Troubleshooting

The library reads and writes the files of /sys/fs/cgroup, so the kernel reports its refusals as file system errors:

Exception	Usual cause	Fix
`UnauthorizedAccessException`	The process may not change this part of the hierarchy	Run as root, or work in the part of the hierarchy delegated to your user or service
`UnauthorizedAccessException` when setting a limit	The file of the limit does not exist: the controller is not enabled on the parent, or the kernel does not support the feature	Enable the controller on the parent; GetAvailableControllers lists the controllers you can enable
`IOException` when enabling a controller	The control group contains processes	Move the processes to a child control group, and enable the controller on the group above them
`IOException` when setting a limit	The kernel refuses the value, such as a CPU that does not exist in SetCpusetCpus	Check the value against the machine
`IOException` from Delete	The control group still has processes or children	Kill the processes, wait for them to exit, and delete the children first
`DirectoryNotFoundException` when reading	The control group no longer exists	Create it again, or drop the stale CGroup2 instance

Reading a value of a controller that is not enabled does not throw: the value is Unavailable. See Reading values.
A control group that no longer exists is not reported as a group without controllers: reading it throws a DirectoryNotFoundException, so a stale instance is noticed.
The library supports cgroups v2 only. On a machine that still mounts cgroups v1, /sys/fs/cgroup does not have the files the library uses.