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https://github.com/coder/coder.git
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7d412c2272
This change adds a new `docker-devcontainer` template which allows you to provision a workspace running in Docker, that also creates workspaces via Docker running inside (DinD). - **chore(examples/templates): rename `docker-devcontainer` to `docker-envbuilder`** - **feat(examples/templates): add `docker-devcontainer` example template**
102 lines
4.2 KiB
Bash
Executable File
102 lines
4.2 KiB
Bash
Executable File
#!/bin/sh
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set -e
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# Docker-in-Docker setup for Coder dev containers using host.docker.internal
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# URLs. When Docker runs inside a container, the "docker0" bridge interface
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# can interfere with host.docker.internal DNS resolution, breaking
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# connectivity to the Coder server.
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if [ "${CODER_AGENT_URL#*host.docker.internal}" = "$CODER_AGENT_URL" ]; then
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# External access URL detected, no networking workarounds needed.
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sudo service docker start
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exit 0
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fi
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# host.docker.internal URL detected. Docker's default bridge network creates
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# a "docker0" interface that can shadow the host.docker.internal hostname
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# resolution. This typically happens when Docker starts inside a devcontainer,
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# as the inner Docker daemon creates its own bridge network that conflicts
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# with the outer one.
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# Enable IP forwarding to allow packets to route between the host network and
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# the devcontainer networks. Without this, traffic cannot flow properly
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# between the different Docker bridge networks.
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echo 1 | sudo tee /proc/sys/net/ipv4/ip_forward
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sudo iptables -t nat -A POSTROUTING -j MASQUERADE
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# Set up port forwarding to the host Docker gateway (typically 172.17.0.1).
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# We resolve host.docker.internal to get the actual IP and create NAT rules
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# to forward traffic from this workspace to the host.
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host_ip=$(getent hosts host.docker.internal | awk '{print $1}')
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echo "Host IP for host.docker.internal: $host_ip"
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# Extract the port from CODER_AGENT_URL. The URL format is typically
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# http://host.docker.internal:port/.
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port="${CODER_AGENT_URL##*:}"
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port="${port%%/*}"
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case "$port" in
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[0-9]*)
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# Specific port found, forward it to the host gateway.
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sudo iptables -t nat -A PREROUTING -p tcp --dport "$port" -j DNAT --to-destination "$host_ip:$port"
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echo "Forwarded port $port to $host_ip"
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;;
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*)
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# No specific port or non-numeric port, forward standard web ports.
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sudo iptables -t nat -A PREROUTING -p tcp --dport 80 -j DNAT --to-destination "$host_ip:80"
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sudo iptables -t nat -A PREROUTING -p tcp --dport 443 -j DNAT --to-destination "$host_ip:443"
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echo "Forwarded default ports 80/443 to $host_ip"
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;;
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esac
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# Start Docker service, which creates the "docker0" interface if it doesn't
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# exist. We need the interface to extract the second IP address for DNS
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# resolution.
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sudo service docker start
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# Configure DNS resolution to avoid requiring devcontainer project modifications.
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# While devcontainers can use the "--add-host" flag, it requires explicit
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# definition in devcontainer.json. Using a DNS server instead means every
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# devcontainer project doesn't need to accommodate this.
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# Wait for the workspace to acquire its Docker bridge IP address. The
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# "hostname -I" command returns multiple IPs: the first is typically the host
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# Docker bridge (172.17.0.0/16 range) and the second is the workspace Docker
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# bridge (172.18.0.0/16). We need the second IP because that's where
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# devcontainers will be able to reach us.
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dns_ip=
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while [ -z "$dns_ip" ]; do
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dns_ip=$(hostname -I | awk '{print $2}')
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if [ -z "$dns_ip" ]; then
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echo "Waiting for hostname -I to return a valid second IP address..."
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sleep 1
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fi
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done
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echo "Using DNS IP: $dns_ip"
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# Install dnsmasq to provide custom DNS resolution. This lightweight DNS
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# server allows us to override specific hostname lookups without affecting
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# other DNS queries.
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sudo apt-get update -y
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sudo apt-get install -y dnsmasq
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# Configure dnsmasq to resolve host.docker.internal to this workspace's IP.
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# This ensures devcontainers can find the Coder server even when the "docker0"
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# interface would normally shadow the hostname resolution.
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echo "no-hosts" | sudo tee /etc/dnsmasq.conf
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echo "address=/host.docker.internal/$dns_ip" | sudo tee -a /etc/dnsmasq.conf
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echo "resolv-file=/etc/resolv.conf" | sudo tee -a /etc/dnsmasq.conf
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echo "no-dhcp-interface=" | sudo tee -a /etc/dnsmasq.conf
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echo "bind-interfaces" | sudo tee -a /etc/dnsmasq.conf
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echo "listen-address=127.0.0.1,$dns_ip" | sudo tee -a /etc/dnsmasq.conf
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sudo service dnsmasq restart
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# Configure Docker daemon to use our custom DNS server. This is the critical
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# piece that ensures all containers (including devcontainers) use our dnsmasq
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# server for hostname resolution, allowing them to properly resolve
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# host.docker.internal.
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echo "{\"dns\": [\"$dns_ip\"]}" | sudo tee /etc/docker/daemon.json
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sudo service docker restart
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