Ext4
Definition
The fourth extended file system, the default Linux file system used for the userdata partition on most Android devices before widespread F2FS adoption. Uses a journal for metadata consistency, stores file metadata in inodes, and supports extents for large files. Deleted file recovery is possible when inode entries and journal entries have not yet been overwritten.
- Full name
- Fourth extended file system
- Platform
- Default Android userdata filesystem before F2FS adoption
- Metadata structure
- Inodes plus a journal for consistency
- Large file support
- Extents
- Recovery condition
- Possible if inode and journal entries not yet overwritten
Common questions
Why does ext4's journal matter for forensic recovery of deleted files?+
The journal records metadata changes for crash consistency, and deleted-file metadata can sometimes survive briefly in journal entries even after the directory entry and inode are marked free, giving an examiner a short window to recover file information.
Why did many Android devices move from ext4 to F2FS?+
F2FS was designed specifically for NAND flash storage and generally offers better write performance and wear characteristics on flash media than ext4, which was originally designed for spinning disks, though ext4 remains in use on some devices and partitions.
Related terms
- APFS (Apple File System)
- The default file system on iOS devices since iOS 10.3. Features include 64-bit inode numbers, copy-on-write metadata, file-level encryption using per-file keys,...
- App Sandbox (iOS)
- The iOS isolation mechanism combining UNIX file permissions, signed entitlements, and TrustedBSD mandatory access control. Each app is confined to a container...
- Data Protection Classes (iOS)
- iOS encrypts each file under one of four protection classes that control when the file's encryption key is available: Complete (key available...
- F2FS (Flash-Friendly File System)
- A log-structured file system designed for NAND flash, used on the userdata partition of many modern Android devices including Samsung Galaxy and...
- UID-Based Sandbox (Android)
- Android's application isolation model in which each installed app receives a unique Linux user ID at install time. The app's private data...