Sempre que executo o apt-get update e upgrade recebo várias mensagens de erro diferentes.
Existem muitos serviços 503 indisponíveis, mas posso fazer ping nos endereços IP e obter respostas. Além disso, o gnutls_handshake () falhou: Erro na função pull.
Abaixo estão os erros que estou recebendo no final do apt-get update
E: Failed to fetch http://security.ubuntu.com/ubuntu/dists/xenial-security/main/binary-amd64/Packages 503 Service Unavailable [IP: 91.189.88.152 80]
E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial/main/binary-amd64/Packages 503 Service Unavailable [IP: 91.189.88.161 80]
E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-updates/main/binary-amd64/Packages 503 Service Unavailable [IP: 91.189.88.161 80]
E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/xenial-backports/main/binary-amd64/Packages 503 Service Unavailable [IP: 91.189.88.161 80]
E: Failed to fetch http://dl.concerto-signage.org/packages/dists/jessie/main/binary-amd64/Packages 503 Service Unavailable [IP: 173.232.104.112 80]
E: Failed to fetch https://oss-binaries.phusionpassenger.com/apt/passenger/dists/saucy/main/binary-amd64/Packages gnutls_handshake() failed: Error in the pull function.
E: Failed to fetch https://oss-binaries.phusionpassenger.com/apt/passenger/dists/xenial/main/binary-amd64/Packages gnutls_handshake() failed: Error in the pull function.
E: Some index files failed to download. They have been ignored, or old ones used instead.
Qualquer ajuda que você possa fornecer seria muito apreciada.