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CGCONFIG.CONF(5) File Formats Manual CGCONFIG.CONF(5)

NAME

cgconfig.conf - libcgroup configuration file

DESCRIPTION

cgconfig.conf is a configuration file used by libcgroup to define control groups, their parameters and their mount points. The file consists of mount , group and default sections. These sections can be in arbitrary order and all of them are optional. Any line starting with '#' is considered a comment line and is ignored.

mount section has this form:


mount {
<controller> = <path>;
...
}

Name of the kernel subsystem. The list of subsystems supported by the kernel can be found in /proc/cgroups file. Named hierarchy can be specified as controller "name=<somename>". Do not forget to use double quotes around this controller name (see examples below). Apart from named hierarchy, additional mount options may be specified by putting the controller and the options in quotes. Options supported are nosuid, noexec and nodev.

Libcgroup merges all subsystems mounted to the same directory (see Example 1) and the directory is mounted only once.

The directory path where the group hierarchy associated to a given controller shall be mounted. The directory is created automatically on cgconfig service startup if it does not exist and is deleted on service shutdown.

If no mount section is specified, no controllers are mounted.

group section has this form:


group <name> {
[permissions]
<controller> {
<param name> = <param value>;
...
}
...
}

Name of the control group. It can contain only characters, which are allowed for directory names. The groups form a tree, i.e. a control group can contain zero or more subgroups. Subgroups can be specified using '/' delimiter.

The root control group is always created automatically in all hierarchies and it is the base of the group hierarchy. It can be explicitly specified in cgconfig.conf by using '.' as group name. This can be used e.g. to set its permissions, as shown in Example 6.

When the parent control group of a subgroup is not specified it is created automatically.

Permissions of the given control group on mounted filesystem. root has always permission to do anything with the control group. Permissions have the following syntax:
perm {
task {
uid = <task user>;
gid = <task group>;
fperm = <file permissions>
}
admin {
uid = <admin name>;
gid = <admin group>;
dperm = <directory permissions>
fperm = <file permissions>
}
}

Name of the user and the group, which own the tasks file of the control group. Given fperm then specify the file permissions. Please note that the given value is not used as was specified. Instead, current file owner permissions are used as a "umask" for group and others permissions. For example if fperm = 777 then both group and others will get the same permissions as the file owner.
Name of the user and the group which own the rest of control group's files. Given fperm and dperm control file and directory permissions. Again, the given value is masked by the file/directory owner permissions.

Permissions are only apply to the enclosing control group and are not inherited by subgroups. If there is no perm section in the control group definition, root:root is the owner of all files and default file permissions are preserved if fperm resp. dperm are not specified.

Name of the kernel subsystem. The section can be empty, default kernel parameters will be used in this case. By specifying controller the control group and all its parents are controlled by the specific subsystem. One control group can be controlled by multiple subsystems, even if the subsystems are mounted on different directories. Each control group must be controlled by at least one subsystem, so that libcgroup knows in which hierarchies the control group should be created.

The parameters of the given controller can be modified in the following section enclosed in brackets.

Name of the file to set. Each controller can have zero or more parameters.
Value which should be written to the file when the control group is created. If it is enclosed in double quotes `"', it can contain spaces and other special characters.

If no group section is specified, no groups are created.

default section has this form:


default {
perm {
task {
uid = <task user>;
gid = <task group>;
fperm = <file permissions>
}
admin {
uid = <admin name>;
gid = <admin group>;
dperm = <directory permissions>
fperm = <file permissions>
}
}
}

Content of the perm section has the same form as in group section. The permissions defined here specify owner and permissions of groups and files of all groups, which do not have explicitly specified their permissions in their group section.

template section has the same structure as group section. Template name uses the same templates string as cgrules.conf destination tag (see (cgrules.conf (5)). Template definition is used as a control group definition for rules in cgrules.conf (5) with the same destination name. Templates does not use default section settings.

/etc/cgconfig.d/ directory can be used for additional configuration files. cgrulesengd searches this directory for additional templates.

EXAMPLES

Example 1

The configuration file:

mount {
cpu = /sys/fs/cgroup/cpu;
cpuacct = /sys/fs/cgroup/cpu;
}

creates the hierarchy controlled by two subsystems with no groups inside. It corresponds to the following operations:

mkdir /sys/fs/cgroup/cpu
mount -t cgroup -o cpu,cpuacct cpu /sys/fs/cgroup/cpu

Example 2

The configuration file:

mount {
cpu = /sys/fs/cgroup/cpu;
"name=scheduler" = /sys/fs/cgroup/cpu;
"name=noctrl" = /sys/fs/cgroup/noctrl;
}
group daemons {
cpu {
cpu.shares = "1000";
}
}
group test {
"name=noctrl" {
}
}

creates two hierarchies. One hierarchy named scheduler controlled by cpu
  subsystem, with group daemons inside. Second hierarchy is named
  noctrl without any controller, with group test. It corresponds
  to following operations:





mkdir /sys/fs/cgroup/cpu
mount -t cgroup -o cpu,name=scheduler cpu /sys/fs/cgroup/cpu
mount -t cgroup -o none,name=noctrl none /sys/fs/cgroup/noctrl
mkdir /sys/fs/cgroup/cpu/daemons
echo 1000 > /sys/fs/cgroup/cpu/daemons/www/cpu.shares
mkdir /sys/fs/cgroup/noctrl/tests




The daemons group is created automatically when its first
    subgroup is created. All its parameters have the default value and only root
    can access group's files.


Since both cpuacct and cpu subsystems are mounted to
    the same directory, all groups are implicitly controlled also by
    cpuacct subsystem, even if there is no cpuacct section in any
    of the groups.








Example 3


The configuration file:






mount {




cpu = /sys/fs/cgroup/cpu;
cpuacct = /sys/fs/cgroup/cpu;




}
group daemons/www {




perm {




task {




uid = root;
gid = webmaster;
fperm = 770;




}
admin {




uid = root;
gid = root;
dperm = 775;
fperm = 744;




}




}
cpu {




cpu.shares = "1000";




}




}
group daemons/ftp {




perm {




task {




uid = root;
gid = ftpmaster;
fperm = 774;




}
admin {




uid = root;
gid = root;
dperm = 755;
fperm = 700;




}




}
cpu {




cpu.shares = "500";




}




}





creates the hierarchy controlled by two subsystems with one group and two
  subgroups inside, setting one parameter. It corresponds to the following
  operations (except for file permissions which are little bit trickier to
  emulate via chmod):







mkdir /sys/fs/cgroup/cpu
mount -t cgroup -o cpu,cpuacct cpu /sys/fs/cgroup/cpu
mkdir /sys/fs/cgroup/cpu/daemons
mkdir /sys/fs/cgroup/cpu/daemons/www
chown root:root /sys/fs/cgroup/cpu/daemons/www/*
chown root:webmaster /sys/fs/cgroup/cpu/daemons/www/tasks
echo 1000 > /sys/fs/cgroup/cpu/daemons/www/cpu.shares


 # + chmod the files so the result looks like:


 # ls -la /sys/fs/cgroup/cpu/daemons/www/


 # admin.dperm = 755:


 # drwxr-xr-x. 2 root webmaster 0 Jun 16 11:51 .


 #


 # admin.fperm = 744:


 # --w-------. 1 root webmaster 0 Jun 16 11:51 cgroup.event_control


 # -r--r--r--. 1 root webmaster 0 Jun 16 11:51 cgroup.procs


 # -r--r--r--. 1 root webmaster 0 Jun 16 11:51 cpuacct.stat


 # -rw-r--r--. 1 root webmaster 0 Jun 16 11:51 cpuacct.usage


 # -r--r--r--. 1 root webmaster 0 Jun 16 11:51 cpuacct.usage_percpu


 # -rw-r--r--. 1 root webmaster 0 Jun 16 11:51 cpu.rt_period_us


 # -rw-r--r--. 1 root webmaster 0 Jun 16 11:51 cpu.rt_runtime_us


 # -rw-r--r--. 1 root webmaster 0 Jun 16 11:51 cpu.shares


 # -rw-r--r--. 1 root webmaster 0 Jun 16 11:51 notify_on_release


 #


 # tasks.fperm = 770


 # -rw-rw----. 1 root webmaster 0 Jun 16 11:51 tasks
mkdir /sys/fs/cgroup/cpu/daemons/ftp
chown root:root /sys/fs/cgroup/cpu/daemons/ftp/*
chown root:ftpmaster /sys/fs/cgroup/cpu/daemons/ftp/tasks
echo 500 > /sys/fs/cgroup/cpu/daemons/ftp/cpu.shares


 # + chmod the files so the result looks like:


 # ls -la /sys/fs/cgroup/cpu/daemons/ftp/


 # admin.dperm = 755:


 # drwxr-xr-x. 2 root ftpmaster 0 Jun 16 11:51 .


 #


 # admin.fperm = 700:


 # --w-------. 1 root ftpmaster 0 Jun 16 11:51 cgroup.event_control


 # -r--------. 1 root ftpmaster 0 Jun 16 11:51 cgroup.procs


 # -r--------. 1 root ftpmaster 0 Jun 16 11:51 cpuacct.stat


 # -rw-------. 1 root ftpmaster 0 Jun 16 11:51 cpuacct.usage


 # -r--------. 1 root ftpmaster 0 Jun 16 11:51 cpuacct.usage_percpu


 # -rw-------. 1 root ftpmaster 0 Jun 16 11:51 cpu.rt_period_us


 # -rw-------. 1 root ftpmaster 0 Jun 16 11:51 cpu.rt_runtime_us


 # -rw-------. 1 root ftpmaster 0 Jun 16 11:51 cpu.shares


 # -rw-------. 1 root ftpmaster 0 Jun 16 11:51 notify_on_release


 #


 # tasks.fperm = 774:


 # -rw-rw-r--. 1 root ftpmaster 0 Jun 16 11:51 tasks





The daemons group is created automatically when its first
    subgroup is created. All its parameters have the default value and only root
    can access the group's files.


Since both cpuacct and cpu subsystems are mounted to
    the same directory, all groups are implicitly also controlled by the
    cpuacct subsystem, even if there is no cpuacct section in any
    of the groups.








Example 4


The configuration file:








mount {




cpu = /sys/fs/cgroup/cpu;
cpuacct = /sys/fs/cgroup/cpuacct;




}
group daemons {




cpuacct{
}
cpu {
}




}



creates two hierarchies and one common group in both of them. It corresponds to
  the following operations:





mkdir /sys/fs/cgroup/cpu
mkdir /sys/fs/cgroup/cpuacct
mount -t cgroup -o cpu cpu /sys/fs/cgroup/cpu
mount -t cgroup -o cpuacct cpuacct /sys/fs/cgroup/cpuacct
mkdir /sys/fs/cgroup/cpu/daemons
mkdir /sys/fs/cgroup/cpuacct/daemons




In fact there are two groups created. One in the cpuacct
    hierarchy, the second in the cpu hierarchy. These two groups have
    nothing in common and can contain different subgroups and different
  tasks.








Example 5


The configuration file:








mount {




cpu = /sys/fs/cgroup/cpu;
cpuacct = /sys/fs/cgroup/cpuacct;




}
group daemons {




cpuacct{
}




}
group daemons/www {




cpu {




cpu.shares = "1000";




}




}
group daemons/ftp {




cpu {




cpu.shares = "500";




}




}



creates two hierarchies with few groups inside. One of the groups is created in
  both hierarchies.

It corresponds to the following operations:






mkdir /sys/fs/cgroup/cpu
mkdir /sys/fs/cgroup/cpuacct
mount -t cgroup -o cpu cpu /sys/fs/cgroup/cpu
mount -t cgroup -o cpuacct cpuacct /sys/fs/cgroup/cpuacct
mkdir /sys/fs/cgroup/cpuacct/daemons
mkdir /sys/fs/cgroup/cpu/daemons
mkdir /sys/fs/cgroup/cpu/daemons/www
echo 1000 > /sys/fs/cgroup/cpu/daemons/www/cpu.shares
mkdir /sys/fs/cgroup/cpu/daemons/ftp
echo 500 > /sys/fs/cgroup/cpu/daemons/ftp/cpu.shares



Group daemons is created in both hierarchies. In the cpuacct
  hierarchy the group is explicitly mentioned in the configuration file. In the
  cpu hierarchy the group is created implicitly when www is
  created there. These two groups have nothing in common, for example they do
  not share processes and subgroups. Groups www and ftp are
  created only in the cpu hierarchy and are not controlled by the
  cpuacct subsystem.







Example 6


The configuration file:






mount {




cpu = /sys/fs/cgroup/cpu;
cpuacct = /sys/fs/cgroup/cpu;




}
group . {




perm {




task {




uid = root;
gid = operator;




}
admin {




uid = root;
gid = operator;




}




}
cpu {
}




}
group daemons {




perm {




task {




uid = root;
gid = daemonmaster;




}
admin {




uid = root;
gid = operator;




}




}
cpu {
}




}





creates the hierarchy controlled by two subsystems with one group having some
  special permissions. It corresponds to the following operations:





mkdir /sys/fs/cgroup/cpu
mount -t cgroup -o cpu,cpuacct cpu /sys/fs/cgroup/cpu
chown root:operator /sys/fs/cgroup/cpu/*
chown root:operator /sys/fs/cgroup/cpu/tasks
mkdir /sys/fs/cgroup/cpu/daemons
chown root:operator /sys/fs/cgroup/cpu/daemons/*
chown root:daemonmaster /sys/fs/cgroup/cpu/daemons/tasks




Users which are members of the operator group are allowed
    to administer the control groups, i.e. create new control groups and move
    processes between these groups without having root privileges.


Members of the daemonmaster group can move processes to the
    daemons control group, but they can not move the process out of the
    group. Only the operator or root can do that.








Example 7


The configuration file:








mount {




cpu = /sys/fs/cgroup/cpu;
cpuacct = /sys/fs/cgroup/cpuacct;




}
group students {




cpuacct{
}
cpu {
}




}
template students/%u {




cpuacct{
}
cpu {
}




}
mkdir /sys/fs/cgroup/cpu/daemons
mkdir /sys/fs/cgroup/cpuacct/daemons




The situation is the similar as in Example 4. The only difference
    is template, which is used if some rule uses "/students/%u" as a
    destination.








Example 8


The configuration file:








mount {




"cpu,nodev,nosuid,noexec" = /mnt/cgroups/cpu;




}





This is the same as mount -t cgroup cgroup -o
    nodev,nosuid,noexec,cpu /mnt/cgroups/cpu It mounts the cpu controller with
    MS_NODEV, MS_NOSUID and MS_NOEXEC options passed.












RECOMMENDATIONS




Keep hierarchies separated


Having multiple hierarchies is perfectly valid and can be useful
    in various scenarios. To keeps things clean, do not create one group in
    multiple hierarchies. Examples 4 and 5 show how unreadable and confusing it
    can be, especially when reading somebody elses configuration file.








Explicit is better than implicit


libcgroup can implicitly create groups which are needed for
    the creation of configured subgroups. This may be useful and save some
    typing in simple scenarios. When it comes to multiple hierarchies, it's
    better to explicitly specify all groups and all controllers related to
  them.










FILES



  
/etc/cgconfig.conf

  
default libcgroup configuration file

  
/etc/cgconfig.d/

  
default libcgroup configuration files directory
    

  








SEE ALSO


cgconfigparser (8)








BUGS


Parameter values must be single strings without spaces. Parsing of
    quoted strings is not implemented.