Unix: add dns static ip blog
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@ -24,25 +24,25 @@ easily get *inward* access to any port.
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The easiest method, and probably recommended for most users, is using Software
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Driven WAN (SDWAN). This is similar to a VPN, but unlike Wireguard, ZeroTier One
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doesn't [[1]] require a centralized server.
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doesn't<sup>1</sup> require a centralized server.
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Advantages:
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- Free version is good enough for most small groups
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- Very simple setup
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- Very fast through UDP hole-punching
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- Very low latency through UDP hole-punching
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- Free (for up to 25 clients)
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Drawbacks:
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- Limit of 25 clients (on the [free
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version](https://www.zerotier.com/pricing/))
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- Requires installing separate software on all clients
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- Sometimes fails to connect for up to an hour... very hard to debug when it
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happens
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- Can only be used by clients on the VPN. For example, a public webserver won't
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be able to use this
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- Limit of 25 clients (on the [free
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version](https://www.zerotier.com/pricing/))
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To use ZeroTier:
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1. Sign up for an account at [zerotier.com](https://www.zerotier.com/)
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2. Under "Networks" create a network and give it a name. Ensure access control
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2. Under "Networks" create a network and give it a name. Ensure Access Control
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is private.
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3. Install ZeroTier One on all clients you'd like to connect. You can add more
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later.
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@ -168,3 +168,163 @@ ssh -p 8022 emiliko@172.27.10.10
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```
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This will be forwarded to port 22 on the server!
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### Reverse Proxy without a Static IP
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If you're planning to use a home computer, you'll quickly find that most
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internet service providers do not offer static IPs for consumer plans. Luckily,
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there's a very simple way around this: Domain Name Servers (DNS).
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You will need a domain to achieve this. Domains should not cost more than
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$20/year. Here I'll use the domain `example.com` as an example.
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The idea is that a domain will point to a specific IP, but this IP is determined
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through a lookup to the DNS. This means that if we change the IP the DNS has
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every time our computer's IP changes, we'll appear to have a static IP!
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First, put your nameservers on a good DNS provider. I use
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[Cloudflare](https://pages.cloudflare.com/), it's free and fast. You'll need to
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find the DNS page. The URL will look something like:
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```
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https://dash.cloudflare.com/<long-project-id>/example.com/dns/records
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```
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There, you'll want to add an "A Record". The name will be the subdomain. So if
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my computer is called `mycomputer` and that's in the name field, it'll be
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accessible at `mycomputer.example.com`.
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Now you need to identify your IP address. This is your PUBLIC IP address, not
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your LOCAL IP address. One easy way to do this is `curl -q
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https://ifconfig.me/ip`.
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Make sure "Proxy Status" is OFF. Proxying the connection appears to make this
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whole idea break down very quickly, so don't.
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With that "A Record" set, try `host mycomputer.example.com` to see when the DNS
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updates. This can take up to 4 hour, but usually takes under a minute in
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practice. With this, you should be able to access your computer using the
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domain! Of course, make sure your router's ports are forwarding to your
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computer.
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We now need to make your computer update Cloudflare's DNS, whenever the IP
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changes. I use the script below to do this. Fill in the `HOST`, `DOMAIN`,
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`TOKEN`, `ZONE_ID`. The `TOKEN` is your Cloudflare application token:
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```bash
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#!/usr/bin/env bash
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declare wan_ip_record wan_ip cf_records host_record cf_host_ip cf_rec_id
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declare -r HOST='mycomputer'
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declare -r DOMAIN='example.com'
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declare -r TOKEN='...'
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declare -r ZONE_ID='...'
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#╔─────────────────────────────────────────────────────────────────────────────╗
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#│ Gετ WΛN IP |
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#╚─────────────────────────────────────────────────────────────────────────────╝
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if ! wan_ip_record="$(curl ifconfig.me)"; then
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echo "Hosts timed out" >&2
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exit 1
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fi
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wan_ip="$wan_ip_record"
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#wan_ip="$(echo "$wan_ip_record" | tail -n1 | awk '{ split($0, a, " "); print a[4] }')"
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#╔─────────────────────────────────────────────────────────────────────────────╗
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#│ Gετ Λ rεcδrd δη Clδμdflαrε |
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#╚─────────────────────────────────────────────────────────────────────────────╝
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if ! cf_records="$(curl -s --request GET \
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--url https://api.cloudflare.com/client/v4/zones/${ZONE_ID}/dns_records \
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--header 'Content-Type: application/json' \
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--header "Authorization: Bearer $TOKEN")"
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then
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echo "Failed to retrive cloudflare zone records" >&2
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exit 1
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fi
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for i in {0..4000}; do # Assuming 4000 is enough
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record="$(echo "$cf_records" | jq --raw-output ".result[${i}].name")"
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if [[ "$record" == "${HOST}.${DOMAIN}" ]]; then
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host_record="$(echo "$cf_records" | jq -r ".result[${i}]")"
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break
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elif [[ "$record" == null ]]; then
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echo "No record found for ${HOST}.${DOMAIN}" >&2
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exit 1
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fi
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done
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#╔─────────────────────────────────────────────────────────────────────────────╗
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#│ Sετ Λ rεcδrd τδ cμrrεητ WΛN |
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#╚─────────────────────────────────────────────────────────────────────────────╝
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cf_host_ip="$(echo "$host_record" | jq -r '.content')"
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cf_rec_id="$(echo "$host_record" | jq -r '.id')"
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if [[ -z "$cf_host_ip" || "$cf_host_ip" == null ]]; then
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echo "Failed to find content of A record for ${HOST}.${DOMAIN}" >&2
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exit 1
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elif [[ -z "$cf_rec_id" || "$cf_rec_id" == null ]]; then
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echo "Failed to find A record ID for ${HOST}.${DOMAIN}" >&2
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exit 1
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fi
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if [[ "$cf_host_ip" == "$wan_ip" ]]; then
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echo "Cloudflare is up to date @ $(date)" >&2
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else
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echo "Updating Cloudflare's A record from $cf_host_ip to $wan_ip" >&2
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patch_response="$(curl -s --request PATCH \
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--url "https://api.cloudflare.com/client/v4/zones/${ZONE_ID}/dns_records/${cf_rec_id}" \
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--header 'Content-Type: application/json' \
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--header "Authorization: Bearer $TOKEN" \
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--data '{
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"comment": "'"${HOST} @ $(date)"'",
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"content": "'"$wan_ip"'",
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"name": "'"${HOST}.${DOMAIN}"'",
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"proxied": false,
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"ttl": 1
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}')"
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if [[ "$(echo "$patch_response" | jq -r '.success')" == true ]]; then
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echo "Update to $wan_ip succeeded @ $(date)" >&2
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else
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echo "Failed to update A record. DUMP:"
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echo "$patch_response"
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exit 1
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fi
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fi
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```
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Now we need a systemd-timer to run this script. I run it once every 15 minutes.
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Please refer to the [systemd-timers]() blog for more information, but breifly I
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use:
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```ini
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[Unit]
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Wants=update_a_record.timer
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Wants=network-online.target
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After=network-online.target
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[Service]
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Type=oneshot
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ExecStart=/usr/local/bin/set_a_records.sh
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```
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Timer:
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```ini
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[Unit]
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Requires=update_a_record.service
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[Timer]
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Unit=update_a_record.service
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OnCalendar=*-*-* *:00,15,30,45:00
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RandomizedDelaySec=15min
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[Install]
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WantedBy=timers.target
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```
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Then start it with `systemctl enable update_a_record.service`. The name of the
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service will be different based on what you called the files.
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