Updating Debian 8 Packages

I've seen lots of threads all with slightly different answers. Tried all I could but I think they're now all outdated.

So we're running Debian 8 (Can't upgrade as it's not our server) the result of cat /etc/os-release is

PRETTY_NAME="Debian GNU/Linux 8 (jessie)"
NAME="Debian GNU/Linux"
VERSION_ID="8"
VERSION="8 (jessie)"
ID=debian
HOME_URL="http://www.debian.org/"
SUPPORT_URL="http://www.debian.org/support"
BUG_REPORT_URL="https://bugs.debian.org/"

Output from cat /etc/debian_version is:

8.3

The /etc/apt/sources.list is

deb http://archive.debian.org/debian/ jessie main non-free contrib
deb-src http://archive.debian.org/debian/ jessie main non-free contrib

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

Inside /etc/apt/sources.list.d I have...

-rw-r--r-- 1 root root  244 Feb 17  2016 backports.list
-rw-r--r-- 1 root root   82 Feb  4 09:04 google-cloud-monitoring.list
-rw-r--r-- 1 root root   82 Feb  4 09:08 jessie-backports.list
-rw-r--r-- 1 root root   79 Feb  4 09:08 jessie.list
-rw-r--r-- 1 root root  183 Jul 18  2016 mod-pagespeed.list

Inside these there are..... (combined list)

deb http://httpredir.debian.org/debian/ jessie-backports main
deb-src http://httpredir.debian.org/debian/ jessie-backports main
deb http://http.debian.net/debian jessie-backports main
deb-src http://http.debian.net/debian jessie-backports main

deb https://packages.cloud.google.com/apt google-cloud-monitoring-jessie-all main

deb [check-valid-until=no] http://archive.debian.org/debian jessie-backports main

deb [check-valid-until=no] http://cdn-fastly.deb.debian.org/debian jessie main

### THIS FILE IS AUTOMATICALLY CONFIGURED ###
# You may comment out this entry, but any other modifications may be lost.
deb http://dl.google.com/linux/mod-pagespeed/deb/ stable main

However we get the following error which suggests maybe the sources need changing again to working ones?

W: GPG error: http://archive.debian.org jessie Release: The following signatures were invalid: KEYEXPIRED 1587841717
W: Failed to fetch http://httpredir.debian.org/debian/dists/jessie-backports/main/source/Sources  404  Not Found
W: Failed to fetch http://httpredir.debian.org/debian/dists/jessie-backports/main/binary-amd64/Packages  404  Not Found
W: Failed to fetch http://http.debian.net/debian/dists/jessie-backports/main/source/Sources  404  Not Found
W: Failed to fetch http://http.debian.net/debian/dists/jessie-backports/main/binary-amd64/Packages  404  Not Found
W: Failed to fetch http://archive.debian.org/debian-security/dists/jessie/updates/main/source/Sources  404  Not Found [IP: 130.89.148.13 80]
W: Failed to fetch http://archive.debian.org/debian-security/dists/jessie/updates/non-free/source/Sources  404  Not Found [IP: 130.89.148.13 80]
W: Failed to fetch http://archive.debian.org/debian-security/dists/jessie/updates/contrib/source/Sources  404  Not Found [IP: 130.89.148.13 80]
W: Failed to fetch http://archive.debian.org/debian-security/dists/jessie/updates/main/binary-amd64/Packages  404  Not Found [IP: 130.89.148.13 80]
W: Failed to fetch http://archive.debian.org/debian-security/dists/jessie/updates/non-free/binary-amd64/Packages  404  Not Found [IP: 130.89.148.13 80]
W: Failed to fetch http://archive.debian.org/debian-security/dists/jessie/updates/contrib/binary-amd64/Packages  404  Not Found [IP: 130.89.148.13 80]
E: Some index files failed to download. They have been ignored, or old ones used instead.                         

The full stack is..

root@generational-vm:/var/lib/apt# apt-get update
Ign http://dl.google.com stable InRelease
Hit http://dl.google.com stable Release.gpg
Ign http://cdn-fastly.deb.debian.org jessie InRelease
Hit http://dl.google.com stable Release
Ign http://httpredir.debian.org jessie-backports InRelease
Ign http://http.debian.net jessie-backports InRelease
Hit http://cdn-fastly.deb.debian.org jessie Release.gpg
Hit http://cdn-fastly.deb.debian.org jessie Release
Get:1 http://dl.google.com stable/main amd64 Packages [2,043 B]
Ign http://httpredir.debian.org jessie-backports Release.gpg
Ign http://httpredir.debian.org jessie-backports Release
Ign http://archive.debian.org jessie InRelease
Get:2 http://cdn-fastly.deb.debian.org jessie/main amd64 Packages [6,818 kB]
Hit https://packages.cloud.google.com google-cloud-monitoring-jessie-all InRelease
Ign http://archive.debian.org jessie/updates InRelease
Get:3 http://cdn-fastly.deb.debian.org jessie/main Translation-en [4,581 kB]
Hit http://archive.debian.org jessie-backports InRelease
Ign http://http.debian.net jessie-backports Release.gpg
Ign http://dl.google.com stable/main Translation-en_US
Ign http://http.debian.net jessie-backports Release
Ign http://dl.google.com stable/main Translation-en
Get:4 http://archive.debian.org jessie Release.gpg [2,420 B]
Get:5 https://packages.cloud.google.com google-cloud-monitoring-jessie-all/main amd64 Packages [582 B]
Get:6 https://packages.cloud.google.com google-cloud-monitoring-jessie-all/main Translation-en_US [1,449 B]
Get:7 https://packages.cloud.google.com google-cloud-monitoring-jessie-all/main Translation-en [1,449 B]
Get:8 https://packages.cloud.google.com google-cloud-monitoring-jessie-all/main Translation-en_US [1,449 B]
Get:9 https://packages.cloud.google.com google-cloud-monitoring-jessie-all/main Translation-en [1,449 B]
Get:10 https://packages.cloud.google.com google-cloud-monitoring-jessie-all/main Translation-en_US [1,449 B]
Get:11 https://packages.cloud.google.com google-cloud-monitoring-jessie-all/main Translation-en [1,449 B]
Get:12 https://packages.cloud.google.com google-cloud-monitoring-jessie-all/main Translation-en_US [1,449 B]
Get:13 https://packages.cloud.google.com google-cloud-monitoring-jessie-all/main Translation-en [1,449 B]
Get:14 https://packages.cloud.google.com google-cloud-monitoring-jessie-all/main Translation-en_US [1,449 B]
Ign https://packages.cloud.google.com google-cloud-monitoring-jessie-all/main Translation-en_US
Ign http://archive.debian.org jessie/updates Release.gpg
Get:15 https://packages.cloud.google.com google-cloud-monitoring-jessie-all/main Translation-en [1,449 B]
Ign https://packages.cloud.google.com google-cloud-monitoring-jessie-all/main Translation-en
Err http://http.debian.net jessie-backports/main Sources

Ign http://archive.debian.org jessie-backports/main amd64 Packages/DiffIndex
Ign http://archive.debian.org jessie-backports/main Translation-en/DiffIndex
Err http://http.debian.net jessie-backports/main Sources

Hit http://archive.debian.org jessie Release
Ign http://archive.debian.org jessie Release
Err http://http.debian.net jessie-backports/main Sources

Ign http://archive.debian.org jessie/updates Release
Err http://http.debian.net jessie-backports/main Sources

Ign http://archive.debian.org jessie/main Sources/DiffIndex
Err http://http.debian.net jessie-backports/main Sources
  404  Not Found
Err http://http.debian.net jessie-backports/main amd64 Packages
  404  Not Found
Ign http://http.debian.net jessie-backports/main Translation-en_US
Ign http://http.debian.net jessie-backports/main Translation-en
Ign http://archive.debian.org jessie/non-free Sources/DiffIndex
Ign http://archive.debian.org jessie/contrib Sources/DiffIndex
Ign http://archive.debian.org jessie/main amd64 Packages/DiffIndex
Ign http://archive.debian.org jessie/non-free amd64 Packages/DiffIndex
Ign http://archive.debian.org jessie/contrib amd64 Packages/DiffIndex
Err http://httpredir.debian.org jessie-backports/main Sources
  404  Not Found
Err http://httpredir.debian.org jessie-backports/main amd64 Packages
  404  Not Found
Ign http://httpredir.debian.org jessie-backports/main Translation-en_US
Ign http://httpredir.debian.org jessie-backports/main Translation-en
Hit http://archive.debian.org jessie-backports/main Translation-en
Hit http://archive.debian.org jessie/contrib Translation-en
Hit http://archive.debian.org jessie/main Translation-en
Hit http://archive.debian.org jessie/non-free Translation-en
Hit http://archive.debian.org jessie-backports/main amd64 Packages
Hit http://archive.debian.org jessie/main Sources
Hit http://archive.debian.org jessie/non-free Sources
Hit http://archive.debian.org jessie/contrib Sources
Hit http://archive.debian.org jessie/main amd64 Packages
Hit http://archive.debian.org jessie/non-free amd64 Packages
Hit http://archive.debian.org jessie/contrib amd64 Packages
Ign http://archive.debian.org jessie/contrib Translation-en_US
Ign http://archive.debian.org jessie/main Translation-en_US
Ign http://archive.debian.org jessie/non-free Translation-en_US
Err http://archive.debian.org jessie/updates/main Sources
  404  Not Found [IP: 130.89.148.13 80]
Err http://archive.debian.org jessie/updates/non-free Sources
  404  Not Found [IP: 130.89.148.13 80]
Err http://archive.debian.org jessie/updates/contrib Sources
  404  Not Found [IP: 130.89.148.13 80]
Err http://archive.debian.org jessie/updates/main amd64 Packages
  404  Not Found [IP: 130.89.148.13 80]
Err http://archive.debian.org jessie/updates/non-free amd64 Packages
  404  Not Found [IP: 130.89.148.13 80]
Err http://archive.debian.org jessie/updates/contrib amd64 Packages
  404  Not Found [IP: 130.89.148.13 80]
Ign http://archive.debian.org jessie/updates/contrib Translation-en_US
Ign http://archive.debian.org jessie/updates/contrib Translation-en
Ign http://archive.debian.org jessie/updates/main Translation-en_US
Ign http://archive.debian.org jessie/updates/main Translation-en
Ign http://archive.debian.org jessie/updates/non-free Translation-en_US
Ign http://archive.debian.org jessie/updates/non-free Translation-en
Fetched 3,002 B in 13s (228 B/s)
W: GPG error: http://archive.debian.org jessie Release: The following signatures were invalid: KEYEXPIRED 1587841717
W: Failed to fetch http://httpredir.debian.org/debian/dists/jessie-backports/main/source/Sources  404  Not Found
W: Failed to fetch http://httpredir.debian.org/debian/dists/jessie-backports/main/binary-amd64/Packages  404  Not Found
W: Failed to fetch http://http.debian.net/debian/dists/jessie-backports/main/source/Sources  404  Not Found
W: Failed to fetch http://http.debian.net/debian/dists/jessie-backports/main/binary-amd64/Packages  404  Not Found
W: Failed to fetch http://archive.debian.org/debian-security/dists/jessie/updates/main/source/Sources  404  Not Found [IP: 130.89.148.13 80]
W: Failed to fetch http://archive.debian.org/debian-security/dists/jessie/updates/non-free/source/Sources  404  Not Found [IP: 130.89.148.13 80]
W: Failed to fetch http://archive.debian.org/debian-security/dists/jessie/updates/contrib/source/Sources  404  Not Found [IP: 130.89.148.13 80]
W: Failed to fetch http://archive.debian.org/debian-security/dists/jessie/updates/main/binary-amd64/Packages  404  Not Found [IP: 130.89.148.13 80]
W: Failed to fetch http://archive.debian.org/debian-security/dists/jessie/updates/non-free/binary-amd64/Packages  404  Not Found [IP: 130.89.148.13 80]
W: Failed to fetch http://archive.debian.org/debian-security/dists/jessie/updates/contrib/binary-amd64/Packages  404  Not Found [IP: 130.89.148.13 80]
E: Some index files failed to download. They have been ignored, or old ones used instead.

Solution 1:

You've shown us /etc/apt/sources.list but you have a lot of other apt repositories defined, so those are probably present in files under /etc/apt/sources.list.d.

Debian 8 is so old that all of these other repositories are unlikely to still support it. They should probably be removed.

Also the debian-security repository is not yet on archive.debian.org, which is why you get 404 Not Found. For that you should be using:

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

though it is out of support now so still won't see any updates, it just won't give any errors.