diff --git a/osbase/build/mkerofs/def.bzl b/osbase/build/mkerofs/def.bzl
new file mode 100644
index 0000000..45f00d8
--- /dev/null
+++ b/osbase/build/mkerofs/def.bzl
@@ -0,0 +1,64 @@
+load("//osbase/build:def.bzl", "build_pure_transition", "build_static_transition")
+load("//osbase/build/fsspec:def.bzl", "FSSpecInfo", "fsspec_core_impl")
+
+def _erofs_image_impl(ctx):
+    fs_name = ctx.label.name + ".img"
+    fs_out = ctx.actions.declare_file(fs_name)
+
+    fsspec_core_impl(ctx, ctx.executable._mkerofs, fs_out)
+
+    return [DefaultInfo(files = depset([fs_out]))]
+
+erofs_image = rule(
+    implementation = _erofs_image_impl,
+    doc = """
+        Build an EROFS. All files specified in files, files_cc and all specified symlinks will be contained.
+        Executable files will have their permissions set to 0555, non-executable files will have
+        their permissions set to 0444. All parent directories will be created with 0555 permissions.
+    """,
+    attrs = {
+        "files": attr.string_keyed_label_dict(
+            mandatory = True,
+            allow_files = True,
+            doc = """
+                Dictionary of Labels to String, placing a given Label's output file in the EROFS at the location
+                specified by the String value. The specified labels must only have a single output.
+            """,
+            # Attach pure transition to ensure all binaries added to the initramfs are pure/static binaries.
+            cfg = build_pure_transition,
+        ),
+        "files_cc": attr.string_keyed_label_dict(
+            allow_files = True,
+            doc = """
+                 Special case of 'files' for compilation targets that need to be built with the musl toolchain like
+                 go_binary targets which need cgo or cc_binary targets.
+            """,
+            # Attach static transition to all files_cc inputs to ensure they are built with musl and static.
+            cfg = build_static_transition,
+        ),
+        "symlinks": attr.string_dict(
+            default = {},
+            doc = """
+                Symbolic links to create. Similar format as in files and files_cc, so the target of the symlink is the
+                key and the value of it is the location of the symlink itself. Only raw strings are allowed as targets,
+                labels are not permitted. Include the file using files or files_cc, then symlink to its location.
+          """,
+        ),
+        "fsspecs": attr.label_list(
+            default = [],
+            doc = """
+                List of file system specs (osbase.build.fsspec.FSSpec) to also include in the resulting image.
+                These will be merged with all other given attributes.
+            """,
+            providers = [FSSpecInfo],
+            allow_files = True,
+        ),
+
+        # Tools, implicit dependencies.
+        "_mkerofs": attr.label(
+            default = Label("//osbase/build/mkerofs"),
+            executable = True,
+            cfg = "exec",
+        ),
+    },
+)