Monitoring RAM usage on server

The RAM on a server can be monitored using /proc/meminfo and awk commands. /proc/ is a special file system created by the Linux kernel which contains kernel related information such as CPU and memory usage. /proc/meminfo contains information about memory usage.

The following bash script can be used to extract memory usage information from /proc/meminfo. It uses the awk text processing command for parsing memory information. It uses bc command for performing floating point operations. The bash scripting language does not support arithmetic operations on floating point numbers so an external tool like bc is needed

# the total memory. the MemTotal row is extracted using awk. the second column of this row is then extracted and saved to total variable
total=$( awk '/MemTotal/ {print $2}' < /proc/meminfo )
# the available memory. the MemAvailable row is extracted using awk. the second column of this row is then extracted and saved to available variable
available=$( awk '/MemAvailable/ {print $2}' < /proc/meminfo )
# the formula for calculating percentage of available memory is piped to bc command. the output of bc command is saved to memory_available variable
memory_available=$(echo "($available*100/$total)" | bc)
# if the available memory is less than 30%
if [ "$memory_available" -lt "30" ];
    # the body of the alert email is saved to a temprary file
    echo "Hello Admin. The Memory usage on server is $memory_available%. Please check!" > /tmp/mail_body.txt
    # the mailx command is used to sent the email. it sends the email using gmail server.
    # this is useful on servers that have limited access to email servers such as Google Compute instance
    mailx -s "Memory usage on server is more than 70%. Please check!." -r "reply_email" -S smtp="" -S    \<br/>smtp-use-starttls -S smtp-auth=login -S smtp-auth-user="gmail_address" -S smtp-auth-password="gmail_password" -S \<br/>ssl-verify=ignore recepiant_email &lt; /tmp/mail_body.txt
    # the temprary file is removed
    rm -rf /tmp/mail_body
Published 10 Feb 2017

Pak Jiddat provides open source scripts and tutorials related to Web Development and System Administration.