UFO Core 0.9 Released

The 0.9 UFO coin client is now completed and released for use. Downloads are available from the home page of this website. Updates to this version are explained in detail below.

Autotools build system

For 0.9.0 we switched to an autotools-based build system instead of individual (q)makefiles.

Using the standard “./autogen.sh; ./configure; make” to build Bitcoin-Qt and bitcoind makes it easier for experienced open source developers to contribute to the project.

Be sure to check doc/build-*.md for your platform before building from source.


Another change in the 0.9 release is moving away from the bitcoind executable functioning both as a server and as a RPC client. The RPC client functionality (“tell the running bitcoin daemon to do THIS”) was split into a separate executable, ‘bitcoin-cli’. The RPC client code will eventually be removed from bitcoind, but will be kept for backwards compatibility for a release or two.

walletpassphrase RPC

The behavior of the walletpassphrase RPC when the wallet is already unlocked has changed between 0.8 and 0.9.

The 0.8 behavior of walletpassphrase is to fail when the wallet is already unlocked:

> walletpassphrase 1000
walletunlocktime = now + 1000
> walletpassphrase 10
Error: Wallet is already unlocked (old unlock time stays)

The new behavior of walletpassphrase is to set a new unlock time overriding the old one:

> walletpassphrase 1000
walletunlocktime = now + 1000
> walletpassphrase 10
walletunlocktime = now + 10 (overriding the old unlock time)

This release contains a few fixes for transaction ID (TXID) malleability issues:

  • -nospendzeroconfchange command-line option, to avoid spending zero-confirmation change
  • IsStandard() transaction rules tightened to prevent relaying and mining of mutated transactions
  • Additional information in listtransactions/gettransaction output to report wallet transactions that conflict with each other because they spend the same outputs.
  • Bug fixes to the getbalance/listaccounts RPC commands, which would report incorrect balances for double-spent (or mutated) transactions.
  • New option: -zapwallettxes to rebuild the wallet’s transaction information

Transaction Fees

This release drops the default fee required to relay transactions across the network and for miners to consider the transaction in their blocks to 0.01mBTC per kilobyte.

Note that getting a transaction relayed across the network does NOT guarantee that the transaction will be accepted by a miner; by default, miners fill their blocks with 50 kilobytes of high-priority transactions, and then with 700 kilobytes of the highest-fee-per-kilobyte transactions.

The minimum relay/mining fee-per-kilobyte may be changed with the minrelaytxfee option. Note that previous releases incorrectly used the mintxfee setting to determine which low-priority transactions should be considered for inclusion in blocks.

The wallet code still uses a default fee for low-priority transactions of 0.1mBTC per kilobyte. During periods of heavy transaction volume, even this fee may not be enough to get transactions confirmed quickly; the mintxfee option may be used to override the default.


Bitcoin Core version 0.9.0
Bitcoin Core version 0.9.2
Bitcoin Core version
Bitcoin Core version 0.9.3