Add post on raspi as backup server

content/post/raspi-backup.md

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+---
+title: "Raspberry Pi as Offsite Backup"
+date: 2022-10-23T10:12:54+02:00
+draft: false 
+image: "uploads/logos/raspi_backup.png"
+categrories: ["homelab"]
+tags: ["english"]
+---
+
+
+# Use Case
+
+You have one (or more) servers at a hosting provider and a raspberry pi at home. You want to have an offsite backup of the websites, apps and databases at home.
+
+# Prerequesits
+
+You configure your raspberry pi to be reachable from *the internet* using DynDNS. In the following we assume that it is reachable at offsite.example.com.
+
+# Preparing your backup raspberry pi
+
+We want to make sure that backups on the raspberry pi can come from multiple sources and one source can not delete another. 
+
+## Create an additional user
+
+and change to that user afterwards. You can change service1 to the name of the service that this user should backup.
+
+```
+sudo useradd service1_backup
+sudo su service1_backup
+cd ~
+```
+
+
+## Create an SSH key for the user
+
+This SSH key will later be used by your server to push backups automatically. Therefore you should not set a passphrase for the key (just press enter until the key is generated)
+
+```
+$ ssh-keygen -t ed25519
+```
+
+## Create your backup directory
+
+```
+mkdir backup && cd backup
+```
+
+If you want to use an external drive you can mount it to this users home directory.
+
+## Initialzie the borg repository
+
+```
+borg init --encryption=repokey ./
+```
+
+Make sure to set a strong passphrase and note it down somewhere safe. Without it you will not be able to access you backup!
+
+
+## Make sure the user can only access the backup directory
+
+Put the following in `~/.ssh/authorized_keys` and make sure everything is in one line. The last values are simply your public key that can be found in `~/.ssh/id_ed25519.pub`
+
+```
+command="borg serve --restrict-to-repository /home/<user>/backup",restrict <key type> <key> <key host>
+```
+
+**Done with the raspberry pi**
+
+# Configure your server
+
+In this guide we will use [borgmatic](https://torsion.org/borgmatic/) to configure and automatically run the backup in the server.
+
+## Install borgmatic
+
+```
+sudo pip3 install --user --upgrade borgmatic
+```
+
+## Configure borgmatic
+
+The following is a small configuration example. Place it in `/etc/borgmatic.d/servic1.yaml`. If you need more options check out the [full configuration file reference](https://torsion.org/borgmatic/docs/reference/configuration/)
+
+```
+location:
+    source_directories:
+        - /home/service1/static
+    repositories:
+        - ssh://service1_backup@offsite1.example.com/./backup
+storage:
+    encryption_passphrase: "ThePassphraseouUsedOnYourRaspi"
+    ssh_command: ssh -i /etc/borgmatic.d/service1_backup_key
+retention:
+    # Number of daily archives to keep.
+    keep_daily: 7
+hooks:
+    # List of one or more shell commands or scripts to execute
+    # before creating a backup, run once per configuration file.
+    before_backup:
+        - echo "Starting a backup."
+   # List of one or more shell commands or scripts to execute
+    # after creating a backup, run once per configuration file.
+    after_backup:
+        - echo "Finished a backup."
+    after_everything:
+        - echo "Completed actions."
+
+    postgresql_databases:
+        - name: service1
+    # mysql_databases:
+          # - name: users
+```
+
+
+## Place the private SSH key
+
+The server will need the private SSH key so connect to your raspberry pi
+
+On the raspberry pi use
+
+```
+cat ~/.ssh/id_ed25519
+```
+
+to get the private key and place it on your server in the file `/etc/borgmatic.d/service1_backup_key`.
+As this is a private SSH key it must only be readable by the user. Ro change its permissions correctly use 
+
+```
+chown 600 service1_backup_key
+```
+
+## Check if the backup works
+
+Create your backup with
+
+```
+sudo borgmatic create --verbosity 1 --list --stats
+```
+
+
+Now check out the [borgmatic configuration](https://torsion.org/borgmatic/docs/how-to/set-up-backups/#autopilot) on how to properly set up automated backups
+
+
+# Done
+
+Congrats, you should now have a fully functioning backup configuration!
+
+{{< chat raspi-backup>}}