我买了一台预装了 Ubuntu Focal Fossa 的新电脑。我将 UI 更改为 Kubuntu，并从软件更新程序升级到 Groovy Gorilla（更新后，它告诉我有可用的升级，我只需选择“升级”按钮），它似乎运行良好（PC 行为总体上很好，软件源是 Groovy），但后来我意识到它仍然在 os-release 中报告“Focal”，并不断告诉我有可用的升级（Groovy）
我使用 sudo do-release-upgrade 完成升级，尝试过，但失败了。更新存储库信息后，显示以下内容：
- 更新存储库信息
- 第三方源已禁用 您的 sources.list 中的某些第三方条目已禁用。您可以在升级后使用“software-properties”工具或包管理器重新启用它们。
- 要继续，请按 [ENTER]
然后我按下 ENTER 键后，它继续计算更改，然后：
- 计算变化
- 恢复原始系统状态
- 正在中止
- 正在读取软件包列表...完成
- 构建依赖关系树
- 正在读取状态信息...完成
我确认“软件和更新”中显示的所有源都已选中且未被禁用，但这没有帮助。我怀疑有些源（Focal 源？）已经消失，但这次升级需要它们。
在我之前的电脑上，我从 Gutsy Gibbon 开始就一直使用 Kubuntu，从来没有遇到过这样的问题。有什么想法吗？我知道我可以从头开始重新安装，但如果我能避免它......
谢谢。
更新5/9/21：main.log中有一个错误：
2021-05-09 14:35:36,406 错误安装/升级“baloo-kf5”失败
我尝试安装 baloo-kf5，但它已经安装好了。因此，我卸载了它并重新启动升级，但它只是重新安装了它，我的情况与之前相同 - 重新启动后，它完成了安装，但出现相同的错误。
日志中的最后几行是：
2021-05-09 14:35:36,950 DEBUG Upgradable, but held- back:
2021-05-09 14:35:36,950 DEBUG Remove:
2021-05-09 14:35:36,950 DEBUG Install:
2021-05-09 14:35:36,950 DEBUG Upgrade:
2021-05-09 14:35:36,973 DEBUG apt btrfs snapshots supported: False
2021-05-09 14:35:36,973 DEBUG cache aufs_rw_dir: /tmp/
2021-05-09 14:35:36,974 DEBUG Free space on /: 175477112832
2021-05-09 14:35:36,974 DEBUG Dir /usr mounted on /
2021-05-09 14:35:36,974 DEBUG Dir /var mounted on /
2021-05-09 14:35:36,974 DEBUG Dir /boot mounted on /
2021-05-09 14:35:36,974 DEBUG Dir /var/cache/apt/archives mounted on /
2021-05-09 14:35:36,974 DEBUG Dir /tmp mounted on /
2021-05-09 14:35:36,974 DEBUG Dir /home mounted on /
2021-05-09 14:35:36,974 DEBUG Dir /tmp mounted on /
2021-05-09 14:35:36,974 DEBUG fs_free contains: '{'/': <DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7feb66a411f0>, '/usr': <DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7feb66a411f0>, '/var': <DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7feb66a411f0>, '/boot': <DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7feb66a411f0>, '/var/cache/apt/archives': <DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7feb66a411f0>, '/tmp': <DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7feb66a411f0>, '/home': <DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7feb66a411f0>}'
2021-05-09 14:35:37,242 DEBUG dir '/var/cache/apt/archives' needs '0' of '<DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7feb66a411f0>' (175477112832.000000)
2021-05-09 14:35:37,242 DEBUG dir '/usr' needs '0' of '<DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7feb66a411f0>' (175477112832.000000)
2021-05-09 14:35:37,242 DEBUG dir '/var' needs '0' of '<DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7feb66a411f0>' (175477112832.000000)
2021-05-09 14:35:37,242 DEBUG dir '/usr' needs '52428800' of '<DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7feb66a411f0>' (175477112832.000000)
2021-05-09 14:35:37,242 DEBUG dir '/boot' needs '85309190.4' of '<DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7feb66a411f0>' (175424684032.000000)
2021-05-09 14:35:37,242 DEBUG dir '/tmp' needs '5242880' of '<DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7feb66a411f0>' (175339374841.600006)
2021-05-09 14:35:37,242 DEBUG dir '/' needs '10485760' of '<DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7feb66a411f0>' (175334131961.600006)
2021-05-09 14:35:37,242 DEBUG dir '/tmp' needs '0.0' of '<DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7feb66a411f0>' (175323646201.600006)
2021-05-09 14:35:37,242 DEBUG dir '/usr' needs '0.0' of '<DistUpgrade.DistUpgradeCache.MyCache.checkFreeSpace.<locals>.FreeSpace object at 0x7feb66a411f0>' (175323646201.600006)
2021-05-09 14:35:37,242 DEBUG Found writable ESP /dev/nvme0n1p1 /boot/efi vfat rw,relatime,fmask=0077,dmask=0077,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro 0 0
2021-05-09 14:35:37,244 DEBUG demoted: 'libmpdec2'
2021-05-09 14:35:37,244 DEBUG found components: {'groovy': {'universe', 'restricted', 'multiverse', 'main'}, 'groovy-updates': {'universe', 'restricted', 'multiverse', 'main'}, 'groovy-security': {'universe', 'restricted', 'multiverse', 'main'}}
2021-05-09 14:35:37,244 DEBUG abort called
2021-05-09 14:35:37,245 DEBUG openCache()
2021-05-09 14:35:38,564 DEBUG Comparing 5.8.0-50 with
2021-05-09 14:35:38,624 DEBUG /openCache(), new cache size 67707
我不明白是什么导致了“中止调用”。