When you query `ContainerMemory` and encounter the error:

open /sys/fs/cgroup/memory.max: no such file or directory

This error mostly affects Raspberry Pi OS, but might also affect older Debian-based systems as well.

<details><summary>Add cgroup_memory and cgroup_enable to cmdline.txt:</summary>

1. Confirm the list of existing cgroup controllers doesn't include `memory`:

```console

```

1. Add cgroup entries to `cmdline.txt` in `/boot/firmware` (or `/boot/` on older Pi OS releases):

```text

```

You can use `sed` to add it to the file for you:

```bash

sudo sed -i '$s/$/ cgroup_memory=1 cgroup_enable=memory/' /boot/firmware/cmdline.txt

```

1. Reboot:

```bash

sudo reboot

```

1. Confirm that the list of cgroup controllers now includes `memory`:

```console

```

Read more about cgroup controllers in [The Linux Kernel](https://docs.kernel.org/admin-guide/cgroup-v2.html#controlling-controllers) documentation.

</details>