Re: Overmounting a filesystem

Jeff Voskamp [MFCF] (javoskam@math.uwaterloo.ca)
Wed, 10 Apr 1996 09:18:42 -0400 (EDT)


>>>On Tue, 9 Apr 1996, H. Peter Anvin wrote:
>>>> > On 9 Apr 1996, H. Peter Anvin wrote:
>>
>>[snip]
>>
>>>Why would you want to do such a thing anyway? If you need a filesystem
>>>mounted onto another, make a subdirectory for that filesystem. Mounting a
>>>filesystem in a populated directory hides the existing files anyway, how
>>>do you benefit?
>>
>>Design a "overlay" filesystem.
>
>I had a need to "enlarge" a file system, and since linux does not have
>a lvm (logical volume manager) like aix [yet] I was wondering about multiple
>device mounts on the same mount point to "join" different drives to that
>mount point. As long as the filesystem is read only, no problems, but what
>to do in a write situation.

If it's not in the root directory of the partition, put it on the same
partition as the parent directory. If it's at the root partition, put
it on the top partition. I was going to suggest the partition with the
most free space, but that needs too much smarts in the file system for
my taste. You may occasionally have to mount the overlays in different
locations to manually rebalance the loads.

Hmmm.. how would mount handle this?

>I wanted to use md to enlarge the partition, but to add a drive, you have to
>remake the filesystem, destroying the current data (Humm, theres an idea,
>dynamic device adding to md drives!)

Tell me about it. Next time I'll get a really big drive and make /usr/src
_THIS_BIG_.

>[more snipped]
>
>>>IMHO, this all seems to boil down to laziness.
>>
>>Nope, just wanting to do strange things.
>
>I solved my problem by using symlinks, ie
>cd /as
>ln -s /as2/* .
>
>/dev/sda1 /as
>/dev/hdd1 /as2

What to you do if you have to export this as an NFS drive? Everything
would have to mount both partitions as /foo/as (can be renamed) and /as2
(cannot be renamed due to symlinks).

>Just my 1/20 of $.01,
>
>Walter L. Preuninger II

Jeff

-- 
Jeff Voskamp  Math Faculty Computing Facility     University of Waterloo
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