我正在尝试在运行 Debian 9.13 Stretch 的 Google Cloud Platform Debian 实例上安装 NPM。但是，如果我尝试使用$ sudo apt install npm我会收到以下消息
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
npm : Depends: nodejs (>= 6.11~) but 4.8.2~dfsg-1 is to be installed
Depends: node-abbrev (>= 1.1.1~) but 1.0.9-1 is to be installed
Depends: node-ansi-regex (>= 3.0~) but 2.0.0-1 is to be installed
Depends: node-cacache (>= 10.0.4~) but it is not going to be installed
Depends: node-config-chain (>= 1.1.11~) but it is not going to be installed
Depends: node-glob (>= 7.1.2~) but 7.1.1-1 is to be installed
Depends: node-hosted-git-info (>= 2.6~) but 2.1.5-1 is to be installed
Depends: node-ini (>= 1.3.5~) but 1.1.0-1+deb9u1 is to be installed
Depends: node-npm-package-arg but it is not going to be installed
Depends: node-jsonstream (>= 1.3.2~) but 1.0.3-4 is to be installed
Depends: node-libnpx (>= 10.0.1~) but it is not going to be installed
Depends: node-lockfile (>= 1.0.3~) but 0.4.1-1 is to be installed
Depends: node-lru-cache (>= 4.1.1~) but 4.0.2-1 is to be installed
Depends: node-move-concurrently (>= 1.0.1~) but it is not going to be installed
Depends: node-normalize-package-data (>= 2.4~) but 2.3.5-2 is to be installed
Depends: node-gyp (>= 3.6.2~) but 3.4.0-1 is to be installed
Depends: node-resolve-from (>= 4.0~) but 2.0.0-1 is to be installed
Depends: node-npmlog (>= 4.1.2~) but 0.0.4-1 is to be installed
Depends: node-osenv (>= 0.1.5~) but 0.1.0-1 is to be installed
Depends: node-read-package-json (>= 2.0.13~) but 1.2.4-1 is to be installed
Depends: node-request (>= 2.83~) but 2.26.1-1 is to be installed
Depends: node-retry (>= 0.10.1~) but 0.6.0-1 is to be installed
Depends: node-rimraf (>= 2.6.2~) but 2.5.4-2 is to be installed
Depends: node-semver (>= 5.5~) but 5.3.0-1 is to be installed
Depends: node-sha (>= 2.0.1~) but 1.2.3-1 is to be installed
Depends: node-slide (>= 1.1.6~) but 1.1.4-1 is to be installed
Depends: node-strip-ansi (>= 4.0~) but 3.0.1-1 is to be installed
Depends: node-tar (>= 4.4~) but 2.2.1-1 is to be installed
Depends: node-boxen (>= 1.2.1~) but it is not going to be installed
Depends: node-latest-version (>= 3.0~) but it is not going to be installed
Depends: node-which (>= 1.3~) but 1.2.11-1 is to be installed
E: Unable to correct problems, you have held broken packages.
我使用默认源列表，并尝试$sudo apt install -f npm多次运行sudo apt update标准命令来查找问题。有什么想法吗？也找不到此问题的错误报告。
编辑：输出sudo apt-cache policy npm
\npm:
Installed: (none)
Candidate: 5.8.0+ds6-2~bpo9+1
Version table:
5.8.0+ds6-2~bpo9+1 100
100 http://deb.debian.org/debian stretch-backports/main amd64 Packages
答案1
npm有点不寻常的情况是，仅在 Stretch 向后移植中可用，而不是在主要的 Debian 9 存储库中可用，同时还需要来自向后移植的其他软件包。因为后者不是默认安装候选者，所以您需要告诉apt考虑它们：
sudo apt install -t stretch-backports npm