我运行 aptautoremove apt upgrade apt upgrade并得到：
Reading package lists... Done
Building dependency tree
Reading state information... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
然后运行do-release-upgrade并得到
Checking for a new Ubuntu release
Get:1 Upgrade tool signature [1,554 B]
Get:2 Upgrade tool [1,341 kB]
Fetched 1,343 kB in 0s (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 …upgrade ×1