---
name: "erofs"
section: "5"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/erofs"
---

# erofs(5)

the Enhanced Read-Only File System

## NAME

erofs - the Enhanced Read-Only File System

## DESCRIPTION

**erofs** is a create-once read-only filesystem, with support for compression and a multi-device backing store.

There are two inode formats:

- •

  32-byte compact with 16-bit UID/GID, 32-bit file size, and no file times

- •

  64-byte extended with 32-bit UID/GID, 64-bit file size, and a modification time (*st\_mtim*).

### Mount options

- **user\_xattr** **nouser\_xattr**

  Controls whether *user* extended attributes are exposed. Defaults to yes.

- **acl** **noacl**

  Controls whether POSIX [**acl**(5)](/acl/5.md)s are exposed. Defaults to yes.

- **cache\_strategy**=**disabled**\|**readahead**\|**readaround**

  Cache allocation for compressed files: never, if reading from start of file, regardless of position. Defaults to **readaround**.

- **dax** **dax**=**always**\|**never**

  Direct Access control. If **always** and the source device supports DAX, uncompressed non-inlined files will be read directly, without going through the page cache. **dax** is a synonym for **always**. Defaults to unset, which is equivalent to **never**.

- **device**=***blobdev***

  Add extra device holding some of the data. Must be given as many times and in the same order as **--blobdev** was to [**mkfs.erofs**(1)](/mkfs.erofs/1.md).

- **domain\_id**=***did*** **fsid**=***id***

  Control CacheFiles on-demand read support. To be documented.

## VERSIONS

**erofs** images are versioned through the use of feature flags; these are listed in the **-E** section of [**mkfs.erofs**(1)](/mkfs.erofs/1.md),

## CONFIGURATION

Linux must be configured with the **CONFIG\_EROFS\_FS** option to mount EROFS filesystems. There are sub-configuration items that restrict the availability of some of the parameters above.

## SEE ALSO

[**mkfs.erofs**(1)](/mkfs.erofs/1.md), [**fsck.erofs**(1)](/fsck.erofs/1.md), [**dump.erofs**(1)](/dump.erofs/1.md)

*Documentation/filesystems/erofs.rst* in the Linux source.