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### Official Ubuntu Repositories ###
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# Gutsy Final Release Repository
deb http://archive.ubuntu.com/ubuntu gutsy main restricted universe multiverse
#deb-src http://archive.ubuntu.com/ubuntu gutsy main restricted universe multiverse

# Gutsy Security Updates
deb http://security.ubuntu.com/ubuntu gutsy-security main restricted universe multiverse
#deb-src http://security.ubuntu.com/ubuntu gutsy-security main restricted universe multiverse

# Gutsy Bugfix Updates
deb http://archive.ubuntu.com/ubuntu gutsy-updates main restricted universe multiverse
#deb-src http://archive.ubuntu.com/ubuntu gutsy-updates main restricted universe multiverse

# Gutsy Backports (new software versions, provided by the Ubuntu Backports Project)
deb http://archive.ubuntu.com/ubuntu gutsy-backports main restricted universe multiverse
#deb-src http://archive.ubuntu.com/ubuntu gutsy-backports main restricted universe multiverse

# Ubuntu Commercial
deb http://archive.canonical.com/ubuntu gutsy partner
#deb-src http://archive.canonical.com/ubuntu gutsy partner
                   

Running apt-get update, aptitude update or synaptic (reload button gives):

http://archive.ubuntu.com/ubuntu/dists/gutsy/Release.gpg: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy/main/i18n/Translation-en_GB.bz2: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy/restricted/i18n/Translation-en_GB.bz2: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy/universe/i18n/Translation-en_GB.bz2: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy/multiverse/i18n/Translation-en_GB.bz2: Could not resolve ‘omicron’
http://security.ubuntu.com/ubuntu/dists/gutsy-security/Release.gpg: Could not resolve ‘omicron’
http://security.ubuntu.com/ubuntu/dists/gutsy-security/main/i18n/Translation-en_GB.bz2: Could not resolve ‘omicron’
http://security.ubuntu.com/ubuntu/dists/gutsy-security/restricted/i18n/Translation-en_GB.bz2: Could not resolve ‘omicron’
http://security.ubuntu.com/ubuntu/dists/gutsy-security/universe/i18n/Translation-en_GB.bz2: Could not resolve ‘omicron’
http://security.ubuntu.com/ubuntu/dists/gutsy-security/multiverse/i18n/Translation-en_GB.bz2: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy-updates/Release.gpg: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy-updates/main/i18n/Translation-en_GB.bz2: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy-updates/restricted/i18n/Translation-en_GB.bz2: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy-updates/universe/i18n/Translation-en_GB.bz2: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy-updates/multiverse/i18n/Translation-en_GB.bz2: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy-backports/Release.gpg: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy-backports/main/i18n/Translation-en_GB.bz2: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy-backports/restricted/i18n/Translation-en_GB.bz2: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy-backports/universe/i18n/Translation-en_GB.bz2: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy-backports/multiverse/i18n/Translation-en_GB.bz2: Could not resolve ‘omicron’
http://archive.canonical.com/ubuntu/dists/gutsy/Release.gpg: Could not resolve ‘omicron’
http://archive.canonical.com/ubuntu/dists/gutsy/partner/i18n/Translation-en_GB.bz2: Could not resolve ‘omicron’
http://archive.canonical.com/ubuntu/dists/gutsy/partner/binary-amd64/Packages.gz: Could not resolve ‘omicron’
http://security.ubuntu.com/ubuntu/dists/gutsy-security/main/binary-amd64/Packages.gz: Could not resolve ‘omicron’
http://security.ubuntu.com/ubuntu/dists/gutsy-security/restricted/binary-amd64/Packages.gz: Could not resolve ‘omicron’
http://security.ubuntu.com/ubuntu/dists/gutsy-security/universe/binary-amd64/Packages.gz: Could not resolve ‘omicron’
http://security.ubuntu.com/ubuntu/dists/gutsy-security/multiverse/binary-amd64/Packages.gz: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy/main/binary-amd64/Packages.gz: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy/restricted/binary-amd64/Packages.gz: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy/universe/binary-amd64/Packages.gz: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy/multiverse/binary-amd64/Packages.gz: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy-updates/main/binary-amd64/Packages.gz: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy-updates/restricted/binary-amd64/Packages.gz: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy-updates/universe/binary-amd64/Packages.gz: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy-updates/multiverse/binary-amd64/Packages.gz: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy-backports/main/binary-amd64/Packages.gz: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy-backports/restricted/binary-amd64/Packages.gz: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy-backports/universe/binary-amd64/Packages.gz: Could not resolve ‘omicron’
http://archive.ubuntu.com/ubuntu/dists/gutsy-backports/multiverse/binary-amd64/Packages.gz: Could not resolve ‘omicron’