https://twitter.com/go_vargo/status/1215281798948642817?s=20
I wasn't familiar with the sar command among the ones introduced in the above Tweet, so I did some research.
sar (System Activity Reporter) is one of the monitoring tools for Linux.
A command that displays statistics such as memory, CPU usage, disk IO, network, and load average, and is included in the sysstat package.
It is possible to display not only real-time stats but also past stats, Since you can see the information retroactively, it is useful for investigating the cause when dealing with a failure.
The type of statistics to display is optionally specified.
sar [...options]
In [... options], specify which resource information to display.
If no option is specified, the resource information for the current day will be acquired. The default information acquisition interval is 10 minutes.
With Amazon Linux 2, past data will be saved under / var / log / sa.
[ec2-user@xxx ~]$ ls -la /var/log/sa
Total 2652
drwxr-xr-x 2 root root 167 May 24 05:14 .
drwxr-xr-x 8 root root 4096 May 24 05:14 ..
-rw-r--r--1 root root 91760 October 12 2019 sa12
-rw-r--r--1 root root 336992 October 13 2019 sa13
-rw-r--r--1 root root 336992 October 14 2019 sa14
-rw-r--r--1 root root 238880 October 15 2019 sa15
-rw-r--r--1 root root 290320 October 17 2019 sa17
-rw-r--r--1 root root 336992 October 18 2019 sa18
-rw-r--r--1 root root 16960 October 19 2019 sa19
-rw-r--r--1 root root 5328 May 24 05:30 sa24
-rw-r--r--1 root root 68488 October 12 2019 sar12
-rw-r--r--1 root root 249044 October 13 2019 sar13
-rw-r--r--1 root root 249044 October 14 2019 sar14
-rw-r--r--1 root root 214675 October 17 2019 sar17
-rw-r--r--1 root root 249044 October 18 2019 sar18
The number after sar ** indicates the last few days.
The file itself is stored in binary, You can view the contents of the file via sar.
[ec2-user@xxx ~]$ sar -r -f /var/log/sa/sa12
Linux 4.14.123-111.109.amzn2.x86_64 (localhost)October 12, 2019_x86_64_ (1 CPU)
17:23:29 LINUX RESTART
17:30:01 kbmemfree kbmemused%memused kbbuffers kbcached kbcommit %commit kbactive kbinact kbdirty
17:40:01 493536 513796 51.01 2088 390136 593996 58.97 166828 253464 252
17:50:01 493540 513792 51.01 2088 390300 593996 58.97 166892 253532 252
18:00:01 493004 514328 51.06 2088 390636 593988 58.97 167000 253844 216
After the command, you can limit the data displayed in real time with [Acquisition interval] [Acquisition count].
If you want to learn the information 3 times every 1 second, follow the steps below.
[ec2-user@xxx ~]$ sar -r 1 3
Linux 4.14.146-119.123.amzn2.x86_64 May 24, 2020_x86_64_ (1 CPU)
05:37:41 kbmemfree kbmemused%memused kbbuffers kbcached kbcommit %commit kbactive kbinact kbdirty
05:37:42 585824 421468 41.84 2088 323892 531260 52.74 154588 198628 128
05:37:43 584948 422344 41.93 2088 323892 531260 52.74 155608 198628 128
05:37:44 584568 422724 41.97 2088 323892 531260 52.74 155884 198628 128
Average value: 585113 422179 41.91 2088 323892 531260 52.74 155360 198628 128
##Saves real-time memory information in a file called mem three times at 1-second intervals
[ec2-user@xxx ~]$ sar -r 1 3 -o mem
##View statistics saved in mem file
[ec2-user@xxx ~]$ sar -r -f mem
You can specify the resources to be displayed by changing the options.
--CPU usage
[ec2-user@xxx ~]$ sar -P ALL 1
Linux 4.14.146-119.123.amzn2.x86_64 May 24, 2020_x86_64_ (1 CPU)
05:39:43 CPU%user %nice %system %iowait %steal %idle
05:39:44 all 0.00 0.00 0.00 0.00 0.00 100.00
05:39:44 0 0.00 0.00 0.00 0.00 0.00 100.00
--Memory usage
[ec2-user@xxx ~]$ sar -r 1
Linux 4.14.146-119.123.amzn2.x86_64 May 24, 2020_x86_64_ (1 CPU)
05:41:24 kbmemfree kbmemused%memused kbbuffers kbcached kbcommit %commit kbactive kbinact kbdirty
05:41:25 586180 421112 41.81 2088 323940 526944 52.31 154808 198444 0
05:41:26 586180 421112 41.81 2088 323940 526944 52.31 154808 198444 0
05:41:27 586180 421112 41.81 2088 323940 526944 52.31 154808 198444 0
--Network
Receive/Number of packets sent
[ec2-user@xxx ~]$ sar -n DEV 1
Linux 4.14.146-119.123.amzn2.x86_64 (ip-172-31-63-105.ap-northeast-1.compute.internal)May 24, 2020_x86_64_ (1 CPU)
05:42:33 IFACE rxpck/s txpck/s rxkB/s txkB/s rxcmp/s txcmp/s rxmcst/s
05:42:34 eth0 2.00 0.00 0.10 0.00 0.00 0.00 0.00
05:42:34 lo 0.00 0.00 0.00 0.00 0.00 0.00 0.00
05:42:34 IFACE rxpck/s txpck/s rxkB/s txkB/s rxcmp/s txcmp/s rxmcst/s
05:42:35 eth0 1.01 1.01 0.05 0.39 0.00 0.00 0.00
05:42:35 lo 0.00 0.00 0.00 0.00 0.00 0.00 0.00
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