chore(server): add example on how to re-create server from backup (#340)

examples/create_and_restore_backup.md

@@ -0,0 +1,100 @@
+# Backup a server and re-create it using the backup
+
+This example demonstrates how to backup a server with `upctl` and use the created backup to re-create the server.
+
+To keep track of resources created during this example, we will use common prefix in all resource names.
+
+```env
+prefix=example-upctl-backup-
+```
+
+We will first create a ssh-key into the current working directory for configuring an nginx server via SSH connection.
+
+```sh
+ssh-keygen -t ed25519 -q -f "./id_ed25519" -N "" -C "upctl example"
+```
+
+We will then create a server with a single network interface and default template settings.
+
+```sh
+upctl server create \
+    --hostname ${prefix}source-server \
+    --zone pl-waw1 \
+    --ssh-keys ./id_ed25519.pub \
+    --network type=public \
+    --wait
+```
+
+To have something to backup, we will install a nginx server and configure a non-default HTML content to serve.
+
+```sh filename=configure-nginx.sh
+#!/bin/sh -xe
+
+apt install nginx -y
+echo "Hello from $(hostname)"'!' > /var/www/html/index.html
+```
+
+To configure the server, we will parse the public IP of the server and run the above script using SSH connection. We can then use `curl` to ensure that the HTTP server serves the content we defined.
+
+```sh
+# Parse public IP of the server with jq
+ip=$(upctl server show ${prefix}source-server -o json | jq -r '.networking.interfaces[] | select(.type == "public") | .ip_addresses[0].address')
+
+# Wait for a moment for the ssh server to become available
+sleep 30
+
+# Run the script defined above
+ssh -i id_ed25519 -o StrictHostKeyChecking=accept-new root@$ip "sh" < configure-nginx.sh
+
+# Validate HTTP server response
+test "$(curl -s $ip)" = 'Hello from example-upctl-backup-source-server!'
+```
+
+We will then backup the OS disk of the created server.
+
+```sh
+upctl storage backup create ${prefix}source-server-OS --title ${prefix}source-server-backup
+```
+
+After creating the backup, we can delete the source server and its storages.
+
+```sh
+upctl server stop --type hard --wait ${prefix}source-server
+upctl server delete ${prefix}source-server --delete-storages
+```
+
+We can then create a new server based on the backup of the source servers disk.
+
+```sh
+upctl server create \
+    --hostname ${prefix}restored-server \
+    --zone pl-waw1 \
+    --ssh-keys ./id_ed25519.pub \
+    --network type=public \
+    --storage action=clone,storage=${prefix}source-server-backup \
+    --wait
+```
+
+To validate that the server was re-created successfully, we will parse the public IP of the server and use curl to see that the HTTP server is running.
+
+```sh
+# Parse public IP of the server with jq
+ip=$(upctl server show ${prefix}restored-server -o json | jq -r '.networking.interfaces[] | select(.type == "public") | .ip_addresses[0].address')
+
+# Wait until server returns expected response
+for i in $(seq 1 9); do
+    test "$(curl -s $ip)" = 'Hello from example-upctl-backup-source-server!' && break || true;
+    sleep 15;
+done;
+```
+
+Finally, we can cleanup the created resources.
+
+```sh
+# Delete the restored server and its storages
+upctl server stop --type hard --wait ${prefix}restored-server
+upctl server delete ${prefix}restored-server --delete-storages
+
+# Delete the backup
+upctl storage delete ${prefix}source-server-backup
+```