0
W: Failed to fetch http: //ppa.launchpad.net/picaso/octave/ubuntu/dists/trusty/main/binary-amd64/Packages  404  Not Found

W: Failed to fetch http: //ppa.launchpad.net/picaso/octave/ubuntu/dists/trusty/main/binary-i386/Packages  404  Not Found

W: Failed to fetch http: //ppa.launchpad.net/kilian/f.lux/ubuntu/dists/trusty/main/binary-amd64/Packages  404  Not Found

W: Failed to fetch http: //ppa.launchpad.net/kilian/f.lux/ubuntu/dists/trusty/main/binary-i386/Packages  404  Not Found

E: Some index files failed to download. They have been ignored, or old ones used instead.

I`m not being able to update my ubuntu 14.04 And i face some 404 not found too.

1

You added some PPA that is now no longer reachable.

Deactivate the PPA from Software Sources.

See for example: https://itsfoss.com/how-to-remove-or-delete-ppas-quick-tip/

| improve this answer | |

Not the answer you're looking for? Browse other questions tagged or ask your own question.