Turns out it's because I have not enough memory and swap is not configured.
https://medium.com/@jm_c/mysql-crashing-innodb-mmap-bytes-failed-errno-12-64d5b801b2f2
$ sudo grep -i "mysql" /var/log/syslog
Dec 28 07:31:20 m3a kernel: [767100.510836] [ 801] 107 801 404353 45265 733184 0 0 mysqld
Dec 28 07:31:20 m3a kernel: [767100.510978] Out of memory: Kill process 801 (mysqld) score 381 or sacrifice child
Dec 28 07:31:20 m3a kernel: [767100.511040] Killed process 801 (mysqld) total-vm:1617412kB, anon-rss:181060kB, file-rss:0kB, shmem-rss:0kB
Dec 28 07:31:20 m3a kernel: [767100.521099] oom_reaper: reaped process 801 (mysqld), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
$ free -m
total used free shared buff/cache available
Mem: 465 310 34 7 121 135
Swap: 0 0 0