InformationThe --cgroup-parent option allows you to set the default cgroup parent to use for all containers. If there is no specific usage requirement for this, the setting should be left at its default.
System administrators typically define cgroups under which containers are supposed to run. Even if cgroups are not explicitly defined by the system administrators, containers run under docker cgroup by default.
It is possible to attach to a different cgroup other than the one which is the default, however this type of usage should be monitored and confirmed because attaching to a different cgroup other than the one that is a default, it could be possible to share resources unevenly causing resource utilization problems on the host.
SolutionThe default setting is in line with good security practice and can be left in situ. If you wish to specifically set a non-default cgroup, pass the --cgroup-parent parameter to the Docker daemon when starting it.
By default, docker daemon uses /docker for fs cgroup driver and system.slice for systemd cgroup driver.