我在使用Artison迁移和播种识别课程时遇到了问题。我已经读过，composer dumpautoload可以解决这个问题，但我现在在Cloud9上运行dump-autoload时遇到了问题。
当我跑步时：$ composer dump-autoload
我收到以下错误：
[ErrorException]
file_put_contents(/home/ubuntu/workspace/vendor/composer/autoload_namespaces.php): failed to open stream: Permission denied
当我跑步时：
$ composer update
我得到以下内容：
Cannot create cache directory /home/ubuntu/.composer/cache/repo/https---packagist.org/, or directory is not writable. Proceeding without cache
Cannot create cache directory /home/ubuntu/.composer/cache/files/, or directory is not writable. Proceeding without cache
You are running composer with xdebug enabled. This has a major impact on runtime performance. See https://getcomposer.org/xdebug
Loading composer repositories with package information
Updating dependencies (including require-dev)
- Removing symfony/yaml (v3.1.5)
Update failed (Could not delete /home/ubuntu/workspace/vendor/symfony/yaml/Dumper.php: )
它看起来像是权限问题。我的问题是：如何在Cloud9环境中解决这些问题？