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@srv-rhsoft:~/Desktop]$ tar -p -cJf 1.tar.xz test.bin [harry@srv-rhsoft:~/Desktop]$ tar -p -cJf 2.tar.xz test.bin [harry@srv-rhsoft:~/Desktop]$ tar -p -cJf 3.tar.xz test.bin [harry@srv-rhsoft:~/Desktop]$ tar -p -cJf 4.tar.xz test.bin [harry@srv-rhsoft:~/Desktop]$ tar -p -cJf 5.tar.xz test.bin [harry@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@srv-rhsoft:~/Desktop]$ tar -p -cjf 1.tar.bz2 test.bin [harry@srv-rhsoft:~/Desktop]$ tar -p -cjf 2.tar.bz2 test.bin [harry@srv-rhsoft:~/Desktop]$ tar -p -cjf 3.tar.bz2 test.bin [harry@srv-rhsoft:~/Desktop]$ tar -p -cjf 4.tar.bz2 test.bin [harry@srv-rhsoft:~/Desktop]$ tar -p -cjf 5.tar.bz2 test.bin [harry@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@srv-rhsoft:~/Desktop]$ tar -p -czf 1.tar.gz test.bin [harry@srv-rhsoft:~/Desktop]$ tar -p -czf 2.tar.gz test.bin [harry@srv-rhsoft:~/Desktop]$ tar -p -czf 3.tar.gz test.bin [harry@srv-rhsoft:~/Desktop]$ tar -p -czf 4.tar.gz test.bin [harry@srv-rhsoft:~/Desktop]$ tar -p -czf 5.tar.gz test.bin [harry@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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