On Mon, 2008-02-11 at 01:53 -0800, Chris Stromsoe wrote:
> On Mon, 11 Feb 2008, Ian Kent wrote:
> > On Sun, 2008-02-10 at 00:29 -0800, Chris Stromsoe wrote:
> >
> >> I have a set of directories that are created and removed
> >> programmatically, and are hashed three levels deep
> >> (/top/hash/hash/name). The depth is constant, the hashes and names are
> >> not. There are around 35k at any time. I would like to bind mount a
> >> common directory into each top-level (/top/hash/hash/name/data) on
> >> demand.
> >
> > I'm not clear on what you mean by "top"?
>
> "/top" is the root of my directory tree. I have roughly 35k directories
> that are stored as /top/hash1/hash2/name, where hash1 is one hash of
> "name" and hash2 is a different hash of "name". Beneath "name" there are
> a variety of other files and directories. New "name" directories are
> hashed, created, and populated on the fly.
>
> I would like to bind mount a common directory onto
> /top/hash1/hash2/name/data, so that I can chroot into .../name/ and run
> common code, minimizing exposure to the rest of the system. I would like
> to use autofs if possible, so that I don't have to copy 20Mb+ of data 35k
> times or maintain 35k bind mounts or do something else that continously
> uses resources.
>
> I also don't want to have to edit auto.master every time I add or remove a
> "name" directory, or have to maintain 35k entries in a flat file.
>
> >> Can I use autofs to do that without having to explicitly list all of
> >> the directory paths in auto.master?
> >
> > What version of autofs are you using?
>
> I've been playing with 4.1.4, from Debian stable, but am more than willing
> to use 5.0.3 if it will do what I need.
>
> Playing around so far, the best I've been able to come up with is doing a
> bind mount of /top/hash1/hash2/name to a simpler /mnt/name (using a
> program map to compute the hashes), then hopfully submounting the "/data"
> directory, but I haven't been able to figure out how to get /mnt/name/data
> mounted. Can you do submounts of a program map?
So let me see if I've got this yet.
You're happy to use a program map to generate the hash
directory, /top/hash1/hash2/name on something like /mnt/name.
You need to be able to submount path /top/hash1/hash2/name/data onto
something like /mnt/name/data.
>
> My auto.master is:
>
> /mnt /etc/auto.mnt
>
> And /etc/auto.mnt is (I'm using bogus "hash" values for test purposes):
>
> #!/usr/bin/perl
> my $f = lc shift @ARGV;
> my $d = sprintf "/top/a/a/%s", $f;
> exit 1 if ! -d $d;
> printf ":%s\n", $d;
So if my reading is correct then you probably need to generate a mount
string from the program map that looks something like (I haven't had to
work with macro defines for a while so the syntax might not be quite
right):
-fstype=autofs -Dhash1=$h1 -Dhash2=$h2 -Dname=$f /etc/auto.submount
In the above the $h1, $h2 and $f need to be substituted with the values
computed by the script, probably using something like you're printf
above.
The /etc/auto.submount would be something like:
* :/top/$(hash1}/$hash2}/${name}/data
or if "data" was actually the key
* :/top/$(hash1}/$hash2}/${name}/&
Other thoughts.
I can't be sure this will work so you'll need to try it out and see how
you go.
The $f above in -Dname=$f might be able to be substituted with &, the
value of the key, but that might confuse the autofs macro substitution
code.
I can't remember whether we have to ":" escape the leading "/" of a
submount map, I'm sure you'll work that out fairly quickly though.
There are clearly a number of variations on this but you will need to
work out what is best.
Ian
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