I took a deeper research into this and it looks like every you interact on there is temporary (Other than storing data on your drive). To change something like crontab you will have to edit “config.xml” located “/usr/local/config” .
… which I believe the WD firmware checksums the entire read-only partition and it does not like the user modifying the read-only partition. You could end up bricking your PR4100 is you mess the read only firmware partition.
I’ve got mine running a few apps not from WD, but I’m using entware to achieve this.
I would advise not to mess with WD’s own firmware. Entware survives WD’s firmware updates and if you alter the core firmware it’s possible the next firmware release could brick your NAS. I think what WD does is install an image over what’s already in protected storage so any alterations would be removed.
Watching processes that run using htop (obtained from Entware software library) there seems to be a periodic check of the core firmware and some process that checks a checksum so I guess some sort of fail-safe may be triggered if the user updates the core firmware without recalculating the check-sum.
Invoke the program mtd_check. It’ll perform some checks and show you the checksums.
I guess it’s best to use Entware. Powerful small facility. Allows me to use the likes of tmux, a persistent home folder for root, use of qbtorrent, SoftEther VPN backup to the one running on a SoC board I have, etc…