Blockchain synchronization fails, bus error

Question

I am using monerod 0.10.3.1 on Arch Linux. Towards the end of the process the synchronization with the blockchain fails:

2017-05-29 09:20:27.451 [P2P1]  WARN    net.dns 
src/common/dns_utils.cpp:531    WARNING: no two valid MoneroPulse DNS 
checkpoint records were received
2017-05-29 09:20:27.902 [P2P3]  INFO    global  
src/cryptonote_protocol/cryptonote_protocol_handler.inl:293 
[66.228.41.201:18080 OUT] Sync data returned a new top block 
candidate: 1237496 -> 1320640 [Your node is 83144 blocks (115 days) 
behind] 
SYNCHRONIZATION started
 Bus error (core dumped)

Any idea what might be going wrong?

Answer 1

A bus error here is almost invariably due to a corrupt blockchain, so I'm afraid the only way out is to resync:

• delete the chain (the files in in ~/.bitmonero/lmdb)
• start monerod again, and wait for it to resync

You can get more info on that particular error, by running monerod again after running, in the same terminal: ulimit -c unlimited, then running gdb on the core which will be generated after the crash:

gdb monerod core*

Then, in gdb:

bt

You'll most likely find a stack trace crashing somewhere in the LMDB code, but if not, I'm interested to know where.