What Is tmpfs in Linux? How tmpfs Works, Use Cases & Best Practices

tmpfs is a temporary in-memory file system used in Linux to store files directly in RAM instead of on disk. It is designed for fast read/write operations, making it an ideal choice for storing runtime data, temporary files, and volatile information that does not need to persist after reboot.

In a Linux server environment, understanding how tmpfs works is essential for optimizing performance, reducing I/O load, and improving overall system efficiency.

How tmpfs Works

When you create a tmpfs mount, Linux allocates storage in RAM (and swap, if available). Unlike traditional disk-based file systems, tmpfs dynamically grows and shrinks based on the data stored in it.

Key characteristics:

• Stored in system RAM (very fast)
• Data is lost on reboot
• Size is dynamic (up to a specified limit)
• Can use both RAM and swap memory
• Ideal for temporary or ephemeral data

Where tmpfs Is Used in Linux

Modern Linux systems automatically create several tmpfs mounts for system operations.

Common default mounts include:

• /run – system runtime data
• /dev/shm – shared memory
• /tmp (in some distributions)
• /run/user/<UID> – user session data
• /sys/fs/cgroup – cgroup hierarchy (systemd)

In containerized environments like Docker, Podman, or Kubernetes, additional tmpfs mounts may appear for isolated runtime directories.

Benefits of Using tmpfs

1. Extremely Fast Performance
Data is stored in RAM, providing near-zero latency and very high throughput.

2. Reduced Disk I/O
Helps extend SSD lifespan and reduce bottlenecks in high I/O workloads.

3. Automatically Clears on Reboot
Useful for temporary or sensitive data that should not persist.

4. Flexible and Dynamic
Grows and shrinks depending on actual usage.

5. Improves Application Performance
Ideal for caching, sessions, and temporary build files.

Common Use Cases of tmpfs

• Storing temporary application files
• Web server session storage (e.g., NGINX, Apache)
• Build and compilation directories
• High-performance caching (Redis, Memcached)
• Database temporary directories (MySQL, PostgreSQL)
• Container runtime storage
• Fast log buffering and analytics

How to Create a tmpfs Mount

You can create a tmpfs mount manually using the following command:

sudo mount -t tmpfs -o size=1G tmpfs /mnt/mytmp

This creates a 1 GB RAM-based temporary file system at /mnt/mytmp.

To make it persistent across reboots, add it to /etc/fstab:

tmpfs   /mnt/mytmp   tmpfs   size=1G,mode=1777   0  0

How to Check tmpfs Usage

You can list all tmpfs mounts:

mount | grep tmpfs

Or check memory usage:

df -hT | grep tmpfs

Security Considerations

Although tmpfs operates in memory, it is still important to secure it properly.

• Use permissions to restrict access.
• Limit size to prevent memory exhaustion.
• Use nodev, nosuid, noexec mount options for additional security.

Example secure mount:

tmpfs /tmp tmpfs size=2G,noexec,nodev,nosuid 0 0

Best Practices

• Do not allocate too much RAM to tmpfs on production servers.
• Monitor memory usage regularly to prevent OOM issues.
• Use tmpfs only for data that can safely be lost.
• For sensitive runtime data, apply strict permissions.
• Use swap only if appropriate for your workload.

Conclusion

tmpfs is a powerful and efficient memory-based file system that plays a crucial role in Linux performance and runtime operations. It provides exceptional speed, flexibility, and low overhead, making it ideal for temporary storage, application caching, and system processes.

By understanding how tmpfs works and applying proper configuration and security practices, administrators can significantly enhance system performance and reliability.

Frequently Asked Questions (FAQ)