Question: after downloading the update of new osx, macbook failed to restart
I downloaded the new OSX Siera, and left my macbook air to install.
when I came back, i found folder icon blinking with a question mark on it, and could do nothing but force shutdown and restart and go back to the same issue.
How can I either restart or recover to my old osx siera?
Note that I didn't take any backup, and while downloading the new update from the app store, it was interrupted several times, and I restarted the donwload.
thanks to help with this.
MacBook Pro, OS X Yosemite (10.10.1)