Can I add external hard drive to start9 server?
Yes, but it would need to be in place during the installation of StartOS. Once installed, there is not currently a way to expand the data drive horizontally. There is a process to move it from one drive to another though (the same process that is used to upgrade your server to a larger drive).
Can I limit the blockchain I am downloading somehow like don’t need all of it right can I say last 200GB of blockchain?
I haven’t used it myself, but there is the option to enable pruning under Config > Advanced
I did pruning but sparrow wallet doesn’t like that setting and wants me to download whole chain. is the core lightning the same thing as a wallet? I don’t think electrum worked either without full bitcoin block chain.
I’ve never rune a pruned node myself. I can say that Knots or Core on Start9 cannot be used as a wallet, though. Behind the scenes, they only run bitcoind (the wallets interface is part of the native bitcoin-qt UI, which does not run on Start9). You will need a wallet software integrated with your node. I don’t know which ones support pruned nodes.
Are you connecting Sparrow up directly to Knots/Core, or are you connecting via electrs? You might try connecting Sparrow through electrs if you haven’t tried that yet.
Actually, NM, it looks like electrs also requires a full node.
Hmm… Sparrow’s documentation actually implies that it supports pruned nodes:
What specific error did Sparrow give you when you tried to connect to your node?
Says recommends electrs over Bitcoin core and can’t get Electrs because it requires all the blockchain
Recommends does not mean requires, though. Electrs is not required for Sparrow. Under File > Settings > Server you can select the Bitcoin Core tab instead of the Private Electrum tab.