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@@ -1,5 +1,78 @@ -This is an `unionfs' translator for the Hurd. It is simple, but it is -definitely not a joke. +This is the unionfs translator for the GNU Hurd. + +The unionfs translator was originally written by Moritz Schulte +<moritz@duesseldorf.ccc.de> and currently mantained by Gianluca Guida +<glguida@gmail.com>. + + + +Introduction. + +An unionfs is a filesystems that joins many filesystems into one, meaning +that you can see into an "unionfs" all files contained in the filesystems +that are part of the union. + +When two or more directories with the same path are found in different +filesystems, their content is joined. +When two or more files with the same path are found in different filesystems, +unionfs has to solve this conflict. See below (Internals section) for +information on what this implementation does in such case. + +Example: +To join "foo/" "bar/" and "baz/" in the directory "quux/", just do: + + settrans -capfg quux/ /hurd/unionfs foo/ bar/ baz/ + +If you want to join even quux/ contents in the union itself, add -u as a +translator argument. +You can add filesystems at run-time with the fsysopts command. + + + +Stowing feature. + +This unionfs implements stowing feature, i.e. the translator will watch a +directory, called 'stow', that contains the directories to unite. +When a directory is added or removed in the stow, it will be added to or +removed from the unionfs. + +Example: +To use "/stow" as the stow for the directory "foo/", do: + + settrans -capfg foo/ /hurd/unionfs --stow=/stow + +All directories contained in /stow/ will then be joined together in foo/; +you can delete or add directory at run-time and you will see unionfs adding +or removing files in foo/ automatically. + +Another interesting feature of stow support of unionfs is the pattern matching +option. +For example, by using: + + settrans -capfg foo/ /hurd/unionfs -m bar --stow=/stow + +You will get joined in foo/ all sub-sub-directories of /stow matching "bar", +i.e. /stow/*/bar/; pattern matching will be done too in run-time added stow +subdirectories. +Furthermore, you can specify more complex matching pattern to the option, +like -m bar\* (to get all stow's sub-sub-directories beginning with "bar") +or specify multiple -m options. + +Example: +This command + + settrans -capfg /myfaketree/bin -m bin -m sbin --stow=/stow + +will join in /myfaketree/bin all files that are in /stow/*/bin and +/stow/*/sbin. It is equivalent to: + + settrans -capfg /myfaketree/bin -m [s]bin --stow=/stow + + + +Internals. + +This `unionfs' translator is simple, but it is definitely not a joke. It works by keeping in memory a dynamically updated tree of nodes, each node representing a directory in the unionfs. A node contains an array @@ -15,7 +88,5 @@ At the moment, underlying filesystem ordering is set by option ordering. See CAVEAT for other unexpected behaviour that could happen. -The unionfs translator was originally written by Moritz Schulte -<moritz@duesseldorf.ccc.de> and currently mantained by Gianluca Guida -<glguida@gmail.com>. +Please send all bug reports to Gianluca Guida <glguida@gmail.com>. |