[conspire] symlinks vs mount --bind [Re: Partitioning revisited briefly]

[Rick Moen]

Quoting Tony Godshall (tony at of.net):

> A little off the direct topic, but using symlinks can cause trouble-
> I've been using mount --bind lately instead of symlinks since I've
> found a couple of instances[1][2] where symlinking gave trouble.

Interesting idea.  That actually hadn't occurred to me.

Here's an article about both tmpfs and bind mounts:
http://www.funtoo.org/en/articles/linux/ffg/3/

I do worry about recursive commands that will carefully avoid traversing
symlinks (e.g, rm[1] and mv) but will not hesitate to follow bind
mounts.  Also, problematic as symlinks sometimes are, they're at least a
bit self-documenting in that you might notice the 'l' special file type
and the link location data, whereas there's nothing visible in the file
tree (i.e., unless you happen to look at the 'mount' command's output)
to remind you that a bind-mounted subtree is now reachable via multiple
paths.

Making one mount be 'ro' (e.g., for backups) and the other rw could help
address this problem in particular cases.  At one point in the past,
that was supposed to work but didn't yet; I imagine it's fixed by now.

(Disclaimer:  I've not tested anything discussed here.)


[1] At minimum, you'd want to carefully cultivate the habit of including
the '--one-file-system' flage with your rm operations.  Not a bad idea
anyway, arguably, albeit it's hideously verbose.  With rsync, you get
the '-x' flag for the same thing.