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OVERVIEW
--------

Shadowfs is a FUSE filesystem that is used to "shadow" a filesystem
directory to another location. All read operations access the master
location, while modifications are written to both the master and the
secondary locations. 

One typical use case would be a developer who wants to have source
code on a laptop's local hard drive, but the code needs to be built
and/or run on a remote system. By NFS mounting the remote drive and
using shadowfs, then all read operations are fast but edits go to the
remote location.

INSTALLATION
------------
Make sure that you have a recent version of FUSE installed with all
development headers and libraries.

Run 'make' to build.

CONFIGURATION
-------------
To set up shadowfs for use on a laptop to shadow some number of
directories from the user's local home directory to the NFS home
directory, assume a Mac with an NFS mounted location called 'my-nfs'
on which the user's home directory is accessible at /u/username.

USERNAME=username
LOCALHOME=/Users/$USERNAME
NFSHOME=/u/$USERNAME
NFSMOUNT=/Volumes/my-nfs/$USERNAME

The goal is to have a shadowed directory 'foo' to be accessible using
the path /u/$USERNAME/foo on both the laptop and the remote system.
This directory path maps to the shadowfs directory on the laptop but
the nfs backed directory on other machines. This lets you have source
code in the shadowfs directory but to be able to run builds on remote
machines.

Initial setup steps:

ln -s /Users /u
mkdir $LOCALHOME/shadowfs_data
mkdir $LOCALHOME/shadowfs_data/.config
mkdir $LOCALHOME/shadowfs

For now the process of setting up shadowed directories is manual. So
assuming that you have some directory 'foo' in $LOCALHOME that you
want to be shadowed to $NFSMOUNT, do the following:

rsync -rav $LOCALHOME/foo $NFSMOUNT/foo
mv $LOCALHOME/foo $LOCALHOME/shadowfs_data/foo
ln -s $LOCALHOME/shadowfs/foo $LOCALHOME/foo
cd $LOCALHOME/shadowfs_data/.config
ln -s $NFSMOUNT/foo

Now restart shadowfs (see run_shadowfs.sh script).

shadowfs $* -oallow_other -odefault_permissions -s /u/$USER/shadowfs/

If all goes well, you should now see the contents of directory
$LOCALHOME/foo mirrored to both $LOCALHOME/shadowfs_data/foo and
$NFSMOUNT/foo.