$ sudo apt install sysstat
$ dpkg-query -W sysstat 
sysstat 12.5.2-2

ログがないとエラーになるので，

$ sar
Cannot open /var/log/sysstat/sa21: No such file or directory

起動時に実行されるようにする．

$ sudo git -C /etc diff /etc/default/sysstat
diff --git a/default/sysstat b/default/sysstat
index dfeb7e0..17fb007 100644
--- a/default/sysstat
+++ b/default/sysstat
@@ -6,5 +6,5 @@
 # Should sadc collect system activity informations? Valid values
 # are "true" and "false". Please do not put other values, they
 # will be overwritten by debconf!
-ENABLED="false"
+ENABLED="true"
 

初回は手動で起動する

$ sudo systemctl start sysstat

とりあえずエラーが起こらなくなる

$ sar
Linux 5.10.0-3-amd64 (t430s)    02/21/2021      _x86_64_        (4 CPU)

11:01:41 PM  LINUX RESTART      (4 CPU)

実行間隔はこのようになっている．変更したい場合編集する．

$ cat /etc/cron.d/sysstat
# The first element of the path is a directory where the debian-sa1
# script is located
PATH=/usr/lib/sysstat:/usr/sbin:/usr/sbin:/usr/bin:/sbin:/bin

# Activity reports every 10 minutes everyday
5-55/10 * * * * root command -v debian-sa1 > /dev/null && debian-sa1 1 1

# Additional run at 23:59 to rotate the statistics file
59 23 * * * root command -v debian-sa1 > /dev/null && debian-sa1 60 2

例えば10分間隔 → 1分間隔にしたい場合は，

$ sudo git -C /etc diff /etc/cron.d/sysstat
diff --git a/cron.d/sysstat b/cron.d/sysstat
index 66325ce..875a27d 100644
--- a/cron.d/sysstat
+++ b/cron.d/sysstat
@@ -3,7 +3,7 @@
 PATH=/usr/lib/sysstat:/usr/sbin:/usr/sbin:/usr/bin:/sbin:/bin
 
 # Activity reports every 10 minutes everyday
-5-55/10 * * * * root command -v debian-sa1 > /dev/null && debian-sa1 1 1
+* * * * * root command -v debian-sa1 > /dev/null && debian-sa1 1 1
 
 # Additional run at 23:59 to rotate the statistics file
 59 23 * * * root command -v debian-sa1 > /dev/null && debian-sa1 60 2

ログがなくても現在の状況は確認できる．

メモリの利用率を1秒間隔で表示．Ctrl+cで終了．

$ sar -r 1
Linux 5.10.0-3-amd64 (t430s)    02/21/2021      _x86_64_        (4 CPU)

11:10:50 PM kbmemfree   kbavail kbmemused  %memused kbbuffers  kbcached  kbcommit   %commit  kbactive   kbinact   kbdirty
11:10:51 PM    383304   6421272   7606556     46.93     12704   7716236  32752996     79.71   5276944   9342360     17680
11:10:52 PM    386588   6425468   7602744     46.91     12704   7716740  32748344     79.70   5277100   9338972     18828
11:10:53 PM    387764   6427724   7603648     46.91     12704   7714684  32745276     79.69   5277328   9337024     20036
11:10:54 PM    379116   6419980   7592428     46.84     12704   7734528  32715276     79.61   5277492   9332988     21216
11:10:55 PM    379780   6421696   7593704     46.85     12704   7732684  32712464     79.61   5277692   9332428     22288
11:10:56 PM    384980   6427876   7587436     46.81     12704   7733696  32706376     79.59   5277916   9326488      8584
11:10:57 PM    383668   6427644   7590216     46.83     12704   7732188  32705704     79.59   5278092   9327160      9776
^C

Average:       383600   6424523   7596676     46.87     12704   7725822  32726634     79.64   5277509   9333917     16915

CPU利用率を1秒間隔で5回表示

$ sar -u 1 5
Linux 5.10.0-3-amd64 (t430s)    02/21/2021      _x86_64_        (4 CPU)

11:12:33 PM     CPU     %user     %nice   %system   %iowait    %steal     %idle
11:12:34 PM     all     10.62      0.00      4.15      0.00      0.00     85.23
11:12:35 PM     all     10.88      0.00      4.51      0.00      0.00     84.62
11:12:36 PM     all     11.37      0.00      5.68      0.00      0.00     82.95
11:12:37 PM     all     13.08      0.00      6.67      0.00      0.00     80.26
11:12:38 PM     all     13.20      0.00      5.58      0.00      0.00     81.22
Average:        all     11.84      0.00      5.33      0.00      0.00     82.83

同様に

-q load average
-b I/O

ログがある場合，期間指定ができる

$ sar -s 12:00:00 -e 12:59:59
Linux 5.10.0-3-amd64 (t430s)    02/22/2021      _x86_64_        (4 CPU)

12:00:01 PM     CPU     %user     %nice   %system   %iowait    %steal     %idle
12:10:04 PM     all      9.46      0.00      5.82      0.11      0.00     84.61
12:20:04 PM     all      9.55      0.00      6.05      0.19      0.00     84.21
12:30:01 PM     all      9.37      0.00      5.63      0.11      0.00     84.89
12:40:04 PM     all      9.19      0.00      6.02      0.11      0.00     84.68
12:50:04 PM     all      9.59      0.00      5.90      0.19      0.00     84.32
Average:        all      9.43      0.00      5.88      0.14      0.00     84.54