v2: update cgroups.txt instead of creating a new file Cc: Li Zefan <lizefan@xxxxxxxxxx> Cc: Tejun Heo <tj@xxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Hillf Danton <dhillf@xxxxxxxxx> Cc: Lennart Poettering <lpoetter@xxxxxxxxxx> Signed-off-by: Aristeu Rozanski <aris@xxxxxxxxxx> --- Documentation/cgroups/cgroups.txt | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-) Index: github/Documentation/cgroups/cgroups.txt =================================================================== --- github.orig/Documentation/cgroups/cgroups.txt 2012-08-16 10:24:48.437596817 -0400 +++ github/Documentation/cgroups/cgroups.txt 2012-09-07 10:23:19.974357952 -0400 @@ -29,7 +29,8 @@ 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 @@ 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' ? -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
