After running the loop much more time, the log file has been rotated: $ ls -lh /var/log/supervisor/ total 53M -rw-r--r-- 1 root root 3,0M 8 oct. 14:33 supervisord.log -rw-rw-rw- 1 root root 51M 26 sept. 16:55 supervisord.log.1 $ ls -l /var/log/supervisor/ total 54184 -rw-r--r-- 1 root root 3041778 8 oct. 14:33 supervisord.log -rw-rw-rw- 1 root root 52428822 26 sept. 16:55 supervisord.log.1
It seems the rotation occurs when the size goes from 50 to 51M. The file rotation works so I think this bug report can be closed with a 'unreproducible' tag. -- Stéphane