NAND Full Requirement

[pgf at laptop.org]

erik wrote:
 > On Tue, Jul 22, 2008 at 04:01:35PM -0400, Greg Smith wrote:
 > > Hi All,
 > > 
 > > Here's the requirement for Uruguay NAND full situation.
 > > 
 > > I need this fixed ASAP.
 > > 
 > > - The XO must always boot up to sugar including allowing access to the 
 > > journal. That is no matter the fullness of the NAND
 > > - If the NAND has less than nnMB (50?) free, warn the user that they are 
 > > low on space.
 > > - Must be installable on 656 in the Uruguay configuration
 > > - Must not delete any user created files
 > > - Must not disable any activities or other functionality
 > > 
 > > So far they have:
 > > - a dialog box which warns when you get low on space
 > > - Chris's script which allows deleting stuff automaticaly but probably 
 > > user stuff
 > > 
 > > What else they want, not sure... I will talk to Emliano ASAP and let you 
 > >   know.
 > > 
 > > Erik will propose one solution (related to RamFS I believe).
 > > 
 > 
 > See: http://dev.laptop.org/ticket/7587#comment:4
 > 
 > On boot, check NAND discomfort level.  If high, use unionfs(4) to mount
 > a read/write tmpfs over top of a read-only jffs2 rootfs.  Set unionfs
 > flags to enable file deletion from the 'ro' root partition (or if this
 > is impossible, mount the fs in another location to allow deletions).
 > Set a flag to tell olpc-session or Sugar to enter into a deletion
 > dialog.  
 > 
 > Benefits:
 > This solution theoretically allows all software to run an a NAND-full
 > machine.  Thus students who arrive at school with a NAND-full machine
 > could still work with their XO through lessons and manage flash cleanup
 > as time is available.  Requires minimal code-level changes to enable.

what happens when they fill up tmpfs while still working through
lessons?

the idea is intriguing, but it would have to be a limited mode
of operation:  i.e., no activity startup, please reboot soon.

paul

 > 
 > Drawbacks:
 > Working on this solution may distract from efforts to get our system to
 > boot cleanly on top of a read-only root fs.  C. Scott and others have
 > suggested that we ultimately want to do this.
 > 
 > Issues: 
 > Currently unionfs is untested on the XO.  I am waiting for a
 > unionfs-enabled kernel (currently building).  Theoretically it will
 > work, as per every Linux livecd under the sun.
 > 
 > Erik
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=---------------------
 paul fox, pgf at laptop.org