Question about LTTng Context

[Amir Najafi Zadeh]

Michael, Kienan, Thank you both for your replies. As you mentioned the
cgroup namespace, it isn’t very helpful in some cases. Containers may share
the same cgroup namespace, and the container runtime often avoids giving
each container a private cgroup namespace for performance and security
reasons. Because of this, the cgroup namespace can’t be used as a reliable
or unique label for filtering trace logs.

In my case, with container-d you can inspect a container, find its PID, and
then check /proc/<pid>/ns/cgroup, but you’ll see that different containers
often have the same cgroup namespace ID (e.g., in the following logs you
can see the calico-node and kube-proxy containers sharing a cgroup ns).

```
Name: calico-node  CID:
b5624afe31b005725f4ba53c7b6fe758f3c09fabf013085231ff8b97588f6ace  PID: 2243
 cgroup_ns_inode: 4026531835
Name: kube-proxy  CID:
52f3c12def7a680f61a925ac92dd5ebd5eba6cad17d671efbfd1d40db7dff624  PID: 1851
 cgroup_ns_inode: 4026531835
  >> MATCH FOUND: shares ns with container:
b5624afe31b005725f4ba53c7b6fe758f3c09fabf013085231ff8b97588f6ace
(calico-node)
```

Thanks again for your answers. I hope this feature appears in a future
patch.

Best,
Amir

On Thu, Dec 11, 2025 at 9:57 AM Michael Jeanson <mjeanson at efficios.com>
wrote:

> On 12/11/25 09:30, Kienan Stewart via lttng-dev wrote:
> > Hi Amir,
> >
> > On 12/10/25 9:40 PM, Amir Najafi Zadeh via lttng-dev wrote:
> >> Hello everyone,
> >>
> >> I hope you’re doing well. My name is Amir, and I’m a PhD student in
> >> the Computer Science department at Stony Brook University, New York.
> >>
> >> I have a question about the LTTng context that I haven’t been able to
> >> find an answer for in the docs or man pages. Does LTTng support adding
> >> the cgroup ID or cgroup path as a context field? I want to filter my
> >> trace results based on cgroups.
> >>
> >
> > I think you're looking for the `cgroup_ns` context which adds the inum
> > of the cgroup namespace as a context field.
>
> This will give you the ID of the cgroup namespace but we don't have
> contexts for cgroups themselves. It's probably something we would like
> to have but there is no concrete plans on implementing this at the moment.
>
> >
> >> If this isn’t supported, are there any plans to add it in future
> >> versions, such as 2.14?
> >>
> >> For reference, I’m currently using LTTng 2.13 on Ubuntu 24.04 with
> >> kernel 6.8.0-87-generic.
> >>
> >> Cheers,
> >> Amir
> >> --
> >> *Amirhossein Najafizadeh*
> >> *PhD Student, Computer Science Department, Stony Brook University, N.Y.
> >> File systems and Storage Lab (FSL)
>
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