Comment 27 for bug 1543280

kroenecker (agent-smith) wrote :

Check to see if you have an _apt user:

cat /etc/passwd | grep apt

_apt:x:105:65534::/nonexistent:/bin/false

If you do, no need to add the user. Otherwise,

adduser --force-badname --system --home /nonexistent --no-create-home --quiet _apt || true

I haven't verified that it creates precisely the user necessary. If I remember correctly, /bin/false means no shell access so make sure the user created does in fact have /bin/false in passwd. Also it has no group (65534). That is it really.

Finally check the directory situation:

ls -la /var/lib/update-notifier/package-data-downloads/

drwxr-xr-x 2 _apt root 4096 Nov 9 10:23 partial

As you can see "_apt" is properly listed as the owner. If not,

sudo chown _apt /var/lib/update-notifier/package-data-downloads/partial/

My system already had an _apt user, but did not have proper directory permissions. At least, I have to assume that this is a proper fix. If not, somebody more knowledgeable should be speaking up and sorting this out...