Mike Hommey wrote: > On Tue, Mar 24, 2009 at 02:34:09PM +0100, Jerome Warnier > <jwarn...@beeznest.net> wrote: > >> Giacomo A. Catenazzi wrote: >> >>> Jerome Warnier wrote: >>> >>>> Raphael Hertzog wrote: >>>> >>>>> On Tue, 24 Mar 2009, Jerome Warnier wrote: >>>>> >>>>> >>>>>> For files from packages, though, deduplication might be a good >>>>>> idea, as >>>>>> dpkg is supposedly the only one to ever modify the files (under >>>>>> /usr for >>>>>> example). >>>>>> I don't know however how dpkg treats hardlinks. Does it "break" the >>>>>> hardlink before replacing a file or does it replace the file whatever >>>>>> its real nature is? >>>>>> >>>>>> >>>>> IIRC dpkg preserves hardlinks inside a binary package but I don't >>>>> see how >>>>> it could do the same across multiple binary packages. >>>>> >>>>> >>>> Oh, I didn't expect it to. I just wanted to know its behaviour when it >>>> upgrades a package. >>>> Before the upgrade, the file is a hardlink (because I hardlinked it >>>> manually), then it tries to upgrade the file/hardlink. Does it "break" >>>> the hardlink* before upgrading the file or does it overwrite the >>>> file/hardlink and all of its "siblings"? >>>> >>> Do you really care? (not theoretically, but in normal use). >>> I would expect that same content will be delivered: >>> - by "brother" packages (same source), thus usually updated >>> at the same time. >>> - in documentation (so maybe not so important for your use). >>> >>> I think the most problem are in files outside "dpkg" control, >>> i.e. /var and /etc. >>> >>> I'm just curious: do you have a list of "same" content files? >>> maybe I'm completely wrong. >>> >> Here you are, for /usr on a typical Lenny AMD64 server (generated with >> "finddup -n" from package perforate): >> http://glouglou.beeznest.org/~jwarnier/usr-duplicates.list.gz >> > > $ zcat usr-duplicates.list.gz | awk '{t+=$1*(NF-2)}END{print t}' > 33142129 > > You would free 33MB. How big is your disk ? Is it worth bothering ? > I'm not an awk god, but isn't that supposed to just be the total size of the files it could take if deduplicated? In this case, it is not the size I would reclaim, as there are sometimes up to 4 copies of the same content. > You can get much more free space than that by reducing the number of inodes > supported by your filesystem: > For instance, on my / fs, that contains /usr, and is only 3GB: > Inode count: 384000 > Free inodes: 314133 > > I will obviously never use that many inodes... Now, consider an inode > is 128 bytes (or even 256 in some cases), and do some maths... > > Mike >
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