https://DevOpsCloud.io -- Cloud Monk Losang Jinpa, Ph.D., MCSE/MCT, GitOps DevOps Engineer

Return to Filesystems, Android

The Android operating system utilizes several filesystems to manage different types of data, ensuring efficient storage, accessibility, and file security. Each of these filesystems serves specific purposes, from storing app data to managing system resources. Below is a detailed look at the commonly used filesystems in Android:

ext4 is the default filesystem for Android's internal storage. It provides improved performance, filesystem journaling, and support for large files and partitions. ext4 ensures faster read/write operations and better crash recovery, making it ideal for handling the system and application data.

f2fs (Flash-Friendly File System) is optimized for NAND flash-based storage, commonly used in smartphones. It improves write performance and endurance by reducing the impact of random writes and enhancing wear-leveling across the storage.

erofs (Enhanced Read-Only File System) is designed for better read performance, primarily used for system partitions. Since these partitions are typically read-only, erofs improves space efficiency and read speeds.

yaffs2 (Yet Another Flash File System 2) was initially used for NAND storage in earlier versions of Android. It’s now less common but still relevant in legacy devices or special embedded systems with older flash memory requirements.

These filesystems are typically used for external storage devices like SD cards. vfat offers compatibility with older operating systems, while exFAT supports larger files and better storage handling for modern multimedia files.

• **squashfs**

   [[squashfs]] is a compressed, read-only filesystem used in some parts of the [[Android]] system, such as boot or recovery partitions. It reduces storage requirements while keeping data accessible for system processes.

• **tmpfs**

   [[tmpfs]] is used for temporary data storage during runtime. Since it exists in memory, it ensures faster access but gets erased upon device reboot, making it suitable for caches and temporary files.

• **ramfs**

   [[ramfs]] is another memory-based filesystem, similar to [[tmpfs]], but it does not support swapping. It is used for specific temporary data that requires fast access but doesn’t need persistence.

• **overlayfs**

   [[overlayfs]] allows multiple filesystems to coexist by stacking them. It is used during over-the-air (OTA) updates and debugging processes to temporarily modify the system without permanently changing the underlying files.

Android leverages multiple filesystems, each optimized for specific storage needs, balancing speed, reliability, and security. With the evolution of storage technologies, newer filesystems like f2fs and erofs have become essential to enhance performance, particularly for flash-based storage. Understanding these filesystems helps developers and administrators manage devices efficiently, especially in scenarios involving updates, custom ROMs, or troubleshooting storage-related issues.