Hello,
I would like to perform some analysis on a secondary virtual machine's hard drive, but don't want to accidentally alter the data. Is there a way to set a virtual machine's hard drive read-only in proxmox, or within the conf file please?
Not really through our GUI. You could create a clone of the VM, or a snapshot and roll back afterwards. Also there is a 'kiosk mode' that could be set (see the link). https://bugzilla.proxmox.com/show_bug.cgi?id=894