2.3. Attaching Subsystems to, and Detaching Them From, an Existing Hierarchy

To add a subsystem to an existing hierarchy, detach it from an existing hierarchy, or move it to a different hierarchy, edit the mount section of the /etc/cgconfig.conf file as root, using the same syntax described in Section 2.2, “Creating a Hierarchy and Attaching Subsystems”. When cgconfig next starts, it will reorganize the subsystems according to the hierarchies that you specify.

Alternative method

To add an unattached subsystem to an existing hierarchy, remount the hierarchy. Include the extra subsystem in the mount command, together with the remount option.

Example 2.2. Remounting a hierarchy to add a subsystem

The lssubsys command shows cpu, cpuset, and memory subsystems attached to the cpu_and_mem hierarchy:

~]# lssubsys -am
cpu,cpuset,memory /cgroup/cpu_and_mem
net_cls
ns
cpu
cpuacct
devices
freezer
blkio

We remount the cpu_and_mem hierarchy, using the remount option, and including cpuacct in the list of subsystems:

~]# mount -t cgroup -o remount,cpu,cpuset,cpuacct,memory cpu_and_mem /cgroup/cpu_and_mem

The lssubsys command now shows cpuacct attached to the cpu_and_mem hierarchy:

~]# lssubsys -am
cpu,cpuacct,cpuset,memory /cgroup/cpu_and_mem
net_cls
ns
devices
freezer
blkio

Analogously, you can detach a subsystem from an existing hierarchy by remounting the hierarchy and omitting the subsystem name from the -o options. For example, to then detach the cpuacct subsystem, simply remount and omit it:

~]# mount -t cgroup -o remount,cpu,cpuset,memory cpu_and_mem /cgroup/cpu_and_mem