Sar
Monitoring server resources is a crucial part of identifying any bottlenecks and possible issues on your server.
sar stands for “System Activity Reporter” and provides a wide range of metrics related to system usage, including CPU utilization, memory usage, disk I/O, network activity.
on Ubuntu, sar can be installed by following[1]
#install sar
$ sudo apt-get install -y sysstat
# Enable data collecting
sed -i 's/false/true/g' /etc/default/sysstat
# Change the collection interval from every 10 minutes to every 2 minutes
sed -i 's/5-55\/10/*\/2/g' /etc/cron.d/sysstat
# Restart service
$ sudo systemctl start sysstat
sar system service and log location
sar can be run as system service as well,
- sudo systemctl start sysstat
- sudo systemctl enable sysstat
- This will add the required cron jobs so that the system data is collected accordingly. The cron jobs will be added at cat /etc/cron.d/sysstat
Using systemd service, we can easily set sar up to run automatically on your system, store its collected stats in daily files.
On Ubuntu, sar log files will be stored in /var/log/sysstat folder.
Command and options
sar has a lot of arguments and options and basic comman syntax is following,
$ sar -[ options ] time_interval number_of_tines_to_display
$sar --help
Full description is available in sar man page[2]
Here are few examples, geeksforgeeks site has more examples to use sar[3]
| Options | Description | output format |
|---|---|---|
sar -u 2 30
|
-u for all CPU,
|
12:14:32 PM CPU %user %nice %system %iowait %steal %idle
12:14:34 PM all 0.00 0.00 0.03 0.00 0.00 99.97
12:14:36 PM all 0.00 0.00 0.03 0.00 0.00 99.97
12:14:38 PM all 0.00 0.00 0.00 0.02 0.00 99.98
|
sar -r 2 30
|
-r for memory | 12:15:15 PM kbmemfree kbavail kbmemused %memused kbbuffers kbcached kbcommit %commit kbactive kbinact kbdirty
12:15:17 PM 51770940 128790180 934688 0.71 18792 76432800 1471616 1.10 12511540 64247964 20
12:15:19 PM 51770940 128790180 934688 0.71 18792 76432800 1471616 1.10 12511540 64247964 20
12:15:21 PM 51771048 128790296 934472 0.71 18800 76432800 1471616 1.10 12511544 64247964 48
|
| sar -n DEV 4 | -n for network interfaces,
4 means that the sar command should run every 2 seconds |
12:17:06 PM IFACE rxpck/s txpck/s rxkB/s txkB/s rxcmp/s txcmp/s rxmcst/s %ifutil
12:17:08 PM eno2np1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
12:17:08 PM eno1np0 19.50 15.50 2.42 1.43 0.00 0.00 1.00 0.00
12:17:08 PM docker0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
12:17:08 PM enxb03af2b6059f 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
12:17:08 PM lo 5.00 5.00 0.39 0.39 0.00 0.00 0.00 0.00
|
| sar -d | -d command to view block device, disk I/O statistics, including IOPS | 12:00:01 PM DEV tps rkB/s wkB/s dkB/s areq-sz aqu-sz await %util
12:02:01 PM dev259-0 1.74 0.10 9.10 0.00 5.28 0.00 3.36 0.31
12:02:01 PM dev8-0 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
12:02:01 PM dev8-16 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
12:02:01 PM dev8-32 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
|
| sar -b 1 3 | I/O Operation Details | 12:20:37 PM tps rtps wtps dtps bread/s bwrtn/s bdscd/s
12:20:38 PM 0.00 0.00 0.00 0.00 0.00 0.00 0.00
12:20:39 PM 0.00 0.00 0.00 0.00 0.00 0.00 0.00
12:20:40 PM 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Average: 0.00 0.00 0.00 0.00 0.00 0.00 0.00
|
sar report into file
# To save the output from a command like this in a file
$ sar -o sarfile 6 2
# To display sarfile
$ sar -f sarfile