[Sugar-devel] Enhancing Sugar to support multiple users

Hal Murray hmurray at megapathdsl.net
Mon Sep 6 19:33:00 EDT 2010

dsd at laptop.org said:
> When we discussed this while I was in Peru, one requirement they identified
> is that the kid would log onto an XO one day and do some work, and then log
> onto another XO the following week and continue the same work.

> Assuming this still stands, this strongly calls for a network-based home
> directory system with some kind of network login service (but someone with
> experience in such areas should comment). This would require a number of
> changes at the OS level and server level, but Sugar would be left untouched,
> as far as I can think. 

I think there are two approaches.

One is for /home to live on the file server and XOs to access their files via 
NFS.  There may be interesting alternatives to NFS, but I'm not familiar with 
any of them.

The other is to have a working copy of files on the local machine and 
manually slosh files back and forth, probably using a program to automate 

I don't think either would be great, but both could probably be made to work.

Both depend on reasonable network support.  Somebody would have to do some 
experimenting to see how many users the typical WiFi setup can support.

I've worked at two places that mounted /home on our personal workstations via 
NFS.  We did occasionally login from other machines but the main reason for 
using NFS was for sharing and centralizing the backup.

Both worked, but there were lots of quirks, and nobody tried to take their 
machines home at night.

Note that in addition to /home, you have to keep /etc/passwd and various 
other files synchronized.

Another consideration when using NSF is security.  It has a long history of 
weak security.  At both of the places where I used NFS, we lived with it.  
(We were all mature adults working for the same company and such.  Personnel 
and payroll were on different systems. ...)  In the context of schools, it 
might get interesting if the teachers are storing their files on the same 


It's been a long time since I worked with a slosh by hand system.  I've 
forgotten all the details.  We were happy with it, but we weren't switching 
workstations often.

I'd expect there are lots of modern software packages designed to keep 
laptops synchronized.  One of them might fit the XO usage pattern.  With the 
right wrapper, one of the source-control packages might work.

It might be reasonable to modify the current backup/restore code to do the 

One catch for an XO is that the file system is tiny so you would have to 
delete the previous user's files to make room for the next user.  NB: You 
really don't want to delete them if they haven't been copied back yet.

Another possible problem is that the network load is likely to be 
synchronized, say at the beginning of the school day when the machines get 
handed off from one user to the next.


What's the backup mechanism on current school servers?  If the truth lives on 
my XO and the school server is "just" a backup, I might be willing to not 
backup the school server.  On the other hand, if the truth lives on the 
school server, I'd really want another layer or two of backup.

Here is another alternative...  Give each child their own SD card.  Patch 
Sugar to look there.  Or patch the system to mount /home/olpc there.  ...

These are my opinions, not necessarily my employer's.  I hate spam.

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