升级 Ubuntu 时出现“无候选版本”软件包该怎么办？

Question

将服务器从 18.04 升级到 20.04 我得到了无候选版本包的列表。我该如何处理这个列表？是否应该将它们移除并清理干净？

例如，我知道我不需要旧版本的 PHP 包，但如果我遇到类似systemd-services我不知道的东西，我如何检查这些是否是必需的，并在必要时安全地删除它们？

忽略此警告不会阻止升级完成。

No candidate ver:  libxcb-util0
No candidate ver:  libxmlada4.1
No candidate ver:  libxmlada4.4.0
No candidate ver:  libxp6
No candidate ver:  libxtables10
No candidate ver:  libyahoo2-11
No candidate ver:  libzeroc-ice35
No candidate ver:  linux-image-3.13.0-123-generic
No candidate ver:  linux-image-3.13.0-48-generic
No candidate ver:  linux-image-3.13.0-68-generic
No candidate ver:  linux-image-4.4.0-121-generic
No candidate ver:  linux-image-4.4.0-140-generic
No candidate ver:  linux-image-4.4.0-178-generic
No candidate ver:  linux-image-4.4.0-185-generic
No candidate ver:  linux-image-4.4.0-83-generic
No candidate ver:  linux-image-extra-4.4.0-121-generic
No candidate ver:  linux-image-extra-4.4.0-140-generic
No candidate ver:  linux-image-extra-4.4.0-83-generic
No candidate ver:  linux-modules-4.4.0-178-generic
No candidate ver:  linux-modules-4.4.0-185-generic
No candidate ver:  linux-modules-extra-4.4.0-178-generic
No candidate ver:  linux-modules-extra-4.4.0-185-generic
No candidate ver:  lxc-common
No candidate ver:  mountall
No candidate ver:  mysql-server-5.5
No candidate ver:  perl-modules
No candidate ver:  php5-cli
No candidate ver:  php5-common
No candidate ver:  php5-curl
No candidate ver:  php5-gd
No candidate ver:  php5-intl
No candidate ver:  php5-json
No candidate ver:  php5-mcrypt
No candidate ver:  php5-mysql
No candidate ver:  php5-readline
No candidate ver:  php7.0-bz2
No candidate ver:  php7.0-cli
No candidate ver:  php7.0-common
No candidate ver:  php7.0-curl
No candidate ver:  php7.0-gd
No candidate ver:  php7.0-intl
No candidate ver:  php7.0-json
No candidate ver:  php7.0-mbstring
No candidate ver:  php7.0-mcrypt
No candidate ver:  php7.0-mysql
No candidate ver:  php7.0-opcache
No candidate ver:  php7.0-readline
No candidate ver:  php7.0-xml
No candidate ver:  php7.0-zip
No candidate ver:  python3-aptdaemon.pkcompat
No candidate ver:  python3.4
No candidate ver:  python3.4-minimal
No candidate ver:  python3.5-minimal
No candidate ver:  ruby1.9.1
No candidate ver:  systemd-services
No candidate ver:  systemd-shim
No candidate ver:  sysv-rc
No candidate ver:  upstart
No candidate ver:  webmin

正如评论中提到的，据我所知，这最初是 Ubuntu 14.04 服务器，并且也一直升级到 16.04。

Answer 1

看来这些是可以清除的旧的未使用的包：

sudo apt purge `dpkg --list | grep ^rc | awk '{ print $2; }'`

（我在这里找到此信息：https://butwt.wordpress.com/2020/06/29/problems-upgrading-ubuntu-server-lts/）