Week 3 · Day 7 & Day 8

Backup Scripts &
Mini Project

Day 7 teaches you to back up and restore log files using tar and gzip. Day 8 brings everything together into a fully automated L2 mini project — the script that detects and fixes problems on its own.

Day 7 — Backup Script Day 8 — Mini Project targzip Service MonitorFull Automation

Day 7 Backup Script — tar & gzip

01 The Simple Idea

Real-life Analogy

Think of log files like important paper documents in an office. Every day new documents are created. If the office catches fire, everything is gone.

A backup is like photocopying all documents, putting them in a sealed box, and storing them in a different building. If something goes wrong — the box is safe. You unpack it and continue.

tar creates the box. gzip compresses it so it takes up less storage space.

02 tar & gzip — How They Work

tar — bundles files into one archive

tar takes a whole folder of files and puts them into a single file — like zipping many documents into one envelope. On its own it doesn't compress — it just bundles.

gzip compresses the tar file to make it smaller — like vacuum-sealing the envelope. Combined as .tar.gz, you get a compressed archive.

⌨️ tar Flags — What Each One Does

Flag	Meaning	Used for
-c	Create a new archive	Making a backup
-z	Compress with gzip	Making it smaller
-f	Filename follows next	Always needed — name your file
-t	List contents of archive	Peeking inside without extracting
-x	Extract the archive	Restoring a backup
-v	Verbose — show each file	See what is happening
-C	Change to this directory first	Controlling where files go

tar — quick reference commands

# Create a compressed backup
tar -czf backup.tar.gz /folder/to/backup/

# List what's inside a backup (don't extract)
tar -tzvf backup.tar.gz

# Extract a backup into a specific folder
tar -xzf backup.tar.gz -C /where/to/restore/

# Backup with a timestamp in the filename
TS=$(date +"%Y-%m-%d_%H-%M-%S")
tar -czf "backup-$TS.tar.gz" /folder/

03 Day 7 Scripts

01-setup-lab.sh

Script 1 — Setup Lab Folders & Sample Logs

01 Run First

01-setup-lab.sh

#!/bin/bash
# Creates ~/logs, ~/backups, ~/scripts folders
# and 3 sample log files for testing

mkdir -p "$HOME/logs" "$HOME/backups" "$HOME/scripts"

cat > "$HOME/logs/payment-service.log" << 'EOF'
[2024-03-15 14:02:05] [ERROR] DB_CONNECTION_TIMEOUT failed to acquire connection
[2024-03-15 14:02:05] [ERROR] TXN-9821 FAILED unable to write to database
[2024-03-15 14:02:16] [INFO ] TXN-9824 processed successfully Status: SUCCESS
EOF

cat > "$HOME/logs/api-service.log" << 'EOF'
[2024-03-15 13:45:01] [ERROR] NullPointerException at PaymentProcessor.java:142
[2024-03-15 14:30:00] [INFO ] Scheduled job completed successfully
EOF

cat > "$HOME/logs/system.log" << 'EOF'
[2024-03-15 16:00:00] [ERROR] Disk usage: 92% - critical level reached
[2024-03-15 08:01:00] [INFO ] All services started
EOF

echo "Setup complete. Folders and logs created."

✅ How to run: chmod +x 01-setup-lab.sh && ./01-setup-lab.sh

02-backup-logs.sh

Script 2 — Backup the Logs Folder

02 Day 7 Lab

02-backup-logs.sh

#!/bin/bash
# Backs up ~/logs to ~/backups as a timestamped .tar.gz
# Deletes backups older than 7 days automatically

LOGS_DIR="$HOME/logs"
BACKUP_DIR="$HOME/backups"
TIMESTAMP=$(date +"%Y-%m-%d_%H-%M-%S")
BACKUP_FILE="$BACKUP_DIR/logs-backup-$TIMESTAMP.tar.gz"
KEEP_DAYS=7

mkdir -p "$BACKUP_DIR"

echo "Creating backup: $BACKUP_FILE"
tar -czf "$BACKUP_FILE" -C "$HOME" logs/

if [ $? -eq 0 ]; then
  SIZE=$(du -sh "$BACKUP_FILE" | awk '{print $1}')
  echo "SUCCESS: Backup created ($SIZE)"
else
  echo "ERROR: Backup failed!"; exit 1
fi

# Remove backups older than KEEP_DAYS
find "$BACKUP_DIR" -name "logs-backup-*.tar.gz" -mtime +$KEEP_DAYS -delete
echo "Old backups cleaned. Current backups:"
ls -lh "$BACKUP_DIR"

✅ How to run: chmod +x 02-backup-logs.sh && ./02-backup-logs.sh

03-restore-backup.sh

Script 3 — Restore a Backup

03 Restore

03-restore-backup.sh

#!/bin/bash
# Lists available backups and restores chosen one

BACKUP_DIR="$HOME/backups"
RESTORE_DIR="$HOME/logs-restored"

echo "Available backups:"
ls -lh "$BACKUP_DIR"/*.tar.gz
echo ""
echo "Enter the full path of backup to restore:"
read BACKUP_FILE

if [ ! -f "$BACKUP_FILE" ]; then
echo "ERROR: File not found."; exit 1
fi

echo "Contents of backup:"
tar -tzvf "$BACKUP_FILE"
echo ""

mkdir -p "$RESTORE_DIR"
tar -xzf "$BACKUP_FILE" -C "$RESTORE_DIR"
echo "SUCCESS: Restored to $RESTORE_DIR"

✅ How to run: chmod +x 03-restore-backup.sh && ./03-restore-backup.sh

04 Day 7 Lab — Backup Logs Folder

🔬 Lab: Create, Inspect & Restore a Backup

Kali Linux

Setup and run the backup

Run setup first, then backup.

terminal

chmod +x ~/scripts/*.sh
./01-setup-lab.sh
./02-backup-logs.sh

→ Backup file created in ~/backups/ ✅

Inspect the backup without extracting

Use tar -tzvf to see what's inside.

terminal

tar -tzvf ~/backups/logs-backup-*.tar.gz

→ Shows all files inside the archive with sizes ✅

Delete the logs folder and restore

Simulate a disaster — delete logs, then restore from backup.

terminal

rm -rf ~/logs/
./03-restore-backup.sh

→ Logs restored to ~/logs-restored/ from backup ✅

Day 8 Mini Project — Full Bash Automation

05 The Simple Idea

Real-life Analogy

Think of a self-driving car's safety system. It constantly checks everything — tire pressure, engine, fuel, road conditions. The moment something is wrong it takes action — sounds an alarm, slows down, pulls over. It doesn't wait for you to notice.

Your mini project script is that safety system for your server. It runs on a loop, checks disk + memory + services + logs, and automatically restarts anything that has stopped — all without you having to do anything.

06 Day 8 Scripts

05-service-monitor.sh

Script 5 — Auto Detect & Restart Failed Service

05 Mini Project

05-service-monitor.sh — runs in a loop

#!/bin/bash
# Monitors services in a loop.
# Auto-restarts if a service is down.
# Press Ctrl+C to stop.

SERVICES=("ssh" "cron")
CHECK_INTERVAL=30
LOG_FILE="$HOME/logs/monitor.log"
MAX_RESTARTS=3

log() { echo "[$(date '+%Y-%m-%d %H:%M:%S')] $1" | tee -a "$LOG_FILE"; }

check_disk() {
  D=$(df / | awk 'NR==2{print $5}' | tr -d '%')
  [ "$D" -ge 85 ] && log "[DISK] WARNING: $D%" || log "[DISK] OK: $D%"
}

check_memory() {
  SW=$(free -m | awk 'NR==3{print $3}')
  [ "$SW" -gt 100 ] && log "[MEM ] WARNING: Swap ${SW}MB" || log "[MEM ] OK: Swap ${SW}MB"
}

check_service() {
  SVC="$1"; RC=0
  if systemctl is-active --quiet "$SVC" 2>/dev/null; then
    log "[SVC ] OK: $SVC is RUNNING"
  else
    log "[SVC ] DOWN: $SVC — attempting restart..."
    while [ $RC -lt $MAX_RESTARTS ]; do
      RC=$((RC+1))
      sudo systemctl restart "$SVC" 2>/dev/null; sleep 3
      if systemctl is-active --quiet "$SVC" 2>/dev/null; then
        log "[SVC ] SUCCESS: $SVC restarted (attempt $RC)"; return
      fi
    done
    log "[SVC ] CRITICAL: $SVC failed after $MAX_RESTARTS attempts!"
  fi
}

mkdir -p "$HOME/logs"
log "Monitor started. Services: ${SERVICES[*]}"
echo "Running... Press Ctrl+C to stop. Log: $LOG_FILE"

LOOP=1
while true; do
  log "--- Check #$LOOP ---"
  check_disk
  check_memory
  for S in "${SERVICES[@]}"; do check_service "$S"; done
  LOOP=$((LOOP+1))
  sleep "$CHECK_INTERVAL"
done

✅ How to run: chmod +x 05-service-monitor.sh && ./05-service-monitor.sh — Press Ctrl+C to stop

06-l2-daily-runbook.sh

Script 6 — Full L2 Daily Runbook (The Main Script)

06 ⭐ Main Script

⭐ This is the key script of the whole mini project. One command — runs every check, logs every result, creates a backup, and saves a full daily report. This is what runs at 8 AM every morning via crontab.

06-l2-daily-runbook.sh — abbreviated for reference

#!/bin/bash
# Full daily runbook — disk + RAM + services + logs + backup
# Run every morning. Saves a dated report file.

REPORT_FILE="$HOME/daily-runbook-$(date +%Y-%m-%d).txt"
SERVICES=("ssh" "cron")
ISSUES=0

plog() { echo "$1"; echo "$1" >> "$REPORT_FILE"; }

plog "=== L2 DAILY RUNBOOK — $(date) ==="

# 1. Disk check
D=$(df / | awk 'NR==2{print $5}' | tr -d '%')
[ "$D" -ge 90 ] && { plog "DISK CRITICAL: $D%"; ISSUES+=1; } || plog "DISK OK: $D%"

# 2. Memory check
SW=$(free -m | awk 'NR==3{print $3}')
[ "$SW" -gt 200 ] && { plog "MEM WARNING: Swap ${SW}MB"; ISSUES+=1; } || plog "MEM OK"

# 3. Service checks
for S in "${SERVICES[@]}"; do
systemctl is-active --quiet "$S" && plog "SVC OK: $S" || { plog "SVC DOWN: $S"; ISSUES+=1; }
done

# 4. Log errors
E=$(grep -c "ERROR" "$HOME/logs/payment-service.log" 2>/dev/null || echo 0)
[ "$E" -gt 0 ] && { plog "LOG WARNING: $E errors found"; ISSUES+=1; } || plog "LOG OK"

# 5. Backup
TS=$(date +"%Y-%m-%d_%H-%M-%S")
tar -czf "$HOME/backups/logs-backup-$TS.tar.gz" -C "$HOME" logs/ && plog "BACKUP OK" || plog "BACKUP FAILED"

plog "=== DONE — $ISSUES issue(s) found. Report: $REPORT_FILE ==="

✅ How to run: chmod +x 06-l2-daily-runbook.sh && ./06-l2-daily-runbook.sh

07-schedule-all.sh

Script 7 — Schedule All Scripts with Crontab

07 Run Last

07-schedule-all.sh

#!/bin/bash
# Gives all scripts permission and schedules cron jobs

chmod +x "$HOME/scripts"/*.sh
echo "Permissions set."

# Daily runbook at 8 AM every weekday
(crontab -l 2>/dev/null; echo "0 8 * * 1-5 $HOME/scripts/06-l2-daily-runbook.sh >> $HOME/logs/runbook.log 2>&1") | crontab -

# Midnight backup daily
(crontab -l 2>/dev/null; echo "0 0 * * * $HOME/scripts/02-backup-logs.sh >> $HOME/backups/backup.log 2>&1") | crontab -

echo "Cron jobs scheduled:"
crontab -l

✅ How to run: chmod +x 07-schedule-all.sh && ./07-schedule-all.sh — run this last

07 Day 8 Lab — Auto Detect + Restart Failed Service

🔬 Lab: Run the Full Mini Project

Kali Linux · Full Automation

Run the service monitor

Starts the loop — watches services every 30 seconds.

terminal

./05-service-monitor.sh

→ Watch the output. It logs disk, memory, service status every 30s. Press Ctrl+C to stop.

Run the full daily runbook

One command — does everything and saves a report.

terminal

./06-l2-daily-runbook.sh

→ Full report saved to ~/daily-runbook-DATE.txt ✅

Read the report

See what the runbook found.

terminal

cat ~/daily-runbook-$(date +%Y-%m-%d).txt

→ Shows all check results and issue count for today ✅

Schedule everything with crontab

Run the final script to automate everything permanently.

terminal

./07-schedule-all.sh
crontab -l

→ All cron jobs confirmed active ✅

08 All Scripts — Summary

📋 Complete Script Reference

Script	Day	What it does	Run order
01-setup-lab.sh	Day 7	Creates ~/logs, ~/backups, ~/scripts + 3 sample log files	First
02-backup-logs.sh	Day 7	Backs up ~/logs as timestamped .tar.gz, cleans old backups	Second
03-restore-backup.sh	Day 7	Restores a chosen backup to ~/logs-restored/	After backup
04-scheduled-backup.sh	Day 7	Schedules backup with crontab at midnight	Optional
05-service-monitor.sh	Day 8	Monitors services in a loop, auto-restarts if down	Interactive
06-l2-daily-runbook.sh	Day 8	Full daily runbook — disk + RAM + services + logs + backup	Every morning
07-schedule-all.sh	Day 8	Sets permissions + adds all cron jobs at once	Last

09 Real L2 Scenarios

Disk fills up at 3 AM and the payment service stops writing logs. The backup that ran at midnight has all the logs safely stored. You restore from backup, identify the issue from the archived logs, and fix it before 8 AM. No data lost.

A service crashes at 2 AM. The service monitor running in the background detects it within 30 seconds, tries restarting it automatically up to 3 times, logs each attempt, and alerts you if all 3 fail. You wake up to a log showing the service restarted successfully at 2:01 AM.

Manager asks for this morning's server health report. You open ~/daily-runbook-2024-03-15.txt — the full disk, memory, service status and error count from 8 AM is already there. You paste it in the reply. Done in 10 seconds.

Client accidentally deletes their transaction log and asks if you can recover it. The backup from last midnight has it. You run the restore script, locate the file inside the archive, and send it to the client within 5 minutes.

✅ Week 3 · Day 7 & 8 Outcomes

Understand what tar and gzip do and why .tar.gz is the standard backup format
Use tar -czf to create a compressed backup and tar -xzf to restore it
Use tar -tzvf to inspect a backup without extracting it
Build a backup script with timestamps, automatic cleanup of old backups, and size reporting
Build a restore script that lists available backups and extracts the chosen one safely
Build a service monitor script that runs in a loop and auto-restarts failed services
Build the full L2 daily runbook — the one script that does all checks and saves a report
Schedule all scripts with crontab — runbook at 8 AM, backup at midnight
Understand how full bash automation makes you proactive as an L2 engineer

Backup Scripts &Mini Project

tar — bundles files into one archive

Script 1 — Setup Lab Folders & Sample Logs

Script 2 — Backup the Logs Folder

Script 3 — Restore a Backup

🔬 Lab: Create, Inspect & Restore a Backup

Script 5 — Auto Detect & Restart Failed Service

Script 6 — Full L2 Daily Runbook (The Main Script)

Script 7 — Schedule All Scripts with Crontab

🔬 Lab: Run the Full Mini Project

✅ Week 3 · Day 7 & 8 Outcomes

Backup Scripts &
Mini Project