Simple procedure to update an XO.

First
{{{
# umount /dev/sda
umount: /dev/sda: not mounted
}}}

Format dev:
{{{
# mkdosfs -I /dev/sda
}}}

/etc/fstab must be like this:
{{{
/dev/sda /media/usb vfat rw,user,auto 0 0
}}}

Then:
{{{
$ mount /media/usb
}}}

Then:
{{{
$ cd /home/user/
$ wget http://olpc.download.redhat.com/olpc/autoupdate/olpc385_b87.zip (Auntoreinstallation image)
}}}

Then:
{{{
$ cd /media/usb
$ unzip /home/user/olpc385_b87.zip
}}}
And finally we have tu plug the USB key in the XO,power-on then wait
and enjoy!!