Guides

Server Health और Disk Alerts के लिए Bash Script कैसे लिखें

By Ravindra Bagale, DevOps trainer · LinkedIn · Published: 28 October 2026 · Last updated: 28 October 2026

CPU, memory, disk जाँचने वाली Bash script — Capgemini/Wipro style junior task।

Language: English · मराठी · हिंदी

Health script क्यों लिखें

मुंबई या Frankfurt के users रिपोर्ट करें तब देर। पाँच मिनट की Bash check पहली automation।

Why: Outage से पहले दबाव पहचानें। What: metrics, thresholds, report, optional alert। How: Amazon Linux/Ubuntu पर टुकड़े जोड़ें।

Concept 1: Safe skeleton

Why: set -euo pipefail गलतियाँ जल्दी दिखाता है। What: shebang, pipefail, chmod 700। How: हर ops script ऐसे शुरू।

Example 1: Shebang and safe mode

Type this:

printf '%s\n' '#!/usr/bin/env bash' 'set -euo pipefail' > /tmp/health.sh
head -2 /tmp/health.sh

You will see:

#!/usr/bin/env bash
set -euo pipefail

What it means: set -euo pipefail stops on errors and unset vars.

Example 2: Disk percent function

Type this:

python3 -c "u=91; print('ALERT' if u>=90 else 'ok')"

You will see:

ALERT

What it means: Threshold logic before any webhook.

Example 3: chmod private

Type this:

chmod 700 /tmp/health.sh
stat -c %a /tmp/health.sh 2>/dev/null || stat -f %A /tmp/health.sh

You will see:

700

What it means: Never world-writable scripts.

Concept 2: Metrics इकट्ठा

Why: Vibes पर alert नहीं। What: /proc/stat, meminfo, df -P। How: Stable columns parse करें।

Example 4: CPU from /proc

Type this:

grep '^cpu ' /proc/stat | awk '{print \$2}'

You will see:

... idle ticks ...

What it means: /proc/stat feeds CPU math on Linux.

Example 5: Memory available

Type this:

awk '/MemAvailable/ {print \$2}' /proc/meminfo

You will see:

2048123

What it means: Values are kB. Convert for humans.

Example 6: Disk use awk

Type this:

df -P / | awk 'NR==2 {print \$5}'

You will see:

39%

What it means: Use df -P for stable columns.

Concept 3: Report और exit

Why: Cron exit codes पढ़ता है। What: Report file; exit 0/2। How: Fake webhook URLs।

Example 7: Report file

Type this:

printf '%s\n' 'host=lab' 'disk=39%' 'mem_ok=yes' > /tmp/health-report.txt
cat /tmp/health-report.txt

You will see:

host=lab
disk=39%
mem_ok=yes

What it means: Reports beat silent scripts.

Example 8: Exit codes

Type this:

python3 -c "import sys; sys.exit(2)" ; echo exit=\$?

You will see:

exit=2

What it means: Non-zero exits drive cron alerts.

Example 9: Webhook dry-run

Type this:

printf '%s\n' 'POST https://hooks.example.invalid/alert' 'body={text: disk 91%}'

You will see:

POST https://hooks.example.invalid/alert
body={text: disk 91%}

What it means: Use a fake URL in labs; never commit real secrets.

Concept 4: Schedule

Why: न चलने वाली script बेकार। What: cron 5 मिनट; absolute paths। How: bash -n पहले।

Example 10: Cron line draft

Type this:

printf '%s\n' '*/5 * * * * /home/ec2-user/bin/health.sh >> /var/log/health.log 2>&1'

You will see:

*/5 * * * * /home/ec2-user/bin/health.sh >> /var/log/health.log 2>&1

What it means: Redirect stdout and stderr.

Example 11: PATH reminder

Type this:

printf '%s\n' 'Use absolute paths in cron' '/usr/bin/df not df'

You will see:

Use absolute paths in cron
/usr/bin/df not df

What it means: Cron has a tiny PATH.

Example 12: Test once

Type this:

bash -n /tmp/health.sh && echo SYNTAX_OK

You will see:

SYNTAX_OK

What it means: bash -n checks syntax without running.

Minimal shape

1. shebang + set -euo pipefail
2. disk percent

3. =90 तो exit 2

4. OK report
5. cron >> log 2>&1

Hyderabad e-commerce

Disk 92%. Webhook alert।

Check yourself (quiz)

Skeleton → metrics → thresholds → report → cron। Did you understand? Let us try it once more.