Essential Bash Scripts for Linux Ops: Monitoring, Deployment & Automation

1. Monitor MySQL Master‑Slave Sync Status

<code>#!/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
</code>

2. Directory Change Monitoring & Real‑time Sync

<code>#!/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
</code>

3. Batch Create 100 Users with Random Passwords

<code>#!/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
</code>

4. Batch Check Website Availability

<code>#!/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
</code>

5. Remote Command Execution on Multiple Hosts

<code>#!/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 {\n          \"(yes/no)\" {send \"yes\r\"; exp_continue}\n          \"password:\" {send \"$PASS\r\"; exp_continue}\n          \"$USER@*\" {send \"$COMMAND\r exit\r\"; exp_continue}\n       }\n    "
    echo "-------------------"
done
</code>

6. One‑Click LNMP (Linux‑Nginx‑MySQL‑PHP) Deployment Script

<code>#!/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 - platform check failed!"
    make -j 4
    command_status_check "Nginx - compile failed!"
    make install
    command_status_check "Nginx - install failed!"
    mkdir -p $INSTALL_DIR/nginx/conf/vhost
    cp -rf $PWD_C/nginx.conf $INSTALL_DIR/nginx/conf
    rm -rf $INSTALL_DIR/nginx/html/*
    echo "ok" > $INSTALL_DIR/nginx/html/status.html
    echo '<?php echo "ok"?>' > $INSTALL_DIR/nginx/html/status.php
    $INSTALL_DIR/nginx/sbin/nginx
    command_status_check "Nginx - start failed!"
}

function install_php() {
    cd $TMP_DIR
    yum install -y gcc gcc-c++ make gd-devel libxml2-devel \
        libcurl-devel libjpeg-devel libpng-devel openssl-devel \
        libmcrypt-devel libxslt-devel libtidy-devel
    wget http://docs.php.net/distributions/php-${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 - platform check failed!"
    make -j 4
    command_status_check "PHP - compile failed!"
    make install
    command_status_check "PHP - install 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
</code>

7. One‑Click Server Resource Utilization Report

<code>#!/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
</code>

8. Find High CPU/Memory Processes

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

ps -eo user,pid,pcpu,pmem,args --sort=-pmem | head -n 10
</code>

9. Automated Java (Tomcat) Project Deployment

<code>#!/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

# Pull code
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

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

# Deploy
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
</code>

10. Automated PHP Project Deployment

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

# Pull code
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

# Deploy
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
</code>