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What the `c' flag means

The `c' flag in lsattr output doesn't show whether or not the file is compressed; it is just a "request" for that.

$ gzip -9 fred
$ chattr +c fred.gz
$ lsattr fred.gz
--c---- 32 gzip9   fred.gz
$ e2ratio -l fred.gz
467     467     100.0%  fred.gz

In the above, `fred.gz' could not be compressed (as can be seen from the e2ratio output), but it still has the `c' (EXT2_COMPR_FL) attribute set -- which indicates that for any further writes to the file (e.g. if you append a text file onto the end of `fred.gz'), the kernel will attempt to compress the affected clusters.

$ chattr +c bigfile
$ dd if=/dev/zero of=deleteme
dd: deleteme: No space left on device
5234+0 records in
5233+0 records out
$ chattr -c bigfile
$ e2ratio -l bigfile
3766    1442     38.3%  bigfile
$ lsattr bigfile
------- 32 gzip9   bigfile

In the above example, on the other hand, the `c' flag is not set for the file, but it is plainly still compressed (as evidenced by both the e2ratio output and the lsattr output -- which still shows a compression algorithm and cluster size).

The usual reason that it would still be compressed is that the disk is full, or was full when you did `chattr -c'. See section What if I decompress a file on a full device?.

Another reason could be that it is still decompressing. However, you wouldn't usually see this, because chattr doesn't return until decompression is finished. In any case, just wait a couple of seconds (duration proportional to size of file, and slowness and load of your CPU) and try again.

Another could be that an error (other than `disk full') occurred during decompression. In this case there should be a `E' (or `*') in column 3 of lsattr output. The solution here is to run e2decompress on the file, and then have a look at the file to see if there's any damage.

These are the only situations I can think of. If there's anything else, write to the e2compr maintainer (see section Contact details for e2compr maintainer), as it may be a bug.

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