目前，我已经安装了 Ubuntu 18.04.5 LTS。
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=18.04
DISTRIB_CODENAME=bionic
DISTRIB_DESCRIPTION="Ubuntu 18.04.5 LTS"
现在，我想从 Ubuntu 18.04.5 LTS 更新到 Ubuntu 20.04 LTS。我遵循了以下步骤。
sudo apt update
Fetched 70.0 kB in 32s (2,195 B/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
All packages are up to date.
sudo apt list --upgradable
Listing... Done
sudo apt upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
sudo reboot
sudo apt --purge autoremoveReading package lists... Done
Building dependency tree
Reading state information... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
sudo apt install update-manager-core
sudo do-release-upgrade
已开始处理更新
Checking for a new Ubuntu release
Get:1 Upgrade tool signature [1,554 B]
Get:2 Upgrade tool [1,336 kB]
Fetched 1,338 kB in 6s (0 B/s)
authenticate 'focal.tar.gz' against 'focal.tar.gz.gpg'
extracting 'focal.tar.gz'
Reading cache
Checking package manager
Reading package lists... Done
Building dependency tree
Reading state information... Done
Fetched 70.0 kB in 6s (0 B/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
Restoring original system state
Aborting
Reading package lists... Done
Building dependency tree
Reading state information... Done
由于某种原因，它停止升级。有人能帮助我吗？谢谢。