From where does a node download a copy of the ledger

Question

From where does a node download the latest copy of ledger initially? Is this information stored in a 'central server'?

Let's say a node is offline for a while, after coming back how will the node get to know the ledger is up-to-date or not?

Answer 1

Good question, This is a quote from article that i have just read, where its described in a pretty simple way:

Now when you first open up a Full Node client like Bitcoin Core, most people are sitting behind a firewall. In this case, your Full Node is limited in the number of connections it can connect to (around 8) and only looks for Super Nodes a.k.a. Listening Nodes. The reason for this is because your Full Node isn’t publicly connectable yet.

In a distributed network, a Super Node functions as a highly connected redistribution point as well as a relay station. Therefore this would be an appropriate term to describe a publicly connectable Full Bitcoin Node. This means many nodes can connect to it to obtain relayed transactional data and blockchain history.

Original article: https://hackernoon.com/lets-talk-about-bitcoin-nodes-e9502193198c

So basically you get your data from publicly connectable Full Bitcoin Nodes

Answer 2

The very word 'node' means there's no servers and clients, every running software is equivalent. No 'central' anything, Bitcoin was created to be a decentralized system. The initial copy and any future updates can be donwloaded from any other node.