I believe @Lonk 's VPN project may be helpful here as VPNs track their packets much more so than general network interfaces which could provide for greater visibility for any app by simply adding it to the VPN profile & data path.
Until @girish gets a more general solution in for all of Cloudron and perhaps containers in general.
A Nestybox system container is an enhanced Docker container, designed to package not just applications but also low-level system software.
What type of system software are we talking about? Currently Systemd and Docker, but in the near future software such as Kubernetes, graphical display servers, and others.
The following figure illustrates the difference.
But can’t you do this on a regular Docker container? No you can’t. Not properly.
For example, in order to run Docker inside a regular container (i.e., Docker-in-Docker) you need to run the container in “privileged” mode. This significantly weakens isolation between the container and the underlying host, posing a strong security risk (especially if you don’t trust the workloads running inside the container).
But in some cases even privileged mode is not sufficient. For example, some system level programs read resource consumption information from the kernel (e.g., via the Linux /proc directory). In order for the program to work properly inside a container, such information must be provided relative to the resources assigned to the container itself, not the resources of the underlying host. A regular container does not do this, even when running in privileged mode.
Nestybox system containers are designed to solve these problems.
We can summarize the key properties of a Nestybox system container as:
Runs low-level system workloads (as well as applications).
Provides strong isolation from the underlying host.
Presents a more complete abstraction of a virtual host to its workloads.
Typically runs multiple applications within it (rather than just one app).
One way to look at it is that a regular container packages applications. In contrast, a Nestybox system container packages virtual host environments capable of running applications as well as system-level workloads.
See it work!
But why would you want to run such system-level software inside a container in the first place? I.e., Why do we need system containers?
There are several use cases.
For example, by virtue of running Docker inside the container (securely), the system container can be used for:
CI/CD pipelines (where the need for a container to run another container arises).
Docker sandboxing (e.g., to run multiple Docker instances with total isolation between them).
Our blog site contains articles with practical examples of such use cases.
In the near future, as we add support for more system-level workloads inside the system container, more use cases will open up.
In general, if you have a need for a virtual host that runs many of the same workloads that you could run on a VM, yet is faster and more efficient, then a Nestybox system container is a good fit.
Key Features and Benefits
Deployment with Docker (and Kubernetes)
This allows you to leverage the power of these amazing tools to build, deploy, and manage system containers. No need to learn new tools.
Fast & Efficient
Just like regular application containers.
Strong Container Isolation
Nestybox system containers always use the Linux user namespace.
This means the root user in the system container has full capabilities inside the system container, but none outside of it.
In addition, Nestybox system containers use exclusive Linux user namespace user-ID and group-ID mappings for each system container.
If a process inside the container escapes the container sandbox, it will find itself without privileges to access resources of the host or of other containers.
A Nestybox system container image can be created with Docker, just like any Docker container.
However, it typically is configured with an environment resembling a virtual host (e.g., process manager, multiple apps, docker, app containers, graphical display server, etc), although you can also configure it with a single system-level application (e.g., Docker) if you wish. It’s up to you to choose what’s in the image and the entry-point.
You can deploy Nestybox system containers on any Linux machine, whether it’s bare-metal, a local VM, or a cloud VM, in a data-center, your laptop, an edge device, or even an IoT device.
And as with any Docker container you have the flexibility to move the system container around as you wish. Just upload it to your repo and deploy it on the target machine with Docker.
Partially virtualized procfs
In Nestybox system containers, portions of the Linux procfs (/proc) are virtualized. The goal is to make the system container more closely resemble a real host or VM. For example, the /proc/uptime file returns the container’s uptime, not the underlying host’s uptime.
How does it work?
Nestybox system containers are made possible by Sysbox, our system container runtime.
Sysbox is software that installs on the Linux host machine, integrates with Docker (and soon Kubernetes), and works under the covers.
Users interact with Docker to create the system container image and deploy it, just as with application containers. The difference is that this image can now include system-level software such as Docker itself (for Docker-in-Docker), etc.
The following figure illustrates this.
Running the system container is simple, it only requires passing the --runtime=sysbox-runc flag to Docker:
$ docker run --runtime=sysbox-runc -it my-syscont-image
Under the covers, Sysbox takes care of setting up the system container abstraction so that it can properly run system level workloads.
It’s easy. And you avoid the need for unsecure privileged containers or complex container configurations.
Is it a VM?
No, it’s not. It’s an enhanced container. As with all containers, it uses OS-level virtualization and shares the Linux kernel with the rest of the system. In contrast, VMs use hardware-level virtualization (i.e., emulate hardware in software) and have a dedicated OS per VM.
The following figure illustrates the differences.
This gives system containers and VMs different properties. In particular system containers are faster, more efficient, and more portable (see above) but offer a lesser degree of isolation from the underlying host.
From a workload perspective however, Nestybox is working to make our system containers support as many workloads as VMs can run such that they can present a viable alternative to VMs in some scenarios.
the prompt that everybody confirms without even reading
haha, so true. Yeah I got a pop-up that was like "This is a new key" or something and just accepted it. Basically the same kind of message that happens with SSH. I just have certificate-based SSH though where it needs my key to even connect (i.e. you couldn't connect to my server over SSH without it), so I was surprised I didn't need that on my SFTP connection, thought I'd maybe need something similar. But I guess this makes sense then the more I think about it. Just caught me off guard. haha.
@ianhyzy I registered a new domain just for this purpose. It's not ideal but I don't have to use a relay so it works out in the end. I'm hosting with DigitalOcean so the PTR record is set by changing the server (droplet) name to match the mail server domain. Last I checked my headers, all were good and pointing to the new domain setup.
Edit: BTW, I've used Amazon SES for my newsletters in the past and they're pretty cheap. IIRC, I sent like 9k emails for under $1 USD.
@girish Interesting, and not something I'd considered. That pigs option is similarly interesting, though seems to have gone silent since 2017. Curiously, it's a similar story with pbzip2 (the same idea for bzip2) as far as I can tell. Decent roundup of options for Ubuntu at https://askubuntu.com/questions/258202/multi-core-compression-tools in case you want to review. It will be interesting to see the GCP results for sure. I'll pull some metrics after the migration/restore as well as after the manual backup and see how it does across CPU/Disk/Network in the process.
@marcusquinn I think DNS automation (provider specific) atleast needs to come from elasticemail itself ideally. It's not possible to keep track of all the DNS records each provider wants to set and if it's even available with API. It's basically impossible to test on our side atleast.