With the most recent versions of FreeNAS the only way to install additional software is through jails. Installing the Amanda client directly under FreeNAS is not supported.
If you don't need to do ZFS send/recieve you can install the plug-in in a jail and then add access for that jail to your storage.
If you're not keen on monkeying around in the internals of your FreeNAS box, you'll probably be reduced to doing the backup the same way that Windows boxes were backed up for many years: mount the shares on a box that can run the Amanda client, and then back the data up from there. Messy, but it works well enough.
With the most recent versions of FreeNAS the only way to install additional software is through jails. Installing the Amanda client directly under FreeNAS is not supported.
If you don't need to do ZFS send/recieve you can install the plug-in in a jail and then add access for that jail to your storage.
This discussion on the FreeNAS forum covers this exact topic.
As I understand it, FreeNAS is based on FreeBSD, so you'd presumably be able to install the Amanda client for FreeBSD somehow.
If you're not keen on monkeying around in the internals of your FreeNAS box, you'll probably be reduced to doing the backup the same way that Windows boxes were backed up for many years: mount the shares on a box that can run the Amanda client, and then back the data up from there. Messy, but it works well enough.