I’m trying to find the most convenient and maintainable LTTng setups supporting collection of traces generated from a container.

Here is what I’ve tried:

host:

• lttng-sessoind (root/user)
• lttng-relayd (root/user)

container:

• liblttng-ust executable

I create snapshot and live sessions on the host which filter traces containing a specific field. Inside the containers I just generate traces.

To achieve this, I start the container like this:

podman run 
    -v /var/run/lttng:/var/run/lttng 
    -v /dev/shm/lttng-ust-wait-8:/dev/shm/lttng-ust-wait-8 
    -e LTTNG_HOME=/root 
    image-with-liblttng-ust

The image-with-liblttng-ust image is any image which has an executable producing traces with liblttng-ust.

Here is an example of the setup where the lttng-sessiond is started under a non-root user:

podman run 
    -v /home/username/.lttng:/var/run/lttng 
    -v /dev/shm/lttng-ust-wait-8-1000:/dev/shm/lttng-ust-wait-8 
    -e LTTNG_HOME=/root 
    image-with-liblttng-ust

The first mount doesn’t look bad, the runtime LTTng directory is mounted to establish communication between lttng-sessiond and liblttng-ust, nevertheless it could be enough to mount only /home/username/.lttng/lttng-ust-sock-8 for the maintainability IMO mount of the whole directory is better.
The second mount isn’t that nice, it’s outside the runtime directory, it’s not a directory but a specific shared memory file containing the ABI version and the uid in the name, every LTTng update would require verification of the file name.

I’ve also tried various mount combinations:

+-----------------------+------------------+--------------------------------+-----------------------------+-------+
| HOST RUNDIR           | CONTAINER RUNDIR | HOST SHM                       | CONTAINER SHM               | WORKS |
+-----------------------+------------------+--------------------------------+-----------------------------+-------+
| /home/username/.lttng | /root/.lttng     | /dev/shm/lttng-ust-wait-8-1000 | /dev/shm/lttng-ust-wait-8-0 | yes   |
+-----------------------+------------------+--------------------------------+-----------------------------+-------+
| /home/username/.lttng | /var/run/lttng   | /dev/shm/lttng-ust-wait-8-1000 | /dev/shm/lttng-ust-wait-8   | yes   |
+-----------------------+------------------+--------------------------------+-----------------------------+-------+
| /var/run/lttng        | /var/run/lttng   | /dev/shm/lttng-ust-wait-8      | /dev/shm/lttng-ust-wait-8   | yes   |
+-----------------------+------------------+--------------------------------+-----------------------------+-------+
| /var/run/lttng        | /root/.lttng     | /dev/shm/lttng-ust-wait-8      | /dev/shm/lttng-ust-wait-8-0 | no    |
+-----------------------+------------------+--------------------------------+-----------------------------+-------+
| /home/username/.lttng | /root/.lttng     | /dev/shm/lttng-ust-wait-8-1000 | /dev/shm/lttng-ust-wait-8   | no    |
+-----------------------+------------------+--------------------------------+-----------------------------+-------+

Is this a valid approach to enable container support? Are there any better options?