I should also mention that the aforementioned _apt user does exist on my system, it's just that the directory is not owned by them.
$ id _apt uid=125(_apt) gid=65534(nogroup) groups=65534(nogroup) $ ls -ld /var/lib/update-notifier/package-data-downloads/partial drwxr-xr-x 2 root root 4096 Oct 18 07:35 /var/lib/update-notifier/package-data-downloads/partial -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1682017 Title: adobe-flashplugin_20170411.1.orig.tar.gz couldn't be accessed by user '_apt'. - pkgAcquire::Run ... To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/update-notifier/+bug/1682017/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs