System administrators often rely on efficient tools to streamline their daily tasks, especially for dedicated server users. Shell scripts are invaluable assets in a sysadmin’s toolkit, offering automation and enhanced productivity. This article presents five essential shell scripts that every system administrator should have in their arsenal.

1. MySQL Master-Slave Synchronization Monitor

This script monitors the MySQL master-slave synchronization status and sends an email alert if any anomalies are detected:

#!/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" xxx@163.com
    fi
done

2. Real-time Directory Monitoring and File Synchronization

This script monitors a specified directory for changes and synchronizes files in real-time:

#!/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" xxx@163.com
done

3. Batch User Creation with Password Setting

This script enables the creation of multiple users with randomly generated 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

This script checks the availability of multiple websites and reports any access failures:

#!/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

This script allows for the execution of commands on multiple remote 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 Website Platform Deployment Script

This script allows for one-click deployment of the LNMP (Linux, Nginx, MySQL, PHP) website platform:


#!/bin/bash
NGINX_V=1.15.6
PHP_V=5.6.36
TMP_DIR=/tmp

INSTALL_DIR=/usr/local

PWD_C=$PWD

echo
echo -e "\tMenu\n"
echo -e "1. Install Nginx"
echo -e "2. Install PHP"
echo -e "3. Install MySQL"
echo -e "4. Deploy LNMP"
echo -e "9. Quit"

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 - Environment check failed!"
    make -j 4
    command_status_check "Nginx - Compilation failed!"
    make install
    command_status_check "Nginx - Installation failed!"
    mkdir -p $INSTALL_DIR/nginx/conf/vhost
    alias cp=cp ; 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 '' > $INSTALL_DIR/nginx/html/status.php
    $INSTALL_DIR/nginx/sbin/nginx
    command_status_check "Nginx - Startup 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 - Environment check failed!"
    make -j 4
    command_status_check "PHP - Compilation failed!"
    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 - Startup failed!"
}

read -p "Please enter a 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 Check

This script provides a comprehensive overview of server resource utilization, including CPU, memory, disk, and TCP connection status:

#!/bin/bash
function cpu() {
    NUM=1
    while [ $NUM -le 3 ]; do
        util=`vmstat |awk '{if(NR==3)print 100-$15"%"}'`
        user=`vmstat |awk '{if(NR==3)print $13"%"}'`
        sys=`vmstat |awk '{if(NR==3)print $14"%"}'`
        iowait=`vmstat |awk '{if(NR==3)print $16"%"}'`
        echo "CPU - Utilization: $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 , Available: ${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 point: $mounted , Total 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 Connection Status - $summary"
}

cpu
memory
disk
tcp_status

8. Script to Find Processes with High CPU and Memory Usage

These commands help identify the top processes consuming CPU and memory resources:

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 Project Deployment (Tomcat)

This script automates the process of deploying a Java project to a Tomcat server, including code pull, build, and 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

# 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

10. Automated PHP Project Deployment Script

This script streamlines the deployment of a PHP project, handling code retrieval and deployment to the specified web root:

#!/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

These additional Shell scripts complement the previous set, covering crucial aspects of system administration such as resource monitoring, backups, log management, security updates, and network scanning. By incorporating these scripts into your daily routines, you can significantly enhance your efficiency and maintain a more robust and secure system infrastructure.

Remember to review and customize these scripts to fit your specific environment and requirements. Regular testing and updates are essential to ensure their continued effectiveness. With these powerful tools at your disposal, you’ll be well-equipped to handle a wide range of system administration tasks with ease and precision.