34 lines
1.2 KiB
YAML
34 lines
1.2 KiB
YAML
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services:
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coredns:
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image: ${COREDNS_IMAGE}
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container_name: coredns-secondary
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restart: unless-stopped
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command: ["-conf", "/etc/coredns/Corefile"]
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# Host networking is required for two reasons:
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#
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# 1. CoreDNS's `secondary` plugin authorizes inbound NOTIFY by
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# source IP (`transfer from 154.27.180.210`). With bridge
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# networking, Docker's userland proxy rewrites the visible
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# source to a 172.x docker0 address, and the auth check fails.
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#
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# 2. AXFR responses can be large; UDP/TCP source-IP preservation
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# matters for both directions of the conversation.
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#
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# Host networking means this container OWNS host ports 53/udp + 53/tcp.
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# On a dedicated NS box that's exactly what you want.
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network_mode: host
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volumes:
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- ./Corefile:/etc/coredns/Corefile:ro
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# CoreDNS's distroless image has no shell, so the conventional
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# `wget /health` healthcheck silently fails. The `-version` flag
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# exits 0 only if the binary is runnable — a thin but honest probe.
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healthcheck:
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test: ["CMD", "/coredns", "-version"]
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interval: 30s
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timeout: 5s
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retries: 3
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start_period: 10s
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