sudo cp /dev/null mongod.log
@ip:/var/log/mongodb$ ll
total 26475944
drwxr-xr-x 2 mongodb mongodb 4096 Feb 20 2020 ./
drwxrwxr-x 12 root syslog 4096 Sep 25 06:25 ../
-rw------- 1 mongodb mongodb 27111306733 Sep 25 17:37 mongod.log
@ip:/var/log/mongodb$ sudo cp /dev/null mongod.log
@ip:/var/log/mongodb$ ll
total 12
drwxr-xr-x 2 mongodb mongodb 4096 Feb 20 2020 ./
drwxrwxr-x 12 root syslog 4096 Sep 25 06:25 ../
-rw------- 1 mongodb mongodb 3034 Sep 25 17:37 mongod.log