EMMC OS corruption in Beaglebone Black

I am using large number of Beaglebones for a VPN. But some of the beaglebones stopped working due to OS corruption( Not even detecting while connecting directly to PC). It will start working when we reload the OS with the memory card. I would like to install the OS as read only for the prevention of this problem.
How can I install the OS in Beaglebone as read only.