It may be useful to restrict the Docker container usage on resources when running. Docker gives you a lot of possibilities to set constraints on the memory, CPU usage or disk access usage. Let's begin with setting the memory constraints.
It's worth knowing, that by default, that is if you use the default settings without any constraints, the running container can use all of the host memory. To change this behavior we can use the --memory (or -m for short) switch for the docker run command. It takes a usual suffixes k,m, or g for kilobytes, megabytes and gigabytes respectively.
The syntax of the docker run command with memory constraints set will be as follows:
docker run -it -m 512m ubuntu
The preceding command will execute the Ubuntu image with the maximum memory that can be used by container of half of gigabyte.