#### "The Linux Gazette...making Linux just a little more fun!"

# The Answer Guy

#### By James T. Dennis, linux-questions-only@ssc.com
LinuxCare, http://www.linuxcare.com/

### Loopback (localhost) NFS Mounting for FTP

From Mark S. Turczan on Sun, 02 May 1999

James,

Would you know of a way to setup a loopback mount within a `/home/ftp` hierarchy?

Or could you provide a better method to achieve the following?

I've got a set of disks setup under software raid, and I've mounted them under `/mnt/raid.` What I'd like to do is include a link from a directory under `/home/pub/Archive` to the actual files under `/mnt/raid/Archive.` I've tried doing this with a symbolic link, but it doesn't seem to resolve it when I connect through ftp.

> When you connect as "anonymous" or "ftp" through the conventionally configure FTP service, or as any member of a "guestgroup" to a WU-FTP daemon, you are in a chroot jail. This is intended to prevent you (an FTP client) from wandering around the filesystem peeking into things where you don't belong (as an anonymous or guest user).

> Naturally symbolic links don't pierce through a chroot wall.

> It's possible to configure your system to act as an NFS server and client (concurrrently) and to export a directory tree (presumably in read-only mode) to yourself.

> This is one of several tricks that is referred to as a "loopback mount" (not to be confused with the `mount -o loop=`... option which is a way of mounting a file image as a filesystem). In this case you're doing a perfectly normal NFS export, and a perfectly normal NFS mount. The only oddity is that the export and mount are on the same machine and are going through the loopback network interface.

> So you put a line in your `/etc/exports` file like:

> > ``/mnt/raid/ftparea` 127.0.0.1(ro,insecure)`

> ... and possibly some lines like:

> > ``/mnt/raid/ftparea/no/` (noaccess)`

> (to define a set of subdirectories under the exported directory tree to which you want to deny access).

> ... and then you use a command like:

> > `

> > > mount -t nfs 127.0.0.1:/mnt/raid/ftparea `/home/ftp/home`

> > `

> ... or whatever.

> Personally I think it's horrible kludge. But I've done things sort of like this and it does work.

Thanks for any help you can offer.
--
Mark Turczan

> Hope that makes sense.

##### Copyright © 1999, James T. Dennis
Published in The Linux Gazette Issue 42 June 1999

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