~ 8 min read

Monitor CPU Usage and Send Email Alerts in Linux

Let's see how we can monitor CPU usage on a server and receive emails.

Monitoring the CPU is very important on a Linux server as there may be cases when your applications will need more CPU and can consume everything. You would want to be notified via email in case the CPU usage spikes and you need to do some checks.

For your server to be able to send emails you will need to have configured an SMTP Relay or you should have an email server hosted on the VPS that will send the alarm.

In case you are using an online VPS provider like Hetzner or DigitalOcean having such a script can be very useful as it can catch problems coming from your hosting provider or your app. For more details on Hetzner, you can check this review.

In this article, we will configure a script that will run in crontab every 5 minutes and check to see if the CPU usage is above 80% in case that will happen you will be notified via email with the:

  • Current Usage
  • Top 20 processes that consume high CPU
  • Top 10 Processes that consume high CPU using the ps command
  • Memory Utilization on the server

Having all of this in an email will help us better understand what is happening on the server we have. To build the script we are going to use shell commands.

Youtube Video With Details

Shell Script To Be Used

Below is the script that we are going to use to help us monitor the CPU usage, this will help you monitor Ubuntu versions like 20.04 or 22.04 or RedHat distros.

    #!/bin/bash
    cpu_idle=`top -b -n 1 | grep Cpu | awk '{print $8}'|cut -f 1 -d "."`
    cpuuse=`expr 100 - $cpu_idle`
    date=$(date '+%Y-%m-%d %H:%M:%S')
    if [ "$cpuuse" -ge 80 ]; then
    SUBJECT="ATTENTION: CPU load is high on $(hostname) at $(date)"
    MESSAGE="/tmp/Mail.out"
    TO="[email protected]"
      echo "CPU current usage is: $cpuuse%" >> $MESSAGE
      echo "" >> $MESSAGE
      echo "+------------------------------------------------------------------+" >> $MESSAGE
      echo "Top 20 processes that consume high CPU" >> $MESSAGE
      echo "+------------------------------------------------------------------+" >> $MESSAGE
      echo "$(top -bn1 | head -20)" >> $MESSAGE
      echo "" >> $MESSAGE
      echo "+------------------------------------------------------------------+" >> $MESSAGE
      echo "Top 10 Processes which consuming high CPU using the ps command" >> $MESSAGE
      echo "+------------------------------------------------------------------+" >> $MESSAGE
      echo "$(ps -eo pcpu,pid,user,args | sort -k 1 -r | head -10)" >> $MESSAGE
      echo "Memory Utilization on the server" >> $MESSAGE
      echo "+------------------------------------------------------------------+" >> $MESSAGE
      echo "$(ps_mem)" >> $MESSAGE
      mail -s "$SUBJECT" "$TO" < $MESSAGE
      rm /tmp/Mail.out
    else
    echo "$date: Server CPU usage is in under threshold.CPU current usage is: $cpuuse%"
      fi

In this script, you need to change the TO with your email and in case you want to change the threshold you put the value you want in the -ge 80 (now is 80).

Activating the CPU Monitoring Script

Install ps_mem

This is a tool that will show you better the memory usage per process, to install this tool you do:

Get ps_men:

      sudo wget -qO /usr/local/bin/ps_mem https://raw.githubusercontent.com/pixelb/ps_mem/master/ps_mem.py

Make ps_mem executable:

sudo chmod a+x /usr/local/bin/ps_mem

Check the version:

      ps_mem --version

If you are receiving an error message /usr/bin/env: ‘python’: No such file or directory, you need to create a symbolic link for /usr/bin/python. In Ubuntu 20.04 or Ubuntu 22.04, only Python 3 is installed by default.

      sudo ln -s /usr/bin/python3 /usr/bin/python

Put the Script in Crontab

Create a file with the script under /opt/scripts or in any location you want:

vi /opt/scripts/cpu-alert.sh

Make The File Executable:

sudo chmod a+x /opt/scripts/cpu-alert.sh

Execute the Script:

      /opt/scripts/cpu-alert.sh

The output should be on email:

    CPU current usage is: 5%
    +------------------------------------------------------------------+
    Top 20 processes that consume high CPU
    +------------------------------------------------------------------+
    top - 11:27:12 up 6 days, 4:31, 1 user, load average: 0.08, 0.08, 0.07
    Tasks: 204 total, 1 running, 202 sleeping, 0 stopped, 1 zombie
    %Cpu(s): 4.1 us, 0.0 sy, 0.0 ni, 95.9 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
    MiB Mem : 3827.7 total, 556.1 free, 1427.2 used, 1844.4 buff/cache
    MiB Swap: 2048.0 total, 1276.7 free, 771.3 used. 1454.0 avail Mem
    PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
    1959 clp 20 0 1355012 63248 21020 S 6.2 1.6 127:54.60 beam.smp
    1 root 20 0 168072 9940 6204 S 0.0 0.3 2:35.24 systemd
    2 root 20 0 0 0 0 S 0.0 0.0 0:00.11 kthreadd
    3 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 rcu_gp
    4 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 rcu_par_gp
    5 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 netns
    7 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 kworker/0:0H-events_highpri
    10 root 0 -20 0 0 0 I 0.0 0.0 0:00.00 mm_percpu_wq
    11 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcu_tasks_rude_
    12 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcu_tasks_trace
    13 root 20 0 0 0 0 S 0.0 0.0 3:41.85 ksoftirqd/0
    14 root 20 0 0 0 0 I 0.0 0.0 9:58.13 rcu_sched
    15 root rt 0 0 0 0 S 0.0 0.0 0:01.65 migration/0
    +------------------------------------------------------------------+
    Top 10 Processes that consume high CPU using the ps command
    +------------------------------------------------------------------+
    %CPU PID USER COMMAND
    5.0 596375 btdo php-fpm: pool btdo.uk
    3.5 1039 mysql /usr/sbin/mariadbd
    1.4 1959 clp /app/erts-12.0/bin/beam.smp -- -root /app -progname erl -- -home /app -- -noshell -s elixir start_cli -mode embedded -setcookie S4WHAF4LH5WHSPWUHPKIVMSFISQKQJVFWEGHSP7YW6MT5LKCNDCA==== -sname plausible -config /app/releases/0.0.1/sys -boot /app/releases/0.0.1/start -boot_var RELEASE_LIB /app/lib -- -extra --no-halt
    1.2 772 redis /usr/bin/redis-server 127.0.0.1:6379
    0.6 2677 systemd+ /usr/bin/clickhouse-server --config-file=/etc/clickhouse-server/config.xml
    0.4 579396 root nginx: worker process
    0.3 2071 root node server/server.js
    0.1 789 root /usr/bin/containerd
    0.1 14 root [rcu_sched]
    Memory Utilization on the server
    +------------------------------------------------------------------+
    Private + Shared = RAM used    Program
    4.0 KiB + 25.5 KiB = 29.5 KiB    erl_child_setup
    40.0 KiB + 24.5 KiB = 64.5 KiB    epmd
    4.0 KiB + 82.5 KiB = 86.5 KiB    dumb-init
    56.0 KiB + 108.5 KiB = 164.5 KiB    inet_gethost (3)
    144.0 KiB + 56.5 KiB = 200.5 KiB    cron
    148.0 KiB + 52.5 KiB = 200.5 KiB    atd
    320.0 KiB + 0.5 KiB = 320.5 KiB    exim4
    192.0 KiB + 136.0 KiB = 328.0 KiB    agetty (2)
    268.0 KiB + 89.5 KiB = 357.5 KiB    qemu-ga
    340.0 KiB + 104.5 KiB = 444.5 KiB    irqbalance
    304.0 KiB + 361.5 KiB = 665.5 KiB    master
    352.0 KiB + 361.0 KiB = 713.0 KiB    chronyd (2)
    384.0 KiB + 358.5 KiB = 742.5 KiB    unattended-upgr
    728.0 KiB + 111.5 KiB = 839.5 KiB    systemd-udevd
    652.0 KiB + 339.5 KiB = 991.5 KiB    polkitd
    732.0 KiB + 418.5 KiB = 1.1 MiB    systemd-logind
    920.0 KiB + 243.5 KiB = 1.1 MiB    dbus-daemon
    800.0 KiB + 391.5 KiB = 1.2 MiB    systemd-networkd
    4.0 KiB + 1.3 MiB = 1.3 MiB    clckhouse-watch
    820.0 KiB + 516.5 KiB = 1.3 MiB    systemd-resolved
    1.4 MiB + 128.5 KiB = 1.5 MiB    rsyslogd
    328.0 KiB + 1.2 MiB = 1.5 MiB    php-fpm7.1
    660.0 KiB + 902.5 KiB = 1.5 MiB    qmgr
    708.0 KiB + 878.5 KiB = 1.5 MiB    pickup
    1.3 MiB + 458.5 KiB = 1.8 MiB    ModemManager
    776.0 KiB + 1.2 MiB = 1.9 MiB    php-fpm7.2
    2.0 MiB + 49.5 KiB = 2.0 MiB    proftpd
    924.0 KiB + 1.2 MiB = 2.1 MiB    php-fpm7.3
    1.6 MiB + 533.5 KiB = 2.2 MiB    udisksd
    2.5 MiB + 1.1 MiB = 3.6 MiB    tlsmgr
    2.3 MiB + 1.4 MiB = 3.7 MiB    bash (2)
    3.3 MiB + 992.5 KiB = 4.3 MiB    networkd-dispat
    4.3 MiB + 73.5 KiB = 4.4 MiB    memcached
    4.2 MiB + 754.0 KiB = 4.9 MiB    docker-proxy (4)
    3.6 MiB + 1.5 MiB = 5.1 MiB    sshd (2)
    5.4 MiB + 5.0 MiB = 10.5 MiB    systemd (3)
    11.1 MiB + 35.5 KiB = 11.1 MiB    clp-agent
    12.3 MiB + 1.6 MiB = 13.9 MiB    containerd-shim-runc-v2 (5)
    14.5 MiB + 2.6 MiB = 17.1 MiB    php-fpm8.0
    17.4 MiB + 23.5 KiB = 17.4 MiB    containerd
    18.9 MiB + 170.5 KiB = 19.0 MiB    redis-server
    17.0 MiB + 3.8 MiB = 20.8 MiB    php-fpm8.1 (2)
    21.4 MiB + 751.5 KiB = 22.2 MiB    multipathd
    13.9 MiB + 10.2 MiB = 24.1 MiB    systemd-journald
    28.5 MiB + 178.5 KiB = 28.6 MiB    dockerd
    28.9 MiB + 1.3 MiB = 30.2 MiB    clickhouse
    29.6 MiB + 15.6 MiB = 45.2 MiB    postgres (18)
    40.1 MiB + 6.0 MiB = 46.0 MiB    php-fpm7.4 (2)
    47.2 MiB + 8.0 MiB = 55.3 MiB    beam.smp
    82.3 MiB + 82.5 KiB = 82.4 MiB    node
    72.0 MiB + 30.0 MiB = 102.0 MiB    nginx (8)
    807.7 MiB + 398.5 KiB = 808.1 MiB    mariadbd
    ---------------------------------
    1.4 GiB
    =================================

Activating the script in crontab and creating a log for the run:

    #open crontab in edit mode
    contab -e
    #add the bellow line
    */5 * * * * /bin/bash /opt/scripts/cpu-alert.sh >> /opt/scripts/cpu_check_cron.log 2>&1

The above will create a log under /opt/scripts/cpu_check_cron.log with the output when this is not sending an email.