New documentation file is added. It should describe how systemd and libcgroup should work together and how to configure a system to have control groups created by libcgroup's cgconfig service.
I'm going to install this README into /usr/share/doc/libcgroup-*/. I know I am not Shakespeare and also English is not my mother language, feel free to comment also the style and grammar. Missing/wrong articles is my speciality :). Changelog: - updated with review remarks from Martin Prpic and Kevin Constantine Signed-off-by: Jan Safranek <jsafr...@redhat.com> --- README_systemd | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 69 insertions(+), 0 deletions(-) create mode 100644 README_systemd diff --git a/README_systemd b/README_systemd new file mode 100644 index 0000000..6733c2c --- /dev/null +++ b/README_systemd @@ -0,0 +1,69 @@ +Integration with systemd +======================== + +systemd is a system and service manager for Linux, compatible with SysV +and LSB init scripts. systemd heavily uses control groups to manage and control +services. + +Most of the libcgroup tools and APIs can be safely used on systems with systemd +without any problems. This document attempts to describe the configuration of +systemd and libcgroup so they can safely co-exist and mutually benefit each +other. + +References +========== +[1] http://www.freedesktop.org/wiki/Software/systemd +Systemd home page. + +[2] http://www.freedesktop.org/wiki/Software/systemd/PaxControlGroups +This is the most useful document describing systemd expectations on applications +(incl. libcgroup tools). + + +Compilation +=========== +As stated in [2], libcgroup should not interact with the 'name=systemd' +hierarchy. Compile libcgroup with the --enable-opaque-hierarchy configure option +to do so: + +./configure --enable-opaque-hierarchy=name=systemd + +Consequently, the 'name=systemd' hierarchy will not be visible to libcgroup and +all of its tools. For example, the lscgroup command will not list systemd +cgroups and the cgclear command will not remove them. + +Start-up and services +==================== + +Systemd automatically mounts all available controllers on system boot ('cpu' and +'cpuacct' together in one hierarchy by default) and can automatically put +service processes into control groups with configured parameters — by default, +each service is automatically put into the 'cpu,cpuacct:/system/$service_name' +control group. The System Administrator has full control of parameters in each +control group and of which controllers are used. Consult systemd +documentation, mainly systemd.conf(5) and systemd.exec(5) man pages, for +details. + +In the vast majority of use cases, this behavior is sufficient and libcgroup +does not need to be used. + +For specific use cases, e.g. when a different tree of control groups is needed, +libcgroup provides cgconfig service. This service can create arbitrary control +group hierarchies. In this case, follow these steps: + +1. Set 'DefaultControllers=' in /etc/systemd/system.conf so that systemd does +not create control groups for services automatically. + +2. Prepare /etc/cgconfig.conf and enable the cgconfig service. The service will +parse the /etc/cgconfig.conf file during machine boot and create all control +groups which are defined in it. The service automatically sets '+t' ("sticky") +bit on the tasks files as recommended in [2]. + +3. For each service that should start in a specific control group, add the +following lines into its unit file: + After=cgconfig.service + ControlGroup=<name of the control group(s)> + +This ensures the service is started only after cgconfig creates the necessary +hierarchy for it. It also tells systemd which control group it should use to +start the service. ------------------------------------------------------------------------------ 10 Tips for Better Server Consolidation Server virtualization is being driven by many needs. But none more important than the need to reduce IT complexity while improving strategic productivity. Learn More! http://www.accelacomm.com/jaw/sdnl/114/51507609/ _______________________________________________ Libcg-devel mailing list Libcg-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libcg-devel
