How to get CPU usage history by hour on Debian server?

On a Debian server, the standard way to get CPU usage history by hour (and per day) is to use sysstat (sar). It’s the most reliable built-in-style solution for historical performance data.

1. Install CPU monitoring (sysstat)

sudo apt update
sudo apt install sysstat

Enable data collection:

sudo sed -i 's/ENABLED="false"/ENABLED="true"/' /etc/default/sysstat
sudo systemctl enable sysstat
sudo systemctl restart sysstat

On newer Debian versions, this is already handled, but it’s worth checking.

2. How data is collected

sysstat runs via cron/systemd and stores logs in:

/var/log/sysstat/

Files look like:

sa26   (for day 26 of month)
sa27

3. View CPU usage by hour (daily breakdown)

Show full CPU stats for today:

sar -u
Show CPU usage with hourly resolution:

sar -u -f /var/log/sysstat/sa26

Replace sa26 with today’s file.

Filter by time range (very useful)

Example: 10:00 to 18:00

sar -u -f /var/log/sysstat/sa26 -s 10:00:00 -e 18:00:00

4. Convert to “hourly average CPU usage”

To summarize by hour (instead of per 10 min samples):

sar -u -f /var/log/sysstat/sa26 | awk '
NR>3 { cpu[$3]+=(100-$NF); count[$3]++ }
END {
  for (t in cpu)
    printf "%s %.2f%%\n", t, cpu[t]/count[t]
}'

This gives rough per-time-slot averages (depends on sysstat interval).

5. More readable daily summary (recommended)

Install extra tools:

sudo apt install sysstat
sadf -d /var/log/sysstat/sa26 -- -u

This outputs CSV-like data, ideal for Excel/Grafana.

6. If you want proper hourly dashboards (best practice)

For long-term monitoring, use:

Option A — Prometheus + Node Exporter

• real-time + historical graphs
• Grafana dashboards
• best for production servers

Option B — Netdata (fast setup)

bash <(curl -Ss https://my-netdata.io/kickstart.sh)

Gives instant per-hour CPU graphs in browser.

7. Quick check (no installation)

If you only need current snapshot:

• top
• htop

But these do NOT provide history.