feat: drive domain from DOMAIN env var -- no manual find-and-replace

Previously every example.com had to be found and replaced manually.
Now a single DOMAIN=yourdomain.com in .env propagates everywhere:

- .env.example: add DOMAIN=example.com with explanation
- docker-compose.yml: pass DOMAIN into authelia container environment
- authelia/configuration.yml: use {{ env "DOMAIN" }} in totp.issuer,
  access_control.rules, and all four session.cookies[] fields
  (Authelia 4.38+ Go template substitution)
- caddy/Caddyfile: use {env.DOMAIN} in all site block addresses
  (Caddy native env substitution); update header comment explaining
  how to set DOMAIN for system vs dockerized Caddy
- README.md: update step 3 to explain DOMAIN is the only change needed;
  update step 4 to say just uncomment the right rule; update Caddy
  wiring section with DOMAIN env var instructions for both Caddy modes

https://claude.ai/code/session_012eTokAaGiZo7aGt1T2W9BC

.env.example

@@ -4,6 +4,14 @@
 # so they can be mounted into the container without env-var leakage. This
 # .env only holds non-secret tunables.
 
+# ---------------------------------------------------------------------------
+# Your root domain. This single value flows into authelia/configuration.yml
+# (via Authelia's {{ env "DOMAIN" }} template substitution) and into
+# caddy/Caddyfile (via Caddy's {env.DOMAIN} substitution).
+# No manual find-and-replace needed -- just set this.
+# ---------------------------------------------------------------------------
+DOMAIN=example.com
+
 # Pin your image versions. Bump to current stable when you upgrade --
 # check https://github.com/authelia/authelia/releases and
 # https://github.com/crazy-max/docker-fail2ban/releases.

README.md

@@ -209,15 +209,15 @@ openssl rand -hex 32 > authelia/secrets/SESSION_SECRET
 openssl rand -hex 32 > authelia/secrets/STORAGE_ENCRYPTION_KEY
 chmod 600 authelia/secrets/*
 
-# 3) Copy and edit .env.
+# 3) Copy and edit .env -- this is the only place you set your domain.
+#    DOMAIN flows into authelia/configuration.yml and caddy/Caddyfile
+#    automatically via each tool's env-var substitution; no find-and-replace.
 cp .env.example .env
-$EDITOR .env    # set TZ; pin AUTHELIA_VERSION if you want
+$EDITOR .env    # set DOMAIN, TZ; pin image versions if you want
 
-# 4) Edit authelia/configuration.yml.
+# 4) Uncomment access_control.rules in authelia/configuration.yml for the
-#    Replace every `example.com` with your real root domain.
+#    sites you want to gate. The domain is already templated -- just
-#    Look for the four CHANGE comments: totp.issuer, session.cookies[].domain,
+#    uncomment the right case block and choose one_factor or two_factor.
-#    session.cookies[].authelia_url, session.cookies[].default_redirection_url.
-#    Also uncomment access_control.rules entries for the sites you want to gate.
 $EDITOR authelia/configuration.yml
 
 # 5) Create your first user.
@@ -254,11 +254,23 @@ Open `caddy/Caddyfile`. It defines:
 - `(authelia)` -- reusable snippet: add `import authelia` to any site block.
 - `(accesslog)` -- writes Caddy's JSON access log to `/var/log/caddy/access.log`
   so fail2ban's `caddy-4xx` jail can watch it.
-- `auth.example.com` -- the Authelia portal.
+- `auth.{env.DOMAIN}` -- the Authelia portal.
-- Example site blocks for all four cases (cases 1-3 active, case 4 commented).
+- Example site blocks for all four cases.
 
-Copy the relevant blocks into your real Caddyfile, replace `example.com` with
+Copy the relevant blocks into your real Caddyfile and replace `192.168.x.x`
-your domain and `192.168.x.x` with real upstream IPs, then reload Caddy.
+with real upstream IPs. The domain is already templated as `{env.DOMAIN}` --
+just make sure the `DOMAIN` environment variable is available to Caddy:
+
+```bash
+# Dockerized Caddy -- add to its .env or compose environment:
+DOMAIN=yourdomain.com
+
+# System Caddy -- add to /etc/caddy/caddy.env (or wherever systemd reads env):
+echo 'DOMAIN=yourdomain.com' | sudo tee -a /etc/caddy/caddy.env
+# Then make sure the systemd unit loads it:
+# EnvironmentFile=/etc/caddy/caddy.env  (in the [Service] section)
+sudo systemctl daemon-reload && sudo systemctl reload caddy
+```
 
 **Every** site block should have `import accesslog` -- even case 4 sites.
 fail2ban's caddy-4xx jail watches the one log file and covers all your

authelia/configuration.yml

@@ -11,6 +11,10 @@
 # Secrets are NOT in this file. They are loaded from files mounted at
 # /secrets via the AUTHELIA_*_FILE env vars in docker-compose.yml.
 #
+# Your domain comes from the DOMAIN variable in .env -- no manual
+# find-and-replace needed. Authelia 4.38+ processes this file as a Go
+# template, so {{ env "DOMAIN" }} is substituted at startup.
+#
 # After editing, validate before restarting:
 #   docker compose run --rm authelia authelia validate-config --config /config/configuration.yml
 ###############################################################################
@@ -37,7 +41,7 @@ identity_validation:
 
 totp:
   disable: false
-  issuer: 'example.com'      # CHANGE: your root domain (shown in authenticator app)
+  issuer: '{{ env "DOMAIN" }}'   # shown in your authenticator app
   algorithm: 'sha1'
   digits: 6
   period: 30
@@ -75,8 +79,6 @@ authentication_backend:
 # ---------------------------------------------------------------------------
 # WHICH SITES NEED A RULE HERE?
 #
-# There are four ways a site can relate to Authelia:
-#
 # CASE 1 -- App has NO built-in auth (e.g. Pi doorbell PTT page).
 #   -> Rule required + `import authelia` in Caddy.
 #   -> Authelia is the ONLY login. Use two_factor for hardware-control pages.
@@ -104,7 +106,7 @@ access_control:
   rules:
 
     # The Authelia portal itself is always bypass.
-    - domain: 'auth.example.com'                # CHANGE
+    - domain: 'auth.{{ env "DOMAIN" }}'
       policy: 'bypass'
 
     # -------------------------------------------------------------------
@@ -112,24 +114,24 @@ access_control:
     # The Pi doorbell PTT page has no built-in authentication.
     # two_factor is appropriate -- this URL controls a speaker in your house.
     # -------------------------------------------------------------------
-    # - domain: 'doorbell.example.com'          # CHANGE
+    # - domain: 'doorbell.{{ env "DOMAIN" }}'
     #   policy: 'two_factor'
 
     # -------------------------------------------------------------------
     # CASE 2: App supports trusted-header proxy auth -- replace app login.
-    # Frigate 0.14+: set `auth.enabled: False` and configure `proxy:` in
+    # Frigate: set auth.enabled: False and configure proxy: in
-    # frigate_config/config.yml (see README.md "Switching Frigate to Authelia").
+    # frigate_config/config.yml (see README.md). Authelia handles login
-    # Single login: Authelia authenticates, Frigate reads Remote-User/Groups.
+    # and passes Remote-User/Remote-Groups to Frigate for role mapping.
     # -------------------------------------------------------------------
-    # - domain: 'cam.example.com'               # CHANGE
+    # - domain: 'cam.{{ env "DOMAIN" }}'
     #   policy: 'two_factor'
 
     # -------------------------------------------------------------------
     # CASE 3: App keeps its own auth; Authelia adds a 2FA gate in front.
-    # The app's login form is still shown after Authelia passes the request.
+    # User authenticates with Authelia (2FA) then with the app itself.
-    # User logs into Authelia (2FA) then into the app separately.
+    # Add entries for any extra-gated domains here.
     # -------------------------------------------------------------------
-    # - domain: 'nas.example.com'               # CHANGE/REMOVE example
+    # - domain: 'nas.{{ env "DOMAIN" }}'
     #   policy: 'two_factor'
 
     # CASE 4: No rule here, no `import authelia` in Caddy. App handles auth.
@@ -138,9 +140,9 @@ session:
   # secret loaded via AUTHELIA_SESSION_SECRET_FILE
   cookies:
     - name: 'authelia_session'
-      domain: 'example.com'                          # CHANGE: your root domain
+      domain: '{{ env "DOMAIN" }}'
-      authelia_url: 'https://auth.example.com'       # CHANGE
+      authelia_url: 'https://auth.{{ env "DOMAIN" }}'
-      default_redirection_url: 'https://example.com' # CHANGE
+      default_redirection_url: 'https://{{ env "DOMAIN" }}'
       expiration: '1 hour'
       inactivity: '5 minutes'
       remember_me: '1 month'

caddy/Caddyfile

@@ -2,7 +2,7 @@
 # Caddyfile -- Authelia + fail2ban integration
 #
 # Copy this file into your Caddy setup (or merge the relevant blocks into
-# your existing Caddyfile), edit all placeholders, then reload:
+# your existing Caddyfile), then reload:
 #
 #   # System Caddy:
 #   sudo caddy validate --config /etc/caddy/Caddyfile
@@ -11,9 +11,16 @@
 #   # Dockerized Caddy:
 #   docker compose exec caddy caddy reload --config /etc/caddy/Caddyfile
 #
-# Placeholders to replace:
+# Domain is read from the DOMAIN environment variable -- no hardcoded
-#   example.com     -> your real root domain
+# domains in this file. Set it in your Caddy environment before reloading:
-#   192.168.x.x     -> real upstream LAN IPs
+#
+#   # System Caddy (add to /etc/caddy/caddy.env or your systemd override):
+#   export DOMAIN=yourdomain.com
+#
+#   # Dockerized Caddy (add to its .env or compose environment:):
+#   DOMAIN=yourdomain.com
+#
+# Only the upstream IPs need editing: replace 192.168.x.x with real LAN IPs.
 #
 # Requirements:
 #   - Caddy v2.5.1+ (for `forward_auth` directive; tested on v2.11.2)
@@ -90,38 +97,11 @@
 # access_control.rules handles the portal itself. Adding forward_auth here
 # would cause a redirect loop.
 # =============================================================================
-auth.example.com {                                    # CHANGE
+auth.{env.DOMAIN} {
     import accesslog
     reverse_proxy authelia:9091
 }
 
-# =============================================================================
-# CASE 1: Pi doorbell PTT page -- Authelia is the ONLY auth.
-#
-# The Pi's Flask server has no built-in authentication. Authelia gates it.
-# two_factor is appropriate -- this URL controls a speaker in your house.
-# Comment out until the Pi is deployed.
-# Also add (or uncomment) the doorbell.example.com rule in configuration.yml.
-# =============================================================================
-# doorbell.example.com {                              # CHANGE
-#     import accesslog
-#     import authelia
-#
-#     # Same-origin proxy to Frigate so WebRTC fetch works without CORS.
-#     handle_path /frigate/* {
-#         reverse_proxy 192.168.x.x:8971 {
-#             transport http {
-#                 read_timeout  60s
-#                 write_timeout 60s
-#             }
-#         }
-#     }
-#
-#     handle {
-#         reverse_proxy 192.168.x.x:5555
-#     }
-# }
-
 # =============================================================================
 # CASE 2: Frigate UI -- Authelia replaces Frigate's own login form.
 #
@@ -147,11 +127,11 @@ auth.example.com {                                    # CHANGE
 #     # Set the same value as header_up X-Proxy-Secret below.
 #     # auth_secret: 'your-32-byte-hex'
 #
-# Then uncomment the cam.example.com rule in authelia/configuration.yml
+# Then uncomment the cam rule in authelia/configuration.yml and restart:
-# and restart: docker compose restart authelia  (in the authelia stack)
+#   docker compose restart authelia  (in the authelia stack)
-#              docker compose restart frigate   (in the camera stack)
+#   docker compose restart frigate   (in the camera stack)
 # =============================================================================
-cam.example.com {                                     # CHANGE
+cam.{env.DOMAIN} {
     import accesslog
     import authelia
 
@@ -165,6 +145,33 @@ cam.example.com {                                     # CHANGE
     }
 }
 
+# =============================================================================
+# CASE 1: Pi doorbell PTT page -- Authelia is the ONLY auth.
+#
+# The Pi's Flask server has no built-in authentication. Authelia gates it.
+# two_factor is appropriate -- this URL controls a speaker in your house.
+# Comment out until the Pi is deployed.
+# Also uncomment the doorbell rule in authelia/configuration.yml.
+# =============================================================================
+# doorbell.{env.DOMAIN} {
+#     import accesslog
+#     import authelia
+#
+#     # Same-origin proxy to Frigate so WebRTC fetch works without CORS.
+#     handle_path /frigate/* {
+#         reverse_proxy 192.168.x.x:8971 {           # CHANGE IP
+#             transport http {
+#                 read_timeout  60s
+#                 write_timeout 60s
+#             }
+#         }
+#     }
+#
+#     handle {
+#         reverse_proxy 192.168.x.x:5555             # CHANGE IP
+#     }
+# }
+
 # =============================================================================
 # CASE 3: App keeps its own login; Authelia adds a 2FA gate in front.
 #
@@ -173,10 +180,10 @@ cam.example.com {                                     # CHANGE
 # form appears. Two separate logins -- the app's auth is untouched.
 #
 # Also add a rule in authelia/configuration.yml:
-#   - domain: 'nas.example.com'
+#   - domain: 'nas.{{ env "DOMAIN" }}'
 #     policy: 'two_factor'
 # =============================================================================
-# nas.example.com {                                   # CHANGE/REMOVE example
+# nas.{env.DOMAIN} {                                 # CHANGE/REMOVE example
 #     import accesslog
 #     import authelia
 #
@@ -193,7 +200,7 @@ cam.example.com {                                     # CHANGE
 # No `import authelia`. No access_control rule in Authelia.
 # Still import accesslog so fail2ban's caddy-4xx jail covers this site.
 # =============================================================================
-# router.example.com {                               # CHANGE/REMOVE example
+# router.{env.DOMAIN} {                              # CHANGE/REMOVE example
 #     import accesslog
 #     reverse_proxy 192.168.x.x:PORT {              # CHANGE
 #         transport http {

docker-compose.yml

@@ -34,6 +34,9 @@ services:
       - AUTHELIA_SESSION_SECRET_FILE=/secrets/SESSION_SECRET
       - AUTHELIA_STORAGE_ENCRYPTION_KEY_FILE=/secrets/STORAGE_ENCRYPTION_KEY
       - TZ=${TZ:-UTC}
+      # Passed through so authelia/configuration.yml can use {{ env "DOMAIN" }}
+      # instead of hardcoding your domain in the config file.
+      - DOMAIN=${DOMAIN}
     volumes:
       - ./authelia:/config
       - ./authelia/secrets:/secrets:ro