I ran this:
qm set 114 --scsi1 [storage-name]:101/vm-101-disk-1.qcow2,backup=0
Which made a visible change on the web interface in that a second line appeared below the original hard disk configuration line (the original hard disk configuration has the "Backup" box checked by default). That line was "yellow", included the backup=0 and if I clicked the drive there it had a "Revert" button. (It also didn't work, in the sense that if I take a backup it backs up that drive too.)

Nothing I could find (command line wise) would actually apply those changes although this:
https://pve.proxmox.com/pve-docs/qm.1.html
seemed to indicate that it would just work "...better to use the qm command... instantaneously apply most changes to running VM... no need to restart the VM".
Eventually I did vm stop and vm start on that VM. That committed the changes. BUT that also makes further changes not need the stop/start. If I run the same command and set "backup=1" it changes immediately in the web interface (no yellow line, no stop and start), and I can toggle it back and forth from 0 to 1 repeatedly now.
Why? (IE - What becomes different after the one stop/start that allows the instant apply changes, and can anything take that away again, like another reboot for example?)
Thanks.
Just for background (since someone might wonder why I care):
I am looking for a way to take two separate backups of a Proxmox virtual machine (I do not have Proxmox Backup Server, this would just use mounted storage from Proxmox itself).
In one of the backups I want the whole machine.
In the other I want the whole machine, minus one of the hard disks (the storage part of the server, with user-made changes).
(One backup is for "the whole thing crashed, I just need it back" and the other is for "this is an OS issue, I want the OS back, pre-event, but I want all of the server's files current till the moment it I start restoration".)
I have not found a way to do this yet but the idea that got me to this thread was that perhaps I could script/cron "backup=0/backup=1" changes to the disk (timed for when I want each kind of backup).
qm set 114 --scsi1 [storage-name]:101/vm-101-disk-1.qcow2,backup=0
Which made a visible change on the web interface in that a second line appeared below the original hard disk configuration line (the original hard disk configuration has the "Backup" box checked by default). That line was "yellow", included the backup=0 and if I clicked the drive there it had a "Revert" button. (It also didn't work, in the sense that if I take a backup it backs up that drive too.)

Nothing I could find (command line wise) would actually apply those changes although this:
https://pve.proxmox.com/pve-docs/qm.1.html
seemed to indicate that it would just work "...better to use the qm command... instantaneously apply most changes to running VM... no need to restart the VM".
Eventually I did vm stop and vm start on that VM. That committed the changes. BUT that also makes further changes not need the stop/start. If I run the same command and set "backup=1" it changes immediately in the web interface (no yellow line, no stop and start), and I can toggle it back and forth from 0 to 1 repeatedly now.
Why? (IE - What becomes different after the one stop/start that allows the instant apply changes, and can anything take that away again, like another reboot for example?)
Thanks.
Just for background (since someone might wonder why I care):
I am looking for a way to take two separate backups of a Proxmox virtual machine (I do not have Proxmox Backup Server, this would just use mounted storage from Proxmox itself).
In one of the backups I want the whole machine.
In the other I want the whole machine, minus one of the hard disks (the storage part of the server, with user-made changes).
(One backup is for "the whole thing crashed, I just need it back" and the other is for "this is an OS issue, I want the OS back, pre-event, but I want all of the server's files current till the moment it I start restoration".)
I have not found a way to do this yet but the idea that got me to this thread was that perhaps I could script/cron "backup=0/backup=1" changes to the disk (timed for when I want each kind of backup).