do-release-upgrade --proposed on my Ubuntu Server 8.04, I got the message:
The upgrade is completed but there were errors during the upgrade process.
Searching up the upgrade output, I found this:
Setting up tar (1.22-2) ... tar: ./md5sums: Cannot utime: Bad file descriptor tar: ./control: Cannot utime: Bad file descriptor tar: .: Cannot utime: Bad file descriptor tar: Exiting with failure status due to previous errors dpkg-deb: subprocess tar returned error exit status 2 dpkg: error processing /var/cache/apt/archives/diff_1%3a2.8.1-18_all.deb (--unpack): subprocess dpkg-deb --control returned error exit status 2 Errors were encountered while processing: /var/cache/apt/archives/diff_1%3a2.8.1-18_all.deb Exception during pm.DoInstall(): E:Sub-process /usr/bin/dpkg returned an error code (1) Could not install the upgrades The upgrade is now aborted. Your system could be in an unusable state. A recovery will run now (dpkg --configure -a).
I will post the workaround I found as an answer.