How to upgrade QTUM core wallet after the QTUM hard fork

Greetings from MediBloc team.

Recently, the QTUM Mainnet hard fork activated at block 466,600. This hard fork is the first upgrade that took place two years after the launch of the QTUM Mainnet on September 13, 2017. If you have upgraded your wallet to 0.18.1 before reaching the QTUM hard fork, you can send MediBloc QRC20 MED tokens without any problem. However, pre-0.18.1 wallets are separate from the chain and cannot be traded or staked through the QTUM mainchain.

MediBloc is currently operating “mediBridge” to swap QRC20 MED to MED mainnet coin. The token swap period through mediBridge is available until 23:59 (KST) on December 7, 2019, after which the token swap is not possible. MediBloc token holders who still have QRC20 MED in their personal wallets should upgrade their QTUM wallet to version 0.18.1 through this notice and proceed token swap.

[How to upgrade QTUM core wallet(pre- 0.18.1version wallet)]

1. Backup your QTUM core wallet.

After backing up your wallet.dat file, update your wallet to version 0.18.1.

2. Delete your local copy of the blockchain.

Delete your local copy of the blockchain with these steps. Note that most systems will hide application data folders, so you may need to unhide all folders to find the Qtum data folder.

1) Exit the wallet (File — Exit for Qtum-Qt and the stop command for qtumd).
2) Navigate to your Qtum data directory

3) Delete the folders “blocks”, “stateQtum”, “database” and the file “banlist.dat”.

3. Launch your wallet and let it sync the entire blockchain.

Alternatively, you can use the new startup command “deleteblockchaindata” which can be used from the command line with qtumd as “-deleteblockchaindata” and with Qtum-Qt by selecting File — Restore Wallet — delete blockchain data and restarting.

[How to recover the wrong transactions]

If you have sent any transactions using pre-0.18.1 version of Qtum core wallet, you can recover coins by “zapping” away from the bad transactions.

The “zapwallettxes=2” command tells the wallet to cancel these transactions and not restore any related metadata. Most of the time this zapping procedure below will restore your coins, if not, please reach out for tech support on the Qtum social media channels.

There are three ways to enter this command: the Qtum-Qt menu, the configuration file, or the command line. Note this command can only be used at wallet startup and is not entered after the wallet is running.

Case 1. Qtum-Qt Menu
This approach works only for Qtum-Qt.

1. You can set to zap your wallet on restart by selecting File — Restore Wallet — zapwallettxes=2, then select OK and YES to exit the wallet, and it will restart to run the Zap command (restart on Windows manually).

When restarted, the Qtum-Qt wallet will show “Rescanning…” status for a few minutes and then launch normally.

Case2. Configuration File
This approach works for both Qtum-Qt and qtumd.

The configuration file “qtum.conf” is read by the wallet on startup, so we can enter the “zapwallettxes=2” command, and restart the wallet. Use these steps to create the configuration file (assumes you are not using the configuration file already. If so, just add the command).
Make a configuration file with the “zapwallettxes=2” command. Using a text editor, make this file (instructions for the text editor on Windows, Mac, Linux)

Save the file with the file name “qtum.conf.txt”.

Save the file as a plain text, not rich text or any other formatting. Rename the file to “qtum.conf” and move the file into the Qtum data directory (as given above).

Launch your wallet the usual way. Qtum-Qt will show “Rescanning…” (qtumd will show zapping and rescanning debug.log messages).

In the Qtum data directory delete the “qtum.conf” file or rename it to “qtum.conf.sav” so you don’t zap and rescan with every restart.


Please check the version of your personal Qtum core wallet before sending the MediBloc tokens to mediBridge. Additional questions can be found in the Qtum Hard Fork FAQ.

Thank you
MediBloc team.




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