Guide for LXD about how-to-secure-a-linux-server HOT 7 CLOSED

This is great. I will work to add it in. Might be a few as we just moved and I'm knee deep in unpacking.

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Sounds good, a couple things I noticed/forgot to mention.

The mounts being read only or read/write depends on their owner and permissions which I usually set to 755 (so they're not actually read only by default if you use 777). To actually make them read only, regardless of permissions, use
lxc config device add <container name> <device name> disk source=<path on host> path=<path on container> readonly=true
edit: this is better than what I wrote before about using a read-only bind mount on the host

The other thing is ufw doesn't start after a reboot if using netfilter-persistent (at least on ubuntu). The fix found here is to add the line After=netfilter-persistent.service after Before=network.target in the file /lib/systemd/system/ufw.service

from how-to-secure-a-linux-server.

Another thing I found that might be of interest is that a compromised container could potentially do MAC or IP spoofing on the bridge (source)

To prevent this, you can enable MAC and IP filtering by running this command for every container (if you already ran your containers, it'll probably be assigned a new IP address, which you can also set yourself by setting ipv4.address on the eth0 device)
lxc config device override <container name> eth0 security.mac_filtering=true security.ipv4_filtering=true

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Have you thought about creating a new guide just for LXD? I worry if we merge the two it might create confusion for folks who aren't using LXD? Thoughts?

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Have you thought about creating a new guide just for LXD? I worry if we merge the two it might create confusion for folks who aren't using LXD? Thoughts?

I was starting to work on one but stopped due to no longer using LXD myself and migrating my setup to use just docker.

I also agree, combining LXD with this guide might create confusion for people who probably don't need LXD and just be too much. It's probably still worth mentioning along with AppArmor for people who wish to go that route and that's it. I think you took a good approach by sticking to the base OS and this is a great guide as it is.

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Thank you!

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I think we can close this issue now, I was going to add a couple links mentioning this to the AppArmor section, but since it hasn't been written yet and I'm not familiar enough to write anything on it, I'll just leave it up to whoever does to decide if they want to mention this.

• LXD Guide (unprivileged and uses AppArmor by default) (this one goes a bit more in depth in some areas I didn't mention)
• AppArmor profiles for Docker
• Run Docker in rootless mode (alternative to using AppArmor to mitigate some potential vulnerabilities)
• Podman compose (drop-in replacement for docker compose with goal of being rootless)

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