Estou tentando atualizar minha máquina Ubuntu usando o comando
sudo apt-get update
mas a atualização não pode ser concluída. Os erros são:
root@muhammad-VirtualBox:~# apt-get update
Get:1 archive.canonical.com/ubuntu precise InRelease
Err:1 archive.canonical.com/ubuntu precise InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:2 extras.ubuntu.com/ubuntu precise InRelease
Err:2 extras.ubuntu.com/ubuntu precise InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:3 mirror.ni.net.tr/ubuntu xenial InRelease
Err:3 mirror.ni.net.tr/ubuntu xenial InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:4 mirror.ni.net.tr/ubuntu xenial-updates InRelease
Err:4 mirror.ni.net.tr/ubuntu xenial-updates InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:5 mirror.ni.net.tr/ubuntu xenial-security InRelease
Err:5 mirror.ni.net.tr/ubuntu xenial-security InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:6 mirror.ni.net.tr/ubuntu xenial-backports InRelease
Err:6 mirror.ni.net.tr/ubuntu xenial-backports InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:7 mirror.symnds.com/ubuntu precise InRelease
Err:7 mirror.symnds.com/ubuntu precise InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:8 mirror.symnds.com/ubuntu precise-updates InRelease
Err:8 mirror.symnds.com/ubuntu precise-updates InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:9 mirror.symnds.com/ubuntu precise-backports InRelease
Err:9 mirror.symnds.com/ubuntu precise-backports InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:10 mirror.symnds.com/ubuntu precise-security InRelease
Err:10 mirror.symnds.com/ubuntu precise-security InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:11 security.ubuntu.com/ubuntu xenial-security InRelease
Err:11 security.ubuntu.com/ubuntu xenial-security InRelease
Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Fetched 405 kB in 6s (64,4 kB/s)
Reading package lists... Done
E: Failed to fetch mirror.symnds.com/ubuntu/dists/precise/InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: Failed to fetch mirror.symnds.com/ubuntu/dists/precise-updates/InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: Failed to fetch mirror.symnds.com/ubuntu/dists/precise-backports/InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: Failed to fetch mirror.symnds.com/ubuntu/dists/precise-security/InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: Failed to fetch archive.canonical.com/ubuntu/dists/precise/InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: Failed to fetch extras.ubuntu.com/ubuntu/dists/precise/InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: Failed to fetch mirror.ni.net.tr/ubuntu/dists/xenial/InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: Failed to fetch security.ubuntu.com/ubuntu/dists/xenial-security/InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: Failed to fetch mirror.ni.net.tr/ubuntu/dists/xenial-updates/InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: Failed to fetch mirror.ni.net.tr/ubuntu/dists/xenial-security/InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: Failed to fetch mirror.ni.net.tr/ubuntu/dists/xenial-backports/InRelease Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: Some index files failed to download. They have been ignored, or old ones used instead.
Como posso resolver isso?