log2ram issue

I am using Oanrge Pi Zero 512MB,  receive root mail everyday

/etc/cron.daily/log2ram:
sending incremental file list
./
alternatives.log
auth.log
daemon.log
dpkg.log
kern.log
lastlog
mail.info
mail.log
messages
...................
mysql/error.log.5.gz
mysql/error.log.6.gz
mysql/error.log.7.gz

sent 31,199,258 bytes  received 1,265 bytes  4,160,069.73 bytes/sec
total size is 40,359,412  speedup is 1.29
/etc/cron.daily/logrotate:
Warning: Unit file of apache2.service changed on disk, 'systemctl daemon-reload' recommended.
?
No applicable message
?
No applicable message
 

I also have orange pi pc, and check by " df"

PC has  " log2ram ......................../var/log", but didn't see it on Zero. 

Anything wrong?