After adding a third camera (a Reolink RLC-520) to my Zoneminder server, I found that I couldn’t get all three cameras to come up at the same time. I would restart and 2 would successfully enter the “Running” state but a third (not always the same one, either) would not.
I then noticed that
/dev/shm was red and at 100% in the status bar. After some research, I found that this is usually caused by the cameras’ resolution being set to high for the RAM the server has.
I lowered my resolution to 1080P on two cameras and 3MP on the third. This dropped the
/dev/shm usage to what is seen in the screenshot above.
My server has 8GB of RAM, which I may upgrade soon. If you run into this problem, try lowering the resolution of your camera(s) in Zoneminder’s config for each one.