lxd-docker-firewall-conflict SKILL.md skillA
lxd-docker-firewall-conflict from soulmachine/skills is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add soulmachine/skills/lxd-docker-firewall-conflict@git:20260611.94752b4Pins git:20260611.94752b4 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- soulmachine/skills
- Path
lxd-docker-firewall-conflict/SKILL.md- Versions recorded
- 1
- Latest version
- git:20260611.94752b4, committed Jun 11, 2026
- Size
- 7,518 bytes
- Repository stars
- 3
- License
- MIT
Diagnose and fix the well-known Docker/LXD firewall conflict on a host running both. Docker sets the iptables FORWARD chain policy to DROP and accepts only its own bridges, so forwarded traffic from the LXD bridge (lxdbr0) is silently dropped and LXD containers/VMs get no outbound internet (the host itself is fine). Fix: accept the LXD bridge in the DOCKER-USER chain, then persist it with a systemd unit ordered after docker.service. Use when an LXD container has no internet or cannot reach…
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# LXD ↔ Docker firewall conflict (FORWARD DROP) When Docker and LXD share a host, **Docker sets the iptables `FORWARD` chain policy to `DROP`** and only ACCEPTs traffic for its own bridges. Forwarded packets from the LXD bridge (`lxdbr0`) match nothing and fall through to the DROP policy, so **LXD containers/VMs lose all outbound internet** — even though the host itself is fine and the LXD bridge has `ipv4.nat=true`. The fix is to ACCEPT the LXD bridge in Docker's `DOCKER-USER` chain and persist it. ⚠️ This is **not** a NAT, DNS, or LXD-config problem. The bridge's `ipv4.nat=true` and `net.ipv4.ip_forward=1` are already correct — packets are dropped at the `FORWARD` hook before NAT ever applies. Don't waste time reconfiguring the bridge, DNS, or `lxd init`. ## Quick start ```bash # Detects managed LXD bridges, adds DOCKER-USER ACCEPT rules, and installs a # systemd unit so they survive reboots + docker restarts. Idempotent; re-runnable. bash scripts/fix-lxd-docker-forward.sh ``` ## Symptoms - Inside an LXD container, `apt update` / `apt-get` / `curl` **times out** on IPv4 (`connection timed out`, `Failed to fetch`) and/or instantly says `Network is unreachable` on IPv6. …
Read the whole file at its exact version.
How to install
mdr add soulmachine/skills/lxd-docker-firewall-conflict@sha256:e2c403800b760900The line at the top of this page pins the label git:20260611.94752b4, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_t7lha3vuhcqd34m7)
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Versions
The registry has recorded 1 version of this file, committed on Jun 11, 2026.
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (7518 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
soulmachine/skills · 3 stars · license MIT · pushed 2026-10-31 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_t7lha3vuhcqd34m7 GET https://markdownregistry.com/api/v1/resolve?ref=soulmachine/skills/lxd-docker-firewall-conflict GET https://markdownregistry.com/api/v1/blob/e2c403800b760900c78152e605cfb24b2992522f11b64bf107c03c80ddb075f4
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.