On 12/11/25 10:51, Amir Najafi Zadeh wrote:
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).
If you want to track containers, the pid namespace is the one used by
most container runtimes but I don't know specifically for container-d.
```
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 <[email protected]
<mailto:[email protected]>> 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)
