Elasticsearch リポジトリからの apt dist-upgrade の失敗に関するトラブルシューティング

Problem

The system could run:

sudo apt update

but failed during:

sudo apt dist-upgrade

with:

403 Forbidden
https://artifacts.elastic.co/packages/9.x/apt/.../elasticsearch-9.4.2-amd64.deb

That means package lists were updated successfully, but APT could not download a specific Elasticsearch package archive.

Why this happened

This was not an Ubuntu mirror issue.

Key evidence:

apt update succeeded.
The failure came only from artifacts.elastic.co.
The failing request used IPv6: 2600:1901:0:1d7::.
A direct request to the same package URL succeeded over IPv4.

So the root cause was a network/IPv6 path problem to the Elasticsearch repo, not a bad package or repository configuration.

Solution found

Temporary fix

Force APT to use IPv4 for the current operation:

sudo apt -o Acquire::ForceIPv4=true update
sudo apt -o Acquire::ForceIPv4=true dist-upgrade

This bypassed the broken IPv6 route and allowed the package download to succeed.

Permanent fix

Persist the IPv4-only setting for APT:

echo 'Acquire::ForceIPv4 "true";' | sudo tee /etc/apt/apt.conf.d/99force-ipv4

Then run normal updates again:

sudo apt update
sudo apt dist-upgrade

What this means

The system itself is healthy enough to update package metadata.
The error was isolated to Elasticsearch package retrieval over IPv6.
Using IPv4 is a practical workaround when a repo is reachable over IPv4 but not over IPv6.

Optional follow-up

For a cleaner long-term solution, investigate IPv6 connectivity on the host or network. But for now, the immediate problem is solved by forcing APT to use IPv4.