Info.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>EXAppExtensionAttributes</key>
	<dict>
		<key>EXExtensionPointIdentifier</key>
		<string>com.apple.fskit.fsmodule</string>
		<key>FSActivateOptionSyntax</key>
		<dict>
			<key>shortOptions</key>
			<string>m:d:</string>
			<key>pathOptions</key>
			<dict>
				<key>m</key>
				<string>Path</string>
				<key>d</key>
				<string>Directory</string>
			</dict>
		</dict>
		<key>FSCheckOptionSyntax</key>
		<dict>
			<key>shortOptions</key>
			<string>nqy</string>
		</dict>
		<key>FSFormatOptionSyntax</key>
		<dict>
			<key>shortOptions</key>
			<string>v</string>
		</dict>
		<key>FSMediaTypes</key>
		<dict/>
		<key>FSPersonalities</key>
		<dict>
			<key>FSKitExpExtensionPersonality</key>
			<dict>
				<key>FSName</key>
				<string>MyFS</string>
				<key>FSfileObjectsAreCaseSensitive</key>
				<false/>
			</dict>
		</dict>
		<key>FSRequiresSecurityScopedPathURLResources</key>
		<false/>
		<key>FSShortName</key>
		<string>MyFS</string>
		<key>FSSupportsBlockResources</key>
		<true/>
		<key>FSSupportsGenericURLResources</key>
		<false/>
		<key>FSSupportsPathURLs</key>
		<false/>
		<key>FSSupportsServerURLs</key>
		<false/>
	</dict>
</dict>
</plist>

mount.sh

mount -F -t MyFS -o -m=./build.sh,-d=./  /dev/disk5 ./test

MyVolume.swift

import FSKit
import Foundation
import os


final class MyFSVolume: FSVolume {
    private let resource: FSResource
    var urls: [URL?]?
    var mount3: FSTaskOptions? = nil


    init(resource: FSResource) {
        self.resource = resource

        super.init(
            volumeID: FSVolume.Identifier(uuid: Constants.volumeIdentifier),
            volumeName: FSFileName(string: "Test1")
        )
    }
}

extension MyFSVolume: FSVolume.Operations {
    func activate(options: FSTaskOptions) async throws -> FSItem {
        self.p = [
            options.url(forOption: "m"),
            options.url(forOption: "d"),
        ]

        self.mount3 = options
    }
}