Comment 17 for bug 1963725

Dunno if it helps, but I'm trying to create a custom autoinstall ubuntu 22.04.2 image and I'm experiencing this error. Inside the shell, by running

curtin in-target -t ... -- apt-get update

I get a file not found and permission denied errors on /cdrom/dists/jammy Packages files. When I look at the CDROM content there is only the Packages.gz file and the apt user is not allowed to read the file anyway.

I'm fixing it (brutally) by unpacking the Packages.gz files and by allowing _apt to read it

```
for f in $BUILD/dists/jammy/*/*/Packages.gz; do
  if [[ ! -f ${f/.gz/} ]]; then
    gunzip -k $f
    chmod o+r $f
    chmod o+r ${f/.gz/}
  fi
done
```

The custom ISO is built with the parameters obtained by running xorriso -indev ubuntu-22.04.2-live-server-amd64.iso report_el_torito as_mkisofs. The autoinstall user-data doesn't configure apt in any way.