There are options to download some parts of it only and trust the rest. But by downloading all blocks, you can verify all transactions without needing to trust someone else. You need all previous transactions because how the Blockchain technology works with each block referencing the previous one.
This.
Also, if you already have downloaded the whole blockchain and are spinning up another node for whatever reason, you can just strait copy the blockchain files from one node to the other.
For a LN node, especially if is a public node, is better to have full sync.
But if you run it on a limited machine, you could use those mentioned methods. LN only needs to link to a source of blocks to verify and sync the graph and txs. Nothing else.
There are options to download some parts of it only and trust the rest. But by downloading all blocks, you can verify all transactions without needing to trust someone else. You need all previous transactions because how the Blockchain technology works with each block referencing the previous one.
You don't have to. You could use Neutrino or SPV sync or even trustedcoin plugin by fiatjaf https://github.com/nbd-wtf/trustedcoin
This. Also, if you already have downloaded the whole blockchain and are spinning up another node for whatever reason, you can just strait copy the blockchain files from one node to the other.
What are the downside of this
all depends what do you want to do
Self custody
long term? short term? cold storage? LN node?
Mid-term Ln node
For a LN node, especially if is a public node, is better to have full sync. But if you run it on a limited machine, you could use those mentioned methods. LN only needs to link to a source of blocks to verify and sync the graph and txs. Nothing else.
Also if you have a private LN node, you don't really need to run a full BTC node and a LN node. Check my guides about private LN nodes: https://darthcoin.substack.com/p/private-lightning-nodes
Good So i can self custody without downloading hundred of Gbs
There are ways around this as already mentioned. But it comes back to 'dont trust, verify'.
That means verifying every block.
What are the downside of using another node files ?
If it is a source you trust, none.
In theory (never done this myself), you could copy the block file themselves and get the new node to validate them.