3.6. Moving a Process to a Control Group

Move a process into a cgroup by running the cgclassify command:

~]# cgclassify -g controllers:path_to_cgroup pidlist

~]# cgclassify -g controllers:path_to_cgroup pidlist

where:

If the -g option is not specified, cgclassify automatically searches /etc/cgrules.conf and uses the first applicable configuration line. According to this line, cgclassify determines the hierarchies and cgroups to move the process under. Note that for the move to be successful, the destination hierarchies have to exist. The subsystems specified in /etc/cgrules.conf has to be also properly configured for the corresponding hierarchy in /etc/cgconfig.conf.

You can also add the --sticky option before the pid to keep any child processes in the same cgroup. If you do not set this option and the cgred service is running, child processes will be allocated to cgroups based on the settings found in /etc/cgrules.conf. The process itself, however, will remain in the cgroup in which you started it.

It is also possible to use the cgred service (which starts the cgrulesengd service) that moves tasks into cgroups according to parameters set in the /etc/cgrules.conf file. Use cgred only to manage manually attached controllers. Entries in the /etc/cgrules.conf file can take one of the two forms:

For example:

maria			net_prio		/usergroup/staff

maria			net_prio		/usergroup/staff

This entry specifies that any processes that belong to the user named maria access the devices subsystem according to the parameters specified in the /usergroup/staff cgroup. To associate particular commands with particular cgroups, add the command parameter, as follows:

maria:ftp		devices		/usergroup/staff/ftp

maria:ftp		devices		/usergroup/staff/ftp

The entry now specifies that when the user named maria uses the ftp command, the process is automatically moved to the /usergroup/staff/ftp cgroup in the hierarchy that contains the devices subsystem. Note, however, that the daemon moves the process to the cgroup only after the appropriate condition is fulfilled. Therefore, the ftp process can run for a short time in an incorrect group. Furthermore, if the process quickly spawns children while in the incorrect group, these children might not be moved.

Entries in the /etc/cgrules.conf file can include the following extra notation: