The root problem here is that Ubuntu 21.10 (Impish Indri) reached its End of Life (EOL) on July 14, 2022. When a Ubuntu release reaches EOL, Canonical moves its packages from the main repositories to old-releases.ubuntu.com.

The key error messages reveal the issue:

Err:2 http://security.ubuntu.com/ubuntu impish-security Release
  404  Not Found

This occurs because:

• Main repositories have been archived
• Security updates are no longer maintained
• The Release files have been removed

You have three practical options:

Option 1: Upgrade to a Supported Release

The recommended approach is to upgrade to Ubuntu 22.04 LTS:

sudo do-release-upgrade -d

Option 2: Point to Old Releases

If you must keep 21.10, edit your sources list:

sudo sed -i 's|http://.*ubuntu.com|http://old-releases.ubuntu.com|g' /etc/apt/sources.list
sudo sed -i 's|http://security.ubuntu.com|http://old-releases.ubuntu.com|g' /etc/apt/sources.list

Option 3: Manual Package Installation

For critical packages, download them directly:

wget http://old-releases.ubuntu.com/ubuntu/pool/main/p/package-name/package.deb
sudo dpkg -i package.deb

After making changes, run:

sudo apt update
sudo apt --fix-broken install

Best practices for repository management:

• Always use LTS (Long Term Support) releases for servers
• Monitor Ubuntu release cycles at ubuntu.com/release-cycle
• Set up automatic notifications for EOL dates

For PPAs like the graphics-drivers in your error output:

sudo add-apt-repository --remove ppa:oibaf/graphics-drivers
sudo apt update

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The errors you're seeing indicate that Ubuntu 21.10 (Impish Indri) has reached its End of Life (EOL) on July 14, 2022. Canonical typically maintains Ubuntu repositories for 9 months after release for non-LTS versions. When a release reaches EOL:

• Official repositories are moved to old-releases.ubuntu.com
• Security updates are discontinued
• The Release files are removed from standard repositories

First confirm your current Ubuntu version:

lsb_release -a
cat /etc/os-release

You have several options to resolve this:

Option 1: Upgrade to a Supported Version

The recommended approach is to upgrade to Ubuntu 22.04 LTS:

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

Option 2: Switch to Old Releases Repository

If you must stay on 21.10 temporarily, modify your sources:

sudo sed -i 's|http://.*ubuntu.com|http://old-releases.ubuntu.com|g' /etc/apt/sources.list
sudo sed -i 's|http://security.ubuntu.com|http://old-releases.ubuntu.com|g' /etc/apt/sources.list

Then clean and update:

sudo apt clean
sudo rm -rf /var/lib/apt/lists/*
sudo apt update

Option 3: Handle Specific PPAs

For third-party repositories like docker or netdata, you may need to:

sudo add-apt-repository --remove ppa:oibaf/graphics-drivers
sudo rm /etc/apt/sources.list.d/oibaf-ubuntu-graphics-drivers-impish.list

For production systems, always use LTS releases and monitor EOL dates:

ubuntu-support-status

Consider setting up automatic updates with:

sudo apt install unattended-upgrades
sudo dpkg-reconfigure unattended-upgrades

If issues persist, try these diagnostic commands:

apt-config dump | grep -i uri
curl -I http://old-releases.ubuntu.com/ubuntu/dists/impish/Release
apt-get update -o Debug::Acquire::http=true

Remember that continuing to use EOL releases poses security risks. The old-releases repository doesn't receive security patches. For critical systems, upgrading should be your top priority.