How to change configure system.log file in macOS?
Your settings for for the syslog are found in /etc/asl.conf.

There's a section that governs how the system log operates.

# Rules for /var/log/system.log
&gt; system.log mode=0640 format=bsd rotate=seq compress file_max=5M all_max=50M
? [= Sender kernel] file system.log
? [&lt;= Level notice] file system.log
? [= Facility auth] [&lt;= Level info] file system.log
? [= Facility authpriv] [&lt;= Level info] file system.log


Specifically, the log will rotate (by default) when it hits 5M in size, not overnight and the whole set of log files will rotate when it hits 50M cumulatively (10 files in total).  If you wan to increase the size, just edit the line as you see fit.

&gt; system.log mode=0640 format=bsd rotate=seq compress file_max=5M all_max=50M


I wouldn't increase the size of the individual files themselves, but rather the collective total.

That said, if you are collecting logs for a number of machines, you should be using a syslog server.