./tezos-node run --rpc-addr 127.0.0.1:8732
Aug 29 13:13:38 - node.main: Starting the Tezos node...
Aug 29 13:13:38 - node.main: No local peer discovery.
Aug 29 13:13:38 - node.main: Peer's global id: idts1aYiNgUVV3dehNx6qRmd4UzTgA
Aug 29 13:13:38 - main: shell-node initialization: bootstrapping
Aug 29 13:13:38 - main: shell-node initialization: p2p_maintain_started
Aug 29 13:13:38 - shell.validation_process.fork: Initialized
Aug 29 13:13:38 - shell.validation_process.fork: Block validation started on pid 13389
Aug 29 13:13:39 - main: validator-block : Worker started(2019-08-29T13:13:39-00:00)
Aug 29 13:13:39 - node.validator: activate chain NetXdQprcVkpaWU
Aug 29 13:13:39 - p2p.maintenance: Too few connections (0)
Aug 29 13:13:39 - main: validator-chain_1 : Worker started for NetXdQprcVkpa(2019-08-29T13:13:39-00:00)
Apparently, the format of the "pack" backend (in experimental branch
mainnet-pack-validator) recently changed. It is possible that by updating to the latest version of this branch, you went from the old format to the new format. In that case you probably need to start from the beginning, unfortunately.