In the release of Fedora 42, scheduled for the end of April, it is planned to transition the entire distribution from SquashFS to the erofs file system, with support implemented in the tools for creating boot images Dracut 103. The proposal is pending approval by the Fesco Committee (Fedora Engineering Steering Committee), responsible for the technical development of the Fedora distribution.
The reasons for the transition include the more active development of EROFS (the latest tooling for the instrumentation squashfs was in spring of 2023) and the expanded capabilities offered by erofs for future involvement. EROFS aims to transition all builds to using system images in read-only mode, such as Live editions with KDE, XFCE, BUDGIE, LXQT, MIRACLEWM, and COSMIC, as well as the Fedora Kde Plasma Mobile and Fedora Coreos Live editions.
Squashfs and EROFS file systems are optimized for read-only mode and provide compact metadata representation and storage of compressed data. EROFS (Extendable Read-Only File System) was developed by Huawei with a focus on maximizing performance. EROFS uses a unique data compression method involving fixed size compressed blocks (unlike other file systems where block sizes vary post-compression). When accidentally accessed, EROFS outperforms EXT4 by a significant margin (with a compression level of 4, EROFS was almost three times faster on Flash storage compared to 6 times slower on a hard drive).