Messages in this thread | | | Date | Mon, 12 Apr 1999 02:31:27 -0700 (PDT) | From | Michael Hasenstein <> | Subject | 2.2.5:fs/super.c comment indicates stacked mounts possible? |
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in fs/super.c do_mount(): * [21-Mar-97] T.Schoebel-Theuer: Now this can be overridden when * supplying a leading "!" before the dir_name, allowing "stacks" of * mounted filesystems. The stacking will only influence any pathname lookups * _after_ the mount, but open file descriptors or working directories that * are now covered remain valid. For example, when you overmount /home, any * process with old cwd /home/joe will continue to use the old versions, * as long as relative paths are used, but absolute paths like /home/joe/xxx * will go to the new "top of stack" version. In general, crossing a * mount point will always go to the top of stack element. * Anyone using this new feature must know what he/she is doing.
This seems to indicate I can mount several filesystems under one mount point? (I didn't find any further comments/code for this)
I'm asking because I'm thinking about an overlay mount function, which means you can mount a filesystem on top of another one on the same mount point. Purpose: for example, I could overlay my minimal /usr installation with a big nfs-mounted /usr filesystem, and all the files that don't exist locally on the disk are taken (transparently) from the nfs filesystem. The question above has not much to do with this except that I'm curious now that I discovered that comment, but maybe some people who're familiar with the fs-implementation could comment on the idea. === -- Michael Hasenstein http://www.csn.tu-chemnitz.de/~mha/ Private Pilot (ASEL) since 1998 _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com
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