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I have a file test.txt at:

./a/test.txt                    (1 KB, old one)
./unionWritableFolder/test.txt  (2 KB, should be overriding)
./unionMergedFolder/test.txt    (1 KB, old one)

if I do this:

echo 3 | sudo -k tee /proc/sys/vm/drop_caches

the newest modified file on an AUFS unionMergedFolder will be the correct one:

./unionWritableFolder/test.txt

Otherwise it will keep showing the old file: ./a/test.txt

It is like the cache is not being updated? I don't really understand what is going on. Is there some way to make the cache work properly? so I don't need to drop it all the time?

P.S.: I don't intend to stop using AUFS as it is very good to understand and use, very user friendly.

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  • By the way, you probably don't need to say ./directory_name/file_name — you use ./file_name for a file in the current directory; otherwise, directory_name/file_name should work fine. – G-Man Says 'Reinstate Monica' Jan 29 '17 at 2:47
  • @G-Man the problem is that I need to access it thru ./unionMergedFolder/test.txt, actually the application will look for that file, it doesnt know about the other directories. – Aquarius Power Jan 29 '17 at 2:55
  • But have you tried saying unionMergedFolder/test.txt instead? – G-Man Says 'Reinstate Monica' Jan 29 '17 at 2:57
  • @G-Man that would be on a terminal, with ./ or without. The application probably uses relative path and is failing. Anyway, using nautlius F5 I see no changes on the file, unless I drop caches, when also the application will access the new file. – Aquarius Power Jan 29 '17 at 3:57
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    Hmm, if writing to vm/drop_caches has any observable effect other than performance, that's surely a bug somewhere. – Gilles 'SO- stop being evil' Jan 29 '17 at 22:54
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Answering to: 'Is there some way to make the cache work properly?' (well to actually make aufs writes work properly)

when mounting the aufs, it seems to ONLY work properly if we use -o sync toguether with br like in -o sync,br="..."

now it is finally working great concerning making write updates ready, even timestamps!

PS.: The problem still happens at ubuntu 16.04, making sync required.

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