8459ch02.fm Draft Document for Review December 11, 2019 1:55 pm During build process only the changed layer is rebuilt, and this is the reason Docker  remains lightweight which makes it small and fast.  – Container - Container is executable instance built from the image which can be started,  stopped, moved or deleted, using Docker API or CLI. Containers can be connected to  one or multiple network, storage to be added and a new container can be built using an  existing Container. – Services - Services allow you to scale co ntainers across multiple Docker daemons,  which all work together as a swarm with multiple managers and workers. Each member  of a swarm is a Docker daemon, and the daemons all communicate using the Docker  API.  – NameSpace - In context to Docker,  nameSpace  is the technology which provides  isolated workspace for container (Table 2-1). Each container encapsulates all its  features within the namespace associated with that particular container.  Table 2-1 NameSpace Namespace Description PID Process isolation (PID:  Process ID) NET Managing network  interfaces (NET:  Networking) IPC Managing access to IPC  resources (IPC:  InterProcess  Communication) MNT Managing file system mount  points (MNT: Mount) UTS Isolating kernel and version  identifiers. (UTS: UNIX  Timesharing System) – Control groups: Control Group or  cgroup  is the technology that limits an application to a  specific set of resources. This feature allow Docker Engine to share available hardware  resources to containers and optionally enforce limits and constraints.  – Union file system: Union file  systems, or UnionFS, are file systems that operate by  creating layers, making them lightweight and fast. Docker Engine uses UnionFS to  provide the building blocks for containers.  – Container format: Container format is the wrapper around namespaces, control groups,  and UnionFS. The default container format is libcontainer.  20  Red Hat OpenShift and IBM Cloud Paks on IBM Power Systems: Volume 1