Problem with prune mode

[BlackHatCoiner]

I have tried running bitcoin core in prune mode, but it seems that it'll take hours to finish syncing. Am I surely pruning and not syncing on a full node?





What is going on? This is my bitcoin.conf:

Code:

prune=550

I'm generally experimenting with Bitcoin Core these days, so excuse me for any "dumb" questions.

[ranochigo]

Pruning doesn't mean that the Core doesn't have to synchronize from the start. The synchronization is still done to validate and build the chainstate, same as with any other full node but the main difference is only with the fact that Core will discard blocks to maintain the buffer as indicated.

You can go to Settings>Options and check if the configuration is active.

[BlackHatCoiner]

Pruning doesn't mean that the Core doesn't have to synchronize from the start. The synchronization is still done to validate and build the chainstate, same as with any other full node but the main difference is only with the fact that Core will discard blocks to maintain the buffer as indicated.

Oh okay, I confused it with something else. I thought that on pruning you're trusting other nodes to send you their last blocks. This is why it seemed weird, that's against the "Verify, don't trust" principles. Does the option exist btw?

You can go to Settings>Options and check if the configuration is active.

Yep.

[ranochigo]

Oh okay, I confused it with something else. I thought that on pruning you're trusting other nodes to send you their last blocks. This is why it seemed weird, that's against the "Verify, don't trust" principles. Does the option exist btw?

Nope. I don't think they would incorporate it right into the client.

You can probably get the pre-validated files from somewhere on the internet but there isn't any guarantees about its authenticity or any possible problems arising with it.

**Note that the pre-validated files has to be downloaded as it is, the entire 300GB without any pruning done or Bitcoin Core will ask you to reindex again when importing your own wallet.dat.

[ranochigo]

Reindex? Do you mean rescan blockchain since the index for UTXO should be exist?

If the downloaded files are already pruned, then it wouldn't be possible for the user's wallet to be imported and be able to see all the transactions without the client reindexing.

[BlackHatCoiner]

Why should one rescan the entire blockchain? And what does reindex do?

[ABCbits]

Reindex? Do you mean rescan blockchain since the index for UTXO should be exist?

If the downloaded files are already pruned, then it wouldn't be possible for the user's wallet to be imported and be able to see all the transactions without the client reindexing.

You're right, i forgot Bitcoin Core need to obtain transaction history, not only list of UTXO. But i think "redownload whole blockchain" is more accurate than "reindex"

Why should one rescan the entire blockchain?

Usually you do it when open existing wallet.dat or import private key/address to obtain all transaction history. On Bitcoin Core, you use command

Code:

rescanblockchain ( start_height stop_height )

And what does reindex do?

Reindex means re-creating index of UTXO from existing blockchain files. Usually happen if files inside chainstate folder is corrupted/removed.

[LoyceV]

You can probably get the pre-validated files from somewhere on the internet but there isn't any guarantees about its authenticity or any possible problems arising with it.

I made a topic about this in 2019: Bitcoin Core pruned blockchain: download it here! (DON'T DO THIS!), but stopped updating it. My latest pruned files are over 14 months old now.

There was consensus on the title:

yep, don't do this

Yes, don't do this!

Just in case it wasn't clear yet:

It's NOT recommended to download the blockchain any other way than having Bitcoin Core download it on it's own. Don't do it! Seriously, don't!
~
On Reddit, theymos wrote this 3 years ago:

This is massively insecure. Bitcoin Core trusts its block database files absolutely. /u/nullc has said that it is not particularly unlikely that a maliciously-modified block database could be used for arbitrary code execution. And even if that's not possible, all sorts of more obvious evil could be done, such as allowing the provider of the block database to create a special killswitch transaction which forks everyone who used his block database, or having everyone who used his block database think that he actually owns 22 million BTC.

Nobody should ever receive block database files from untrusted sources.

Also see: https://en.bitcoin.it/wiki/Data_directory#Transferability

So again: don't do it!

[tranthidung]

I have tried running bitcoin core in prune mode, but it seems that it'll take hours to finish syncing. Am I surely pruning and not syncing on a full node?

Others answered you and I see you got troubles as same as me in the past.

• I did not have too many free data space for full node.
• With prune node, it eats up my computer capacity
• I gave up and don't consider to use full or prune node because of this
• I did not get troubles with prune node and have to re-sync it from genesis block but I did experienced it with altcoin wallets. Therefore, I know what the trouble is. Remember that synchronization with altcoin wallets are faster than bitcoin prune node
• Pros and Cons of Bitcoin Node types (Full node and Prune node) (some good discussions, on chainstates)

[NotATether]

Just in case it wasn't clear yet:

It's NOT recommended to download the blockchain any other way than having Bitcoin Core download it on it's own. Don't do it! Seriously, don't!
~
On Reddit, theymos wrote this 3 years ago:

This is massively insecure. Bitcoin Core trusts its block database files absolutely. /u/nullc has said that it is not particularly unlikely that a maliciously-modified block database could be used for arbitrary code execution. And even if that's not possible, all sorts of more obvious evil could be done, such as allowing the provider of the block database to create a special killswitch transaction which forks everyone who used his block database, or having everyone who used his block database think that he actually owns 22 million BTC.

Nobody should ever receive block database files from untrusted sources.

Also see: https://en.bitcoin.it/wiki/Data_directory#Transferability

So again: don't do it!

A question about the quote from theymos you posted: if one person downloads tampered-with block files and loads them on his node, and tries to spend outputs that do not exist from a transaction containing inputs he is able to sign, his node may view them as invalid, but won't the rest of the network reject those transactions, and continuing to send other nodes those invalid transactions cause the node's IP to be banned?

It means that downloading block files this way will ultimately get you kicked off of most of the network's nodes.

[ranochigo]

A question about the quote from theymos you posted: if one person downloads tampered-with block files and loads them on his node, and tries to spend outputs that do not exist from a transaction containing inputs he is able to sign, his node may view them as invalid, but won't the rest of the network reject those transactions, and continuing to send other nodes those invalid transactions cause the node's IP to be banned?

It means that downloading block files this way will ultimately get you kicked off of most of the network's nodes.

The security risk isn't with the person spending phantom UTXOs but it's with someone relaying it to that specific client and tricking them to take the transaction as valid even though it'll never be confirmed. It's a good way to force a sybil attack on someone though, if they get kicked off the other network.

[BlackHatCoiner]

I want to ask another question about prune mode. The folder "Bitcoin" on Roaming is 4.56 GB, but on Bitcoin Core it says that after 2GB it discards the old blocks. What are the other 2.56 GBs that it keeps?

Also: My free storage space was 54GBs yesterday, but once I left Bitcoin Core opened to prune the blockchain, I saw that free space was slowly decreasing. Right now I only have 46.6GBs available. Does it store any additional information somewhere?

[LoyceV]

What are the other 2.56 GBs that it keeps?

The pruned size is for the blocks directory, you still need the chainstate directory. My chainstate is currently 4.0 GB.