Sar is a system monitor command used to display system activityits installed via the sysstat rpm. Use the command below to install sysstat.
# yum -y install sysstat
# sudo apt-get install sysstat [for ubuntu]
Once installed you can check out the sysstat config file (/etc/sysconfig/sysstat) and configure how long to sar will keep your logfiles, on my system the default was 7 days. I changed this to 30 days.
The cron job for sar is located here (/etc/cron.d/sysstat) if you want to modify it as well.
Once installed and configured to your liking you must ensure that it starts and runs at boot time. I accomplished this via the command below.
# chkconfig sysstat on
# service sysstat start
Once up and running it will write its logs out to /var/log/sa, and you can read those files with the following command (sar -d <filename>, where filename is the name of the file that you want to read). Note that in the examples below, 3 is the interval, and 10 is the count.
Additonally you may run sar interatively, below are a few sample commands.
To report on previously captured data – type :
# sar -u -f filename > file
View disk i/o and transfer rate stats :
# sar -b 3 10
View memory and swap space stats :
# sar -r 3 10
View swapping stats :
# sar -W 3 10
View network stats :
# sar -n DEV 3 10
View CPU stats :
# sar -P ALL 3 10