make settings configurable via environment variables set externally

README.md

@@ -7,7 +7,10 @@ The script uses the package [`libguestfs-tools`](https://libguestfs.org)' `virt-
 ## Building the Template
 
 ### Configuration Options
-Verify that the settings at the beginning of the script are suitable to the cluster you want to create the template from.
+
+The following settings are available for configuration by setting the respective environment variable.
+Verify that the configured settings are suitable for the cluster you want to create the template for.  
+If left unset, the respective default value will be used.
 
 | Variable  | Default                                 | Description                                                            |
 | --------- | --------------------------------------- | ---------------------------------------------------------------------- |

build-proxmox-template

@@ -5,11 +5,11 @@
 # Needs apt install libguestfs-tools
 #
 
-VMID=9023
-STORAGE=local-zfs
-OS=debian-12
-NAME=chaos-${OS}-tmpl-$(date -u +%Y-%m-%d)
-BRIDGE=vmbr0,tag=208
+: "${VMID:=9023}"
+: "${STORAGE:=local-zfs}"
+: "${OS:=debian-12}"
+: "${NAME:=chaos-${OS}-tmpl-$(date -u +%Y-%m-%d)}"
+: "${BRIDGE:=vmbr0,tag=208}"
 
 set -eE