Redirect disk writes

LoLth

I have a question for anyone familiar with linux filesystems

Is there any way to nominate an existing directory and have any disk writes to that folder redirected to a different folder instead so that the original folder remains untouched?

If it can be done, can it be done without requiring a restart? Can it be done like a switch, ie: redirection on / redirection off ?

no specific reason for this or real world application, more if a curiosity question than anything.

being theoretical the OS doesnt really matter but for arguments sake lets say Fedora 15 or Ubuntu 11 (desktop or server doesnt matter).

Johnboy1951

Create a file of required size.
Create a filesytem in that file

When required, mount the file at the location of the directory.

Once mounted all writes to the directory will go into the file.

When required, unmount the file, and none of the writes are in the directory ..... they are in the filesystem in the file.

niallb

Read up on "Union Mounts" before you jump into it as there are a few restrictions,
but in general it's quite straightforward.

timbyr

You can use a bind mount.
This link has a decent quick tutorial.
http://backdrift.org/how-to-use-bind-mounts-in-linux

leeroybrown

The best way to do what you want under Linux is to place that specific directory in a filesystem on an LVM volume. You can then create snapshot volumes based on this volume whenever you want. The original directory continues to be used normally and the snapshot can be mounted to access the files exactly as they were at that point in time.

LoLth

tyvm guys. I always think its best to research before asking questions but my google skills let me down on this one. (I was quite confused when "redirect disk writes to alternate directory" didnt return anything useful. I began to wonder if it was possible at all)

Thanks for the reference points to get started (and the advice)

much appreciated.