In general, keep a working snapshot (or ten) of the system around in the form of a disk image. You never know. It would be good to automate this to take periodic backups.
The new kernel (as opposed to v3.6) requires a new bootloader, as described by mdrjr here: http://forum.odroid.com/viewtopic.php?f=23&t=1213. Follow his link for instructions on how to install the new bootloader.
If this happens:
curl error: Peer certificate cannot be authenticated with given CA certificates
Set your date correctly (i.e., not Jan 1, 2000) manually using date or automatically using ntpdate.
One way in which to decrease the size of the image you create is by squeezing the partitions down to a minimum size (e.g., using gparted) and doing something like this:
dd if=/dev/sdd of=sd.img bs=1024 count=$[3766*1024]
This will take an SD card at /dev/sdd and create an image file named sd.img in the current directory with a block size of 1 MB and a total size of 3.68 GB (3766*1024*1024 bytes = 3.68 GB, see?).
Run:
systemctl mask tmp.mount
and reboot. By default, the system will have been configured to set up /tmp in RAM as tmpfs with half the size of available RAM, but compiling ros-groovy-opencv2, for example, will want much more than this, even with single-threaded make.