Am Donnerstag, 7. September 2017, 17:46:27 CEST schrieb Helmut Jarausch: > Hi, > > sorry, this question is not Gentoo specific - but I know there are many > very knowledgeable people on this list. > > I'd like to "hard-link" a file X to Y - i.e. there is no additional > space on disk for Y. > > But, contrary to the "standard" hard-link (ln), file Y should be stored > in a different place (inode) IF it gets modified. > With the standard hard-link, file X is the same as Y, so any changes to > Y are seen in X by definition. > > Is this possible > - with an ext4 FS > - or only with a different (which) FS
This has come to be referred to as reflinks (see, e.g., the cp(1) man page). I don't think ext4 supports them, but both btrfs and xfs do (xfs only very recently, though, see for example [0]). There might be other FSs that support it, too (bcachefs?), but I don't know about that. Maybe at some point ext4 will add support for it, but since I mainly use btrfs I don't care that much. [0] http://strugglers.net/~andy/blog/2017/01/10/xfs-reflinks-and-deduplication/ > Many thanks for a hint, > Helmut HTH -- Marc Joliet -- "People who think they know everything really annoy those of us who know we don't" - Bjarne Stroustrup
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