Failed to upgrade from 7.10 to 8.04

Can you post the outputs of:-
cat /etc/apt/sources.list
and
cat /etc/lsb-release

First, ensure you follow the upgrade instructions as stated on

http://www.ubuntu.com/getubuntu/upgrading

If you have followed all the steps in the above page and still don't get a message saying that 8.04 is available, maybe the mirror you are using is a bit behind. Since Ubuntu 8.04 was release yesterday, not all mirrors are up to date. Consider waiting some more time or changing to more up to date mirror. For a list of mirrors and their freshness, please refer to:

https://launchpad.net/ubuntu/+archivemirrors

I tried going to a mirror site that says it is up to date, but the same thing happens. How do I know which version I am actually running? Perhaps it is already updated?

You can check the current version with this command:

cat /etc/lsb-release

If hardy has been installed it should say something like:

DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=8.04
DISTRIB_CODENAME=hardy
DISTRIB_DESCRIPTION="Ubuntu 8.04"

Thank you for this suggestion

I get

DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=7.10
DISTRIB_CODENAME=gutsy
DISTRIB_DESCRIPTION="Ubuntu 7.10"

So clearly it did not update. I tried several UK mirror sites, with no effect. I am assuming I use "Software Sources" to update the mirror site?

Here is answer to Pramod Dematagoda's question above:-

alan@alan-desktop:~$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=7.10
DISTRIB_CODENAME=gutsy
DISTRIB_DESCRIPTION="Ubuntu 7.10"
alan@alan-desktop:~$ cat /etc/sources.list
cat: /etc/sources.list: No such file or directory
alan@alan-desktop:~$ cat /etc/apt/sources.list
# deb cdrom:[Ubuntu 7.10 _Gutsy Gibbon_ - Release i386 (20071016)]/ gutsy main restricted
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.

deb http://ubuntu.positive-internet.com/ubuntu/ gutsy main restricted
deb-src http://ubuntu.positive-internet.com/ubuntu/ gutsy main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://ubuntu.positive-internet.com/ubuntu/ gutsy-updates main restricted
deb-src http://ubuntu.positive-internet.com/ubuntu/ gutsy-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## universe WILL NOT receive any review or updates from the Ubuntu security
## team.
deb http://ubuntu.positive-internet.com/ubuntu/ gutsy universe
deb-src http://ubuntu.positive-internet.com/ubuntu/ gutsy universe
deb http://ubuntu.positive-internet.com/ubuntu/ gutsy-updates universe
deb-src http://ubuntu.positive-internet.com/ubuntu/ gutsy-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://ubuntu.positive-internet.com/ubuntu/ gutsy multiverse
deb-src http://ubuntu.positive-internet.com/ubuntu/ gutsy multiverse
deb http://ubuntu.positive-internet.com/ubuntu/ gutsy-updates multiverse
deb-src http://ubuntu.positive-internet.com/ubuntu/ gutsy-updates multiverse

## Uncomment the following two lines to add software from the 'backports'
## repository.
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
# deb http://gb.archive.ubuntu.com/ubuntu/ gutsy-backports main restricted universe multiverse
# deb-src http://gb.archive.ubuntu.com/ubuntu/ gutsy-backports main restricted universe multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository. This software is not part of Ubuntu, but is
## offered by Canonical and the respective vendors as a service to Ubuntu
## users.
deb http://archive.canonical.com/ubuntu gutsy partner
# deb-src http://archive.canonical.com/ubuntu gutsy partner

deb http://ubuntu.positive-internet.com/ubuntu/ gutsy-security main restricted
deb-src http://ubuntu.positive-internet.com/ubuntu/ gutsy-security main restricted
deb http://ubuntu.positive-internet.com/ubuntu/ gutsy-security universe
deb-src http://ubuntu.positive-internet.com/ubuntu/ gutsy-security universe
deb http://ubuntu.positive-internet.com/ubuntu/ gutsy-security multiverse
deb-src http://ubuntu.positive-internet.com/ubuntu/ gutsy-security multiverse

how do i get the installation of 8.04 LTS goin again if it failed?it told me to retry

Try

update-manager --dist-upgrade

from the command line. This should force the update manager to check for new distro release.

Some problem
not appears in update manager button for upgrade, fom 7.10 to 8.04.

my /etc/lsb-release is:
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=7.10
DISTRIB_CODENAME=gutsy
DISTRIB_DESCRIPTION="Ubuntu 7.10"
/etc/lsb-release (END)

my /etc/apt/sources.list is:
# deb cdrom:[Ubuntu 7.10 _Gutsy Gibbon_ - Release i386 (20071016)]/ gutsy main restricted
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.

# deb http://archive.ubuntu.com/ubuntu/ edgy main universe
# deb http://wine.budgetdedicated.com/apt edgy main

## Major bug fix updates produced after the final release of the
## distribution.
deb http://archive.ubuntu.com/ubuntu/ gutsy-updates main

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## universe WILL NOT receive any review or updates from the Ubuntu security
## team.

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.

## Uncomment the following two lines to add software from the 'backports'
## repository.
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
# deb http://it.archive.ubuntu.com/ubuntu/ gutsy-backports main restricted universe multiverse
# deb-src http://it.archive.ubuntu.com/ubuntu/ gutsy-backports main restricted universe multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository. This software is not part of Ubuntu, but is
## offered by Canonical and the respective vendors as a service to Ubuntu
## users.
# deb http://archive.canonical.com/ubuntu gutsy partner
# deb-src http://archive.canonical.com/ubuntu gutsy partner

deb http://archive.ubuntu.com/ubuntu/ gutsy main
deb http://security.ubuntu.com/ubuntu/ gutsy-security main
deb http://archive.ubuntu.com/ubuntu/ gutsy-security main

#AUTOMATIX REPOS START

# deb http://www.getautomatix.com/apt gutsy main

#AUTOMATIX REPOS END

Can you help me? I Whould not like reinstall instead of upgrade.
Thank you very much
Italo Canepa