Cron 작업으로 Ubuntu 시스템 유지 관리 자동화

Keeping your Ubuntu server healthy requires more than installing package updates. Over time, unused packages, cached APT files, and Docker resources can consume valuable disk space and affect system performance.

By automating routine maintenance with cron, you can ensure your server stays secure, up to date, and clean without manual intervention.

In this guide, you’ll create a maintenance script that:

• Updates package lists
• Installs available package upgrades
• Removes unused packages
• Cleans the APT cache
• Removes unused Docker resources
• Logs maintenance activities
• Prevents overlapping executions

Prerequisites

• Operating System: Ubuntu
• User: admin (sudo privileges)
• Docker: Installed (optional)
• Scripts Directory: /home/admin/linux/scripts

Step 1: Create a Directory for Scripts

Create a dedicated directory to organize your Linux administration scripts.

mkdir -p /home/admin/linux/scripts

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Step 2: Create the Maintenance Script

Create the script.

touch /home/admin/linux/scripts/system_maintenance.sh
chmod +x /home/admin/linux/scripts/system_maintenance.sh

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Open the file and paste the following:

#!/bin/bash

set -euo pipefail

LOG_FILE="/var/log/system_maintenance.log"
LOCK_FILE="/tmp/system_maintenance.lock"

exec 200>"$LOCK_FILE"
flock -n 200 || exit 1

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

log "========== Starting system maintenance =========="

log "Updating package lists..."
sudo apt update

log "Upgrading installed packages..."
sudo apt upgrade -y

log "Removing unused packages..."
sudo apt autoremove -y

log "Cleaning APT cache..."
sudo apt autoclean -y

if command -v docker >/dev/null 2>&1; then
    log "Cleaning Docker resources..."
    sudo docker system prune -af --volumes
fi

log "========== System maintenance completed =========="

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Understanding the Script

Enable Safe Bash Options

set -euo pipefail

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These options make the script more reliable.

• -e Exit immediately if a command fails.
• -u Treat undefined variables as errors.
• pipefail Detect failures inside pipelines.

Prevent Multiple Executions

LOCK_FILE="/tmp/system_maintenance.lock"

exec 200>"$LOCK_FILE"
flock -n 200 || exit 1

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If the previous maintenance job is still running, another instance will not start.

This prevents:

• duplicate updates
• package manager conflicts
• simultaneous Docker cleanup

Update Ubuntu Packages

sudo apt update
sudo apt upgrade -y

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These commands:

• Refresh package indexes.
• Install all available updates automatically.

Remove Unused Packages

sudo apt autoremove -y

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Removes packages that are no longer required by the system.

Clean the APT Cache

sudo apt autoclean -y

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Deletes obsolete package files from the local package cache to reclaim disk space.

Clean Docker Resources

sudo docker system prune -af --volumes

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This removes unused Docker resources, including:

• stopped containers
• dangling images
• unused images
• unused networks
• build cache
• unused volumes

Note: Running containers and resources currently in use are not removed.

Step 3: Create the Log File

Since /var/log is owned by root, create the log file once:

sudo touch /var/log/system_maintenance.log
sudo chown admin:admin /var/log/system_maintenance.log

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Example output:

[2026-07-22 01:00:00] Starting system maintenance
[2026-07-22 01:00:01] Updating package lists...
[2026-07-22 01:00:45] Upgrading installed packages...
[2026-07-22 01:01:10] Removing unused packages...
[2026-07-22 01:01:25] Cleaning APT cache...
[2026-07-22 01:01:40] Cleaning Docker resources...
[2026-07-22 01:01:55] System maintenance completed.

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Step 4: Configure Passwordless sudo

Cron jobs cannot respond to password prompts.

Edit the sudoers file:

sudo visudo

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Add the following line:

admin ALL=(ALL) NOPASSWD: /usr/bin/apt, /usr/bin/docker

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This allows the admin user to execute only the required commands without entering a password.

Step 5: Schedule the Cron Job

Open your crontab.

crontab -e

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Add the following entry:

0 1 * * * /home/admin/linux/scripts/system_maintenance.sh >> /var/log/system_maintenance.log 2>&1

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This runs the maintenance script every day at 1:00 AM.

Check created cronjob:

crontab -l

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Testing the Script

Before relying on cron, execute the script manually.

/home/admin/linux/scripts/system_maintenance.sh

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Recommended Directory Structure

Keeping administration scripts organized makes long-term maintenance easier.

/home/admin/linux/
├── scripts/
│   ├── system_maintenance.sh
│   ├── backup.sh
│   ├── docker_cleanup.sh
│   └── ssl_renew.sh
├── logs/
└── configs/

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Maintenance Tasks Performed

Task Command Update package lists sudo apt update Upgrade packages sudo apt upgrade -y Remove unused packages sudo apt autoremove -y Clean package cache sudo apt autoclean -y Clean Docker resources sudo docker system prune -af --volumes

Conclusion

Automating routine maintenance with cron is an easy way to keep your Ubuntu server secure, efficient, and free from unnecessary disk usage. By combining package updates, cache cleanup, and Docker pruning into a single scheduled task, you reduce manual administration while ensuring your system stays in good condition.

Review the maintenance logs periodically, monitor available disk space, and adjust the schedule as needed to match your server’s workload.