root@Node:~# apt-get update;apt-get dist-upgrade
Ign http://bg.archive.ubuntu.com precise InRelease
Ign http://bg.archive.ubuntu.com precise-updates InRelease
Ign http://bg.archive.ubuntu.com precise-backports InRelease
Get:1 http://bg.archive.ubuntu.com precise Release.gpg [198 B]
Get:2 http://bg.archive.ubuntu.com precise-updates Release.gpg [198 B]
Get:3 http://bg.archive.ubuntu.com precise-backports Release.gpg [198 B]
Hit http://bg.archive.ubuntu.com precise Release
Hit http://bg.archive.ubuntu.com precise-updates Release
Hit http://bg.archive.ubuntu.com precise-backports Release
Err http://bg.archive.ubuntu.com precise Release

Err http://bg.archive.ubuntu.com precise-updates Release

Err http://bg.archive.ubuntu.com precise-backports Release

Ign http://extras.ubuntu.com precise InRelease
Ign http://security.ubuntu.com precise-security InRelease
Get:4 http://extras.ubuntu.com precise Release.gpg [72 B]
Get:5 http://security.ubuntu.com precise-security Release.gpg [198 B]
Hit http://extras.ubuntu.com precise Release
Err http://extras.ubuntu.com precise Release

Hit http://security.ubuntu.com precise-security Release
Err http://security.ubuntu.com precise-security Release

Fetched 864 B in 0s (3,917 B/s)
Reading package lists... Done
W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://bg.archive.ubuntu.com precise Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <ftpmaster@ubuntu.com>

W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://bg.archive.ubuntu.com precise-updates Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <ftpmaster@ubuntu.com>

W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://bg.archive.ubuntu.com precise-backports Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <ftpmaster@ubuntu.com>

W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://extras.ubuntu.com precise Release: The following signatures were invalid: BADSIG 16126D3A3E5C1192 Ubuntu Extras Archive Automatic Signing Key <ftpmaster@ubuntu.com>

W: A error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://security.ubuntu.com precise-security Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <ftpmaster@ubuntu.com>

W: Failed to fetch http://bg.archive.ubuntu.com/ubuntu/dists/precise/Release

W: Failed to fetch http://bg.archive.ubuntu.com/ubuntu/dists/precise-updates/Release

W: Failed to fetch http://bg.archive.ubuntu.com/ubuntu/dists/precise-backports/Release

W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/precise/Release

W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/precise-security/Release

W: Some index files failed to download. They have been ignored, or old ones used instead.
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
root@Node:~#