This happens during an apt update and is related to an issue with sources.list, which is particularly troubling, if you are doing a "live-build".
P: Configuring file /etc/apt/sources.list
Hit:1 http://deb.debian.org/debian bullseye InRelease
Get:2 http://deb.debian.org/debian bullseye-updates InRelease [39.4 kB]
Ign:3 http://security.debian.org bullseye/updates InRelease
Err:4 http://security.debian.org bullseye/updates Release
404 Not Found [IP: 151.101.194.132 80]
Get:5 http://deb.debian.org/debian bullseye/main Sources [8627 kB]
Get:6 http://deb.debian.org/debian bullseye/main Translation-en [6241 kB]
Get:7 http://deb.debian.org/debian bullseye-updates/main Sources [1868 B]
Get:8 http://deb.debian.org/debian bullseye-updates/main amd64 Packages [2596 B]
Get:9 http://deb.debian.org/debian bullseye-updates/main Translation-en [2343 B]
Reading package lists... Done
E: The repository 'http://security.debian.org bullseye/updates Release' does not 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.
P: Begin unmounting filesystems...
P: Saving caches...
Reading package lists... Done
Building dependency tree... Done
The issue is with bullseye/updates which should be bullseye-security
Change this in sources.list:
deb http://security.debian.org/debian-security/ bullseye/updates main
deb-src http://security.debian.org/debian-security/ bullseye/updates main
To this:
deb http://security.debian.org/debian-security/ bullseye-security main
deb-src http://security.debian.org/debian-security/ bullseye-security main
--security=false
in your lb config line (eg. lb config --security=false)
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