apt update error

Submitted by 세벌 on 2021.08.28.(Sat) - 03:46

apt update 하면
기존:1 http://ftp.kr.debian.org/debian bullseye InRelease                                                  
기존:2 http://ftp.kr.debian.org/debian bullseye-updates InRelease                                          
기존:3 http://ftp.kr.debian.org/debian bullseye-backports InRelease
무시:4 http://security.debian.org/debian-security bullseye-updates InRelease
오류:5 http://security.debian.org/debian-security bullseye-updates Release
  404  Not Found [IP: 151.101.90.132 80]
패키지 목록을 읽는 중입니다... 완료
E: The repository 'http://security.debian.org/debian-security 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.

이런 메시지가 나오네요. 어떻게 하면 되나요?

아래는 /etc/apt/source.lit 파일 내용.

#

# deb cdrom:[Debian GNU/Linux 10.7.0 _Buster_ - Official amd64 NETINST 20201205-11:16]/ bullseye main

#deb cdrom:[Debian GNU/Linux 10.7.0 _Buster_ - Official amd64 NETINST 20201205-11:16]/ bullseye main

deb http://ftp.kr.debian.org/debian/ bullseye main contrib non-free
deb-src http://ftp.kr.debian.org/debian/ bullseye main contrib non-free

deb http://security.debian.org/debian-security bullseye-updates main contrib non-free
deb-src http://security.debian.org/debian-security bullseye-updates main contrib non-free

# bullseye-updates, previously known as 'volatile'
deb http://ftp.kr.debian.org/debian/ bullseye-updates main contrib non-free
deb-src http://ftp.kr.debian.org/debian/ bullseye-updates main contrib non-free

deb http://ftp.kr.debian.org/debian/ bullseye-backports main contrib non-free
deb-src http://ftp.kr.debian.org/debian/ bullseye-backports main contrib non-free

# This system was installed using small removable media
# (e.g. netinst, live or single CD). The matching "deb cdrom"
# entries were disabled at the end of the installation process.
# For information about how to configure apt package sources,
# see the sources.list(5) manual.