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NetAlertX/docs/REVERSE_DNS.md
2024-02-13 08:16:00 +11:00

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## Setting up better name discovery with Reverse DNS
If you are running a DNS server, such as **AdGuard**, set up **Private reverse DNS servers** for a better name resolution on your network. Enabling this setting will enable PiAlert to execute dig and nslookup commands to automatically resolve device names based on their IP addresses.
> Example 1: Reverse DNS `disabled`
>
> ```
> jokob@Synology-NAS:/$ nslookup 192.168.1.58
> ** server can't find 58.1.168.192.in-addr.arpa: NXDOMAIN
>
> ```
> Example 2: Reverse DNS `enabled`
>
> ```
> jokob@Synology-NAS:/$ nslookup 192.168.1.58
> 45.1.168.192.in-addr.arpa name = jokob-NUC.localdomain.
> ```
### Enabling reverse DNS in AdGuard
1. Navigate to **Settings** -> **DNS Settings**
2. Locate **Private reverse DNS servers**
3. Enter your router IP address, such as `192.168.1.1`
4. Make sure you have **Use private reverse DNS resolvers** ticked.
5. Click **Apply** to save your settings.
### Using a custom resolv.conf file
You can configure a custom **/etc/resolv.conf** file in **docker-compose.yml** and set the nameserver to your LAN DNS server (e.g.: Pi-Hole). See the relevant [resolv.conf man](https://www.man7.org/linux/man-pages/man5/resolv.conf.5.html) entry for details.
#### docker-compose.yml:
```yaml
version: "3"
services:
pialert:
container_name: pialert
image: "jokobsk/pi.alert:latest"
restart: unless-stopped
volumes:
- ./config/pialert.conf:/home/pi/pialert/config/pialert.conf
- ./pialert_db:/home/pi/pialert/db
- ./log:/home/pi/pialert/front/log
- ./config/resolv.conf:/etc/resolv.conf # Mapping the /resolv.conf file for better name resolution
environment:
- TZ=Europe/Berlin
- PORT=20211
- HOST_USER_ID=1000
- HOST_USER_GID=1000
ports:
- "20211:20211"
network_mode: host
```
#### ./config/resolv.conf:
The most important below is the `nameserver` entry (you can add multiple):
```
nameserver 192.168.178.11
options edns0 trust-ad
search example.com
```