Essential Bash Scripts for Nginx, MySQL, and Linux System Monitoring

1. Daily Nginx Access Log Rotation

#!/bin/bash
LOG_DIR=/usr/local/nginx/logs
YESTERDAY_TIME=$(date -d "yesterday" +%F)
LOG_MONTH_DIR=$LOG_DIR/$(date +"%Y-%m")
LOG_FILE_LIST="default.access.log"
for LOG_FILE in $LOG_FILE_LIST; do
    [ ! -d $LOG_MONTH_DIR ] && mkdir -p $LOG_MONTH_DIR
    mv $LOG_DIR/$LOG_FILE $LOG_MONTH_DIR/${LOG_FILE}_${YESTERDAY_TIME}
    done
kill -USR1 $(cat /var/run/nginx.pid)

2. Nginx Access Log Analysis Script

#!/bin/bash
# Log format: $remote_addr - $remote_user [$time_local] "$request" $status $body_bytes_sent "$http_referer" "$http_user_agent" "$http_x_forwarded_for"
LOG_FILE=$1

echo "Top 10 IPs (UV)"
awk '{a[$1]++} END {print "UV:", length(a); for (v in a) print v, a[v]}' $LOG_FILE | sort -k2 -nr | head -10

echo "----------------------"

echo "Top IPs in a time window"
awk '$4>="[01/Dec/2018:13:20:25" && $4<="[27/Nov/2018:16:20:49" {a[$1]++} END {for (v in a) print v, a[v]}' $LOG_FILE | sort -k2 -nr | head -10

echo "----------------------"

echo "Top 10 requested pages (PV)"
awk '{a[$7]++} END {print "PV:", length(a); for (v in a) if (a[v]>10) print v, a[v]}' $LOG_FILE | sort -k2 -nr

echo "----------------------"

echo "Status code count per page"
awk '{a[$7" "$9]++} END {for (v in a) if (a[v]>5) print v, a[v]}' $LOG_FILE | sort -k3 -nr

3. One‑Click Server Resource Utilization Overview

#!/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 -v dev="$p" '$1==dev{print $NF}')
        size=$(df -h | awk -v dev="$p" '$1==dev{print $2}')
        used=$(df -h | awk -v dev="$p" '$1==dev{print $3}')
        used_percent=$(df -h | awk -v dev="$p" '$1==dev{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

4. Real‑Time Inode Usage Alert

#!/bin/bash
# Alert when free inodes drop below 100
PATH=/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/sbin:/home/wl/bin
export PATH
for FreeInode in $(df -i | grep -v "Filesystem" | awk '{print $4}'); do
    if [[ $FreeInode -lt 100 ]]; then
        echo -e "$(df -i | grep "$FreeInode")" > /service/script/.FreeInode
        mail -s "FreeInode Warning" wl < /service/script/.FreeInode
    fi
done

5. Block Malicious IPs from Nginx Access Logs

#!/bin/bash
DATE=$(date +%d/%b/%Y:%H:%M)
# Get the last 10000 lines, filter current minute, count per IP, flag >500 requests
ABNORMAL_IP=$(tail -n10000 access.log | grep $DATE | awk '{a[$1]++} END {for(i in a) if(a[i]>500) print i}')
for IP in $ABNORMAL_IP; do
    if [ $(iptables -vnL | grep -c "$IP") -eq 0 ]; then
        iptables -I INPUT -s $IP -j DROP
    fi
done

6. Batch Rename File Extensions

#!/bin/bash
# Usage: script.sh old_ext new_ext
for i in `ls *.$1`; do
    mv $i ${i%.*}.$2
done

7. Scheduled Log Truncation and Size Recording

#!/bin/bash
logfile=/tmp/$(date +%H-%F).log
hour=$(date +%H)
if [ $hour -eq 00 ] || [ $hour -eq 12 ]; then
    for i in `find /data/log/ -type f`; do
        > $i
    done
else
    for i in `find /data/log/ -type f`; do
        du -sh $i >> $logfile
    done
fi

8. Apache (httpd) Process Monitoring and Auto‑Restart

#!/bin/bash
check_service() {
    j=0
    for i in `seq 1 5`; do
        /usr/local/apache2/bin/apachectl restart 2>/var/log/httpderr.log
        if [ $? -eq 0 ]; then
            break
        else
            j=$((j+1))
        fi
        if [ $j -eq 5 ]; then
            mail.py exit
        fi
    done
}
while :; do
    n=$(pgrep -l httpd | wc -l)
    if [ $n -gt 500 ]; then
        /usr/local/apache2/bin/apachectl restart
        if [ $? -ne 0 ]; then
            check_service
        else
            sleep 60
            n2=$(pgrep -l httpd | wc -l)
            if [ $n2 -gt 500 ]; then
                mail.py exit
            fi
        fi
    fi
    sleep 10
done

9. Single‑Loop MySQL Database Backup

#!/bin/bash
DATE=$(date +%F_%H-%M-%S)
HOST=localhost
USER=backup
PASS=123.com
BACKUP_DIR=/data/db_backup
DB_LIST=$(mysql -h$HOST -u$USER -p$PASS -s -e "show databases;" 2>/dev/null | egrep -v "Database|information_schema|mysql|performance_schema|sys")
for DB in $DB_LIST; do
    BACKUP_NAME=$BACKUP_DIR/${DB}_$DATE.sql
    if ! mysqldump -h$HOST -u$USER -p$PASS -B $DB > $BACKUP_NAME 2>/dev/null; then
        echo "$BACKUP_NAME backup failed!"
    fi
done

10. Multi‑Loop MySQL Database Backup (per table)

#!/bin/bash
DATE=$(date +%F_%H-%M-%S)
HOST=localhost
USER=backup
PASS=123.com
BACKUP_DIR=/data/db_backup
DB_LIST=$(mysql -h$HOST -u$USER -p$PASS -s -e "show databases;" 2>/dev/null | egrep -v "Database|information_schema|mysql|performance_schema|sys")
for DB in $DB_LIST; do
    BACKUP_DB_DIR=$BACKUP_DIR/${DB}_$DATE
    [ ! -d $BACKUP_DB_DIR ] && mkdir -p $BACKUP_DB_DIR >/dev/null
    TABLE_LIST=$(mysql -h$HOST -u$USER -p$PASS -s -e "use $DB;show tables;" 2>/dev/null)
    for TABLE in $TABLE_LIST; do
        BACKUP_NAME=$BACKUP_DB_DIR/${TABLE}.sql
        if ! mysqldump -h$HOST -u$USER -p$PASS $DB $TABLE > $BACKUP_NAME 2>/dev/null; then
            echo "$BACKUP_NAME backup failed!"
        fi
    done
done