I don't know if anyone else will find a need for a backup script specific to Onboot.lst's, but considering I found the script indispensable in saving various custom Onboot.lst configurations I figured someone may one day find this script answer their needs.
I named it Onboot_sos SOS for Save On Shutdown, among other things.
Ok this script supports standard or multiple custom Onboot.lst's and performs these functions in this order
1. On first run creates a backup of the original Onboot.lst to a hidden file then sets permissions to prevent inadvertent deletion
2. creates a backup of the current Onboot.lst
3. maintains only the the most recent 9 backups, rotating old backups beyond 9 out to the trash on each subsequent backup creation.
4. Sorts the contents of current Onboot.lst(s) alphabetically
This backup script has functioned successfully to the point where I made an extension with a startup script which adds the backup command to shutdown.sh, effectively creating a new backup efficiently on each shutdown.
If anyone would like to try the extension please pm me, meanwhile the script is attached.
I wondered whether 9 backups was a little to much, but it has saved the day more than once being able to restore a previous onboot configuration after messing up an onboot lst. You don't expect this to happen, but stuff happens when you least expect it.
Note: some level of tce persistence is obviously required (at minimum a tce directory installed to a drive).
As always, feedback, suggestions is welcome.