The new buzz word going around is Docker and it is a big buzz word for a reason. Docker is a powerful tool that can be thought about as a virtual machine. It is not virtual machine but and “emulator” of different Linux distros. Think of it this way. If you have Fedora we would run the command yum to update, you could create a docker container to run Debian and update using its container by running apt. Another difference is the size of the container. A VM can be upwards of Gigabytes because it has to have the operating system installed and visualizer the hardware. Docker does not do this, it utilizes the hardware already on the system. This is easy accomplished because at the root of it all Linux runs ruffly the same kernel and just as binary’s that change the way it is used.
Lets create a simple container
pi@raspberrypi:docker-test $ ls Dockerfile pi@raspberrypi:~/docker-test $ sudo docker build . Sending build context to Docker daemon 2.048kB Step 1/2 : FROM debian latest: Pulling from library/debian ec26d49abcad: Pulling fs layer ec26d49abcad: Downloading 2.241MB/43.81MB ec26d49abcad: Extracting 42.66MB/43.81MB ec26d49abcad: Pull complete Digest: sha256:5fafd38cdee6c7e6b97356092b97389faa0aa069595f1c3cc3344428b5fd2339 Status: Downloaded newer image for debian:latest ---> 8401d69fdde8 Step 2/2 : CMD /bin/echo Hello World ---> Running in c23645ab4049 ---> 8adcef220ed4 Removing intermediate container c23645ab4049
As you can see above our simple image is only 43.81MB big this is so small in comparison
Running a container
Lets run the container and see how intensive it is.
%Cpu(s): 9.7 us, 7.7 sy, 0.0 ni, 81.3 id, 1.3 wa, 0.0 hi, 0.0 si, 0.0 st KiB Mem: 945512 total, 645252 used, 300260 free, 54260 buffers KiB Swap: 102396 total, 0 used, 102396 free. 486964 cached Mem PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 746 root 20 0 930688 54012 24700 S 6.9 5.7 18:21.21 dockerd 1 root 20 0 22896 3940 2740 S 2.3 0.4 0:07.33 systemd 840 root 20 0 886916 9128 6076 S 2.3 1.0 9:52.37 docker-containe
Running docker on the Pi 3 we can see it is taking a total of 11% of the memory and 68MB of memory