Romfs

{{Short description|Simple read-only file system used chiefly for early boot and embedded systems}} {{ infobox file system | name = romfs | developer = | full_name = | variants = | introduction_date = | introduction_os = | partition_id = | directory_struct = | file_struct = | file_types = | bad_blocks_struct = | bootable = | min_volume_size = | max_volume_size = | max_file_size = | file_size_granularity = | max_files_no = | max_filename_size = | max_dirname_size = | max_directory_depth = | filename_character_set = | dates_recorded = | date_range = | date_resolution = | forks_streams = | attributes = | file_system_permissions = | compression = | encryption = | data_deduplication = | copy_on_write = | OS = Unix-like systems | website = }}

{{Portal|Free and open-source software}} '''ROMFS''' (Read-Only Memory File System) is a minimal, read-only computing file system designed for storing files in read-only memory, particularly in Electrically Erasable Programmable Read-Only Memory (EEPROM) or similar ROM media. Due to its small size and straightforward design, it's commonly used in devices where system resources are limited. It's a part of the Linux Kernel since version 2.1.21<ref>{{cite web|url=https://romfs.sourceforge.net/|title=romfs information}}</ref> and can be implemented on other Unix-like systems with appropriate support.<ref>{{cite web |title=ROMFS - ROM File System |url=https://docs.kernel.org/filesystems/romfs.html |website=Linux Kernel Documentation |access-date=14 August 2025}}</ref>

== Usage == ROMFS is often used as an initial ROM or initial RAM disk containing kernel modules or essential system files that can be loaded during the boot process.<ref>{{cite web |title=Is this exactly what RomFS in the Linux kernel does? |url=https://stackoverflow.com/questions/10595624/is-this-exactly-what-romfs-in-linux-kernel-does |website=Stack Overflow |access-date=14 August 2025}}</ref> Its implementation requires minimal code, making it suitable for embedded systems and boot floppies.<ref>{{cite book |last=Yaghmour |first=Karim |title=Building Embedded Linux Systems |publisher=O'Reilly Media |year=2003 |isbn=978-0596002220}}</ref> The primary advantage of ROMFS is the ability to decrease the size of a kernel. (excluding modules) <ref>{{cite web|url=https://docs.kernel.org/filesystems/romfs.html|title=ROMFS - ROM File System}}</ref>

== Technical details == ROMFS stores files sequentially in contiguous blocks. The description of the filesystem layout is documented in the Linux kernel source tree and can be accessed through the LXR romfs.rst.<ref>{{cite web |title=ROMFS filesystem layout |url=http://lxr.linux.no/source/Documentation/filesystems/romfs.rst |website=LXR Cross Referencer |access-date=14 August 2025}}</ref> ROMFS does not store modification dates or UNIX-like permissions.<ref>{{cite web|url=https://romfs.sourceforge.net/|title=romfs information}}</ref>

== Limitations == ROMFS works on data aligned to 16 byte boundaries, yet most hardware works on data aligned to 1024 byte boundaries.<ref>{{cite web|url=https://docs.kernel.org/filesystems/romfs.html|title=ROMFS - ROM File System}}</ref> As a result, the file system must be padded.

== Platform Support and Tools == Apart from support in the Linux Kernel Nikolay Aleksandrov developed romfser (ROMFS Extractor/Reader), an open-source tool to extract and manipulate ROMFS images, which primarily intended for the BSD family of operating systems, which do not include native ROMFS support.<ref>{{cite web |title=romfser GitHub repository |url=https://github.com/NikAleksandrov/romfser |access-date=14 August 2025}}</ref> Another tool is genromfs, which is a user program for creating a romfs filesystem.<ref>{{cite web|url=https://docs.kernel.org/filesystems/romfs.html|title=ROMFS - ROM File System}}</ref>

== References == {{Reflist}}

== External links == * [https://docs.kernel.org/filesystems/romfs.html Linux Kernel Documentation – ROMFS] * [http://lxr.linux.no/source/Documentation/filesystems/romfs.rst ROMFS layout on LXR]

Category:Free special-purpose file systems Category:File systems supported by the Linux kernel