Essential Bash Scripts for Linux System Monitoring and Automation

Shell Script Collection for Linux Operations

The following Bash scripts address common system‑administration tasks, offering ready‑to‑run solutions for monitoring, automation, and deployment on Linux servers.

1. Monitor MySQL master‑slave synchronization status

#!/bin/bash
HOST=localhost
USER=root
PASSWD=123.com
IO_SQL_STATUS=$(mysql -h$HOST -u$USER -p$PASSWD -e 'show slave status\G' 2>/dev/null | awk '/Slave_.*_Running:/{print $1$2}')
for i in $IO_SQL_STATUS; do
    THREAD_STATUS_NAME=${i%:*}
    THREAD_STATUS=${i#*:}
    if [ "$THREAD_STATUS" != "Yes" ]; then
        echo "Error: MySQL Master-Slave $THREAD_STATUS_NAME status is $THREAD_STATUS!" | mail -s "Master-Slave Staus" [email protected]
    fi
done

2. Directory change monitoring and real‑time sync

#!/bin/bash
MON_DIR=/opt
inotifywait -mqr --format %f -e create $MON_DIR |\
while read files; do
   rsync -avz /opt /tmp/opt
   # echo "$(date +'%F %T') create $files" | mail -s "dir monitor" [email protected]
 done

3. Bulk creation of 100 users with random passwords

#!/bin/bash
DATE=$@
USER_FILE=user.txt
for USER in $USER_LIST; do
    if ! id $USER &>/dev/null; then
        PASS=$(echo $RANDOM | md5sum | cut -c 1-8)
        useradd $USER
        echo $PASS | passwd --stdin $USER &>/dev/null
        echo "$USER   $PASS" >> $USER_FILE
        echo "$USER User create successful."
    else
        echo "$USER User already exists!"
    fi
done

4. Batch website availability checker

#!/bin/bash
URL_LIST="www.baidu.com www.ctnrs.com"
for URL in $URL_LIST; do
    FAIL_COUNT=0
    for ((i=1;i<=3;i++)); do
        HTTP_CODE=$(curl -o /dev/null --connect-timeout 3 -s -w "%{http_code}" $URL)
        if [ $HTTP_CODE -eq 200 ]; then
            echo "$URL OK"
            break
        else
            echo "$URL retry $FAIL_COUNT"
            let FAIL_COUNT++
        fi
    done
    if [ $FAIL_COUNT -eq 3 ]; then
        echo "Warning: $URL Access failure!"
    fi
done

5. Remote command execution on multiple hosts

#!/bin/bash
COMMAND=$*
HOST_INFO=host.info
for IP in $(awk '/^[^#]/{print $1}' $HOST_INFO); do
    USER=$(awk -v ip=$IP 'ip==$1{print $2}' $HOST_INFO)
    PORT=$(awk -v ip=$IP 'ip==$1{print $3}' $HOST_INFO)
    PASS=$(awk -v ip=$IP 'ip==$1{print $4}' $HOST_INFO)
    expect -c "
       spawn ssh -p $PORT $USER@$IP
       expect {\
          \"(yes/no)\" {send \"yes\r\"; exp_continue}\
          \"password:\" {send \"$PASS\r\"; exp_continue}\
          \"$USER@*\" {send \"$COMMAND\r exit\r\"; exp_continue}\
       }"
    echo "-------------------"
 done

6. One‑click LNMP (Linux‑Nginx‑MySQL‑PHP) deployment script

#!/bin/bash
NGINX_V=1.15.6
PHP_V=5.6.36
TMP_DIR=/tmp
INSTALL_DIR=/usr/local
PWD_C=$PWD

function command_status_check() {
    if [ $? -ne 0 ]; then
        echo $1
        exit
    fi
}

function install_nginx() {
    cd $TMP_DIR
    yum install -y gcc gcc-c++ make openssl-devel pcre-devel wget
    wget http://nginx.org/download/nginx-${NGINX_V}.tar.gz
    tar zxf nginx-${NGINX_V}.tar.gz
    cd nginx-${NGINX_V}
    ./configure --prefix=$INSTALL_DIR/nginx \
        --with-http_ssl_module \
        --with-http_stub_status_module \
        --with-stream
    command_status_check "Nginx configuration failed"
    make -j 4 && make install
    command_status_check "Nginx installation failed"
    $INSTALL_DIR/nginx/sbin/nginx
    command_status_check "Nginx start failed"
}

function install_php() {
    cd $TMP_DIR
    yum install -y gcc gcc-c++ make gd-devel libxml2-devel libcurl-devel libjpeg-devel libpng-devel openssl-devel libmcrypt-devel libxslt-devel libtidy-devel
    wget http://php.net/distributions/php-${PHP_V}.tar.gz
    tar zxf php-${PHP_V}.tar.gz
    cd php-${PHP_V}
    ./configure --prefix=$INSTALL_DIR/php \
        --with-config-file-path=$INSTALL_DIR/php/etc \
        --enable-fpm --enable-opcache \
        --with-mysql --with-mysqli --with-pdo-mysql \
        --with-openssl --with-zlib --with-curl --with-gd \
        --with-jpeg-dir --with-png-dir --with-freetype-dir \
        --enable-mbstring --enable-hash
    command_status_check "PHP configuration failed"
    make -j 4 && make install
    command_status_check "PHP installation failed"
    cp php.ini-production $INSTALL_DIR/php/etc/php.ini
    cp sapi/fpm/php-fpm.conf $INSTALL_DIR/php/etc/php-fpm.conf
    cp sapi/fpm/init.d.php-fpm /etc/init.d/php-fpm
    chmod +x /etc/init.d/php-fpm
    /etc/init.d/php-fpm start
    command_status_check "PHP start failed"
}

read -p "Enter number: " number
case $number in
    1) install_nginx;;
    2) install_php;;
    3) install_mysql;;
    4) install_nginx; install_php;;
    9) exit;;
esac

7. One‑click server resource utilization report

#!/bin/bash
function cpu() {
    NUM=1
    while [ $NUM -le 3 ]; do
        util=$(vmstat | awk '{if(NR==3)print 100-$15"%"}')
        iowait=$(vmstat | awk '{if(NR==3)print $16"%"}')
        echo "CPU - Usage: $util , IO Wait: $iowait"
        let NUM++
        sleep 1
    done
}

function memory() {
    total=$(free -m | awk '{if(NR==2)printf "%.1f",$2/1024}')
    used=$(free -m | awk '{if(NR==2)printf "%.1f",($2-$NF)/1024}')
    available=$(free -m | awk '{if(NR==2)printf "%.1f",$NF/1024}')
    echo "Memory - Total: ${total}G , Used: ${used}G , Free: ${available}G"
}

function disk() {
    fs=$(df -h | awk '/^\/dev/{print $1}')
    for p in $fs; do
        mounted=$(df -h | awk "$1==\"$p\"{print $NF}")
        size=$(df -h | awk "$1==\"$p\"{print $2}")
        used=$(df -h | awk "$1==\"$p\"{print $3}")
        used_percent=$(df -h | awk "$1==\"$p\"{print $5}")
        echo "Disk - Mount: $mounted , Size: $size , Used: $used , Usage: $used_percent"
    done
}

function tcp_status() {
    summary=$(ss -antp | awk '{status[$1]++} END{for(i in status) printf i":"status[i]" "}')
    echo "TCP connections - $summary"
}

cpu
memory
disk
tcp_status

8. List processes with high CPU or memory usage

ps -eo user,pid,pcpu,pmem,args --sort=-pcpu | head -n 10
ps -eo user,pid,pcpu,pmem,args --sort=-pmem | head -n 10

9. Automated Java (Tomcat) project deployment

#!/bin/bash
DATE=$(date +%F_%T)
TOMCAT_NAME=$1
TOMCAT_DIR=/usr/local/$TOMCAT_NAME
ROOT=$TOMCAT_DIR/webapps/ROOT
BACKUP_DIR=/data/backup
WORK_DIR=/tmp
PROJECT_NAME=tomcat-java-demo

cd $WORK_DIR
if [ ! -d $PROJECT_NAME ]; then
   git clone https://github.com/lizhenliang/tomcat-java-demo
   cd $PROJECT_NAME
else
   cd $PROJECT_NAME
   git pull
fi

mvn clean package -Dmaven.test.skip=true
if [ $? -ne 0 ]; then
   echo "maven build failure!"
   exit 1
fi

TOMCAT_PID=$(ps -ef | grep "$TOMCAT_NAME" | egrep -v "grep|$$" | awk 'NR==1{print $2}')
[ -n "$TOMCAT_PID" ] && kill -9 $TOMCAT_PID
[ -d $ROOT ] && mv $ROOT $BACKUP_DIR/${TOMCAT_NAME}_ROOT$DATE
unzip $WORK_DIR/$PROJECT_NAME/target/*.war -d $ROOT
$TOMCAT_DIR/bin/startup.sh

10. Automated PHP project deployment

#!/bin/bash
DATE=$(date +%F_%T)
WWWROOT=/usr/local/nginx/html/$1
BACKUP_DIR=/data/backup
WORK_DIR=/tmp
PROJECT_NAME=php-demo

cd $WORK_DIR
if [ ! -d $PROJECT_NAME ]; then
   git clone https://github.com/lizhenliang/php-demo
   cd $PROJECT_NAME
else
   cd $PROJECT_NAME
   git pull
fi

if [ ! -d $WWWROOT ]; then
   mkdir -p $WWWROOT
   rsync -avz --exclude=.git $WORK_DIR/$PROJECT_NAME/* $WWWROOT
else
   rsync -avz --exclude=.git $WORK_DIR/$PROJECT_NAME/* $WWWROOT
fi

These scripts can be copied, customized, and executed directly to streamline routine Linux system administration tasks.