root@armadillo:~# apt update
Ign:1 http://security.debian.org stretch/updates InRelease
Ign:2 http://download.atmark-techno.com/debian stretch InRelease
Hit:3 http://download.atmark-techno.com/debian stretch Release
Err:4 http://security.debian.org stretch/updates Release
  404  Not Found [IP: 146.75.114.132 80]
Ign:5 http://ftp.jp.debian.org/debian stretch InRelease
Err:6 http://ftp.jp.debian.org/debian stretch Release
  404  Not Found
Reading package lists... Done
E: The repository 'http://security.debian.org stretch/updates Release' does no longer have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://ftp.jp.debian.org/debian stretch Release' does no longer have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.