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 con-
trol groups, their parameters and their mount points. The file con-
sists 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>;
...
}
controller
Name of the kernel subsystem. The list of subsystems supported
by the kernel can be found in /proc/cgroups file. Named hierar-
chy can be specified as controller "name=<somename>". Do not
forget to use double quotes around this controller name (see ex-
amples below). Apart from named hierarchy, additional mount op-
tions 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.
path The directory path where the group hierarchy associated to a
given controller shall be mounted. The directory is created au-
tomatically 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 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
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>
}
}
task user/group 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 speci-
fied. Instead, current file owner permissions
are used as a "umask" for group and others per-
missions. For example if fperm = 777 then both
group and others will get the same permissions
as the file owner.
admin user/group 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.
controller
Name of the kernel subsystem. The section can be empty, default
kernel parameters will be used in this case. By specifying con-
troller 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 dif-
ferent directories. Each control group must be controlled by at
least one subsystem, so that libcgroup knows in which hierar-
chies the control group should be created.
The parameters of the given controller can be modified in the
following section enclosed in brackets.
param name
Name of the file to set. Each controller can have zero or
more parameters.
param value
Value which should be written to the file when the con-
trol 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 per-
missions 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 in-
side. 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 fol-
lowing 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 direc-
tory, 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 direc-
tory, all groups are implicitly also controlled by the cpuacct subsys-
tem, 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 cor-
responds 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 hav-
ing some special permissions. It corresponds to the following opera-
tions:
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 destina-
tion.
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 confus-
ing 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 cre-
ation 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.
CGCONFIG.CONF(5)
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