Nodeos provides various options for replaying blockchain blocks. This can be useful if, for example, a node has downloaded a blocks.log file from the internet (as a faster alternative to synchronizing from the p2p network) and the node wants to use it to quickly catch up with the network, or if you want to know the chain state at specified points in a blockchain's life.

Replaying data can be done in two ways:

• Replay from a snapshot and blocks.log file
• Replay from a V1 History archive

Replay from a snapshot and blocks.log file

Snapshot files can be created from a running nodeos instance. The snapshot contains the chain state for the block referenced when created. It is recommended to use snapshot files created from blocks that are irreversible. Using a snapshot file to replay allows you to quickly start a nodeos instance which has a full and correct chain state at a specified block number.

If you want a full history of transactions up to that block number, you will also need to install the blocks.log file that contains all irreversible transactions on the blockchain. All instances of nodeos write irreversible blocks to the blocks.log file, which is located at the data/blocks directory relative to the nodeos directory. Using a blocks.log file to replay will allow you to start a nodeos instance, which recreates the entire history of the blockchain locally, without adding unnecessary load to the network.

When replaying from a snapshot and a blocks.log file, the blocks.log file must at least contain blocks up to the snapshotted block and may contain additional blocks that will be applied as part of startup. If a blocks.log file is included, but does not contain blocks up to and/or after the snapshotted block then replaying from a snapshot will create an exception.

1. Remove the existing contents of the data, history, and history_index directories. Make sure you back up any existing contents if you wish to keep them.

cd /var/lib
sudo rm -fr fio/data fio/history fio/history_index

2. Obtain a copy of the snapshot and blocks.log files which you wish to replay the blockchain from. Several BPs maintain FIO snapshots for both Testnet and Mainnet. It is important that you trust the source of the snapshot before downloading. We will use the Blockpane history archive in our examples.

wget https://snap.blockpane.com/mainnet-latest-blocks.txz

3. Extract the snapshot to your data/snapshots directory, your blocks.log file to your data/blocks directory, and update the permissions on fio directory. The tar extraction will take several minutes.

sudo apt install pixz
sudo tar -xS -I'pixz' -C /var/lib/fio -f mainnet-latest-blocks.txz
rm -f mainnet-latest-blocks.txz
cd /var/lib
sudo chown -R fio:fio fio

This will install the following files:

4. Enable nodeos daemon at runtime and start nodeos:

sudo systemctl enable fio-nodeos
sudo systemctl start fio-nodeos

Sync status will show in the logs:

tail -f /var/log/fio/nodeos.log

5. Validate your API node

Replay from a V1 History archive

It is not possible to rebuild state from a snapshot for a V1 History node. But, you can bootstrap a history node by downloading a complete tar file of a working FIO node. The following steps describe how to replay from a V1 history node archive.

1. Remove the existing contents of the data, history, and history_index directories. Make sure you back up any existing contents if you wish to keep them.

cd /var/lib
sudo rm -fr fio/data fio/history fio/history_index

2. Otain a copy of the snapshot and blocks.log files which you wish to replay the blockchain from. Several BPs maintain FIO snapshots for both Testnet and Mainnet. It is important that you trust the source of the snapshot before downloading. We will use the Blockpane history archive in our examples.

wget https://snap.blockpane.com/mainnet-latest-history.txz

3. Extract the snapshot to your data/snapshots directory, your blocks.log file to your data/blocks directory, and update the permissions on fio directory. The tar extraction will take several minutes.

sudo apt install pixz
sudo tar -xS -I'pixz' -C /var/lib/fio -f mainnet-latest-history.txz
rm -f mainnet-latest-history.txz
cd /var/lib
sudo chown -R fio:fio fio

This will install the following files:

4. Confirm the V1 history node settings in config.ini

5. Enable nodeos daemon at runtime and start nodeos:

sudo systemctl enable fio-nodeos
sudo systemctl start fio-nodeos

Sync status will show in the logs:

tail -f /var/log/fio/nodeos.log

6. Validate your API node