I found "/var/log/journal" took up 143.1M space! After deleting the directory, I got enough space to transfer sketch. Here is the space available now:
Filesystem Size Used Available Use% Mounted on
/dev/root 463.9M 310.6M 117.5M 73% /
I only experiment with Edison for a couple of days. How can the journal log eat up so much space. Is this a bug?
I know they are working on this. if you have completed configuring your Edison you can issue
systemctl disable configure_edison.service
It appears that the service has been adding 5 entries to the journal every 10-11 seconds.
I am also assuming you have installed the latest firmware
Some users have have experienced the same issue, however there is a workaround posted by @deium in this post:
If you have any more doubts, don't hesitate to ask.