Birch Street Computing -

about me

John M is a Linux fan in Lowell, MA.

I work at at a company writing software. I fool around with Free and Open Source software for fun & profit.

I was big into and you can still see some of what I listen to there. I can also be found using github and recently sourcehut as well as bitbucket (historically). I don't care for most popular social media sites. If I have an account on one or the other it's probably either old and unused or was created just for tinkering.


Links to things I like, use, or otherwise feel is worth sharing. Things I'd like to see get more popular.

Samba in Kubernetes - Status Update 1

As some of you may remember, I've been working on an effort to include SMB, via Samba, in the container ecosystem 1 and Kubernetes. It's been a while since I wrote anything about these projects. I want to give an update on our work to keep others informed, and possibly get others interested in what we've been doing. I hope to make this a regular thing (unless you get annoyed and tell me to stop ;-) ).

We gave a presentation on these projects at sambaXP 2 and also have had a few posts on the samba mailing list about them. Since then we've been doing a lot of varied work and below is a small slice of it.


I took on the task of trying to "containerize" CTDB-enabled Samba over this summer. With assistance of the samba-technical mailing list we successfully started running CTDB in a containerized environment. I proceeded to automate parts of the CTDB configuration in our sambacc library 3. Finally, we created new example YAML files in samba-containers 4 that demonstrate a clustered instance of Samba running under Kubernetes orchestration.

There were a lot of challenges getting CTDB working automatically in a container and there's still a lot to do. For example, the code I wrote to help manage the CTDB nodes file isn't as robust as I'd like it to be and is still generally immature. We'd like to discuss ways we might update CTDB to make the nodes easier to manage through automation (in our environment) and hope such discussions could improve things for other use cases as well.

At the moment, we've been using a Kubernetes based mechanism 5 for getting clients running outside of the cluster access to the shares. Without plunging deep into the particulars of Kubernetes networking; the method works well enough but does not use the CTDB public address mechanism. As such, we feel the failover behavior we have right now may not be as nice at getting clients to quickly fail-over when compared to CTDB's tickle-ack. This is an area we're going to be actively investigating and would like to hear additional feedback on this topic.

We're also adding support for the CTDB enabled Samba instances to the Kubernetes operator code. The plan is to continue to use the single SMB instance by default but add an experimental mode for running a StatefulSet of Pods that include CTDB for clustering across multiple nodes.

We are also discussing the need for using the fileid vfs module on top the clustered file system we intend to use (cephfs). However, we don't want to require a PVC to be any particular file system and so we have been discussing ways to enable the fileid module, and how to configure it, only in cases that we need it in an easy-to-use manner.

ACL Xattr

We are very interested in being able to use NTACLs on the shares that we host in containerized Samba servers. Today, the acl_xattr module stores the NTACL metadata in an xattr named "security.NTACL". The "security" namespaces on Linux requires the use of the CAP_SYS_ADMIN capability - basically the "root user" of Linux capabilities. This would require running the containers with escalated privileges; something we would prefer not to do. So, Günther Deschner, with feedback from Ralph Böhme and Michael Adam and others, has been working on the patches in MR#1908 6.

With these changes in place, we'd be able to configure Samba with a custom xattr for our containerized Samba instances and thus avoid needing to run a privileged container while still supporting NTACLs.

Nightly Builds

We've been looking in an easy way to try out the latest code in Samba and are planning on adding support for building container images based on nightly package builds. Anoop C S has already added support to the sambacc layer in order to support the newer CLI options present in Samba 4.15. Next we plan to add new build rules to the samba-containers project that will create new build tags in our container registry repo(s). Soon we should be able to more easily test and experiment with the latest versions Samba has to offer!


In the slightly longer term, we would like to add metrics support to our pods running in Kubernetes. Our plan is to follow the de-facto standard in this space and export Prometheus metrics. In order to do this we need to get the data out of our Samba stack and rather than try and directly scrape the output of a tool like smbstatus we are very interested in the effort to add JSON output support to samba tools. In our case, we want JSON output from smbstatus. As such we're very interested in MR#1269 7. We'll probably be getting more involved here in the near future.

Offline Domain Join

One new feature that landed in Samba 4.15 is the new Offline Domain Join (ODJ) support. Currently, to connect our containers with Active Directory we're asking users to store a username/password in a Kubernetes secret 8. We are aware that storing a password (even within a secret) isn't the best thing to do, so we're looking forward to trying to integrate the ODJ feature into our projects so that users never have to store a password. Watch this space! :-)

Wrap Up

If you have any questions or comments feel free to ask! I'm hoping this update both serves to inform you of what we're up to as well as serving as a prompt for you to give us feedback.

Thanks for reading!

1Specifically OCI/Docker style containers.
8Not strictly true, as you can leave out the secret and then run a command in the container to complete the join. However, this runs counter to the level of automation we'd like to provide, but is an option.

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