Still reproducible on Ubuntu 26.04, nine years after this was filed. Measured
today, 2026-11-03:

  de.archive.ubuntu.com is an alias for ubuntu.mirror.tudos.de
  ubuntu.mirror.tudos.de   A=5 (141.30.62.22-26)   AAAA=0

So on a host without IPv4 egress the German country mirror is unreachable.
Note the shape of the failure: the name resolves perfectly well, there is
simply no route to any of the five answers, so apt reports "could not connect"
and people go looking at their own networking instead of at the mirror.

What makes it worse is that the failure is partial. archive.ubuntu.com and
security.ubuntu.com are both dual-stack, so security updates keep arriving and
unattended-upgrades keeps reporting success, while main, -updates and
-backports quietly go missing. That is easy to overlook for a long time.

This is also no longer an exotic setup. The large hosting providers now bill
IPv4 addresses separately, so instances are routinely created without one --
in our case an existing server simply had its IPv4 address removed.

It is not a capacity problem either. Germany has 43 registered archive
mirrors, and the larger ones are all dual-stack:

  ftp.uni-stuttgart.de          100 Gbps   2001:7c0:2041:48::41
  ftp.halifax.rwth-aachen.de     20 Gbps   2a00:8a60:e012:a00::21
  mirror.dogado.de               20 Gbps   2a02:2b80:101:269::11
  mirror.netcologne.de           20 Gbps   2001:4dd0:1234:1::deb
  ubuntu.mirror.lrz.de                     2001:4ca0:0:101:0:80:21:1
  ubuntu.mirror.tudos.de         10 Gbps   -- the current DE alias

So either the current operator adds AAAA records, or the DE alias moves to one
of the operators that already has them. To be clear about what is *not* a fix:
per the country mirror requirements there can only be one country mirror per
country and its hosts must sit on the same LAN, so this cannot be patched by
appending another mirror's address to the round-robin. It is a decision about
which mirror serves DE.

The underlying reason this has survived nine years is that the country mirror
requirements at ubuntu.com/project/docs/release-team/mirrors/ ask for HTTP and
optionally rsync, and say nothing about IPv6. That is arguably the actual bug,
and other country mirrors are presumably in the same position. IPv6 has been a
full Internet Standard (STD 86, RFC 8200) since 2017, IANA exhausted the IPv4
pool in 2011, and IPv4 is now a paid extra at most providers. In 2026 a country
mirror reachable only over IPv4 is a mirror reachable only if you pay a
surcharge.

Two notes on process. This bug is filed against debian-installer, which cannot
change a DNS alias or the mirror requirements -- could someone with the rights
retarget it to wherever the *.archive.ubuntu.com aliases are maintained?
And we have taken this up directly as well: a ticket with [email protected]
and a mail to the mirror's registered owner, who may simply not have been aware
that the country alias points at his hosts.

Related: LP #2023460, same root cause for the mirrors:// mechanism.

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https://bugs.launchpad.net/bugs/1716874

Title:
  ipv6-only installation uses ipv4-only archive mirrors

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