When attempting to upgrade an end-of-life (EOL) Ubuntu distribution like Quantal (12.10), you might encounter errors with do-release-upgrade. The tool fails because the repositories and upgrade paths are no longer maintained. Here's a typical error:

Checking for a new Ubuntu release
Your Ubuntu release is not supported anymore.
For upgrade information, please visit:
http://www.ubuntu.com/releaseendoflife

Err Upgrade tool signature
  404  Not Found [IP: 2001:67c:1360:8c01::19 80]
Err Upgrade tool
  404  Not Found [IP: 2001:67c:1360:8c01::19 80]

For EOL releases, you'll need to manually modify your sources and upgrade step-by-step. Here's how:

# First, update your current system as much as possible
sudo apt-get update
sudo apt-get upgrade
sudo apt-get dist-upgrade

# Change sources.list to use old-releases.ubuntu.com
sudo sed -i 's/archive.ubuntu.com/old-releases.ubuntu.com/g' /etc/apt/sources.list
sudo sed -i 's/security.ubuntu.com/old-releases.ubuntu.com/g' /etc/apt/sources.list

# Update again with the new sources
sudo apt-get update

For Ubuntu 12.10 (Quantal), you'll need to upgrade through each intermediate release:

1. 12.10 (Quantal) → 13.04 (Raring)
2. 13.04 (Raring) → 13.10 (Saucy)
3. 13.10 (Saucy) → 14.04 LTS (Trusty)

Here's the command sequence for the first step:

# For Quantal to Raring upgrade
sudo do-release-upgrade -d

For systems that have been EOL for many years (like 12.10), a fresh install might be more reliable:

# Backup your important data first
sudo tar -cvpzf backup.tar.gz --exclude=/backup.tar.gz --one-file-system /

# Then create a bootable USB with the latest Ubuntu LTS
sudo dd if=ubuntu-22.04.iso of=/dev/sdX bs=4M status=progress

If you encounter package conflicts during the upgrade:

# Resolve held packages
sudo apt-mark showhold
sudo apt-mark unhold package_name

# Fix broken packages
sudo apt-get install -f
sudo dpkg --configure -a

After completing the upgrade process, verify your new version:

lsb_release -a
cat /etc/os-release

When attempting to upgrade Ubuntu 12.10 Quantal, you'll encounter the "release not supported" error because:

• Standard repositories are archived
• Security updates ceased in 2014
• Package signatures expire

First, backup critical data:

sudo tar -cvpzf /backup/ubuntu-backup.tar.gz --exclude=/backup --exclude=/proc --exclude=/tmp --exclude=/mnt --exclude=/dev --exclude=/sys --exclude=/run /

Edit your sources.list to point to old-releases:

sudo sed -i 's/archive.ubuntu.com/old-releases.ubuntu.com/g' /etc/apt/sources.list
sudo sed -i 's/security.ubuntu.com/old-releases.ubuntu.com/g' /etc/apt/sources.list

The safest approach is incremental upgrades:

1. 12.10 → 13.04 → 13.10 → 14.04 LTS
2. Then standard LTS upgrade path

After repository changes, run:

sudo apt-get update
sudo apt-get dist-upgrade
sudo apt-get install update-manager-core
sudo do-release-upgrade -d

For production systems, consider fresh install:

# Create bootable USB
dd if=ubuntu-22.04.3-desktop-amd64.iso of=/dev/sdX bs=4M status=progress

After upgrade completion:

lsb_release -a
uname -a
apt list --upgradable