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| -rw-r--r-- | Documentation/cgroups/cgroups.txt | 24 |
1 files changed, 22 insertions, 2 deletions
diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt index 4a0b64c605f..004fd5a09e1 100644 --- a/Documentation/cgroups/cgroups.txt +++ b/Documentation/cgroups/cgroups.txt @@ -29,7 +29,8 @@ CONTENTS: 3.1 Overview 3.2 Synchronization 3.3 Subsystem API -4. Questions +4. Extended attributes usage +5. Questions 1. Control Groups ================= @@ -650,7 +651,26 @@ and root cgroup. Currently this will only involve movement between the default hierarchy (which never has sub-cgroups) and a hierarchy that is being created/destroyed (and hence has no sub-cgroups). -4. Questions +4. Extended attribute usage +=========================== + +cgroup filesystem supports certain types of extended attributes in its +directories and files. The current supported types are: + - Trusted (XATTR_TRUSTED) + - Security (XATTR_SECURITY) + +Both require CAP_SYS_ADMIN capability to set. + +Like in tmpfs, the extended attributes in cgroup filesystem are stored +using kernel memory and it's advised to keep the usage at minimum. This +is the reason why user defined extended attributes are not supported, since +any user can do it and there's no limit in the value size. + +The current known users for this feature are SELinux to limit cgroup usage +in containers and systemd for assorted meta data like main PID in a cgroup +(systemd creates a cgroup per service). + +5. Questions ============ Q: what's up with this '/bin/echo' ? |