E2compr 0.4 User Manual – none

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The “compression algorithm” in `fs/ext2/none.c’ just returns 0,meaning “I couldn’t compress this cluster to any smaller than it is, sojust store it in uncompressed form.”

Changing the method from `none’ to some other algorithm (usingchattr) makes it apply the new compression algorithm to anyuncompressed clusters (and only uncompressed clusters). (Thisis a special case for the `none’ algorithm. Comments welcome on thee2compr list.)

This allows you to defer compression until late at night, so that youwon’t notice the slowdown.

Here’s one example of how it could be used.

Do `touch /timestamp/file; chattr -m none files_and_dirs’.Further writes to these files and within these directories will not usecompression. Then, when you want the compression to take place:

find files_and_dirs -type f -newer /timestamp/file -print0 | xargs -0r chattr -m gzip9;touch /timestamp/file2;find files_and_dirs -type f -newer /timestamp/file -print0 | xargs -0r chattr -m none;mv /timestamp/file2 /timestamp/file

(Of course `/timestamp/file’, `/timestamp/file2′ andfiles_and_dirs should be replaced with whatever’ssuitable/applicable for you.)

Not a perfect solution, but it’s a useful trick.

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