sar utility custom settings

A quick article to point out configurations to customize sar utility.

sar is monitoring utility on Linux which is used to monitor system resource utilization. We have covered different aspects of sar in the past. You can go through the below articles for the same.

• sar tool. All you need to know.
• CPU & Memory reporting using sar
• Disk & Network reporting using sar
• How to install sar in SUSE

In this article, we will walk you though for some custom settings you can configure for sar like below –

1. How to change monitoring frequency in sar
2. How to customize sar log rotation

How to change sar monitoring frequency?

As you are aware sar has 10 minutes default frequency. That means sar utility logs one data point of resource utilization per 10 minutes. If you want to change this frequency then you can do it by altering it in below file –

kerneltalks:~ #  cat /etc/cron.d/sysstat
# crontab for sysstat

# Activity reports every 10 minutes everyday
*/10 * * * * root [ -x /usr/lib64/sa/sa1 ] && exec /usr/lib64/sa/sa1 1 1

So you have to edit number 10 with the frequency of your choice. Let’s make it for 1 minute instead of 10 minutes.

Now, after editing the file you have to wait for that minimum time to pass which you choose as frequency and then you can verify it by using sar command.

kerneltalks:~ # sar
Linux 5.3.18-22-default (kerneltalks)      08/20/20        _x86_64_        (1 CPU)

14:16:18     LINUX RESTART      (1 CPU)

14:20:01        CPU     %user     %nice   %system   %iowait    %steal     %idle
14:21:01        all      0.02      0.00      0.02      0.00      0.00     99.97
14:22:01        all      0.02      0.00      0.03      0.00      0.02     99.93
14:23:01        all      0.00      0.00      0.00      0.00      0.00    100.00
14:24:01        all      0.02      0.00      0.02      0.00      0.00     99.97
Average:        all      0.01      0.00      0.02      0.00      0.00     99.97

You can see now that sar is collecting datapoints with frequency of 1 minute.

How to customize sar log rotation?

saar log rotation is controlled by /etc/sysstat/sysstat file. You can configure below parameters in the file.

kerneltalks:~ # cat /etc/sysstat/sysstat|grep -v ^#|grep -v ^$
HISTORY=60
COMPRESSAFTER=10
SADC_OPTIONS=" -S ALL"
SA_DIR=/var/log/sa
ZIP="xz"

File has a description for all the parameters which are self-explanatory. You can edit each parameter as per your requirement and restart sar process.

I am mentioning short description of each parameters from file here for your quick reference.

• HISTORY How long to keep log files (in days).
• COMPRESSAFTER Compress sa and sar files older than (in days)
• SADC_OPTIONS Parameters for the system activity data collector
• SA_DIR Directory where sa and sar files are saved.
• ZIP Compression program to use. xz, gzip or bzip2