031e1c3415
<message>Add new documentation files for device DNS management via DHCP and dnsmasq configuration. Update cloud-init scripts to ensure proper handling of /etc/resolv.conf and DNS settings, allowing for seamless integration with file.server. Modify existing scripts to support dynamic LAN subnet configuration and improve overall network boot functionality. These changes enhance user experience and streamline the setup process for the CM4 eMMC provisioning service.
102 lines
4.0 KiB
Markdown
102 lines
4.0 KiB
Markdown
# dnsmasq DNS and file.server on the LXC
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This document describes the dnsmasq DNS configuration on the provisioning LXC and the static hostname **file.server** used for the fileserver.
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## What was changed
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### 1. dnsmasq now provides DNS on eth1
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Previously, dnsmasq on the LXC was configured with **`port=0`**, which disabled DNS and provided only DHCP and TFTP on the provisioning interface (eth1).
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**Change:** `port=0` was removed so dnsmasq also acts as a DNS server on eth1 (port 53). Clients that receive DHCP from dnsmasq will use the LXC as their DNS server for the provisioning LAN.
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- **DHCP** on eth1 — unchanged (range from `lan-subnet.conf`, e.g. 10.20.40.100–10.20.40.200).
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- **TFTP/PXE** on eth1 — unchanged (toggle with `/opt/cm4-provisioning/toggle-network-boot-dhcp.sh`).
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- **DNS** on eth1 — **new**: local static records (e.g. `file.server`) plus forwarding of other queries via the LXC’s `/etc/resolv.conf`.
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### 2. Static DNS record: file.server → eth1 IP
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A static A record was added so the hostname **file.server** resolves to the LXC’s eth1 address (the provisioning LAN gateway). That IP is taken from **`/opt/cm4-provisioning/lan-subnet.conf`** as **`LAN_GW`** (e.g. `10.20.40.1`).
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**dnsmasq config (written by `setup-network-boot-on-lxc.sh`):**
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```text
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address=/file.server/${LAN_GW}
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```
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So scripts and devices on the provisioning LAN can use **`http://file.server/...`** (or `file.server` in general) without hardcoding the LXC’s IP. The IP stays correct even if the LAN subnet is changed and the setup script is re-run.
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### 3. Files modified in the repo
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| File | Change |
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|------|--------|
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| **scripts/setup-network-boot-on-lxc.sh** | Removed `port=0`; added `address=/file.server/${LAN_GW}` and comments in the generated `/etc/dnsmasq.d/network-boot.conf`. |
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| **lxc/dnsmasq-network-boot.conf** | Template updated: removed `port=0`, added comment for DNS and `file.server` (commented example). |
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### 4. Applied on LXC (root@10.20.40.1)
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On **2025-03-04** the setup script was run against **root@10.20.40.1**:
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```bash
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./emmc-provisioning/scripts/setup-network-boot-on-lxc.sh root@10.20.40.1
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```
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Result on that LXC:
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- **LAN:** 10.20.40.0/24, gateway 10.20.40.1 (from existing `lan-subnet.conf`).
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- **DHCP:** 10.20.40.100–10.20.40.200 on eth1.
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- **DNS:** Enabled on eth1; **file.server** → **10.20.40.1**.
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- dnsmasq and NAT were (re)configured; TFTP root and network boot toggle unchanged.
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So on the provisioning LAN, **file.server** resolves to **10.20.40.1** (the LXC’s eth1).
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## How to use file.server in scripts
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On devices that get DHCP (and thus DNS) from the LXC on the provisioning LAN:
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- Use **`http://file.server/...`** (or `file.server` as hostname) instead of `http://10.20.40.1/...`.
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- No need to hardcode the LXC IP; if you change the subnet and re-run the setup script, **file.server** will still point at the correct gateway.
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Example:
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```bash
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curl -O http://file.server/cloud-init/seed.img
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```
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## Adding more static DNS entries
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To add more names (e.g. `fileserver` or another hostname), add more **`address=/name/${LAN_GW}`** lines in the heredoc in **scripts/setup-network-boot-on-lxc.sh** (where `network-boot.conf` is generated), or add a separate file under `/etc/dnsmasq.d/` on the LXC with the same format. Then restart dnsmasq:
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```bash
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systemctl restart dnsmasq
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```
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## Re-applying on another or existing LXC
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To apply or refresh this configuration on any LXC:
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```bash
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./emmc-provisioning/scripts/setup-network-boot-on-lxc.sh root@<LXC-IP> [SUBNET]
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```
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Example with explicit subnet:
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```bash
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./emmc-provisioning/scripts/setup-network-boot-on-lxc.sh root@10.20.40.1 10.20.40.1/24
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```
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This rewrites `/etc/dnsmasq.d/network-boot.conf` (including `address=/file.server/${LAN_GW}`) and restarts dnsmasq.
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## Verification on the LXC
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```bash
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# DNS and file.server
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grep -E 'address=|port=' /etc/dnsmasq.d/network-boot.conf
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# Resolve file.server (from a client on the provisioning LAN, or from LXC with server 127.0.0.1)
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getent hosts file.server
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# or: dig @10.20.40.1 file.server
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```
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Expected: **file.server** resolves to the LAN gateway (e.g. 10.20.40.1).
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