diff options
| author | Aristeu Rozanski <aris@redhat.com> | 2012-09-11 16:28:10 -0400 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2012-09-12 11:39:50 -0700 |
| commit | 19ec2567e0a5fe64f4404ad6df697894aec8c493 (patch) | |
| tree | 64424d60857c7ec9192e4113643071a2a727c7cb | |
| parent | a1a71b45a66fd3c3c453b55fbd180f8fccdd1daa (diff) | |
cgroup: add documentation on extended attributes usage
v2: update cgroups.txt instead of creating a new file
Cc: Tejun Heo <tj@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: Lennart Poettering <lpoetter@redhat.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Aristeu Rozanski <aris@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
| -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' ? |