
bd51a4779ca4e2e9377488dc64ccaf1c  4.tar.gz
5506a0cfbf39cb28b05babba6755049a  5.tar.gz


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