Running a new install of Ubuntu 18.04.3 LTS and downloading blocks in bitcoin-qt up to over 70% when pgm quits with "Bus error (core dumped)".
Anyone else gets this or how to fix it? (-rescan didn't help)
There isn't a single condition that triggers a
SIGBUS. Without more details it's impossible to debug this problem remotely.
A Bus Error can be indicative of a hardware problem. Check your motherboard and look for bulged capacitors near where the memory slots are located. If you find any, take your PC to a technician. You may try taking out the memory modules and clean their gold contacts with paper or eraser rubber. It's also recommended you clean out the memory slots themselves from any dust.
To completely rule out a memory problem you can boot your Linux box into
memtest86 (included in most Ubuntu boot options or live images) and leave it running for a few hours. If hardware-related,
memtest86 will find most memory-related problems during its very first test stages.
Software conditions can also trigger a
SIGBUS. Since there isn't currently a specific known issue on Bitcoin Core that triggers a Bus Error, I'd assume it's a problem in your installation. Try rebuilding Bitcoin Core from source or reinstalling/upgrading its prerequisite packages.
Lastly, you may try tweaking Bitcoin Core's memory parameters to see if the Bus Error goes away. If you notice your Linux box is disk thrashing and using too much swap when running Bitcoin, that could be an indication of low memory. Use
htop in different screens to monitor the IO and CPU-bound systems respectively while running Bitcoin Core and see if either disk or CPU are being hogged by a specific process.