[ILUG] Same data on several computers

[Brendan Halpin]

At the risk of waking the dead, I'll disturb a sleeping thread...

Timothy Murphy <tim at birdsnest.maths.tcd.ie> writes:

> I have innumerable files scattered over four or five computers,
> and I would like to work out which are the same,
> and organise them in some rational way.
> Is there a Great Robotic Organizer program that will do this?
> 
> In connection with this,.
> is there any way when I delete a file on one computer
> of saying "and delete this file anywhere on any computer on the system"?

There was some erudite discussion of aspects of this problem, but
no mention of rsync, which will "delete this file anywhere on any
computer on the system" if properly asked (which might mean the
differing computers having similar directory structures etc.). 

The problem is a very general one, and becomes tractable only if
the computers do have similar directory structures and broadly
similar content. And then its tractable only because of the work
that has gone into keeping them in sync over time (like a garden
that is easy to keep looking good, but only because you spend
30mins on it every evening). 

My own solution is a script to identify relevant files which have
changed since a given time point, and zips them onto a removable
device, which I then use to update a second computer (keep work
desktop and home laptop in sync). The hard work is identifying the
relevant files -- not dot-files because they have to do with the
machines' separate setups, but yes .emacs and .bashrc because I want
the same functionality on both machines, all data files, but not my
mail backup because that's too big, etc. 

Some minor glitches: I use RCS and if I check in a file that hasn't
changed recently, it transfers the file.txt,v but not file.txt
because the check-in doesn't change its mtime (which zip uses to
test if it's to be archived; using ctime causes other problems).
Similarly, it doesn't deal with Tim's problem of deleting files in
the other location when you delete in one (and while rsync is
great, it needs the machines to be connected).

At least it makes it reasonably simple to keep the two machines
broadly in sync: 

When leaving work:
$ dumptousb.sh -newer /mnt/usb/Jun14l2w.zip
Later at home:
$ cd / && unzip -u /mnt/usb/Jun15w2h.zip
and vice versa. 

Brendan
-- 
Brendan Halpin,  Department of Sociology,  University of Limerick,  Ireland
Tel: w +353-61-213147 f +353-61-202569 h +353-61-338562; Room F2-025 x 3147
mailto:brendan.halpin at ul.ie  http://www.ul.ie/sociology/brendan.halpin.html