“The sar command collect, report, or save UNIX / Linux system activity information. It will save selected counters in the operating system to the /var/log/sa/sadd file. From the collected data, you get lots of information about your server:
1. CPU utilization
2. Memory paging and its utilization
3. Network I/O, and transfer statistics
4. Process creation activity
5. All block devices activity
6. Interrupts/sec etc.
sar output can be used for identifying server bottlenecks. However, analyzing information provided by sar can be difficult, so use kSar, which can take sar output and plot a nice easy to understand graph over period of time.
sysstat Package
The sar, sa1, and sa2 commands are part of sysstat package:
1. sar : Displays the data.
2. sa1 and sa2: Collect and store the data for later analysis. The sa2 shell script write a daily report in the /var/log/sa directory. The sa1 shell script collect and store binary data in the system activity daily data file.
3. sadc – System activity data collector. You can configure various options by modifying sa1 and sa2 scripts. They are located at the following location:
* /usr/lib64/sa/sa1 (64bit) or /usr/lib/sa/sa1 (32bit) – This calls sadc to log reports to/var/log/sa/sadX format.
* /usr/lib64/sa/sa2 (64bit) or /usr/lib/sa/sa2 (32bit) – This calls sar to log reports to /var/log/sa/sarX format.
How Do I Install sar?
Type the following command:
# yum install sysstat
Sample outputs:
Loaded plugins: downloadonly, fastestmirror, priorities,
: protectbase, security
Loading mirror speeds from cached hostfile
* addons: mirror.cs.vt.edu
* base: mirror.ash.fastserv.com
* epel: serverbeach1.fedoraproject.org
* extras: mirror.cogentco.com
* updates: centos.mirror.nac.net
0 packages excluded due to repository protections
Setting up Install Process
Resolving Dependencies
–> Running transaction check
—> Package sysstat.x86_64 0:7.0.2-3.el5 set to be updated
–> Finished Dependency Resolution
Dependencies Resolved
====================================================================
Package Arch Version Repository Size
====================================================================
Installing:
sysstat x86_64 7.0.2-3.el5 base 173 k
Transaction Summary
====================================================================
Install 1 Package(s)
Update 0 Package(s)
Remove 0 Package(s)
Total download size: 173 k
Is this ok [y/N]: y
Downloading Packages:
sysstat-7.0.2-3.el5.x86_64.rpm | 173 kB 00:00
Running rpm_check_debug
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
Installing : sysstat 1/1
Installed:
sysstat.x86_64 0:7.0.2-3.el5
Complete!
Configuration Files
Edit /etc/sysconfig/sysstat file specify how long to keep log files in days, maximum is a month:
# vi /etc/sysconfig/sysstat
Sample outputs:
# keep log for 30 days
# the default is 7
HISTORY=30
Save and close the file.
The Default Cron Job
The default cron job is located at /etc/cron.d/sysstat:
# cat /etc/cron.d/sysstat
Sample outputs:
# run system activity accounting tool every 10 minutes
*/10 * * * * root /usr/lib64/sa/sa1 1 1
# generate a daily summary of process accounting at 23:53
53 23 * * * root /usr/lib64/sa/sa2 -A
Tell sadc To Report Statistics For Disks
Edit /etc/cron.d/sysstat, enter:
# vi /etc/cron.d/sysstat
Update it as follows to log all disk stats (the -d option force to log stats for each block device and the -I option force report statistics for all system interrupts)
# run system activity accounting tool every 10 minutes
*/10 * * * * root /usr/lib64/sa/sa1 -I -d 1 1
# generate a daily summary of process accounting at 23:53
53 23 * * * root /usr/lib64/sa/sa2 -A
Save and close the file. Turn on the service, enter:
# chkconfig sysstat on
# service sysstat start
Sample outputs:
Calling the system activity data collector (sadc):
How Do I Use sar? How do I View Stats?
Use the sar command to display output the contents of selected cumulative activity counters in the operating system. In this example, sar is run to get real-time reporting from the command line about CPU utilization:
# sar -u 3 10″cyberciti.biz
