您好，我在东芝 Portege R930 上运行 ubuntu 14.10，该电脑配备酷睿 i3 英特尔处理器、8GB RAM 和 320GB HDD。我还使用 Gnome flashback Metacity。我的问题是，当我尝试从终端升级到 15.04 时（经过一些更新后），我收到以下消息：
Checking package manager
Reading package lists... Done
Building dependency tree
Reading state information... Done
Building data structures... Done
Calculating the changes
Calculating the changes
Could not calculate the upgrade
An unresolvable problem occurred while calculating the upgrade.
This can be caused by:
* Upgrading to a pre-release version of Ubuntu
* Running the current pre-release version of Ubuntu
* Unofficial software packages not provided by Ubuntu
If none of this applies, then please report this bug using the
command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal.
Restoring original system state
Aborting
Traceback (most recent call last):
File "/usr/share/appgrid/appdata.py", line 207, in <module>
rebuild_db()
File "/usr/share/appgrid/appdata.py", line 174, in rebuild_db
website text);''')
sqlite3.OperationalError: disk I/O error
Traceback (most recent call last):
File "/usr/share/appgrid/appdata.py", line 207, in <module>
rebuild_db()
File "/usr/share/appgrid/appdata.py", line 174, in rebuild_db
website text);''')
sqlite3.OperationalError: disk I/O error
Reading package lists... Done
Building dependency tree
Reading state information... Done
Building data structures... Done
我想知道错误来源是什么以及如何修复它。此外，如果我运行软件更新程序（即使在软件管理器中选择了检查任何新的 ubuntu 版本），我也会收到您的软件是最新的消息。有人可以帮忙吗？