mirror sync in progress, but the situation improves if `rm -fr /var/lib/apt/lists`

[Dan Bungert]

A not-uncommon bug for Subiquity is one that looks like LP: #2105480, but we have seen many like it and that's just one example. In summary, some files will fail to download from the mirror with the message "Mirror sync in progress?"

For reasons I don't understand just yet, it seems /var/lib/apt/lists can get into a bad state. `apt-get update` just produces the "Mirror sync in progress?". The way to recover from it is to remove /var/lib/apt/lists entirely and start over. After removing /var/lib/apt/lists, `apt-get update` and subsequent operations perform as expected.

I have a live example for you, I don't know if this reproducer requires certain mirror state or not. Attached to this bug is a copy of /var/lib/apt/lists, and if you populate your test system /var/lib/apt/lists with the contents of this tarball and configure the system to hit mirror is.archive.ubuntu.com for series plucky, you may see errors like this:

Err:14 http://is.archive.ubuntu.com/ubuntu plucky/universe amd64 Packages
  404 Not Found [IP: 176.57.227.242 443]
  File has unexpected size (15764540 != 16133052). Mirror sync in progress? [IP: 176.57.227.242 443]

[Seth Arnold (seth-arnold)]

That 3142 sure reminds me of apt-cacher-ng. I've seen this behavior from it before. (I'm aware some people swear by it but I've seen it myself and others have reported size and hash mismatches. I switched to squid-deb-proxy.)

If you've got apt-cacher-ng in your environment, try working around it for a while and see how it goes. I believe I had to clear *both* apt-cacher-ng and apt's downloads in order to work around this when it hit.

Thanks

[Dan Bungert (dbungert)]

Thanks Seth. No apt-cacher-ng in the original failing setup, but I do have squid-deb-proxy in the container I used to test the reproducer. I have re-confirmed, both in the container and the original installer VM, that no apt proxy is required to produce this bug.