ある日突然、WSL2でドメイン名が解決できないためにアップグレードできない事象に陥りました。
$ sudo apt-get update Ign:1 http://archive.ubuntu.com/ubuntu jammy InRelease Ign:2 http://security.ubuntu.com/ubuntu jammy-security InRelease Ign:3 https://ppa.launchpadcontent.net/ondrej/php/ubuntu jammy InRelease Ign:4 http://archive.ubuntu.com/ubuntu jammy-updates InRelease Ign:2 http://security.ubuntu.com/ubuntu jammy-security InRelease (中略) Err:5 http://archive.ubuntu.com/ubuntu jammy-backports InRelease Temporary failure resolving 'archive.ubuntu.com' Reading package lists... Done Building dependency tree... Done Reading state information... Done 34 packages can be upgraded. Run 'apt list --upgradable' to see them. W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/jammy/InRelease Temporary failure resolving 'archive.ubuntu.com' W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/jammy-updates/InRelease Temporary failure resolving 'archive.ubuntu.com' W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/jammy-backports/InRelease Temporary failure resolving 'archive.ubuntu.com' W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/jammy-security/InRelease Temporary failure resolving 'security.ubuntu.com' W: Failed to fetch https://ppa.launchpadcontent.net/ondrej/php/ubuntu/dists/jammy/InRelease Temporary failure resolving 'ppa.launchpadcontent.net' W: Some index files failed to download. They have been ignored, or old ones used instead.