.CRAMFS File Extension
CramFS Filesystem Image
| Developer | Linus Torvalds |
| Popularity |
2.0 | 1 Vote |
What is a CRAMFS file?
A CRAMFS file is a filesystem disk image that stores an entire directory structure in the Compressed ROM File System (CramFS). It contains files, folders, permissions, and basic metadata exactly as they appear in the original filesystem, inside a read-only image compressed to reduce size. The format was designed for small storage environments where saving space matters, such as embedded Linux systems and firmware.
More Information
CramFS uses a simple block-based compression method and does not support modifying files after the image is created. Because it is read-only, systems load it directly into memory and access its contents without first unpacking everything. This feature makes it useful for devices that must boot quickly from limited storage, including routers, network appliances, and older embedded devices.
NOTE: Linus Torvalds developed the Compressed ROM File System (CramFS) format as part of early Linux kernel work on embedded and memory-limited systems. CramFS was later maintained within the Linux kernel codebase and used primarily by embedded Linux developers building firmware for small devices such as routers and appliances.
How to open a CRAMFS file
You can open CRAMFS files with various Linux tools that support the CramFS filesystem. On a Linux system, you can mount the image with the mount command using the cramfs filesystem type, allowing you to browse it like a normal directory. An example command:
sudo mount -t cramfs firmware.cramfs /mnt/cramfs
You can also extract its contents using utilities such as cramfsck or binwalk.