Problem scenario: On some servers you try this command: "apt-get -y install sar", but this command does not work. On some servers with sar installed, you get an error when you run "sar". The error says "Cannot open /var/log/sysstat/sa25: No such file or directory."
Background: The sar utility comes from the acronym for system activity report. It is useful in performance tuning situations.
Solution: If you type "man sar" and get a man page, then it is installed. For these servers with a man page for "man sar," skip to the "Configuration" below. If there is no man page for sar, issue this: apt-get -y install sysstat
1.a) Edit /etc/default/sysstat. 1.b) Find the stanza that says "ENABLED='false'" and change the "false" to "true". 1.c) Save the changes and exit the file.
2) Issue this command: systemctl stop sysstat
If you get "bash: systemctl: command not found" see * below.
3) Issue this command: systemctl start sysstat
* Use this command if "systemctl" is not a recognized command: service sysstat stop; service sysstat start