I have a Macbook pro (late 2015) with two partitions: one with Mac OS and the other one with an Ubuntu 16.04 LTS operating system. It was always booting to Ubuntu by default and I used the Alt-key on startup to boot into Mac OS when I needed to.
A few days ago there was a hardware issue on my macbook, so I brought it to the nearest Apple Store and they fixed the problem. After I received it back from the store, I noticed that it is now booting to Mac OS by default.
I checked the partitions to see, whether the Ubuntu system was removed by the store or if they wiped the HD but everything seems to be in place.
How can I restore the old behavior so my Macbook boots into Ubuntu by default again?
Thanks in advance.