When running sar on Ubuntu, i get error

root@ip-172-31-0-223:~# sar
Cannot open /var/log/sysstat/sa01: No such file or directory
Please check if data collecting is enabled
root@ip-172-31-0-223:~#

To fix, run

dpkg-reconfigure sysstat

This will ask you to activate cronjob for data collection. Select Yes. Now wait some time for cronjob to run, sar will work.

See sar